Effects of Limited Irrigation on Growth and Grain Yield of Common Bean

Water resources are limited in many agricultural areas of West Asia. So, effective use of this scarce resource is very important in this region. Therefore, this research was conducted in 2004 at the Research Farm of the Faculty of Agriculture, University of Tabriz, Iran, to investigate the effects of different irrigation regimes (I1, I2 and I3: irrigation after 60, 80 and 100 mm evaporation from class A pan, respectively) on growth, yield and yield components of three common bean cultivars (COS16, Talash and Khomain). A split-plot experiment based on randomized complete block design in three replications was used, with the irrigation levels in main plots and common bean cultivars in subplots. The results of plant growth analysis on the basis of Growth Degree Days (GDD) showed that Percentage Ground Cover (PGC), Dry Matter Accumulation (DMA), Crop Growth Rate (CGR) and Relative Growth Rate (RGR) were considerably reduced, due to water deficit. In all cultivars, the highest PGC, DMA, CGR and RGR were obtained under I1. PGC at different stages of growth under I3 was much less than that under I1. PGC for Talash was more than that for other cultivars under I3.. CGR of COS16 under well-irrigation (I1) was more than that of other cultivars, but CGR of Talash and COS16 under I3 was almost similar at different stages of growth. All three cultivars had higher RGR at early stages of growth under I1, compared to I2 and I3. However, this difference gradually decreased with increasing degree days. PGC had the practical advantage of easy, quick and non- destructive measurement. Therefore, it can be used as the best growth index for estimating crop performance in the field. Although, mean grain weight of Khomain was more than that of two other cultivars, but Talash and COS16 produced more pods and grains per plant, leading to higher yield per unit area, compared to Khomain. Drought stress led to the reduction of number of pods per plant, grains per plant and grain yield per unit area. However, differences in 1000 grains weight among I1, I2 and I3 were not significant. Yield reduction under limited irrigations was only 9.45-16.5%. These results indicate that limited irrigation can considerably overcome the deleterious effects of drought stress on field performance of common bean