Fertilizer Nitrogen Requirements for Cotton Production as Affected by Tillage and Traffic

Abstract

AbstractSoil compaction and its associated problems have led to interest in investigating the interactive effects of traffic and tillage systems on fertilizer N requirement for cotton (Gossypium hirsutum L.). In 1987, a study was initiated on a thermic Typic Hapludult soil complex with a cropping system of wheat (Triticum aestivum L.)‐cotton double cropped. The experimental design was a split‐split plot with four replications. Main plots were two traffic treatments (conventional and no‐traffic), subplots were four tillage systems for cotton (surface tillage without subsoiling [surface‐only], surface tillage and annual in‐row subsoiling [subsoiling], surface tillage with one‐time‐only complete disruption of the tillage pan [complete], or no surface tillage and in‐row subsoiling [strip‐till]), and sub‐subplots were four N rates (0, 45, 90, and 135 kg N ha−1). In addition, application of 15N‐labeled NH4NO3 was made to microplots inside each tillage‐traffic‐90 kg N ha−1 plot. In 1990 and 1991, increasing N application increased cotton biomass and decreased lint percentage. In the dry year of 1990, no‐traffic decreased seed cotton yield from 1500 to 1360 kg ha−1, while tillage had no significant effects on cotton yield components. Above‐normal rainfall in 1991 resulted in the strip‐till with no‐traffic treatment having the highest seed cotton yield (2749 kg ha−1) and the greatest fertilizer N uptake efficiency (35%). Results indicate that the detrimental effects of traffic on N uptake efficiency may be reduced with conservation tillage systems and that higher fertilizer N application rates may not be needed for conservation tillage practices such as strip‐till in Coastal Plain soils.