Boron Nutrition of Almonds

In 1994 a study was initiated to determine the effect of boron (B) nutrition on flowering, fruit set, and yield of almond following a similar (and very successful) study with pistachio. Spraying B at a rate of 1-2 lb Solubor/100 gal on B deficient almond trees increased fruit set by over 20% and yields by 15 lb/tree or 1200-1500 lb/A or 900-1125 lbs of kernels/A in 1995. Of special note is the frequent positive response of almond trees to supplemental B sprays when no B deficiency symptoms were visible. Boron status of the hulls appears to be a better indicator of tree B status than either leaves or bark. Additional positive results were obtained in 1996 in which foliar B sprays increased fruit set by as much as 40% and actual nuts from about 6,600/tree to over 9,000/ tree. Research has demonstrated that even a 10% response to foliar boron is highly profitable. More studies are needed to evaluate the optimal rates and time of B application.