Effect of supplemental irrigation and splitting nitrogen on quantity and quality of mung bean (Vigna radiata L.)

Introduction Pulses in farming systems have a special role in the world. They use in some developing countries as a source of protein. Mung bean as a pulse crop has more protein than cereals and have important role in nutrition of low-income people in developing countries. Drought stress can reduce photosynthesis and production of mung bean. Nitrogen is an important factor for regulating of plant growth and suitable production. Therefore, it is necessary to use 15 to 30 kg ha-1 nitrogen in planting time. This study was conducted to determine the effect of supplemental irrigation and split nitrogen on yield, yield components and protein yield and suitable treatment. Materials and Methods In order to study effect of supplemental irrigation and split nitrogen on quantity and quality of mung bean (Vigna radiata L.), a split plot experiment based on Randomized Complete Block Design was conducted with three replications at research farm of Gonbad Kavous University during 2016. In this study the line of VC-1973 a mung bean was used. The main factor was supplemental irrigation at four levels of once irrigation (before flowering= I1), Twice irrigation (before flowering+ flowering= I2), three irrigation (before flowering+ flowering+ filling the first pod= I3), four irrigation (before flowering+ flowering+ filling the first pod+ yellowing of the first pod= I4) and the sub factor was split nitrogen in four levels including non application of nitrogen (N0), use of 25% nitrogen in planting time and 75% before flowering (N1), 50% in planting time and 50% before flowering (N2) 75% in planting time and 25% before flowering (N3). To measuring of parameters, 10 plants randomly were selected and number of pods per plant, number of seeds per pod, number of seeds per plant, 1000- seed weight, seed yield, harvest index, protein percent, protein yield and potassium percent were determined. Results and discussion Results showed that effect of supplemental irrigation on number of pods per plant, number of seeds per pod, number of seeds per plant, seed yield, protein yield and potassium percent at p≤0.01 and on harvest index, protein percent and 1000- seed weight at p≤0.05 were significant. Effect of nitrogen on number of pods per plant, number of seeds per pod, number of seeds per plant, harvest index, seed yield, protein yield and potassium percent at p≤0.01 and 1000- seed weight at p≤0.05 were significant. Interaction of nitrogen × supplemental irrigation was not significant about any traits. One time irrigation produced 568.6 kg ha-1. Seed yield in two, three and four irrigation was 836.2, 1028 and 1169 kg ha-1, respectively. By increasing of irrigation, protein content was decreased while protein yield was increased. The highest yield was obtained from consumption of 25% N in sowing date and 75% before flowering with 1175 kg ha-1 and the lowest belonged to none application of nitrogen with 647.3 kg ha-1. Conclusion The study showed that four times irrigation (before flowering+ flowering+ filling the first pod+ yellowing of the first pod) produced the maximum seed and protein yield with 1169 and 275.1 kg ha-1, respectively and the minimum of them belonged to one time irrigation with 568.6 and 140.6 kg ha-1. Traits of harvest index and protein percent in once irrigation (before flowering) was greater than other treatments. The highest seed and protein yield with 1175 and 279.6 kg ha-1, respectively was obtained by application of 25% nitrogen at planting time and 75% before flowering stage while the minimum of them belonged to treatment of none application of nitrogen with 647.3 and 153.8 kg ha-1, respectively. Increasing of seeds per plant and seed weight with increasing of irrigation times and nitrogen consumption, seed yield and protein yield was increased.