Tropical maize response to nitrogen and starter fertilizer under strip and conventional tillage systems in southern Alabama

Abstract

Tropical maize ( Zea mays L.) is a promising new crop for the southeastern US, but optimum management practices have not been established for this alternative crop. Field studies were initiated in 1990 to evaluate its response to N and starter fertilizer under conventional and reduced tillage systems double cropped following wheat ( Triticum aestivum L.). The experiment was conducted on a Dothan sandy loam (fine–loamy, silicious, thermic Plinthic Paleudults) in Southern Alabama. Treatments included conventional (chisel plowing (25 cm depth), disking, and in-row subsoiling) and strip (in-row subsoiling) tillage systems; four N rates (0, 56, 112 and 168 kg ha −1); and five starter fertilizer combinations: (1) no starter; (2) 22.4 kg N ha −1; (3) 22.4 kg P ha −1; (4) 22.4 kg N and 22.4 kg P ha −1; (5) 22.4 kg N, 22.4 kg P and 11.2 kg S ha −1. The depth of subsoiling was 40 cm for both tillage systems. Tropical maize hybrids' Pioneer® Brand X304C (1990) and Pioneer® Brand 3072 (1991 and 1992) were utilized in the study. Maize silage yields (averaged over 1990 and 1991) under conventional tillage were 14% lower than with strip tillage, while grain yields in 1991 were 30% lower. Differences among tillage systems were not significant in 1992 except for the 0 and 168 kg N ha −1 rates where conventional tillage produced slightly higher yields as compared to strip tillage. Silage and grain yields increased with N rate with the largest response to N occurring in 1991 under strip tillage. For silage yields averaged over both tillage systems in 1990 and silage and grain yields in 1991 and 1992 under strip tillage there was a quadratic response to N rate. Silage and grain yields peaked at approximately 112 kg N ha −1. Under conventional tillage in 1991 and 1992, the response of silage and grain to N rate was linear. The best starter for silage was the N and P (NP) treatment. For grain, N alone gave the same yield as the NP starter in 1991, with the greatest response occurring under conventional tillage. In 1992, the NP treatment was the best starter for grain. This study demonstrated that double cropped tropical maize is a promising alternative crop for warm temperate/subtropical regions. High silage yields and reasonable grain yields can be obtained using conservation tillage systems and the addition of N in combination with a starter fertilizer containing N and P.