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Dual Variety Rows Almond Production
John Edstrom, UCCE Farm AdvisorToday’s almond orchards involve closer spacings to maximize early returns. However, tighter spacings tend to exaggerate the development of a floral "wall" during bloom. This can decrease cross row bee activity and limit cross pollination. At the same time, expansion of statewide almond acreage is creating more demand for bees, while mite parasites, Africanized bees and Fireant problems all threaten bee supplies. Supplies of strong hives are particularly stretched. Increased world supplies of almonds may lower prices and further pressure production efficiency. In this new era of almond growing optimal pollination management and innovative orchard designs become even more important. This field trial is evaluating the orchard design strategy of alternating two varieties down the same hedgerow. Solid rows of Padre are compared to solid rows of Mission versus rows alternating with Padre and Mission (M·P·M). Rows of Butte border all experimental rows as an additional pollinizer. All trees are planted to Lovell peach rootstock at 15' x20' spacing for 145 trees per acre on Class II soil, single hose drip irrigated. Four consecutive early harvests have shown a yield advantage to alternating Mission and Padre down the same row. Figures presented in Table I show an increase in yield for this design versus the average yield of solid rows of Mission and solid rows of Padre. The accumulative figures show a 9% yield advantage to alternating during the four years of this trial. Table II shows the yield comparisons for the individual varieties when planted either in solid rows or alternating two variety rows. Yield for Padre in 1996 shows a 14% increase when alternated with Mission. Mission showed little yield increase from alternating that year.
Table I. Multi Variety Rows -- Yields - Lbs/Ac Year 1993 1994 1995 1996 Leaf 5th 6th 7th 8th Ave. Mission-Padre 1831 1776 1705 1843 1788a Mission-Padre Alt. 1921 1948 1916 2000 1954b Increase +5% +10% +12% +8.5% P<0.01 Table II. 1996 Yields lbs./Ac %
Solid Rows Two Variety Rows Increase Padre 1966 2240 14% Mission 1720 1757 2% Yield results for 1997 did not show any differences for dual rows, but Padre harvest for 1998 again showed a yield advantage of 10% in Dual rows, but not for Mission. Yields for 1998 show a 300 lbs/Ac advantage for Padre in M·P rows versus solid Padre rows, again about a 10% increase. But, Mission like 1997, did not gain in yield from the alternating design. Weather patterns at bloom seem to help explain these variations. During years of significant rain at bloom, the advantage of dual rows is at its highest, but during dry bloom periods we find little or no advantage. (See graph) This orchard design seems to have a stabilizing effect on production from year to year.
Dual Variety RowsYields lbs./Ac Year 1993 1994 1995 1996 1997 1998 If this holds true, we can add production to "off" years when crop returns are likely to be higher per pound. The advantage with dual rows would amount to be greater in dollars than the 8-10% yield increase would indicate. The effect of the 50% Butte pollenizers in this block, in effect, seems to be interfering with the alternating effect. Using new genetic lab analyses method (isozyme analysis) to determine male pollen parentage, we found that padre nuts in alternating rows were pollenized by Mission 55% and Butte 40%, while Padre in solid rows had 30% Mission pollen and 65% Butte parentage. Butte pollen is adding a lot to the set in all rows but more so in the solid row and so is diminishing the effect of Mission pollen in dual row. The benefit of alternating two varieties down the same row could be even greater if only two varieties were planted in the block. Here, where Buttes are planted in every other row, the Butte pollen is responsible for much of the Padre (and Mission) set thus limiting the advantage of alternating. Orchards with just two varieties could benefit more than this data shows. Due to the stick tight problem harvesting the Padre variety late, we cannot accomplish a once over harvest operation. Padre nuts require earlier shaking than the Mission to get acceptable nut removal. Two passes down the same row with a shaker is needed on the alternating M·P rows. Sweeping and pickup operations are done in a single pass combining the two varieties. Handlers generally accept P·M loads as Missions. Other varietal combinations may appear more desirable in terms of yield but may lead to more harvest difficulties or result in mixed loads. Butte/Padre, Nonpareil/Carmel and other pairs would be more desirable than Mission/Padre, but cause greater problems at harvest when planted in the same row. This orchard continues to show poorly anchored Padres, many trees are leaning badly or have been pruned severely to rebalance. This "top heave" variety appears to have this tendency but the shallow soil and use of a single hose drip system may also contribute to the problem. Ratings made on individual trees this season showed 13% of all Padre trees leaned significantly while only 1% of all Mission leaned. Many of these will undoubtably fall over. Extra attention seems necessary with Padres to develop vertical trunks (staking), well balanced canopies (classic pruning( and strong roots (deep irrigations) to limit this tree loss problem and avoid the severe pruning necessary to retain trees.
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Send mail to jlschmierer@ucdavis.edu with questions or comments about this web site.
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