Nitrogen Balance as Affected by Application Time and Nitrogen Fertilizer Rate in Irrigated No-Tillage Maize
Hernán R. Sainz Rozasa,
Hernán E. Echeverríab,* and
Pablo A. Barbieric
a Est. Exp. Agropecuaria INTA, Balcarce, Buenos Aires, Argentina
b Est. Exp. Agropecuaria INTA, Balcarce, Buenos Aires, Argentina, and Fac. de Ciencias Agrarias (UNMP) Unidad Integrada Balcarce, C.C. 276, (7620) Balcarce, Buenos Aires, Argentina
c Comisión de Investigaciones Científicas de la Provincia de Buenos Aires, C.C. 276, (7620) Balcarce, Buenos Aires, Argentina

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Fig. 1. Rainfall (R) plus irrigation (I) and maize crop evapotranspiration (CET) during the growing season.
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Fig. 2. Crop N uptake for unfertilized and fertilized treatments in the 19951996 and 19961997 growing seasons in relation to (a) the change in soil microbial biomass N for the period between planting and physiological maturity of the preceding season (19941995 or 19951996) and (b) residual NO3N measured at the physiological maturity growth stage of the preceding season.
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Fig. 3. Components of N balance as a function of different N rates and application times. Available N represents soil NO3N at planting time (0- to 100-cm soil depth) plus N applied (N rates are shown in parentheses) and mineralized N from organic matter. Res. Nit = soil NO3N at physiological maturity (0- to 100-cm soil depth); MBN = change in soil microbial biomass N content (0- to 20-cm soil depth) between physiological maturity (end) and planting (beg), i.e., MBN = MBNend MBNbeg; Ndes = denitrification loss; Nvol = volatilization loss; NL = apparent N loss by leaching; and CNU = N accumulated by the crop.
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Copyright © 2004 by the American Society of Agronomy.