Growth and yield analysis of soybean (Glycine max (L) Merr.) under different irrigation schedules in Castilla-La Mancha, Spain

Abstract

Soybean is a world-wide crop, but the European Community is deficient in its production. Despite different attempts to introduce this crop into Spain, little is grown. This study was conducted to determine the physiological basis of yield variation resulting from six different irrigation schedules. The experiment was carried out at Las Tiesas farm in the province of Albacete (Spain), during 1990. For each water treatment, growth was analyzed by means of some morphological parameters, leaf area index (LAI), dry matter accumulation and some growth indices : crop growth rate (CGR), relative growth rate (RGR), net assimilation rate (NAR) and leaf area duration (LAD). Quantitative and qualitative production and their relationships with irrigation supply were also analyzed.The results showed that irrigation increased dry matter production, which was associated with increased LAI, LAD and CGR. NAR and RGR were not significantly affected by irrigation. Soybean yield increased with the volume of water supply, mainly due to the greater number of grains m−2. Variation in grain yield was related to the growth parameters of dry matter accumulation, LAI, LAD and CGR. Oil concentration in the seed increased with seasonal amount of water, while protein concentration decreased. Both oil and protein yield increased as irrigation increased, although with a diminishing return.