Statistical analyses of soil variability: effects of variability on level-basin irrigation of wheat

Abstract

The transfer of plot-size water-use and yield information to field-size, surface irrigation conditions is generally inadequate due to nonuniform water applications and soil variability. In a two-year level-basin irrigation study, water-use and yield (Y) relationships were characterized for wheat grown under three quantities of seasonal irrigation water on a 4.2-ha, sandy loam field site. The Mohall sandy loam had a sand particle fraction ranging from 46 to 79% with a mean of 61% at the 0 to 1.0-m soil depth. The sand particle fraction, soil water content and grain yield were highly correlated with one another. High sand content was associated with less evapotranspiration and lower yield within the driest irrigation treatment (two irrigations), as well as, higher rates of infiltrated water and lower yield in the wettest irrigation treatment (five irrigations). The inclusion of sand content with seasonal infiltrated water depth improved estimates of yield as much as 42% for specific levels of irrigation management. Estimated yields for a given depth of seasonal infiltrated water varied 1250–1400 kg/ha over the range of sand content within the field site. Knowing the sand content of the field, the farmer should be able to improve the scheduling of both irrigation and fertilizer application rates based on more realistic wheat yield goals.