Effect of Water Deficiencies at Different Stages of Development on Soybean Yield

Abstract

Rainfed soybean [Glycine max (L.) Merill.] is the main crop in Uruguay and yields are lower than those obtained in the region. Water deficiency is the major limiting factor in the production environments, as it negatively affects yield due to the decrease in both dry matter accumulation and biological N2 fixation. Two studies have been carried out during two consecutive years with contrasting climatic characteristics. The aim was to quantify yield losses due to water deficiency at different stages of crop development. Four treatments were defined; without any water deficiency (T1), with water deficiency during the critical period (CP, T2), with water deficiencies during non-critical periods previous to CP (T3) and rainfed (T4). To obtain water deficiencies rainfall was intercepted (PP) by using rain shelters while water availability was achieved by supplementary irrigation. Water deficiencies during CP caused significant differences and lowered the yield from 44 to 50 %. Water stress previous to CV did not produce significant differences and the loss was of 23 %. Without water stress, both during the first and the second year, the yields doubled and tripled the country averages. Yield losses due to water deficiency and yields under no water stress show the need to evaluate different management strategies for irrigation.