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Dual Variety Row Almond
Production John Edstrom Today'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. The accumulative figures show a 9% yield advantage to alternating during the four early years of this trial. Yield results for 1999 show no advantage to alternating two varieties down the same row (Table I). Weather during bloom was quite conducive to bee flight which has been found to diminish the alternating advantage. Frost in April reduced yields in this block, which may have affected test results. The effect of Butte pollen on the set of Padre and Mission is significant in this block. We suspect that Butte pollen fertilizing Padre flowers in solid rows of Padre greatly increases yields and "masks" the real potential advantage of alternating Mission in the row. To examine this we again used paternity testing with the help of Plant Development International, Bakersfield, California. Isozyme analyses of Padre nuts showed 61% Mission pollen parentage in alternating P·M·P rows and only 23% in rows of solid Padre. (Table 2) Only 2% of Padres were set by outside pollen (likely Nonpareil). About 37% Butte parentage was found for Padre in alternating rows and 62% Butte parentage in solid rows. Padre set in solid Padre rows was again greatly affected by Butte. This supports our suspicion that Butte maybe limiting the positive effect of alternating varieties down the row. But even with the equalizing effect of Butte in this test we still find that in many years alternating varieties shows yield advantages. Rows planted with alternating M·P·M or P·B·P would likely show a greater yield advantage verses solid rows of 2 varieties than our test where a third variety, (Butte) is planted. This orchard continues to experience poorly
anchored Padres. Extra attention seems necessary with Padre to develop vertical
trunks, well balanced canopies and strong roots to limit this tree loss problem
or avoid the severe pruning necessary to retain trees. It is unclear so far what
affect the mechanical topping of Padre trees in 1998 has had on the anchorage
problem. Table 1.
Table 2.
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