Soil management and landscape variability affects field-scale cotton productivity

A better understanding of interactions between soil management and landscape variability and their effects on cotton (Gossypium hirsutum L.) productivity is needed for precision management. We assessed management practices and landscape variability effects on seed cotton yield in a 9-ha, Alabama field (Typic and Aquic Paleudults) during 2001-2003. We hypothesize that landscapes have major effects on cotton productivity, but these effects vary based on management and climate. Treatments were established in replicated strips traversing the landscape in a corn (Zea mays L.)-cotton rotation. Treatments included a conventional system with or without 10 Mg ha(-1) yr(-1) dairy manure (CT(manure) or CT), and a conservation system with and without manure (NT(manure) or NT). Conventional systems consisted of chisel plowing/disking + in-row subsoiling without cover crops. Conservation systems combined no surface tillage with in-row subsoiling and winter cover crops. A soil survey, topographic survey, and interpolated surfaces of soil electrical conductivity (EC), soil organic carbon (SOC), and surface soil texture were used to delineate five zones using fuzzy k-means clustering. Overall (2001-2003), conservation systems improved cotton yield compared with conventional systems (2710 vs. 2380 kg ha(-1)); neither manure nor treatment x year interactions were significant. The conservation system was more productive than the conventional system in 87% of the cluster x year combinations. Slope, EC, SOC, and clay content were correlated with yield in all treatments. Soil and terrain attributes explained 16 to 64% of yield variation, however, their significance fluctuated between years and treatments. In dry years, factor analyses suggested variables related with soil quality and field-scale water dynamics had greater impacts on CT yields than NT yields. Our results indicate that management zones developed using relatively static soil-landscape data are relatively more suitable for conservation systems, and these zones are affected by soil management. In addition, the impact of NT on yields is most apparent on degraded soils in dry years.