A Nutrient Budget Approach to Nutrient Management in Almond
A large scale multi-year experiment has been set up to develop a phenology and yield based nutrient model for Almond, to develop fertilizer response curves to relate nutrient demand with fertilizer rate and nutrient use efficiency and to determine nutrient use efficiency of various commercially important N and K fertilizer sources. The goal was to develop an integrated nutrient best management practice for almond. The treatments consists of four rates of nitrogen 140kg/ha, 224kg/ha, 308kg/ha and 392kg/ha and two commercially important sources of nitrogen, UAN 32 and CAN 17. There are three treatments for potassium rates: 112kg/ha, 224kg/ha and 336kg/ha and three sources of potassium: SOP, SOP+KTS and KCl. Leaf and nut samples were collected from the 768 individual trees in April, May, June, July, August and October and analyzed for N, P, K, Ca, S, Mg, B, Zn, Cu, Mn and Fe. A clear effect of N rate on the pattern and total quantity of annual nitrogen accumulation was observed. Changes in the pattern of total fruit N accumulation, leaf and fruit N concentrations suggest that fruit growth is the primary determinant of tree N accumulation and that resorption of N from fruit into perennial tree structures occurs as fruit matures. Similar patterns of resorption were observed for P but not for the other elements measured.