Effect of penetration resistance and timing of rain on grain yield of narrow-row corn in a coastal plain loamy sand

In many soils of the southeastern Coastal Plain of the USA, subsurface hard layers reduce yield by limiting root exploration of the profile, We evalua ted the impact of reduced frequency of deep tillage (and thus increased pen etration resistance) and timing of rain on corn (Zea mays L.) yield for a 0 .38 m row-width management system. Treatments were either disced or not dis ced; treatments were also deep-tilled from 0 to 3 years before sowing corn into a structureless Goldsboro loamy sand, a thermic siliceous fine-loamy A quic Paleudult (fine-loamy Acrisol). Because of a pan at the 0.1-0.3 m dept h. cone indices for disced treatments were greater than for non-disced trea tments. Cone indices were also greater for treatments that had longer times between tillage and sowing corn. increasing on an average of about 200 kPa /year. Whether caused by discing or by reduced tillage frequency, each MPa of increased mean profile cone index reduced corn grain yields by 1. 1-2.4 Mg/ha. Cone index vs. grain yield linear regressions differed among years. Regressions for the 3 years could be combined into a single relationship by including rainfall during 42-56 days after sowing (vegetative growth) and 70-98 days after sowing (silking) to the relationship (R-2 = 0.87). The sam e procedure was then applied to soybean (Glycine max L. Merr.) grown in the same plots for the previous 3 years, giving similar results (R-2 = 0.73). When rainfall for the growing season or selected parts of the growing seaso n based on plant maturity is included in the regression relationship of yie ld as a function of soil cone index. the relationship may be valid for mult iple growing seasons eliminating the need to have individual relationships for each season. (C) 2001 Elsevier Science B.V. All rights reserved.