The influence of the soil spatial variability on management and design of micro-sprinkler irrigation systems and its impact on turf grass production.

Abstract

Not very many studies measuring the effects of soil spatial variability in irrigation management and design have been conducted, and those who have tested this concept in the field have obtained mixed results. More research is necessary especially due to the potential of saving water and to the high water cost in certain areas of the world. In this study, the effects of the soil spatial variability upon the management and design of a micro-sprinkler irrigation system has been addressed. An irrigation system designed to take advantage of the soil spatial structure was installed in a small field (60 ft by 90 ft), and water was applied according to the local soil properties. Bulk density values as well as the soil-water retention curve parameters (field capacity and wilting point) were determined in order to ascertain the irrigation system management. Measurements of the volumetric water content "in situ" were recorded on a daily basis with the help of a T.D.R. probe, and those values were used to indicate the irrigation timing and the water amount to be applied in each plot in the field. Crop yield values were obtained throughout the season, and an analysis of variance was performed in each of the field sub-units. Production was compared within all the sub-units comprising the entire agricultural field, as well as a comparative study between the plots where the soil spatial variability was considered against those previously assumed to be homogeneous. Statistically, no differences in crop yield were observed when the soil was treated as homogeneous or heterogeneous for perennial ryegrass (Lolium perenne L.) turf. However, a decrease in 20% of the seasonal water was observed when the soil spatial structure was taken into account. For this particular study, the economy associated with the lower water consumption was not sufficient to overcome the higher installation costs for the spatially variable irrigation system.