Validation of Nitrogen Management Recommendations for Irrigated Cotton in the Desert Southwest

A field study was carried out during 2011-2012 growing season in an irrigated cotton (Gossypium barbadense) production system to validate and test recently developed nutrient management guidelines. Soil and tissue test samples were analyzed for nutrients for two different sites in southeastern Arizona. Soil samples were collected just after planting and at the end of the season. Plant tissue samples for all plots were collected at the following four stages of growth: first square, first bloom, peak bloom, and first open boll.  All fertilizer and nutrient inputs were monitored, managed, and recorded within current Extension guidelines for irrigated cotton. Nutrients tested included N, Ca, Mg, P, K, Zn, Fe, and B, with the objective of evaluating soil and tissue nutrient concentrations at various stages of crop growth and development. This study also provided the opportunity to compare the use of a nitrate-N based fertilizer (CaN-17) with a more conventional mixed blend N fertilizer ( UAN-32). The application of the current cotton management  guidelines and recommendations with respect to yield potentials were evaluated. Results for soil and tissue analysis were evaluated in relation to yield results. Control fields at site 1 received a total of 3.54 lbs. N/ac. (2 app. of UAN-32, and no CaN-17). Test fields at site 1 received a total of 5.55 lbs. N/ac. (1 app. of UAN-32, and 1 app. of CaN-17). Control fields at site 2 received a total of 70.8 lbs. N/ac. (2 app. of UAN-32, and no CaN17). Test fields at site 2 received a total of 56.9 lbs. N/ac. (1 app. of UAN-32, and 1 app. of CaN-17). Yields were not significantly different, with the control fields, and test fields averaging 1.9 bales/ac. At site 2, yields were similar with control averaging 2.8 bales/ac., and test fields averaging 2.9 bales/ac.