Cotton yield response to fertilizer phosphorus under a range of nitrogen management tactics

Long term crop nutrient removal is leading to decline in available phosphorus (P) in Vertisols. To improve the efficiency of P fertilizer applied for cotton production it is important to understand its interaction with other applied nutrients, particularly nitrogen (N). Four experiments were conducted to investigate the cotton lint yield response to applied P fertilizer (dispersed throughout the beds) under (i) three different N rates, (ii) various split- N application timing treatments, (iii) additional late N application and (iv) two water-run urea application strategies. Cotton lint yield response to applied P fertilizer was influenced by split-N application ratio and timing, but not N rates or water run N strategies. Additional late N application reduced lint yield and P response. Applying all the N fertilizer pre-plant along with P increased cotton lint yield by 37.2% (with 32.5% greater seed yield), compared with applying P before planting and all N fertilizer in-crop. Phosphorus application improved lint turnout by increasing cotton lint and reducing trash. These results indicate improved agronomic efficiency of applied P fertilizer dispersed throughout the beds can be possible by supplying crops with optimum N earlier in the season. The P dispersion throughout the plant beds potentially improved the P acquisition by cotton roots-where more N was applied pre-plant than in-crop. Future research needs to focus on greater understanding of the N-priming effect on cotton root growth and its impact on response to applied P.