Quantitative Soil Moisture Use in Corn Grown Under Conventional and No‐tillage Methods¹

Abstract

Abstract Experiments conducted at the University of Kentucky during 1969, 1970, and 1971 compared corn ( Zea mays L.) production under conventional and no‐tillage systems. The presence of a killed‐sod mulch in the no‐tillage plots almost eliminated the loss of moisture by direct evaporation from the soil surface during the early growing period, but after a full crop canopy had developed, losses from both production methods were about equal. Water loss from the soil during the full‐canopy period was compared with open pan evaporation to determine the rate of loss under varying levels of soil moisture deficiency. The average soil moisture deficiency during the period from about 3 weeks before to 6 weeks after silking was related to final grain yield, and a simple linear relationship indicated that each additional cm of water available to the plant increased yields by about 559 kg/ha. The relationship was tested on regional yield data for the years 1954 to 1968. Soil moisture status was simulated from precipitation and temperature data observed during the growing season by using the Palmer Crop Moisture Index method. The variation in predicted and observed yield follow each other very well, with a linear correlation coefficient of 0.81.