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Placement of UAN for Dryland Winter Wheat in the Central High Plains
Author(s) -
Schlegel A. J.,
Dhuyvetter K. C.,
Havlin J. L.
Publication year - 2003
Publication title -
agronomy journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.752
H-Index - 131
eISSN - 1435-0645
pISSN - 0002-1962
DOI - 10.2134/agronj2003.1532
Subject(s) - agronomy , sowing , loam , straw , tillage , fertilizer , cropping system , summer fallow , environmental science , conventional tillage , ammonium nitrate , no till farming , mollisol , crop , zoology , soil fertility , soil water , biology , chemistry , cropping , soil science , agriculture , ecology , organic chemistry
Research was initiated in 1993 to determine the N fertilizer requirement for dryland winter wheat ( Triticum aestivum L.) grown under reduced tillage systems in western Kansas. Six sites in west‐central Kansas were selected each year for 4 yr in cooperation with area farmers. The typical cropping system was wheat‐fallow with reduced tillage practices. All sites were on silt loam soil that ranged in residual soil nitrate‐N content from 2 to 9 mg kg −1 (0‐ to 60‐cm sample). Crop residue cover at wheat planting averaged 28%. Fluid N (28% N as urea‐ammonium nitrate solution, UAN) was injected in the fall and spring and surface broadcast during the winter and spring at five rates (22, 45, 67, 90, and 112 kg ha −1 ) along with a zero N control. Typical production practices consisted of planting winter wheat in mid‐September with a hoe‐type drill. Grain protein increased linearly with increased N rates with greater than 130 g kg −1 when 112 kg N ha −1 was injected. Apparent fertilizer N recovery decreased with increased N rates, but was consistently higher with fall or spring injected rather than winter or spring broadcast UAN. The straw/yield ratio was greater than 2 across all N rates, which is greater than the commonly used value of 1.7. The soil N test was an indicator of yield response to N fertilization. Grain yields increased in 10 of 13 site‐years with N fertilizer. Average grain yields were 8% greater from spring injected than broadcast UAN. The time of N application had little effect on grain yield. Economic analysis indicated that injecting UAN in the fall or spring was more profitable than topdressing UAN in the winter or spring because of improved yields and/or lower total N costs. These data suggest that N rate recommendations should vary with application method.