Optimizing preplant irrigation for maize under limited water in the High Plains

Authors: KISEKKA, I - Kansas State University; SCHEGEL, A - Kansas State University; Ma, Liwang

Submitted to: Agricultural Water Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/20/2017
Publication Date: 3/20/2017
Citation: Kisekka, I., Schegel, A., Ma, L. 2017. Optimizing preplant irrigation for maize under limited water in the High Plains. Agricultural Water Management. 187:154-163.

Interpretive Summary: Inadequate well capacities have forced many farmers to apply preplant (preseason) irrigation to supplement crop water use during the crop season. A simulation study was conducted to assess the effect of preplant irrigation amounts and irrigation capacity on maize yield, evapotranspiration (ET), and soil water evaporation using longterm historical climatic data from 1986 to 2014 for southwest Kansas. The Ceres-Maize model embedded in the RZWQM2 model was used for maize simulation. Experimental data from 2006 to 2009 was used to calibrate and validate the model. Model performance was satisfactory, but accuracy decreased with increasing water stress. At high irrigation capacity (=0.25 inches/day) preplant irrigation did not substantially improve yields. At 0.15 inches/day irrigation capacity only 4 inches of preplant irrigation produced median yields that were significantly higher than no preplant irrigation. Under very low irrigation capacity of 0.1 inches/day preplant irrigation improved yields. At low irrigation capacity, transpiration increased with increase in preplant irrigation amount. Water losses due to soil water evaporation increased with irrigation capacity and preplant irrigation amount. Overall, increasing irrigation capacity improved maize grain yield and reduced uncertainty due to seasonal variations in weather due to increase in ET. At high irrigation capacity (= 0.25 inches/day), we recommend no preplant irrigation to minimize soil water evaporation losses. However, under very limited well capacity (= 0.15 inches/day) we recommend applying at least 3 inches of preplant irrigation in late spring.

Technical Abstract: Due to inadequate well capacities, many farmers cannot meet inseason crop evapotranspiration demands. Some farmers apply preplant (preseason) irrigation to buffer the crop between irrigation or rainfall events during the season. A simulation study was conducted to assess the effect of preplant irrigation amounts and irrigation capacity on maize yield, evapotranspiration (ET), and soil water evaporation using longterm historical climatic data from 1986 to 2014 for southwest Kansas. The Ceres-Maize model embedded in the RZWQM2 model was used for maize simulation. Experimental data from 2006 to 2009 was used to calibrate and validate the model. Model performance was satisfactory with high index of agreement (IA) ranging between 0.88 and 0.97. Relative root mean square error (RRMSE) ranged between 4.5% and 27 % with accuracy decreasing with increasing water stress. At high irrigation capacity (=6.4 mm/day) preplant irrigation did not substantially improve yields. At 3.8 mm/day irrigation capacity only 100 mm of preplant irrigation produced median yields that were significantly higher than 0 mm preplant irrigation. Under very low irrigation capacity of (2.5 mm/day) preplant irrigation improved yields. At low irrigation capacity, transpiration increased with increase in preplant irrigation amount. Water losses due to soil water evaporation increased with irrigation capacity and preplant irrigation amount. Overall, increasing irrigation capacity improved maize grain yield and reduced uncertainty due to seasonal variations in weather due to increase in ET (there is linear relationship between yield and ET). At high irrigation capacity (= 6.4 mm/day), we recommend no preplant irrigation to minimize soil water evaporation losses. However, under very limited well capacity (= 3.8 mm/day) we recommend applying at least 75 mm of preplant irrigation in late spring. This study demonstrates how an agricultural systems model was applied to explore alternative irrigation water management strategies by extrapolating short term experimental data to different climate, and management strategies.