Late-summer infltration as affected by cropping and grazing management of winter-wheat pastures

ABSTRACT:

Agricultural practices that incorporate grazed winter wheat and associated summer management are vital to the rural economy of the southern Great Plains. In regions where high intensity, late summer storms can occur, limited information exists about the impact of these practices, including summer fallow and dual-cropping summer fields, on infiltration. This study was designed to determine the effects of two winter wheat management strategies: winter wheat with summer fallow and winter wheat with summer legumes simultaneously with two grazing treatments (grazed and ungrazed) on steady-state infiltration rates. Four pastures were planted in conservation winter wheat (Triticum aestivum L.) and grazed over winter when possible from November to March and graze-out from March to May from 1998 to 2002. A dual-cropping management strategy that incorporated summer legumes, Korean Lespedeza (Lespedeza stipulacea Maxim) and Soybean (Glycine max), was replicated on two of the pastures, while the other two pastures utilized summer fallow. A rainfall simulator calibrated to represent late summer, high intensity (1.67 mm/min) summer storms was used to determine the parameters: time to achieve steady-state conditions (Tss), steady-state infiltration (SSI) rates, and percent of applied rainfall infiltrated at steady-state conditions (%ss). These parameters were shown to be significantly (P < 0.10) impacted by the grazing practices in all instances and the management practices associated with winter wheat in some cases. Grazed winter wheat utilizing summer fallow had the lowest infiltration rate with 0.91 mm/min along with the shortest Tss (19 min) and the lowest %ss (56%). Grazed summer legumes and ungrazed summer fallow displayed similar infiltration parameters (SSI = 1.47 and 1.33 mm/min, Tss = 28 and 30 min, %ss = 81% and 81%, respectively) and ungrazed summer legumes had the least impact to the infiltration with a SSI rate of 1.59 mm/min, Tss of 37 min and %ss of 88%. Understanding the mechanism of interaction between late summer storms and summer management practices will lead to formulation of larger scale mitigation strategies to reduce erosion and enhance capture of precipitation and runoff.