AGRONOMY & SOILS Ability of Cotton (Gossypium hirsutum L.) to Recover from Early Season Nitrogen Deficiency

Nitrogen (N) is important for cotton production but if poorly managed it can lead to reduced lint yield and low N use efficiency. This study was conducted to evaluate cotton’s ability to recover from early season N deficiency and determine if a sensor-based N rate calculator (SBNRC) can be used to make mid-season N recommendations in cotton. The effect of sidedress N fertilizer (0, 33, 67, 101, and 134 kg N ha -1 ) applied at early pinhead square (EPHS), first white flower (FWF), 30 d after first white flower (30 DAFWF), and four levels of preplant N (0, 33, 67, and 101 kg ha -1 ), on cotton lint yield was investigated at two locations in Oklahoma. The results indicated that at 0 and 33 kg ha -1 preplant N applications, cotton yield was significantly impacted by the timing of sidedress N. However, at Altus in 2009 and Lake Carl Blackwell (LCB) in 2010, cotton recovered from early season N deficiency and attained near maximum lint yield when sidedress N fertilizer was applied at EPHS or FWF. At Altus in 2010, cotton recovered when sidedress N was applied at EPHS and reduced when sidedress N was delayed until FWF. Yields were significantly (P < 0.05) reduced when application was delayed to 30 DAFWF at all sites. The results indicate normalized difference vegetative index (NDVI) could be used to make sidedress N recommendation for cotton at EPHS or FWF stage. This research validates the use of the SBNRC to improve inseason N recommendations in cotton production.