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Improving Nitrogen Fertilizer Use Efficiency in Subsurface Drip‐Irrigated Cotton in the Desert Southwest
Author(s) -
Bronson Kevin. F.,
Hunsaker Douglas J.,
Meisinger John J.,
Rockholt Sharette M.,
Thorp Kelly R.,
Conley Matthew M.,
Williams Clinton F.,
Norton E. Randall,
Barnes Edward M.
Publication year - 2019
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj2019.07.0210
Subject(s) - loam , lint , drip irrigation , irrigation , agronomy , environmental science , fertilizer , evapotranspiration , irrigation management , surface irrigation , soil test , soil water , soil science , biology , ecology
Declining water availability in the American Southwest continues to generate interest in efficient subsurface drip irrigation (SDI) for cotton ( Gossypium hirsutum L.) production. Fertigating urea ammonium nitrate (UAN) at low rates with high frequency is an important advantage of SDI. However, N fertilizer management guidelines specific to SDI cotton are lacking. A 3‐yr study was conducted on a Casa Grande sandy loam soil in Maricopa, AZ, to test a pre‐plant soil profile NO 3 test algorithm and a canopy reflectance approach to manage in‐season N fertilizer for SDI cotton. Treatments included soil test‐based N management, reflectance‐based N management, and zero‐N at 100% evapotranspiration irrigation replacement. A second irrigation level of 70% evapotranspiration replacement included just the soil test‐based N and zero‐N treatments. The five treatments were replicated three times. Soil test–based N treatments received from 172 to 224 kg N ha −1 , and reflectance‐based N amounts were 112 to 158 kg N ha −1 . Nitrogen recovery efficiency (RE) of UAN‐N was high, with 24 fertigations during 6 wk between first square and mid bloom ranging from 58 to 93%. The isotope dilution method estimated similar RE in 2017. Residual post‐harvest soil NO 3 –N was notable only with 70% irrigation. Lint and seed yields were significantly reduced with the 70% irrigation treatment compared with 100% irrigation. The key result of this study is that reflectance‐based N management saved 17 to 112 kg N ha −1 without reducing lint yields compared with the soil test–based N treatment.