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An Index of Nutrient Efficiency and Its Application to Corn Yield Response to Fertilizer N. I. Derivation, Estimation, and Application 1
Author(s) -
Capurro Eduardo,
Voss Regis
Publication year - 1981
Publication title -
agronomy journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.752
H-Index - 131
eISSN - 1435-0645
pISSN - 0002-1962
DOI - 10.2134/agronj1981.00021962007300010028x
Subject(s) - fertilizer , nutrient , yield (engineering) , mathematics , agronomy , efficiency , crop , quadratic equation , statistics , chemistry , geometry , biology , materials science , organic chemistry , estimator , metallurgy
Improving the efficiency of use of applied nutrients in crop production are agronomic, economic, and environmental goals. The purpose of this study was to develop a methodology for studying the efficiency of fertilizer use, to apply it to the yield response of corn ( Zea mays L.) to fertilizer N, and to use these results to estimate fertilizer N needs for a range of relative corn yields. The derived nutrient efficiency was divided into two components: (a) one depending on the level of relative yield expressed as a percentage of maximum yield (hence, it depends on the nutrient rate and can be estimated from soil test or plant analysis values) and (b) a component termed relative efficiency index (E x ), which can be defined generally as the nutrient efficiency at 99% of maximum yield and is independent of the nutrient rate. for the quadratic polynomial, E x is equal to one‐fifth of the product of the square roots of the quadratic coefficient and of the maximum yield. Relative efficiency index for N, E N , were obtained from quadratic regressions of corn yield on fertilizer N rates for each of 33 experiments conducted on well, moderately well, and somewhat poorly drained soils in Iowa. E N was closely related to the square root of the quadratic coefficient. Values of E N ranged from 2.5 to 9.3, and maximum grain yields varied from 3,600 to 10,200 kg/ha. Nutrient efficiencies were calculated from given values of E N and relative yield, e.g., this gave efficiencies in kg grain/kg N of 14 for E N of 2 and 42 for E N of 6 at a relative yield of 50%. The required increase in N rate for economic optimum yield was calculated from given values of E N , relative yield, maximum yield, and the N to corn price ratio. The E x seems to be a useful index to characterize the response of crop yields to applied nutrients and to derive yield‐applied nutrient relationships.