Effects of deficit irrigation on yield and yield components of vegetable soybean [Glycine max L. (Merr.)] in semi-arid conditions

Abstract

Vegetable soybeans [Glycine max L (Merr.)] are very sensitive crops to environmental conditions during their growth 
stages, especially in term of water scarcity. Water scarcity is one of the major environmental factors influencing 
sustainable agricultural production in arid and semi-arid regions. Careful management irrigation strategies need to 
save irrigation water with marginal yield reduction. The objective of this research was to investigate the effects of the 
water deficit on yield and yield components of soybean in semi-arid conditions. This research was carried out at the 
Agricultural Experimental Field of the Harran University (Sanliurfa, Turkey) on clay soil during the growth periods of 
2006 and 2007. The irrigation treatments were 33% (I33), 67% (I67), 100% (I100) and 133% (I133) ratios of total irrigation 
water applied (IW)/cumulative pan evaporation (CPE) with four day irrigation interval. The average amount of irrigation 
water applied to treatments (I133, I100, I67 and I33) was 1058, 795, 533 and 263 and 1094, 823, 551 and 272 mm for 
Toyokomachi and Toyohomare cultivars, respectively. The maximum green pod yields were 20.6 and 29.1 t ha-1 with 
997 and 922 mm water consumption for Toyohomare and Toyokomachi, respectively in I133 treatments. Yield response 
factor (ky) values of I100, I67 and I33 treatments were determined as 2.17, 0.92 and 0.59 for Toyohomare and 3.50, 0.61 
and 0.61 for Toyokomachi, respectively. The results of the study implied that at least equal (I100) or excess of the 
evaporated water amount is required to produce high yield in soybean. Differences of yield between cultivars in 
response to irrigation levels make it necessary to select less sensitive cultivars to water stress especially in semi-arid 
and arid areas. Varietal characteristics must be considered for successful growing of soybean.