Elevation and infiltration in a level basin. II. Impact on soil water and corn yield

Abstract

The spatial variability of irrigation water recharge and crop yield is affected by a number of factors. Soil surface elevation, infiltration and soil water MAD are the most relevant related to level-basin irrigation. Measurements of soil water recharge (using a neutron probe) were compared to estimates based on ring infiltrometers and observations of the opportunity time. Estimates of cumulative infiltration (ECI) were obtained, separating the variability of infiltration and opportunity time (largely determined by elevation). Soil surface elevation was correlated with measured recharge, grain yield and total dry matter. A correlation was found between infiltration and the measurements of water recharge. While soil surface elevation can be regarded as a management variable, little can be done to reduce the variability of infiltration. Distribution uniformities from ECI were about 20% higher than those obtained from measurements of water recharge. Seasonal uniformity was only marginally higher than average uniformity, confirming the low random component of water recharge in level-basin irrigation. Deep percolation was more intense in areas with low MAD. This finding emphasizes the relevance of characterizing the variability of soil physical properties in surface irrigation. Extrapolation of the results of this research to field-scale irrigation basins should take into account the methodology used: in particular, the reduced scale of the experimental level basin.