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Fluid Journal : Spring 2018
21 The Fluid Journal Spring 2018 Dr.W. Hunter Frame is Field /Crops Agronomist, Department of Crop and Soil Environmental Sciences, Tidewater Agricultural Research and Extension Center, Suffolk, Virginia 23437. to increasing the S content of fluid UAN solutions during the study in 2017. All locations in 2016 had a slight increase in lint yield from 32% UAN to 24-0-0-3S solutions. Soil types at each location during 2017 were heavier in texture and may have had S contributions from the subsoil where leached S may be retained. All soil samples were from the past six site years. This will allow inferences to be made about S contributions from the subsoil and predict when applying S will be needed to achieve optimum lint yields in cotton. Summing up Overall, the 2017 growing season was marked by favorable weather conditions and high lint yields across locations. The cotton variety selected for 2017 showed increased variability in lint yields across environments, though lint yields were satisfactory. Also, this variety did not perform well in the 2017 Virginia cotton variety testing program, thus in 2018 another variety may be selected that is a more consistent high yielding variety across environments. Tissue S concentrations were very responsive to N and S application rates during 2017. The broadcast (dry) N/S management system produced higher petiole and leaf S concentrations compared to fluid N/S sources. Nitrogen rate was the most limiting nutrient at each location during the study and lint yields were maximized at 100 lbs. N per acre across locations, regardless of yield potential. No response to S was observed during 2017. This may be due to varietal S usage or the mining of S from heavier textured subsoil where S has been leached from sandy loam surface horizons. Soil samples taken for PAN analysis will be sent off to determine S availability in lower soil horizons. The differences observed between 2016 and 2017 indicate environment and soil type play critical roles for N/S management in cotton. Sandier soils will be selected during the 2018 growing season to ascertain the effect of soil type on N/S management in the upper Southeast coastal plain.