Author: L.E.C.de MIRANDAPublisher:
ISBN:
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Languages : en
Pages : 316
Book Description
Critical nutrient percentage is defined as the nutrient concentration associated with maximum yield with respect to the nutrient. Objectives of this research were: (1) to compare three methods for calculating maximum yield and associated critical % N and to determine effects of time of leaf sampling at or near silking on critical % N; (2) to determine effects of P fertilizer rates on critical % N and of N rates on critical % P; and (3) to determine effects of crop sequence, plant density, and moisture stress on critical % N and % P in both grain and leaf. Data were from 39 fertilizer experiments at 4 outlying research centers in Iowa. The direct regression method (Yield on % N in the plant part) was generally poorer for estimating critical % N in the grain and leaf than the two-step method (yield and % N on N rates) or graphical method (highest yield based on significance and associated % N). The latter two were similar. Time of leaf sampling and weather factors prior to and during silking affected % N of treatments and critical % N. The P rates increased critical % N in grain as mich as 0,12% and that leaf as much as 0.16%. As N rates increased, critical % P decreased as much as 0.028% in the grain and increased as much as 0.58% in the leaf. The critical % N and % P in the grain of leaf can evaluate N and P fertility status of corn better if levels of both are considered. The critical % N and % P in both grain and leaf were slightly less in C2 than in C1 in a C1-C2-soybean roatation. Increased stand level (...).
Author: Luiz Eugenio Coelho de Miranda
Author: Allen Vaughan Barker
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Author: Paul J. Stangel
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