Effect of Planting Pattern and Irrigation Method on Germination of Mung Bean (Vigna radiate) Harvested at Different Times of Maturation

Abstract

Introduction: Pulses are a group of crops which are important in human nutrition and also sustainability of agronomical systems and economic advantage. Regarding optimum planting density of mung beans (40 plant m -2 ), more than 700 tons of certified seeds of mung bean seeds are needed all over the country, confirming the importance of the production of high quality seeds. Seed quality may be affected by different environmental conditions such as water deficit. Since intercropping can alleviate the negative effects of drought on crop growth, the hypothesis that crops can benefit from intercropping has been formulated in previous studies. Since there is no sufficient information on germination performance and seed weight of mung bean during seed growth and development in response to partial root zone irrigation and intercropping, the current experiment was aimed to evaluate the effect of partial root zone irrigation and intercropping on some quality traits of mung bean and to determine the best time of harvesting to produce high quality seeds in mung bean. Materials and Methods: The experiment was conducted as factorial (3× 2× 5) based on RCBD with three replications. The first factor was planting pattern (including sole mung bean, inter-row maize-mung bean intercropping and within-row maize-mung bean intercropping). The second factor was irrigation method (partial root zone irrigation and conventional irrigation) and the third factor was harvest time (5-day intervals in 5 stages). Germination percentage, 1000-grain weight, root length, shoot length and seedling dry weight were determined for evaluation of seed quality. Results: The results indicated that the interaction of cropping pattern× harvest time and cropping pattern× irrigation× harvest time had no significant effect on traits. However, the interaction of irrigation× harvest time on germination percentage, root length and seedling dry weight was significant (P≤0.01). With increasing growth and maturation of seed, germination percentage increased in both irrigation methods. Germination percentage of mung bean was reduced by partial root zone irrigation. The effect of partial root zone irrigation on germination percentage was higher at the end of seed filling period. Partial root zone irrigation resulted in the reduction of root length. The differences between conventional and partial root zone irrigation for root length at different harvest times were 4, 9, 9, 18 and 15 percent, respectively. In both irrigation methods (i.e., conventional and partial root zone irrigation) seedling dry weight increased with increasing the seed growth and maturation. However, deficit of irrigation had negative effects on seedling dry weight of mung bean. With reduced water availability, 1000-grain weight and shoot length were also reduced. 1000-grain and shoot length of mung bean in conventional irrigation were 11 and 10 percent higher than those of partial root zone irrigation, respectively. Conclusion: Intercropping had no significant effect on seed quality of mung bean. However, deficit of irrigation reduced its seed quality. For harvesting high quality seeds in mung bean, there is a need for plants that experience no drought stress. That the time of reaching the maximum seed quality coincided with the ending of the seed filling period confirms the Harington’s hypothesis.