2019 ASHS Annual Conference

Almond kernels are large nitrogen sinks throughout the growing season. It has been shown that in order to meet their nitrogen demands, developing kernels will compete with adjacent leaves for nitrogen, reducing leaf nitrogen content, and thus reducing leaf photosynthetic capacity, creating a resource deficit. This resource deficit results in ‘June Drop’. Reports also suggest that application of aminoethoxyvinylglycine hydrochloride (AVG), an ethylene biosynthesis inhibitor, increases fruit set. However, studies have shown that an AVG induced increased nut set was followed by an increased ‘June Drop’. The current study was aimed at studying the interaction of supplemental nitrogen with AVG application for enhanced nut set and fruit retention. Fourteen-year-old almond trees of cvs. ‘Butte’ and ‘Padre’ were selected in an orchard in Biola, CA. The experiment was designed as a full factorial with three levels of nitrogen: N1: Grower standard (GS); N2: GS+12%, and N3: GS+25%; and two levels of AVG: ‘AVG’ and ‘no AVG’, 6 treatments in total. Data were taken on blossom number, nut set percent, June Drop percent, yield, chlorophyll content and fruit N content. Treatments with AVG application showed significant differences in nut set in comparison with control. However, data on yield and June drop didn’t show any significant differences. The nuts from the AVG application treatments had significantly higher number of double kernels with 15.2, 12.6 and 14.2 percent in N1, N2 and N3, respectively, while ‘no AVG’ treatments had 4.8, 3.4, and 5.2 percent double kernels, respectively.