CROP EVAPOTRANSPIRATION, CROP COEFFICIENTS, PLANT GROWTH AND YIELD PARAMETERS, AND NUTRIENT UPTAKE DYNAMICS OF MAIZE (Zea mays L.) UNDER FULL AND LIMITED IRRIGATION
Document Type Article
A DISSERTATION Presented to the Faculty of The Graduate College at the University of Nebraska In Partial Fulfillment of Requirements For the Degree of Doctor of Philosophy, Major: Interdepartmental Area of Engineering (Agricultural and Biological Systems Engineering), Under the Supervision of Professor Suat Irmak. Lincoln, Nebraska: July, 2011
Copyright 2011 Koffi Djaman
The effects of full and limited irrigation practices on maize growth parameters, yield, actual crop evapotranspiration (ETa), crop coefficients, and nutrient uptake dynamics were investigated. Field experiments were conducted under a 4-span hydraulic and continuous move center pivot irrigation system at the University of Nebraska-Lincoln, South Central Agricultural Laboratory (SCAL) during the growing seasons in 2009 and 2010. Four irrigation regimes 100% of the fully-irrigated treatment (FIT), 75% FIT, 60% FIT, 50% FIT and rainfed treatment were evaluated.
Maize yields varied from 9.05 tons/ha for the rainfed treatment to 15.51 tons/ha for the 100% FIT in 2009 and 11.74 to 15.45 tons/ha for the same treatments in 2010. There was no statistically significant difference between the 75% FIT and the 100% FIT in terms of grain yield. Crop evapotranspiration increased with irrigation amounts and ranged from 509 to 645 mm in 2009 and from 690 to 748 mm in 2010. In terms of performance in crop water productivity, the 60% and 75% FIT treatments were comparable to the full irrigated treatment and are viable approaches in increasing crop water productivity of maize under these experimental, soil and crop management, and climatic conditions. On average, 60%FIT resulted in the highest irrigation water use efficiency of 4.53 kg/m3.
Mid-season crop grass- and alfalfa-reference crop coefficients (Kco and Kcr) showed variability with the irrigation treatment. The mid-season Kco ranged from 1.08 to 1.26 and the mid-season Kcr ranged between 0.92 and 1.05.
Nitrogen uptake ranged from 154 to 253 Kg/ha and 182 to 270 Kg/ha in 2009 and 2010 respectively. The FIT resulted in the highest and the rainfed treatment had the lowest nitrogen uptake in both years. The FIT had the highest phosphorus uptake with 39 Kg/ha and 53 Kg/ha in 2009 and 2010, respectively. Better potassium uptake was observed in 2010 and it ranged from 414 to 637 Kg/ha while it ranged from 333 to 367 Kg/ha in 2009.
Advisor: Suat Irmak