The effects of several climatic factors and several nitrogen and moisture levels on the yield and evapotranspiration of corn

The purpose of this study was to relate evapotranspiration (ET) and yield of corn to several climatic factors and to several treatments of nitrogen and irrigation. The experiments were conducted at Knoxville and Jackson for five seasons. The experimental design was the split plot with three moisture levels for main plots and six nitrogen levels for the splits. Dixie 29 hybrid corn was planted on beds and thinned to 20,000 plants per acre. Moisture readings were made every 7 or 14 days with a neutron moisture meter. Several climatic factors were recorded at the two experiment stations and these were correlated with ET. Correlations were also made for open pan evaporation with ET from several treatments and with the other climatic factors. Yield, water use efficiency and water use for several treatments were analyzed. All of the climatic factors studied correlated highly with ET and with open pan evaporation. ET from corn was related to open pan evaporation in almost the same way, regardless of the nitrogen or irrigation applied. Yield increases were noted for each 60 lb. increment of nitrogen added up to 120 lb. at Knoxville, and l80 lb. at Jackson. Water use efficiency was increased by added nitrogen. Yields were increased by irrigation for the five year average at both locations but there were no increases due to irrigation during several of the wetter seasons. Water use was greatest during the time of tasseling, silking and kernel formation. The peak water use was 0.22 inches per day at both locations for the average. The irrigated plots used about 2 to 4 inches more water than the unirrigated, during a season. Nitrogen had little effect upon total water use but greatly affected water use efficiency.