Maize yield as affected by water availability, soil depth, and crop management

The aim of this study was to investigate the influence of rainfall, soil depth, and crop management practices on the yield of dryland maize (Zea mays L.) crops of the Argentine Pampas. We were concerned with the relevance of known physiological mechanisms in commercial crops and with developing a framework to quantify the impact of improved management practices on crop yield. Our approach included three steps. First, baseline functions were developed to quantify the relationship between yield and water availability (W) during the critical period for kernel set. Second, baseline functions were tested using an independent data set. Third, using the baseline functions as benchmarks, the effects on yield of soil depth and crop management practices were evaluated. Yield varied between 4.2 and 10 t ha(-1), and most of this variation (>84%) was accounted for by W during the period bracketing flowering. Shallow soils presented lower yield than deep soils at a given rainfall. Using yield vs. W functions to account for the effect of variation in W, we quantified the impact of crop management on productivity. Technology-related yield increases were (a) 2.3 t ha(-1) from the late 1980s to the mid-1990s, mainly explained by P fertilization, better and earlier weed control, and improved hybrids; (b) 0.9 t ha(-1) from the mid-1990s to 1996-1998, related to no-till and higher plant density; and (c) 0.8 t ha(-1) from 1996-1998 to 1999-2000, mainly explained by enhanced rates of N fertilization.