Crop Yield – Irrigation Relationships in a Gypsiferous‐Sodic Soil1

Abstract

AbstractThe effect of irrigation regime on the soil‐water suction, the salinity of the soil solution, and the yields of tomato (Lycopersicum esculantum var. 675) and bell pepper (Capsicum frutescens var. ‘Maor’) in a gypsiferous‐sodic soil was studied. For each of the two crops, three different amounts of water (in terms of pan evaporation) at two different irrigation frequencies (daily irrigation and irrigation every 3 days) were applied. The different irrigation regimes resulted in different soil water suction and salinity profiles, each of which can be characterized by a time average and the variance about this average. Average (over time) soil water potential (ψ) increased as both the amount of irrigation water (Q′) and the irrigation frequency (I) increased. For a given I, the ψ‐Q′ relationships can be described by a hyperbolic function. In the gypsiferous‐sodic soil used, the salinity of the soil solution was highly correlated with the exchangeable Na of the soil, which, in turn, was reduced with added irrigation water. Relative yields, Y, of the two crops were linearly dependent on the variance of the soil‐water potential, independent of the irrigation regime. This implies that the yield‐soil‐water potential relationship can be described by a quadratic function. As opposed to the unique Y‐ψ relationships, the Y‐Q′ relationships depend on the irrigation frequency. For a given Q′ yields of both crops obtained under daily irrigation were higher than the yields obtained under irrigation once in 3 days. Highest fruit yields were 126.1 Mg/ha of tomatoes and 62.7 Mg/ha of bell pepper; the respective amounts of irrigation water were 1,013 and 2,164 mm (109%) and 160% of the evaporation from a Class A pan).