Sequential NLEAP simulations to examine effect of early and late planted winter cover crops on nitrogen dynamics

ABSTRACT:

In different studies conducted during the last 10 years, underground well water NO₃⁻-N concentrations have been found to exceed drinking water standards of 10 mg NO₃⁻-N L⁻¹ (10 ppm) for some areas of the San Luis Valley of south central Colorado. Some of these studies reported that NO₃⁻-N leaching i; a factor that can contribute to these high well water NO₃⁻-N concentrations. Computer models are technology transfer tools that can assess impacts of best irrigation and nutrient management practices. Sequential computer simulations of the effects of winter cover crop planting date on residual soil NO₃⁻-N concentrations have not been previously conducted. The new version 1.2 of the Nitrate Leaching and Economic Analysis Package (NLEAP) model was used to conduct an assessment of the effect of winter cover crop planting date on conservation of water quality. The NLEAP model simulated a lettuce (Lactuca sativa L.) - winter cover wheat (Triticum aesticum L.) and rye (Secale cereale L.) (early- or late-planted) potato (Solanum tuberosum L.) rotation, grown on a center-pivot irrigated Kerber loamy sand. Winter cover crops increased the system N use efficiency (NUE) (P<0.05). The effect of early-planted winter cover crops on conservation of water quality extended into the potato growing season, increasing NUE and reducing NO₃⁻-N leaching (P<0.05).