Evaluation of a Feedback Approach to Nitrogen and Pix Application
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AbstractA single field experiment was conducted in 1996 at Maricopa, AZ to compare a scheduled approach (based on stage of growth) versus a feedback approach (based on vegetative status) to both nitrogen (1V) and mepiquat chloride (PIX™) applications on Upland cotton (Gossypium hirsutum L.). PIX feedback treatments were based upon fruit retention (FR) levels and height to node ratios (HNRs) with respect to established baselines. Scheduled and feedback PIX applications were made for a total of 0.75 and 1.25 pt./acre, respectively, with the scheduled treatments being initiated earlier in the fruiting cycle (early and peak bloom). Feedback PIK treatments consisted of a single 0.75 pt./acre application near peak bloom (approx. 2200 heat units after planting (HUAP), 86/55°F threshold). Scheduled applications of fertilizer N totaled 225 lbs. N/acre from three applications and feedback N treatments received a total of 135 lbs. N/acre from three applications. Treatments consisted of all combinations of scheduled or feedback applications of both N and PIX The highest lint yields were from a treatment receiving feedback N and PIX, but all treatment yields were not significantly different (P ≥ 0.05) from one another. From a practical (economic) standpoint, however, these treatments were different in terms of the differences of fertilizer N and the timing of the PIX applications required to produce comparable yields. Results from 1996 are consistent with 1993, 1994, and 1995 results from the same study.