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Fundamentals of Variable Rate Irrigation and Fertigation in Comparison to Fixed Rate Irrigation and Conventional Fertilizer Management
The potential positive or negative impact(s) of variable rate irrigation (VRI) and fertigation (VRF) technologies on evapotranspiration, grain yield, crop productivity and its economic viability are not well known. Proper management of this technology requires research support which is currently limited. This long-term research is designed to estimate and compare the soil water dynamics, grain yields, actual evapotranspiration, crop water productivities, crop coefficients and economics of VRI, fixed rate irrigation (FRI) and no-irrigation (NI) under fix rate fertigation (FRF), variable rate fertigation (VRF) and pre-plant nitrogen application (PP) management in three soil types as well as to develop best management practices for maize. The research was conducted in south central Nebraska from 2015 to 2017 maize growing seasons. Irrigation and fertilizer amounts were applied using a variable-rate linear move irrigation system. The results of this research showed significant differences in the response of maize to irrigation and nitrogen management methods between soil types and within soil types. In 2016, significant impact of nitrogen and irrigation treatments was observed on ETa. There was significant interactions between soil type, irrigation and nitrogen treatments for the 2017 growing season. There was no significant impact of nitrogen application methods on grain yield in any year. Field topography, especially elevation and slope played a substantial role in yield response to different irrigation methods by redirecting and altering soil water availability. The results of this research show that slopes and intercepts of the linear ETa-yield production functions can differ significantly with differences irrigation and nitrogen management practices such as VRI and FRI as well as with soil types. Crop water use efficiency (CWUE), Irrigation water use efficiency (IWUE) and Evapotranspiration water use efficiency (ETWUE) exhibited substantial variation the irrigation treatments. The results of this research indicated that the magnitude of alfalfa reference crop coefficients (Kcr) and grass reference crop coefficients (Kco) depends upon the amount of irrigation water applied. Also, the magnitude of K cr and Kco are the function of the amount of nitrogen and not the timing of nitrogen. Maximum Kcr usually occurred in high nitrogen treatments. The results of this research indicated that for the same settings as the research, the VRI management is not an economically viable option for maize production in south central Nebraska.^
Sharma, Vasudha, "Fundamentals of Variable Rate Irrigation and Fertigation in Comparison to Fixed Rate Irrigation and Conventional Fertilizer Management" (2018). ETD collection for University of Nebraska - Lincoln. AAI10791744.