Biological Systems Engineering
Date of this Version
Infiltration and runoff are important processes that affect the efficiency of center pivot irrigation systems. No-till planting systems potentially influence the hydraulic properties of soils and the soil surface conditions. The result of long-term use of no-till could be higher infiltration and lower runoff from rainfall and irrigation.
This potential was investigated in Nebraska on two center pivot irrigated sites; Fillmore County and Phelps County, one furrow irrigated site; South Central Agriculture Laboratory (SCAL), and one dryland site; Rogers Farm. Paired treatments were used at each location, one that was no-till planted and one that used two to three operations per year for seed-bed preparation and cultivation. Operations were consistent for at least seven years on all fields before experiments were conducted.
In 2008-2010 runoff was monitored during the cropping season at the center pivot irrigated sites. During this time interval, hydraulic conductivity tests were performed at all sites. Cumulative runoff data showed more runoff on tilled fields, which aligns with findings from the hydraulic conductivity from these fields. Surface satiated hydraulic conductivity was significantly higher for no-till at the center pivot irrigated sites with 6.2 cm h-1 and 8.2 cm h-1 measured for no-till and 3.9 cm h-1 and 2.8 cm h-1 for tilled. However, the dryland corn had significantly higher hydraulic conductivity on the tilled plot (46.3 cm h-1) compared to the no-till (8.3 cm h-1) plot. This discrepancy may be due to soil shrinkage causing surface cracks. Overall, no-till fields had higher hydraulic conductivity and lower runoff.
Using 2010 gathered rainfall data from the center pivot irrigated sites, satiated hydraulic conductivity was predicted using four models: Crust Factor, ROSETTA, Water Erosion Prediction Project (WEPP), and Soil Water Characteristics tool (SWC). The hydraulic conductivity values were compared to both rainfall and irrigation runoff using the Green and Ampt equation. WEPP had the smallest percent bias (28%). The model over predicted runoff at the no-till field at Phelps County. No model predicted an optimal satiated hydraulic conductivity for all fields.
A THESIS Presented to the Faculty of The Graduate College at the University of Nebraska In Partial Fulfillment of Requirements For the Degree of Master of Science, Major: Environmental Engineering, Under the Supervision of Professor Dean E. Eisenhauer. Lincoln, Nebraska: December 2010
Copyright 2010 Jessica H. Deck