By Joe Traynor

Nitrogen fertilization is a very important input in grape culture. Too much nitrogen and fruit - and by extension, wine - quality suffers; too little, and yields fall off significantly. Grapes have a relatively low nitrogen requirement compared to almost any other agricultural crop. Sixty units of nitrogen annually are all that is needed in most cases. Extensive root systems, heavy winter pruning and wide row spacings contribute to this relatively low nitrogen requirement. With recent closer row spacings, we’re seeing a modest increase in nitrogen fertilization rates.

Nitrate analysis of the stalks of leaves, or petioles, is used by most grape growers to fine-tune their nitrogen fertilization programs. Petiole samples are taken at full bloom and the analysis results are compared to standards developed by the University of California for Thompson Seedless and are shown in Chart 1.

Chart 1 is tidy and the six different categories give the impression that the nitrogen status of a given vineyard can be pinpointed by simply plugging petiole nitrate figures in the UC chart. Ag labs, consultants and farm advisors make extensive use of this chart - it dovetails with our desire for tidy solutions to perplexing questions. Unfortunately, it’s not that simple, or tidy.

Chart 1
CATEGORY	NITRATE-N*, PPM
Deficient	below 350
Questionable	350 - 500
Adequate	500 - 1200
More than necessary	over 1200
Excess	over 2000
Possibly toxic	over 3000
* Divide PPM Nitrate by 4.4 to get PPM Nitrate-N

Some Limitations

First, the UC emphasizes that the chart is good only for Thompson Seedless. Second, and most important, cultural practices and weather conditions can have as much of an effect on petiole nitrate as can nitrogen fertilization.

The limitations of petiole nitrate analysis were recognized early on by UC workers. James Cook of the UC Davis viticulture department studied the subject extensively. In a 1966 review based on two UC studies, Cook said, “Perhaps the greatest drawback [of petiole nitrate analysis] to its universal application is the reaction to rainfall or irrigation. It has been shown that the petiole-nitrate level drops rapidly after an irrigation, requiring 10 to 14 days to recover.” Citing his own work, Cook concluded,

” . . .bloomtime petiole nitrate level is correlated inversely with rainfall pattem from bud-break to bloom. Thus, high rainfall in the spring results in barely detectable nitrate levels in vines receiving abundant nitrogen application.”

Unfortunately, Cook’s reservations did not make it into the UC extension literature that accompanied the UC’s petiole chart. Growers took - and still take - the chart as gospel.

Cook later collaborated with UC colleague Mark Kliewer to find a better method of delineating the nitrogen status of vineyards and they concluded that analysis of an amino acid in juice and canes called arginine was superior to petiole analysis. Kliewer and Cook implied the deficiencies in petiole nitrate analysis stating, “It also indicates that petiole nitrate differs only very narrowly between vines with low and high crop yields. For example, vines with petiole nitrate levels of 1000 ppm to 1200 ppm were almost always associated with low yields, whereas vines with 1400 ppm to 1600 ppm petiole nitrate had no reduction in crop weight.”

The UC’s arginine test created a flurry of interest in the 1970s but this interest has waned in ensuing years. Today, many consultants and vineyard managers still rely on petiole studies from the 1950s and petiole standards for nitrate are still provided by UC’s extension service.

I used the UC’s petiole standards when I first got into consulting in the 1970s and it wasn’t long before I got into trouble. I took samples from several lush vineyards that used in excess of 100 units of nitrogen per acre and was confident that petiole analysis results would convince the grower to cut back on nitrogen. When the petiole analysis came back showing nitrate in the deficient range I was stunned. I called the lab and told them they probably made a mistake, but a re-run gave the same results, as did new samples split between two labs.

I found the same inconsistencies in subsequent samples and long ago abandoned petiole-nitrate analysis as a guide to the nitrogen status of vineyards - it just doesn’t work. I now use total nitrogen in the leaves, sampled two or three times during the year. Total nitrogen is much more stable and not subject to the wild fluctuations of petiole nitrate.

The total nitrogen levels shown here in Chart 2 is not nearly as comprehensive as the petiole-nitrate chart, but it is a good guide when used in conjunction with field observations. So far it holds up for varieties other than Thompson.

Chart 2
OPTIMUM NITROGEN LEVELS IN MOST RECENTLY MATURED LEAF*
Bloom (early May)	Veraison (June-July)	Harvest (July-August)
3.3 - 4.0%	2.5 - 3.2%	2.1 - 2.7%
* Usually four or five leaves from the growing point (total nitrogen)

Total nitrogen analysis of leaves, and in some cases, leaves plus petioles, is used extensively in France and other European countries and also in South Africa and Australia. I have found it to be far more reliable than petiole-nitrate analysis. The vineyardist should also rely on what his vines tell him: lush growth indicates excess nitrogen; sparse growth and low yields may indicate insufficient nitrogen. Use this visual information along with leaf analysis for nitrogen to come up with a suitable nitrogen fertilizer program.

More Nutrition Work

UC extension viticulturist Pete Christensen worked extensively on vineyard nutrition in the 1960s, 1970s and 1980s. He also showed “… wide year-to-year variations …” in petiole nitrate over a four-year period from 1964 to 1967. In a subsequent three year study from 1979 to 1981, Christensen compared total nitrogen analysis of leaves with petiole nitrate and conceded that, “Total nitrogen levels were much more stable, especially during the bloom period,” but expressed reservations about using total nitrogen as a diagnostic tool partly because he felt that a portion of the total nitrogen was in a form that was not available for assimilation by plants. (*note - total nitrogen is used extensively in orchard leaf analysis and this question has not been raised by orchard scientists).

Part of the UC’s reluctance to recommend total nitrogen in leaves as a diagnostic tool for grapes could be because petiole analysis is superior to leaf analysis for monitoring potassium status in grapes and it is much more convenient - and economical - to sample one plant part only.

The UC’s James Cook studied vineyard nutrition as much as any individual and his 36 page review in 1966 is a tour de force on the subject. Cook’s review is a thorough discussion of all phases of vineyard nutrition with emphasis on plant analysis and nitrogen status, including over 200 references, 10 of which carry Cook’s name as the principal author. Regarding nitrogen nutrition, Cook’s frustration at the inadequacy of diagnostic tests as a definitive tool is apparent through-out his treatise. As Cook put it, “… whether visual symptoms, soil analysis, or tissue analysis - singly or in combination - are used as diagnostic tools, the proof of their usefulness must be established by well planned, carefully conducted field trials. Survey data can provide a range of values - high, medium and low - for whatever reference analysis system may be established, but calibration of that system to determine critical response levels must be on the basis of actual field-trial data. Without such calibration, statements that ‘low’ values are deficient are only speculative at best, and in many cases may be entirely in error.” A number of such “speculative statements” are being made today on the basis of petiole-nitrate analysis.

Leaf analysis for total nitrogen is not a definitive tool for assessing the nitrogen status of a vineyard, but it can be quite useful. Use it along with field observations and yield data, and be skeptical of using petiole-nitrate analysis as a diagnostic tool; this particular emperor has no clothes.

Grape Grower Magazine, February 2003

Joe Traynor is a certified professional soil scientist, crop scientist and agronomist listed with the American Registry of Certified Professionals in Agronomy, Crops and Soils, Ltd. He holds multiple degrees from the University of California, Davis, is a member of the American Society for Horticultural Science, and is the author of Ideas in Soil and Plant Nutrition, published by Kovak Books.

References

1. Cook, James A. (1966). Grape Nutrition. Chapter 23, pp. 777-812, in the book Nutrition of Fruit Crops, Norman Childers, Ed. Rutgers Horticultural Publications.

2. Kissler, James J. (1957). Nitrate fluctuations and petiole sampling techniques with grape vines. MS thesis, Univ. of Calif., Davis.

3. Cook, James A. and Lloyd Lider. Mineral composition of bloomtime grape petiole in relation to rootstock and scion variety behavior. Proc. Amer. Soc. Hort. Sci. 84:243-254.

4. Kliewer, Mark and James A. Cook. (1974). Arginine levels in grape canes and fruits as indicators of nitrogen status of vineyards. Amer. J. of Enology and Viticulture 25:111-118.

5. Christensen, Peter (1969). Seasonal changes and distribution of nutritional elements in Thompson Seedless grapes. Amer. J. of Enology and Viticulture 20:176-190.

6. Christensen, Peter (1984). Nutrient level comparisms of leaf petioles and blades in twenty-six grape cultivars over three years. Amer. J. of Enology and Viticulture Vol. 35, No. 3.

Healthy orchards and vineyards withdraw potassium from your soils, so be sure to make a deposit.

By Joe Traynor

There has been increasing interest in potassium (K) fertilization of orchards and vineyards in recent years, and with good reason. A high-yielding orchard or vineyard can remove 100 to 300 pounds of K from the soil every year. Multiply this by 10 or 20 years, and it becomes apparent that soils, especially sandy soils, will eventually incur a debt that must be paid. Providing ample K can increase fruit size, even out maturity, and reduce stress.

Two decades ago, the accepted method of applying K to permanent crops was to shank K down the tree or vine row during the winter. Two drawbacks to this method are the possibility of salt injury from high amounts of the K materials normally used, and the fact that most soils will tie up K within weeks of application, rendering it unavailable to the roots.

Orchards and vineyards require virtually all of their K during the period of rapid fruit growth - from post-bloom through May. Winter application of K is simply not efficient.

The proliferation of low-volume sprinkler and drip irrigation over the past 20 years provides growers with the ideal K delivery system. K can be applied when roots are active and at the time of greatest need, during rapid fruit development. Soil tie-up of K is minimized and, should an early frost take the crop, the expense of K fertilization can be eliminated.

Here is a look at the four main K’s.

The Four Fertilizers
A COMPARISON of the four main potassium fertilizers is indicated in the following table. Maintenance application rates should be 100 pounds of K2 (potassium oxide) annually, starting shortly after bloom.
Material	%K2O	Solubility #/100 gallons	Cost Per Ton (estimated)
Muriate of potash (KCI)	61	300	$150
Sulfate of potash	52	100	$240
Potassium carbonate	68	940	$880
Potassium thiosulfate	25	819	$42
Source: Scientific Ag Co.

Muriate Of Potash

Muriate of potash is the K fertilizer of choice in almost all cases because of its significantly lower cost. Muriate’s relatively good solubility makes for easier water-run applications. Some growers hesitate to use muriate of potash because of its chloride content, but at the relatively low rates used for K maintenance this should not be a concern unless irrigation water is high in chloride - over 180 ppm. Growers concerned about chloride should monitor the levels through leaf testing. The level will increase during the season, but should be kept below 0.2%.

Sulfate Of Potash

The only discernible advantage of sulfate of potash for most crops is “free” sulfur nutrition, as the material is 18% sulfur. However, the possibility of sulfur deficiency in orchards and vineyards is remote, as most well water supplies ample sulfur. For other water sources, gypsum (calcium sulfate) is usually applied to maximize water infiltration, and gypsum supplies plenty of sulfur.

Potassium Carbonate

Potassium carbonate (PC) is an intriguing material for orchards and vineyards under low-volume sprinkler or drip irrigation because of its anti-acid properties. PC is amazingly soluble - three times as soluble as muriate of potash and nine times as soluble as sulfate of potash. PC is the K of choice when soil pH is low, but it is more hazardous than other materials because of its alkalinity.

Potassium Thiosulfate

Potassium thiosulfate (KTS) has an acidifying effect on soils and is therefore the K fertilizer of choice on high pH or high-lime soils. Most varieties are tolerant of high-lime soils, but there are exceptions. If trees on a high-lime soil show chlorosis, KTS should be used if K is needed.

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Joe Traynor is the manager of Scientific Ag Co. in Bakersfield, CA. E-mail questions or comments about this article to afg_edit@meisternet.com.

From December 1995 and March 1996 beekeeper newsletters.

10. Your friends think you look better with your veil on.
9. You take off your hat in a restaurant and someone throws a dollar in it.
8. You’re heading back to Montana after the almonds and see a sign saying “Welcome to Phoenix”.
7. You put a little Bee-Go behind your ears before heading out for a night on the town.
6. The Mayo clinic requests permission to use you as an example of the cumulative effect of bee stings.
5. You find your coveralls stuck to the seat at the local cafe and are forced to leave them behind.
4. A biker asks directions to the nearest restaurant and you perform a short waggle dance. He punches your lights out.
3. You wear an Apistan strip around your neck to formal events.
2. You’re asked to give a talk at a local school and you give an hour demonstration on frying varroa with a magnifying glass.
1. Your wife kicks you out of the house in the fall and doesn’t let you back in until spring.

Some Thoughts on Napa Valley and San Joaquin Valley Growers

By Joe Traynor

Most people think of farmers as a homogeneous lot - hard working individuals that make a living off the land and that are, by nature, distrustful of city folk. This is the image portrayed by the media and it generally holds true, although with one notable exception: the Napa Valley grape grower.

The gentrification of the Napa Valley over the past 20 years has created a class of grape growers that is as different from your average farmer as grapes are from grape shot. If an outsider were to base his or her impression of all grape growers solely on a visit to the Napa Valley, that impression would be wrong.

Over the past 20 years, the Napa Valley has seen an influx of “city folk” that have earned their money in a number of fields, including entertainment, law and technology. They have transferred their talents from their chosen fields to fields of grapes, partly because of the desire for a new challenge and partly because of the life style. The results have been the yuppification (which is not necessarily a pejorative term) of the Napa Valley as these new vineyardists have melded their life style with those of long-time Napa Valley vintners.

Old-time Napa valley growers have been confronted with an identity crisis: Am I a farmer or a gentleman farmer? Those that can afford it have resolved this crisis by taking on the role of gentleman farmer while assigning the role of plain “farmer” to a capable manager who handles the nuts and bolts of the farming operation. Those that know they will always be “just” a farmer shake their heads at the current situation and get on with their daily work, although with increased isolation from a changed community.

A World Away in the San Joaquin Valley

The San Joaquin Valley grape grower fits nicely into the conventional image of the farmer. He is free from the outside influences that have changed the Napa Valley and he therefore has no identity crisis. He has no need to keep up with his neighbors because his neighbors are just like him: hard working and focused on the day-to-day tasks of extracting a living from the vineyard.

The San Joaquin Valley wine grape grower has somewhat of an inferiority complex because the price he is paid for his crop is significantly less than what the Napa Valley grower receives. In America, the amount of money one makes is used by many to judge the worth of an individual with higher status and more respect often accorded to those with the most money. In the winegrape industry, the price received per ton of grapes is a status symbol.

San Joaquin Valley growers realizes that Napa Valley’s climate - mainly with its cool nights - produces a superior product, but they feel that the disparity in the price received for that product is far wider than the disparity in quality. This price disparity is particularly galling when San Joaquin Valley growers consider that wines with the Napa Valley appellation are allowed to contain up to 25 percent of wine from other areas, usually from the San Joaquin Valley area.

What the San Joaquin Valley vintner lacks in quality, he makes up for in quantity. Per-acre yields are significantly higher in the San Joaquin Valley coupled with lower overhead costs - including land prices in the San Joaquin Valley at approximately $3000 per acre compared to $25,000 per acre and beyond in the Napa Valley. Add to this the lower costs needed to maintain the San Joaquin Valley grower’s lifestyle and the San Joaquin Valley grower is probably better off than his Napa Valley counterpart.

Joe Traynor is a certified professional soil scientist, crop scientist and agronomist listed with the American Registry of Certified Professionals in Agronomy, Crops and Soils, Ltd. He holds multiple degrees from the University of California, Davis, is a member of the American Society for Horticultural Science, and is the author of Ideas in Soil and Plant Nutrition, published by Kovak Books.

Traynor’s “Different Valleys, Different Worlds” Comparison Chart
	NAPA VALLEY	S.J. VALLEY
Daily dress	Designer jeans	Levis
Formal wear	Tuxedo	Clean Levis
Boots	Tony Lama	Red Wings
Favorite beverage	Dry Martini (when no one’s looking)	Beer (anytime, with anybody)
Favorite saying	“Friends don’t let friends drink White Zinfandel”	“If it ain’t there, It ain’t there”
Favorite magazine	GQ	Field & Stream
Favorite quartet	Kronos	Statler Brothers
Favorite contemporary singer	Joni Mitchell	Johnny Cash
Favorite singer from the past	Edith Piaf	Hank Williams
Usually votes	Republican (but apologizes to Bay Area friends)	Republican (and proud of it)
Favorite sport	Tennis	Football
Language skills	French	Spanish
Radio is tuned to	Classical Music	Rush Limbaugh
Recent event enjoyed	Four course dinner w/fellow vintners	Deep pit barbecue w/fellow growers
What growers came away with from this event	The Euro-dollar will have a big impact on the sales of French wines	Stanford and Cal don’t have the guts to schedule the Bulldogs
Where you can find growers on saturday	On the tennis court or on the golf course	In the vineyard or in the shop
Favorite topic	Why Napa Valley wines are vastly superior to San Joaquin Valley wines	Why we don’t get paid more for our grapes when many of them end up in Napa Valley bottles
Most frequently used word(s)	“Eclectic”	“Horsepucky”
Recurring pleasant dream	The 1976 blind taste test	The last day of harvest
Recurring nightmare	Washington wines win blind taste test	Spring frost and rain during harvest
All time favorite movie	Jules and Jim	High Noon
Favorite restraunt	The French Laundry	Local steak house
Favorite TV show	King of the Hill	King of the Hill

Grape Grower Magazine - August 2002

__________________

Bee Culture - June, 2002
___________________

Joe Traynor

With growing concern about pollen transfer from genetically modified crops and with continued concern about pesticide poisoning of bees, it is becoming increasingly important to know the answer to the question posed above.

The flip answer, “as far as they have to” is also the best answer.

Imagine a large wreath of flowers, encircling a hive (or an apiary) in a barren desert. Gradually expand that wreath and you will find that bees will forage up to seven miles, but that the law of diminishing returns (where hives lose weight) kicks in at about four miles.

In what has been termed a “classic experiment”, J. E. Eckert essentially did the “wreath experiment” in a three year study (1927-1929) that was published in 1933(1). This study should answer the title question for all time. Eckert picked two irrigated areas in Wyoming that were separated by a 17 mile stretch of barren badlands, then placed colonies at increasing distances from the irrigated wares. Roger Morse summed up his study in the table on the next page.

What’s striking about this experiment is that colonies can make a living when the nearest food source is four miles away. From this, it is easy to see that a two mile buffer zone is not sufficient to protect bees from pesticides (or to prevent pollen transfer from two different varieties of plants grown several miles apart).

The area covered by bees increases exponentially with distance from the apiary since the area of a circle is a function of the square of the radius:

Flight range	Acres covered
1 mile 2 3 4	2,011 8,658 18,092 32,166
See Graphic

I have had personal experience learning about the flight range of honey bees as determined by pesticide applications. Around 1981, bee colonies in an almond orchard in Kern county suffered severe poisoning from a spray (parathion) on blooming nectarines well over two miles away. There were approximately 5,000 bee colonies on 2,500 acres of almonds located over two miles south of about 200 acres of nectarines that were in full bloom. The poisoning occurred at the tail end of the almond bloom when pollination was essentially completed and when almond bees greatly expand their foraging radius. The bee kill pattern in the almonds conformed exactly to the distance from the nectarines: the closest bees, a little over two miles from the nectarines, showed a severe kill while bees four miles away suffered what would be considered a “light” kill.

Bees placed on alfalfa seed pollination will travel great distances to get pollen rather than work alfalfa flowers for pollen(2). In an extensive test in the 1980’s, David Chaney (U. C., Davis) found that bees placed for alfalfa pollination collected 10 times as much safflower pollen as alfalfa pollen even though the nearest safflower field was five miles away!(3) a distance greater than the breadth of Celine Dion’s ego!(4).

California laws (and laws in some other states) require pesticide notification to beekeepers within a mile of hazardous spray. Since the nectarine incident described above, I have requested notification for sprays on blooming crops up to two miles away; my request has not been fulfilled and probably never will be although I have made it every year since the incident (saying, essentially, “attention must be paid”).

DISTANCES HONEY BEES WILL FORAGE
Distance from irrigated area (sweet clover and alfalfa)	Average change in Hive Weight over 18 days
0.0 miles	+25.3 pounds
0.5	31.6
1.0	23.3
1.5	21.3
2.0	18.1
3.0	13.8
4.0	5.1
5.0	-3.0
6.0	-6.2
7.0	-8.6

A number of variables affect the hazard of a given pesticide application including the attractiveness of the sprayed crop, the total acreage to be sprayed and the dilution of bees (on other flower sources) in the area. When all conditions are right (”wrong” from the beekeeper’s standpoint) severe pesticide kills can occur from sprays applied well over a mile from apiaries.

It is probably not practical to inform beekeepers of sprays within four miles, or even two miles of apiaries, but area-wide restrictions on pesticide applications could be made. These restrictions could ban the use of a few extremely hazardous materials (e.g., Penncap-M, Sevin, Furadan) in bee “areas” and restrict the use of others.

How far do bees fly? The answer still is . . as far as they have to.

Joe Traynor is a crop consultant and pollination specialist from Bakersfield, CA. He is a frequent contributor to these pages.

References

1. Eckert, J. E. 1933. The flight range of the honeybee. J. of Agricultural Research 47:257-285.

2. Morse, Roger 1984. Research Review (How far will bees fly?). Gleanings in Bee Culture, September 1984, p. 474.

3. Chaney, David circa 1985. Bloom dynamics in alfalfa: Implications for pollination and seed production. M. S. Thesis, International Agricultural Development, University of CA. Davis, CA.

4. Carroll, Jon. San Francisco Chronicle, April 9, 2002. Carroll estimated Dion’s ego at more than a mile, but gave no exact figure.

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Filling Your Buckets
Time, distance and reward are important in foraging.

Its raspberry picking time and you take a couple of buckets out to your favorite patch in back of your house. To your dismay, you find it overgrown with prickly nettles - there are ample raspberries underneath but it will be a chore to extract them. You start picking anyway but soon get discouraged; you sit down and calculate that it will take you all day to fill your buckets.

What to do? You then remember a raspberry patch you stumbled across a few years ago - its an hour drive by car, followed by a mile walk through the woods, but your appetite for raspberries has been whetted and you consider this only a minor inconvenience. You hop in your car, make the journey and after losing your way several times on the trail you finally arrive at the secret patch and discover, to your delight, a bumper crop of ripe raspberries that obviously hasn’t been touched. You fill your buckets in 15 minutes and quicken your pace back to your car as you see someone approaching with a shotgun. You make it to your car and when you arrive back home you calculate that even though you just spent four hours, you’d still be picking raspberries if you’d stayed at the patch in back of your house.

Now, you’re a worker bee in a hive surrounded by blooming alfalfa as far as the eye can see. As alfalfa nectar pours into the hive, your appetite for pollen becomes uncontrollable but you soon find that you have to visit 350 alfalfa flowers to get a load of pollen (about 20 mg)(1). Alfalfa pollen is abundant (because of the millions of flowers per acre) and nutritious(2) but this is far different from that almond orchard this Spring where you only had to visit 20 almond flowers to get a load of pollen(3) and different, also, from that mustard patch you were in yesterday before some unthinking individual moved you last night. To add injury to insult, you get whacked on the head every time you get a smidgen of alfalfa pollen. Anything is better than this, so you fly zigzag upwind two or three miles to where you chance on a field of corn in full tassel. You land, and it only takes 15 minutes to fill your pollen buckets - you’re in honey bee heaven!

When you get back to the hive, you use your language skills to inform your fellow workers of your (their) newly found bounty(4). For the next two days you and your worker kin fill the hive with corn pollen and lift a cup or two each evening to toast your good fortune.

On the third day, you visit the corn field en masse and while you’re in the midst of your chores, you see a low-flying plane approaching. Something buried deep in your genes makes you feel uneasy, but you go on with your work. You feel the spray drench you and find yourself twisting helplessly on the ground. As things get black, you hear a fallen comrade gasp with her dying breath, “there oughta be a law.”

References

1. Vansell, G. H. and F. Todd. (1946) Alfalfa tripping by insects. Amer. Soc. Of Agronomy Journal. 38:470-488

2. Peng, C. S. 1985 The nutritional value of alfalfa pollen to honey bees p. 23-28 in Proceedings, Alfalfa Seed Production Symposium, Fresno, CA, March 12, 1985. U of CA Extension & CA Alfalfa Seeds Production Research Program.

3. DeGrandi-Hoffman, Gloria, Gerald Loper, Robbin Thorp and Dan Eiskowitch (1991) The influence of nectar and pollen availability and blossom density on the attractiveness of almond cultivars to honey bees. Acta Horticulturae 288, 6th Pollination Symposium.

4. Wenner, Adrian and Patrick H. Wells. Anatomy of a Controversy. 1990. Columbia University Press

By Joe Traynor

It is well known that excessive soil lacidity, resulting in a low soil pH, impairs root growth and reduces crop yields. Ideally, soil pH should be in the 6.5 to 7.5 range, with a pH of 7.0 being neutral. When pH drops below 5.5, lime, or calcium carbonate, is applied to raise soil pH.

Lime application and incorporation is easily accomplished in most situations, but for drip-irrigated crops raising soil pH can be a vexing problem. Lime must be incorporated into the soil to be effective and because lime is relatively insoluble, it cannot be applied through drippers.

Many California soils have a good supply of lime in its virgin state - enough to maintain soil pH in a favorable range for many years. On the many soils that don’t have natural lime, growers planning a drip-irrigated permanent crop should incorporate lime into the projected drip line at the rate of 10 tons per acre. On established vineyards, continued use of ammonium-based nilrogen fertilizers over the years coupled with low-salt irrigation water can drop soil pH below 5.5. On vineyards, sulfur application for mildew control will also acidify low-lime soils over a period of years.

When soil pH on established drip-irrigated vineyards drops below 5.5, incorporating lime into the wetted zone is logistically difficult. A possible solution to this dilemma is water-run potassium carbonate. Potassium carbonate (K2C03) is very soluble and applying it through drippers should be feasible. Potassium carbonate can’t compete with lime on a cost basis, nor can it compete as a potassium fertilizer, however the combination fertilizer/amendment properties of potassium carbonate make it an intriguing material for raising soil pH on drip-irrigated crops with a high potassium requirement, such as bearing vineyards.

There are some caveats to running potassium carbonate through drippers, however. If the irrigation water has a moderate calcium level, lime can precipitate out and clog drippers, albeit where high calcium waters are used, low pH problems are not encountered. Once potassium carbonate is added to water, much of the carbonate will convert to bicarbonate and bicarbonate can have a deleterious effect on soils that are not well supplied with calcium. Low pH soils are usually low-calcium soils and calcium levels should be increased on such soils by adding gypsum, or calcium sulfate, and/or by using calcium nitrate as the nitrogen fertilizer. By adding calcium to the soil - followed by or preceded by potassium carbonate - you are essentially making your own lime, or calcium carbonate, in the soil.

Ammonium-based nitrogen fertilizers should never be applied with potassium carbonate because NH3 volatilization could occur. Potassium carbonate is hygroscopic and will clump as it picks up moisture from the air, however the 50-pound bags in which it is sold minimizes this problem. Also, because of its high alkalinity, potassium carbonate is more irritating to skin, eyes and lungs than other potassium materials.

Potassium carbonate has fungicidal properties and it is possible that water-run potassium carbonate could suppress phytophthora or even nematodes.

Fungicidal Properties of K2CO3

Potassium carbonate foliar sprays could also have a place in vineyard management as nutritional sprays and/or fungicides. Once potassium carbonate is added to water some of it is converted to potassium bicarbonate and that compound has been shown to have fungicidal properties. The amount of bicarbonate in a solution is dependent on the pH of the solution. Simply measuring the pH of a spray solution will determine whether potassium carbonate or potassium bicarbonate is dominant. In a lab test, 5 pounds of potassium carbonate in 100 gallons of water gave a pH of 10.9 with tap water and 11.2 with distilled water. One pound in 100 gallons gave a pH of 10.1 and 10.5, respectively. The pH of a beaker of potassium carbonate solution was lowered from 10.5 to 9.0, thereby converting carbonate to bicarbonate, by bubbling in CO2 blown in through a straw for about a minute. Adding dry ice would have the same effect.

Potassium carbonate is relatively unstable in solution since it picks up CO2 from the air. After standing in the lab for a week, the pH of a beaker of potassium carbonate solution dropped from 10.9 to 9.1. It is noted that all irrigation water, whether well water or river water, contains some bicarbonate and the amount found in the water will affect the final pH of any spray solution.

The fungicidal properties of bicarbonates have been known for years. At least two potassium bicarbonate products are currently registered as fungicides: Kaligreen (from Monterey Chemical; cost around $5.50/lb) and Armicarb (from Armand Products; cost around $7/lb). Kaligreen contains 18 percent “inert ingredients” and Armicarb contains 15 percent, with these inert ingredients including spreaders, stickers and other adjuvants that enhance the products’ effectiveness. Recommended application rates are 2 to 5 pounds of material per acre and the manufacturers recommend keeping the pH of the spray solution in the 7.5 to 8.5 range to maintain bicarbonates in solution. Because of its higher analysis, about one-third less potassium carbonate would be needed than potassium bicarbonate. Both Kaligreen and Armicarb are used to eradicate powdery mildew on grapes and on other crops, but their fungicidal activity has not been widely tested against orchard diseases.

If the fungicidal properties of potassium bicarbonate are in part a pH effect, then it is quite possible that potassium carbonate would be even more effective as a fungicide due to its higher pH in a spray solution. It is also possible, however, that the higher pH of potassium carbonate could have a phytotoxic effect on plant tissue. Certainly, the optimum pH for both fungicidal activity and for eliminating phytotoxicity should be studied and determined.

The relatively low rates of potassium carbonate at 2 to 5 pounds per acre recommended for Kaligreen or Armicarb for mildew control would provide only a small nutritional boost from potassium. 20 pounds per acre of material, whether potassium bicarbonate or potassium carbonate, would be best as a nutritional spray and could provide more fungicidal activity, but growers should wait for test results before trying such high rates to be sure there are no phytotoxicity problems.

It should be stressed that although potassium bicarbonate is registered as a fungicide, potassium carbonate is not. Potassium bicarbonate is used as a food additive and therefore could easily jump through the registration hoops. Potassium bicarbonate is also approved for use in organic production while potassium carbonate is not registered for use as a fungicide or foliar spray. It shouldn’t be difficult to convince authorities that when potassium carbonate is added to water and the pH adjusted to 7.5 to 8.5, the resulting solution is essentially potassium bicarbonate.

COMPARISONS OF 4 POTASSIUM MATERIALS

Summary

Because of its high solubility and relatively low cost when compared to potassium bicarbonate, potassium carbonate is an intriguing material in vineyard management. Bearing vineyards have a high potassium requirement with an estimated 100 pounds or more of potassium removed each year by the crop, and in situations where both a pH boost and a nutritional boost were needed, water-run potassium carbonate could be the ideal answer, especially for drip-irrigated plantings.

The proven fungicidal properties of potassium bicarbonate also make potassium carbonate worth looking at as a combination nutritional/fungicide spray. Certainly more work needs to be done to evaluate potential phytotoxicity problems with potassium carbonate and to determine the optimum pH of the spray solution when potassium carbonate is used.

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Joe Traynor is a certified professional soil scientist, crop scientist and agronomist listed with the American Registry of Certified Professionals in Agronomy, Crops and Soils, Ltd. He holds multiple degrees from the University of California, Davis, is a member of the American Society for Horticultural Science, and is the author of Ideas in Soil and Plant Nutrition, published by Kovak Books.

The author would like to thank Growers Testing Service, Visalia, Calif. for running the lab tests described herein.

By Joe Traynor

The nut industry has not been immune to the recent boom in organically grown produce.

Although there has been a market for organic produce for over 100 years, when all produce was organic, the last 30 years have seen increasing interest in organic farming and in sustainable agriculture - terms that are often used interchangeably. This latest boom started between the 1960s and 1970s and corresponded with an anti-establishment “back to nature” trend in the United States.

Organic produce has commanded a premium price since the 1960s and recent years of prosperity have allowed more consumers to go organic. Those that think nothing of paying a dollar for a bottle of water in the grocery store do not blink at paying a premium for food they feel is both safer and more nutritious. Farmers, even those initially skeptical, have been adept at meeting the organic demand. The current downturn in the economy is squeezing the organic market as laid-off Silicon Valley types and others are undoubtedly tightening their food budgets; however the organic market is here to stay.

Seven Organic Points?

Organic advocates blend a mixture of fact and fiction into a witch’s brew that too many people have swallowed. Following are seven points that the “organic crowd” parade to support their cause and a discussion of each:

1. Modern farming practices hurt or “ruin” the soil - This philosophy was recently expressed in a story in the Aug. 19 issue of the San Francisco Chronicle, stating that sustainable agriculture “… maintains the quality of the soil for future generations.” Poppycock! There is not one shred of evidence that several generations of modern ag practices have been detrimental to California soils. Quite the contrary, as crop yields have climbed over the years and show no evidence of declining. Hydroponic, or “soil-less,” culture has shown that plants can produce great crops without soil, using only inorganic nutrients (ironically, such produce is often sold as “organic”). The main - possibly sole - function of soil appears to be to provide physical support for the tree or crop so that it does not fall over.

2. Organic farming “brings the soil to life” - Organic farming practices increase microbe and earthworm levels in soils, but so what? Under current farming practices, soils contain millions of microbes per cubic inch. Would adding millions more actually be beneficial? And would all the added microbes be beneficial ones? Even after soil sterilization, such as with methyl bromide, beneficial microbes in soil rebound remarkably quickly. Increased biological activity in soil is touted to improve soil tilth and aeration, however normal ag management, which includes the use of cover crops, can accomplish much of the same benefits.

3. Organic produce is more nutritious - Highly doubtful. Again, there is absolutely no evidence to support this overblown claim, although a possible case could be made that some organic produce has a lower moisture content, thus providing extra nutrition on a fresh-weight basis. Organic produce may also have slightly higher calcium levels that would have a far greater effect on taste than on nutrition. Curiously, many organic advocates are strongly opposed to crops that have been genetically engineered to provide more nutrition and to reduce pesticide use.

4. Organic produce tastes better - Here, the organic advocates may have a point - but not for nut crops. I can personally attest to the fact that some organically grown produce - such as tomatoes, peaches, raisins - do indeed taste better. Part of the reason is varietal, since often these are varieties that are rarely seen in the market because they don’t ship well. But a major reason is that standard ag practices are overdone. A primary reason for the better taste of some organic produce is that such produce receives significantly less nitrogen. Nitrogen gives better yields in the form of more tonnage, at the expense of taste. Bigger fruit requires more water, thus lowering soluble solids and sugar content. Excess nitrogen also reduces calcium levels in fruit, whereas ample calcium gives a crunchier, more palatable product that has a longer shelf life.

With nut crops, the deleterious effects of high nitrogen would be manifested on the outer hull, not on the kernel. Thus, hulls from organically grown almonds could be more palatable - although there’s no word as to whether cattle prefer organic almond hulls.

The French are more attuned to the “less is more” philosophy than we are. Wine grape growers in France are not allowed to irrigate or use nitrogen fertilizers in the belief that withholding water and nitrogen improves wine quality. Many California vintners, including some table grape growers, have adopted this philosophy that the vines must suffer to produce a quality crop, although most California growers can’t afford not to irrigate.

5. Ag chemicals are a health hazard, causing cancer, etc. - There is no evidence that current pesticide programs cause health problems. This is especially true for nut crops because the edible kernels are well protected from sprays. Todays pesticides are short-lived and those used on nut crops are also widely used on crops where the edible portion is directly exposed to sprays, such as peaches and apples. For almonds, there are significant restrictions on pesticide rise after hull split in mid-June and further restrictions if hulls are to be used as cattle feed, as most are.

There is evidence that some fungal diseases, if not controlled by pesticides, constitute a health hazard. Also, the widespread use of human and animal feces, or manure, in organic farming is a potential health hazard, especially on crops such as nuts, which are picked up directly from the orchard floor. Organic growers often send their clients newsletters during the year with columns such as “What’s Going On at the Farm,” but I know of no such newsletter asking customers to “… join us for our annual ‘Spreading of the Feces’ Day.”

6. Organic fertilizers are both superior and more environmentally friendly than synthetic fertilizers - To organic enthusiasts the word ‘inorganic’ is a pejorative term, yet all plants take up nutrients solely in the inorganic form. Nutrients tied up in organic fertilizers must first be converted via microorganisms to inorganic chemicals prior to uptake by the root system. Organic advocates may not be aware that organic fertilizers also contain significant amounts of nutrients in the inorganic form.
Francis Broadbent, a soil scientist with UC. Davis, put it this way in 1972:

“Virtually all organic fertilizers of natural origin, such as manures and composts, contain a considerable portion of the plant nutrients in mineral form. This is particularly true of phosphorus and potassium. There is a little irony in the fact that the only truly organic fertilizers are the synthetic ones such as urea (CO-NH2).” Broadbent concluded that many “…. have become organic faddists because they lack the background to judge analytically the claims made for organic foods. It is to this group that agricultural scientists must present their side of the story.”

Dr. Broadbent also concluded, “The pollution potential of organic is higher than that of mineral fertilizers when applied at levels equivalent in terms of crop production … ” since nutrients can be leached into water tables when roots are dead or inactive, since many organic fertilizers continually release nitrates. With synthetic fertilizers, the nut grower can time applications to coincide with the period of maximum root activity when the active roots intercept nutrients, thereby minimizing groundwater contamination.

Try this quiz on a family member or an organic friend: The major component of ag crops is an organic nutrient; what is it and where does it come from? Answer: carbon from C0~.

7. Ag chemicals are a hazard to the environment - Organic advocates have a point here. This was brought home in a big way when DBCP contamination of ground water was discovered 20 years ago, resulting in the banning of DBCP. Recent detection of dormant spray materials in surface water supports the organic argument and has led to restrictions on dormant spraying. These findings are forcing growers and scientists to find environmentally friendly ways to control pests, an outcome that is not altogether negative.

Some buyers of organic nuts are smart enough to realize that these nuts are neither safer nor more nutritious; these buyers are making a statement that they don’t want to contribute to the chemical burden on the environment and to the energy consumed in manufacturing ag chemicals. It is difficult not to respect those that take such a stand.

A Mixed Bag of Nuts

The organic influence on nut growers has not been all bad. California almond growers have adopted “organic-type” methods not because they wanted to but because regulations have forced them to. Burning restrictions have resulted in a considerable tonnage of winter prunings being shredded and returned to the soil. Concerns over water contamination have forced growers to find substitutes for organophosphate dormant sprays. Pressure to reduce insecticide applications has spurred efforts toward “clean” methods of insect control such as mating disruption with pheromones (although we’re still waiting for someone to claim that these pheromones affect human behavior). Dust control regulations are looming and should help lower mite control costs, as well as equipment maintenance costs. Many growers that have been forced into using new, environmentally friendly practices now admit, albeit reluctantly, that their operations are better off for it.

Thirty years ago, Boysie Day, the Associate Director of the University of California’s Agricultural Experiment Station, made a statement that is just as applicable today. Day said, “There are sufficient good reasons for organic farming, without giving credit or credence to the phony claims made by cultists.” Arguments made by organic enthusiasts are a mixed bag with some fact, but mostly fiction. That there are people willing to pay a hefty premium for organically grown nuts because they believe such nuts are both safer to eat and more nutritious is proof of PT Barnum’s adage: “There’s a sucker born every minute.”

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Featured in Nut Grower Magazine - October 2001

Joe Traynor is an ag consultant based in Bakersfield and author of the book Ideas in Soil and Plant Nutrition.

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American Bee Journal - April, 2001
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by JOE TRAYNOR
Scientific Ag Co.
P.O. Box 2144
Bakersfield, CA 93303

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Knowing how much pollen a plant species produced would be useful in ranking plants as a food source for both honey bees and wild bees. Beekeepers have a good general idea, as to whether a particular species is a good pollen source (or nectar source), but there is little quantitative information on the subject.

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Past studies have estimated pollen produced per flower, but none have calculated pollen produced per acre. Obviously, the way to calculate pollen production per acre is to multiply the number of flowers per acre by the weight of pollen per flower. These two parameters are estimated below for almonds.

Flowers per acre
The flowers/acre of almonds will vary from year to year (a lighter flower set often follows a heavy almond crop and vice versa). Estimating the number of flowers per tree, then multiplying by trees/acre may be the best way. Trees/acre vary according to planting distance; the most common almond plantings are:

25′ X 25′ = 70 trees/acre
24′ X 24′ = 76 trees/acre
22′ X 24′ = 83 trees/acre

Dan Mayer estimated that an acre of apples produces 1 million flowers.(5) Almonds bloom more profusely than apples and 2 million flowers/acre for almonds is not an unreasonable guess. Two million flowers/acre would give the following flowers/tree for the above 3 planting distances: 28,500, 26,300 and 24,000.

Another method is to calculate flowers/acre from nuts/acre. About 3000 lbs. of nut meats per acre is considererd an excellent yield and to achieve such a high yield, a relatively high percent of flowers must be set. Kester & Griggs(4) obtained a 50% almond set (50% of the flowers set an almond) as did Hill, et al(3), although the latter study did not account for May (aka “June”) drop.

Assuming there are 350 nuts per pound (varieties vary in this regard; Nonpareil produces significantly larger nuts than Fritz) a 3000 lb/acre yield translates to 1,050,000 nuts/acre which in turn translates to 2,100,000 flowers per acre if a 50% set is assumed.

For this discussion, we will assume that an acre of almonds produces 2 million flowers (realizing that this figure can vary greatly from year to year).

Weight of pollen per flower
DeGrandi-Hoffman, et al(2) used sonication to remove pollen from almond flowers; Hill, et al(3) removed anthers from 100 flowers, dehisced the anthers at room temperature, then sieved and weighed the pollen. Both of these research teams came up with a range of around 0.7 to 1.2 mg of pollen per almond flower and both obtained year-to-year variations in pollen production. Oberle & Goertzen(6) also showed significant year-to-year variations in pollen production for a number of deciduous fruit species.

Traynor(7) used the method used by Oberle & Goertzen(6) to count pollen grains per flower: Put pollen (dehisced at room temperature from a flower’s anthers) in 2 ml of 10% calgon solution, shake and count the pollen grains in a small portion of the solution in the counting chamber of a hemacytometer (a simple glass slide used to count red blood cells; Spencer Bright Line, Clay Adams Cat. #@-2440/B).

Traynor obtained a range of 42,000 to 67,000 pollen grains per flower for eight commercial almond varieties and a figure of 44,000 pollen grains per flower for the Nonpareil variety, which comprises about 40% of California’s almond acreage. Traynor did not count the grains in a given weight of almond pollen. However, Bosch(1) determined that an almond pollen provision of Osmia cornuta (a mason bee), that weighed 16.5 mg., contained roughly 300,000 pollen grains. Pollen from one almond flower (44,000 grains for the Nonpareil variety, as calculated by Traynor) would weigh 2.4 mg, considerably higher than the 0.7 to 1.2 mg calculated by the DeGrandi-Hoffman and Hill teams. The “glue” that mason bees use to mold their provisions could have added enough weight to account for the difference.

Pollen per acre
Assuming 2 million almond flowers per acre, the figure of 1 mg of pollen per flower(2,3) translates to 4.4 lbs. of almond pollen per acre, while 2.4 mg/flower(1,7) translates to 10.7 lbs/acre. This is a wide range, but it is in line with the 5 to 8 lbs. of pollen per acre that commercial beekeepers report that they trap from almonds.

Summary
For well over 200 years, biological scientists have counted and classified things in order to achieve a better understanding of Nature. Thomas Jefferson and Charles Darwin were two of the more distinguished classifiers. Classifying plants by pollen production would be of practical benefit as well as of academic interest. From a practical standpoint, it would be helpful to know which wild plants provided the most sustenance for bees (both honey bees and wild bees) with the idea of making efforts to conserve such plants. Knowing the nutritional value of different pollens would also be helpful. Dr. Christine Peng (UC., Davis) and others have done some work on this, but overall information is limited.

Pollen production of plants that produce wind-borne pollen (e.g., Ragweed) is being determined from a public health standpoint(8), but pollen production data of plants producing insect-collected pollen are very limited. Perhaps the reason is that the subject falls squarely in the “no-man’s land” between the disciplines of plant science and apiculture, with either side leery of intruding on another’s territory. The pollen production calculations given above for almonds are simple and it is hoped that others will be encouraged to perform similar calculations on other plant species.

References
1. Bosch, J. 1994. The nesting behaviour of the mason bee, Osmia Cornuta (Latr), with special reference to its pollinating potential. Apidologie. 25: 4-93.

2. Degrandi-Hoffman, Gloria, Gerald Loper, Robbin Thorp and Dan Eisikowitch 1991. The influence of nectar and pollen availability and blossom density on the attractiveness of almond cultivars to honeybees. Acta Horticultureae 288, 6th Pollination Symposium.

3. Hill, S.J., D.W. Stephenson and B.K. Taylor 1985. Almond pollination studies: pollen production and viability and cross-pollination tests. Australian J. Exp. Agric. 25, 697-204.

4. Kester, Dale and W.H. Griggs 1959. Fruit setting in the almond: The effect of cross-pollinating various percentages of flowers and The pattern of flower and fruit drop. Proc. Amer. Soc. Hort. Sci. 74:206-213 and 214-219.

5. Mayer, Dan 1995. How to figure number of bee colonies needed. Good Fruit Grower, April 1.

6. Oberle, G.D. and K.L. Goertzen 1952. A method for evaluating pollen production of fruit species. Proc. Amer. Soc. Hort. Sci. 59:263-265.

7. Traynor, J. 1981. Use of a fast and accurate method for evaluating pollen production of alfalfa and almond flowers. Amer. Bee J. 121 1:23-25.

8. Ziska, Lewis and F. Caulfield 2000. Rising CO2 and pollen production of the common ragweed, a known allergy-inducing species: Implications for public health. Australian J. of Plant Physiology. 27:893-893.

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Goodfruit Grower - April, 2000
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Expanding almond acreage in California benefits PNW orchardists.

by Joe Traynor

California’s almond acreage has doubled over the past 20 years, standing now at 500,000 acres. These 500,000 acres of almonds require one million colonies of bees for pollination. Bees are trucked into California from all over the United States for the February pollination. (Table 1 shows bee colony totals by state.)

Many of the colonies used for almond pollination come from Montana and North Dakota. Colonies from these two states spend part of April in Pacific Northwest tree fruit orchards because it is too cold to return home until May. Prior to the increase in almond acreage, most Montana and North Dakota beekeepers either killed off their colonies in the fall, rebuilding them in the spring, or wintered their bees in Texas.

With some 180,000 acres of apples, 43,000 acres of pears, and more than 30,000 acres of pears in Washington and Oregon, about 380,000 bee colonies are required to pollinate cherry, pear, and apple orchards. A figure of 1.5 colonies per acre is used to determine the bee requirement. The actual requirement is less than this because some colonies are used twice, moving from cherry, pear, and early apple orchards to later blooming orchards in northern Washington.

The large pool of bees created by the expansion of California’s almond acreage has resulted in stable or lower pollination fees for tree fruit orchardists. Pacific Northwest growers also benefit from increased hive strength as the bees used on tree fruit have a good food source from the almond bloom prior to being delivered to Pacific Northwest tree fruit orchards.

California’s almond acreage has a direct impact on bee rentals in the Pacific Northwest. If apple acreage in the Northwest was twice as high as California’s almond acreage (as it once was), bee rental fees would be twice as high as almond pollination fees (as they once were), and bee colony strength for apple bloom would be less.

Almond growers pay $45 to $55 per colony for bee rentals. Thirty years ago, they paid $10. This situation could change if the almond industry develops self-fruitful varieties or varieties that bloom in March. However, such developments are at least 20 years away.

Bee industry in trouble

The economic health of the U.S. bee industry is as bad or worse than that of the Pacific Northwest apple industry. Bee numbers are declining due to a combination of low honey prices and parasitic mites.

Income from almond pollination is the only thing keeping many U.S. beekeepers in business. California’s almond industry is indirectly subsidizing the Pacific Northwest tree fruit industry by maintaining a large pool of bees from which apple, pear, and cherry growers can draw at relatively low pollination fees.

Joe Traynor operates a California-based pollination service for growers and beekeepers. He is also an agricultural consultant specializing in soil fertility and plant nutrition.

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Pacific Nut Producer - March, 2000
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By Joe Traynor

The California almond industry has been trying to develop a commercial self-fruitful almond variety - a high yielding variety that produces a quality nut - for more than 50 years. Such a variety would reduce or eliminate the almond grower’s dependence on honeybee pollination. Although progress has been made in developing self-fruitful varieties, the light at the end of the tunnel is still barely visible.

The recent run-up in almond acreage is putting increased pressure on a bee supply that is static or decreasing. Some growers have reduced their bee needs by planting alternate blocks of early and late-blooming varieties. The five to seven day gap in bloom dates allows these growers to get close to double duty from their bees. There is, however, a limit to the acreage of such early-late plantings since the market for late-blooming hardshells is limited (prices for hardshells are about 10 cents per pound below Nonpareil prices and a significant increase in hard-shell acreage would widen this price differential).

Currently, late-blooming varieties comprise about 14 percent of California’s bearing almond acreage. Interestingly, 25 percent of the non-bearing acreage in 1998 was late blooming if one includes the Butte variety; 22 percent of this non-bearing acreage was Butte, which is currently being included in Nonpareil plantings as well as with Mission (and Ruby and Padre) plantings. Butte blooms a few days before Mission and few days after Nonpareil, thus occupying a “no-mans land” between early and late-blooming varieties.

Pollination prices plummet in March because of the exodus of bees from early-blooming almonds (see diagram). If the almond industry were to develop varieties that bloom in March, the potential bee shortage problem would be solved and almond pollination costs would drop.

Three weeks later, the risk of poor weather during bloom would be greatly reduced and there would be a much more stable supply of almonds. Currently, almond yields are directly correlated with weather conditions during the seven to 10 day period of Nonpareil bloom; this results in significant variations in year to year crops. March-blooming varieties would greatly reduce such year to year variations (and would reduce or eliminate the potential for frost damage for most growers).

There are three ways to develop almond varieties that bloom in March:

1. Breed new varieties - probably the best long-term solution, but will take time.
2. Delay bloom on current varieties with chemicals - Dormex and calcium nitrate are currently widely used by cherry growers to get cherry trees to bloom earlier. There are chemicals (e.g. ethrel, gibberellin) that will delay bloom in almonds but limited tests done a number of years ago gave erratic results. More work should be done in this area and new chemicals should be looked at.
3. Use a late-blooming rootstock and/or interstock - Late-blooming rootstocks or interstocks will delay the bloom of the top variety. It might be difficult to develop a late-blooming root-stock that has the desirable characteristics of current rootstocks, but an interstock - a sandwich variety between the top and rootstock - could be used (see figure).

Late-blooming interstocks are being used on apples and peaches to delay bloom past the period of greatest frost hazard. Late-blooming almond varieties (e.g., Tardy Nonpareil, which blooms in March) are available for interstocks on almonds (the potential of virus or disease transmission via the interstock would have to be addressed).

It is likely that a late-blooming interstock would give only a five to seven day delay in bloom at best (although this should be determined) - not enough for a March-blooming Nonpareil, but if used in conjunction with bloom-delaying chemicals, a March-blooming Nonpareil could become a reality.

A possible concern with a March-bloom Nonpareil (or other varieties) is a late harvest; however, UC. data show that the Tardy Nonpareil variety harvests only a short time later than Nonpareil and well before Mission.

If March-blooming almonds were developed, beekeeper income would decline, but for many beekeepers March-blooming almonds would provide the benefit of providing a food source during a time when money must be spent to feed bee colonies.

The significant benefits to the almond industry of March-blooming almond varieties certainly warrant further work in this area. Such work should be initiated before a diminishing supply of bees has a significant impact on almond yields and/or before rental prices for bees become unaffordable.

Joe Traynor is the manager of Scientific Ag, a bee brokering firm in Bakersfield, Calif