INFLUENCE OF FERTILIZER TREATMENT ON THE CHEMICAL COMPOSITION OF MOORE PECAN LEAVES DURING NUT DEVELOPMENT

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Abstract
Periodic sampling of leaves from 4 differently fertilized blocks of Moore pecan trees bearing a heavy crop of nuts was made at six 3 -week intervals from June 11 to Sept. 24, 1945, and analyzed for N, P, K, Ca and Mg. The trees had received (NH4)2SO4, Cyanamid, complete (N-P-K) fertilizer and no-fertilizer over a 10-yr. period. Curves are presented showing the striking changes in the chemical composition of the leaves during the development and early filling period of the nut for each of the elements detd., as influenced by the different fertilizer treatments. N, P, and K were found to decrease more or less rapidly during the entire period, while Ca accumulated at an equally rapid xate. Mg tended to increase slightly as the leaf matured, but the content varied considerably between sampling dates and fertilizer treatments, while the ash remained more or less constant throughout the period. The highest level of all of the elements occurred in the complete-fertilizer trees, except P which was lowest in the 2 N-fertilizer plots and K, which was lowest in the leaves from the Cyamamid trees. Ca occurred at an unusually low level in the unfertilized trees. Two periods of rapid change in composition were noted, viz., (1) during the first 6 weeks of sampling which marked a rapid decrease N, P and K, and a rapid accumulation of Ca, and (2) between Aug. 13 and Sept. 4, when all elements except Ca were rapidly depleted. The Ca + Mg/K ratio increased rapidly during the entire period for all treatments. Striking chemical changes in leaves were influenced by fact that trees were under stress of producing a heavy crop of nuts, and doubtless due to deficiencies in one or more of the fertilizer elements, causing very poor filling of the nuts.