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Use of soil nitrogen parameters and texture for spatially-variable nitrogen fertilization

Shahandeh, H., Wright, A. L., Hons, F. M.
Precision agriculture 2011 v.12 no.1 pp. 146-163
Zea mays, clay fraction, corn, fertilizer rates, grain yield, growing season, nitrate nitrogen, nitrogen, nitrogen fertilizers, soil heterogeneity, soil sampling, soil texture, soil types, texture, Texas
Recent studies have demonstrated the potential importance of using soil texture to modify fertilizer N recommendations. The objective of this study was to determine (i) if surface clay content can be used as an auxiliary variable for estimating spatial variability of soil NO₃-N, and (ii) if this information is useful for variable rate N fertilization of non-irrigated corn [Zea mays (L.)] in south central Texas, USA across years. A 64 ha corn field with variable soil type and N fertility level was used for this study during 2004-2007. Plant and surface and sub-surface soil samples were collected at different grid points and analyzed for yield, soil N parameters and texture. A uniform rate (UR) of 120 kg N ha⁻¹ in 2004 and variable rates (VAR) of 0, 60, 120, and 180 kg N ha⁻¹ in 2005 through 2007 were applied to different sites in the field. Distinct yield variation was observed over this time period. Yield and soil surface clay content and soil N parameters were strongly spatially structured. Corn grain yield was positively related to residual NO₃-N with depth and either negatively or positively related to clay content depending on precipitation. Residual NO₃-N to 0.60 and 0.90 m depths was more related to corn yield than from shallower depths. The relationship of clay content with soil NO₃-N was weak and not temporally stable. Yield response to N rate also varied temporally. Supply of available N with depth, soil texture and growing season precipitation determined proper N management for this field.