Nutrient Management Research Database

http://ucanr.edu/sites/Nutrient_Management_Solutions/files/212730.pdf

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.

This study consisted of 12 treatments, each of which was applied to five to six blocks with 15 trees in each block.  

Treatments:

• 4 rates of nitrogen: 140kg, 224kg, 308kg, and 392kg N ha^-1 applied as UAN 32 or CAN 17.
  
  • N was applied in 4 fertigation cycles with 20% in February, 30% in April, 30% in June and 20% in October.  
• 3 rates of potassium: 112 kg, 224 kg and 336 kg K ha^-1 applied as sulphate of potash,potassiumthiosulphate and potassium chloride.
  • 60% K was applied as Sulphate of Potash in early February, and the remaining 40% was applied as Potassium Thiosulphate in four fertigation cycles.
• Leaf and nut samples were collected from April to October and analyzed for N, P, K, Ca, S, Mg, B, Zn, Cu, Mn and Fe.
• Yield, crack out percentage and oven dry weight were determined for all sampled trees, and a subset of nuts was assessed to find the ratio of kernel shell/hull and the partitioning of nutrients.  

Highlights of the results include:

• N accumulation was positively correlated witn N supply.
• Total fruit N accumulation declined between 136 and 165 (Days after full bloom) DAFB, suggesting that N from fruit was being remobilized into the tree.
• Increasing N supply increased P uptake. 
• Maximum fruit yield was found in the treatment with highest N inputs.