Evaluation of Yield and Yield Components of Red Beans Under Irrigation Cycle and Nitrogen Fertilizer

Abstract
To investigate the effect of irrigation frequency and nitrogen fertilizer on the yield of two red bean genotypes, an experiment was carried out in the form of factorial split plots of completely randomized blocks with four replications at the research field of University of Tehran in 2016. The main factor included the irrigation cycle (7 days customary in the region, once every 11 and 15 days), nitrogen fertilizer required by the plant (zero or control, 50% and 100% nitrogen) and red bean cultivars (Akhtar and D81083) as sub-plots. The results showed that the irrigation cycle significantly decreased plant height, number of pods per plant, number of seeds per pod, kernel weight, biological yield, seed yield and harvest index. The use of nitrogen fertilizer also significantly increased the values of other traits except the number of seeds per pod. Akhtar cultivar had the highest plant height and total dry matter, while the highest seed and biological yield was observed in D81083 line. The interaction of irrigation cycle and nitrogen fertilizer on 100 seed weight and harvest index was significant. The highest water consumption efficiency (0.44 kg/m3) was obtained in the 7-day irrigation treatment with 100% nitrogen fertilizer in D81083 genotype, but the highest nitrogen consumption efficiency was obtained in 50% nitrogen fertilizer (12.5 kg seeds per fertilizer unit) and in higher nitrogen consumption, despite the noticeable increase in grain yield (3%), nitrogen consumption efficiency decreased by about 41% and water consumption efficiency decreased by about 5%.
Introduction
Iran has a dry and semi-arid climate, and water shortage is one of the basic problems of agriculture, and two-thirds of the agricultural lands are located in semi-arid and dry regions. Drought is one of the most destructive environmental stresses that reduces the performance of crops, especially beans, more than other environmental stresses. In an experiment on beans, it is reported that between different levels of nitrogen (zero, 45, 90 and 135 kg of urea per hectare), a significant difference was observed in terms of yield, and with increasing nitrogen application, grain yield per unit area increased. So that the highest seed yield was obtained with an average of 3144 kg. ha^-1 with the consumption of 135 kg and the lowest yield with an average of 1986 kg. ha^-1 with the consumption of 45 kg of urea fertilizer per hectare. The yield difference between different levels of urea was attributed to the effect of nitrogen in increasing the number of pods and the average weight of 1000 seeds. Therefore, considering the importance of the role of drought as one of the most important stresses faced by the plant and its effect on reducing the amount of production, as well as the need to use nitrogen fertilizer for its biological stabilization, in order to achieve acceptable yields, this research was conducted with the aim of It is necessary to identify the effect of different levels of irrigation and nitrogen alone and together on bean yield, to determine the efficiency of water and nitrogen consumption under water stress conditions, and to determine the most important fertilizer treatment required by beans under water stress conditions.
Material and Methods
To investigate the effect of irrigation frequency and different levels of nitrogen fertilizer on the yield and yield components of two genotypes of red bean, an experiment was conducted in the form of factorial split plots in the form of completely randomized blocks with four replications in the research training farm of Tehran University of Agriculture and Natural Resources Campus (Karaj).), was implemented in the crop year 2015. The experimental factors include the irrigation cycle (7 days customary in the region, once every 11 and 15 days) as the main factor, the nitrogen fertilizer required by the plant (zero amount (control), 50% and 100% nitrogen consumption) and red bean varieties (Akhtar and D81083) were considered as sub-plots.
Result and Discussion
In general, the results of this study showed that increasing the frequency of irrigation (more than once every 7 days) significantly led to a decrease in growth traits and finally a decrease in seed yield in red bean cultivars. On the contrary, increasing the use of urea nitrogen fertilizer led to the improvement of growth traits such as the amount of dry matter produced per unit area, harvest index and finally improved the components of yield and grain yield. In addition, in relation to the effect of different levels of nitrogen, the highest grain yield (2777 kg. ha^-1) was obtained in 100% required nitrogen fertilizer, and since the yield corresponding to this treatment with the yield corresponding to 50% nitrogen fertilizer consumption There was no significant difference and due to the fact that the highest agricultural efficiency of nitrogen consumption was obtained at 50% nitrogen and the lowest at 100% nitrogen consumption, also the highest efficiency of nitrogen consumption was obtained in normal irrigation and the lowest of this trait. It was obtained under severe water deficit stress (15-day irrigation cycle). Therefore, in order to reduce environmental damage, it is recommended to use a lower amount of nitrogen fertilizer in the conditions of water shortage stress or drought stress, but in conventional irrigation without stress, it is better than 100% of nitrogen fertilizer required by the plant to achieve a higher harvest index. be used. In relation to the comparison of red bean cultivars, it was observed that the D81083 line had a higher grain yield (2729 kg. ha^-1) than the Akhtar variety (2514 kg. ha^-1), so that the rate of yield reduction and harvest index of the D81083 line under water stress conditions was lower than It was Akhtar's figure. In order to make optimal use of limited water resources, the use of D81083 line seems desirable for cultivation in similar conditions in this region due to its earlier maturity and higher dry matter production.