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Abstract
Mist, low light, and low temperature during dormancy significantly promoted subsequent floral bud growth in peach (Prunus persica L. Batsch) while high temperature and high light intensity significantly decreased it. Chilling hours at 10°C bud temperature were half as effective as hours at 6°. No significant changes occurred in abscisic acid (ABA) levels in floral bud scales. ABA content of primordia within misted buds was significantly lower than of primordia in other treatments. The data support the concept that fog influences bud rest through temperature, light, and leaching effects. Results also indicate that ABA content in buds may not be the primary factor that determines termination of rest.
A replicated rootstock trial for almond was established in 1986 in the central San Joaquin Valley, a major almond growing area for this most widely planted tree crop in California. `Nonpareil', the major cultivar in California, was used for this trial with `Fritz' grown as the pollenizing cultivar. Two standard rootstocks for almond, `Nemaguard' and `Lovell' peach, were compared to two newer peach-almond hybrid rootstocks, `Bright's' and `Hansen'. After eight years both hybrid rootstocks produced significantly larger trees than the peach rootstocks, based on trunk cross-sectional area. Trees on hybrid rootstocks frequently produced greater yields than those on peach rootstocks; although, differences were not always significant. However, there were generally no significant differences in production per trunk cross-sectional area (yield efficiency). Thus, increased production by trees on hybrid rootstock was the result of larger tree size and not an inherent increase in productive efficiency of the tree itself. Since trees on hybrid rootstock should be planted further apart than those on peach, production per hectare should not be significantly increased, at least under good growing conditions as represented in this trial.
Many citrus growers are hesitant to plant cover crops, particularly perennial types, because of possible increased frost hazard. To quantify the increased risk, temperature relations over a 3-year period were compared between areas in a `Valencia' orange orchard with and without a partial perennial cover crop. The partial perennial cover crop consisted of a mowed perennial planting along the double drip line hoses, and an annually fall-replanted unirrigated strip of groundcover in the middle between the tree rows. This partial perennial cover crop increased the frost hazard compared to uncultivated bare ground even when wind machines were operating.