Role of Potash Fertilization in Reduction of Water Stress in Growth and Yield of Mungbean (Vigna radiata L.)

Abstract

A field experiment was conducted during two autumn seasons of 2012 and 2013 in Al-Anbar province to determine the actual consumptive use by mungbean crop (Vigna radiata L.) under water stress conditions and potassium fertilizer, as well as the assessment of crop and field water use efficiency, growth and yield of mungbean. Four treatments of irrigation were used: I1, irrigation at 50% depletion of available water (control); I2 irrigation at %25 of control used; I3 irrigation at %50 of control used and I4 irrigation at %75 of control used and three levels of potassium fertilizer were: 40, 80 and 120 kg. ha-1 in the form of K2SO4 (41.5 %K), they were termed as K1, K2 and K3, respectively, in addition to the control (K0). A split plot in randomized complete block design was used with three replications to do this experiment. Treatments of irrigation were used as main plots while potassium fertilizer levels were used as sub-plot. A local cultivar of mungbean seeds were planted, depth and date of irrigation were determined according to the soil moisture consumed and plant roots depth. The main results were as follows: 1. The actual water consumption (ETa) of mungbean was differed with irrigation and potassium fertilization treatments. The least average of ETa was in I4 treatment irrigation (220.02 and 183.53 mm.season-1) for the two seasons, respectively. While the least average of ETa was in K3 treatment (298.49 and 252.72 mm.season-1) for the two seasons, respectively. 2. The treatment of I2 was superior in having the highest average of crop water use efficiency (3.02 and 3.01 kg.ha-1 mm-1) and field water use efficiency (2.94 and 2.94 kg.ha-1 mm-1 ) for the two seasons, respectively. K3 treatment was also superior in crop water use efficiency (2.87, 2.79) kg.ha-1 mm-1 and field water use efficiency (2.2.78 and 2.72 kg.ha-1 mm-1 ) for the two seasons, respectively. 3. Results showed no significant difference between I1 treatment(control) and I2 treatment (%25 of control) concerning (plant height, number of branches per plant, number of leaves per plant, leaf area, leaf area index, leaf content of chlorophyll, average of crop growth and relative water content in leaves for two seasons. While K3 treatment showed its superiority for all studied traits in the two seasons and it was not significantly different from K2 in the leaves area of the first season and each of number of branches, number of leaves. Plant-1 and chlorophyll content of the second season. 4. The treatment of I1 achieved the highest values yield and its components (number of pod per plant, pod length, number of seeds per pod, 100 seeds weight and seed yield) which were 35.26 and 33.83 pods. plant-1, 7.49 and 7.41 cm, 7.35 and 6.62 seed. pod-1, 100-seed weight 4.07 and 3.78 gm and 1080.10 and 909.80 kg. ha-1 for the two seasons respectively. It was not significantly different from I2 indicating the possibility of saving 9.67-14.78% of complete irrigation needs without significant reduction in seed yield when irrigation with 25% of the control treatment which gave 1047.1and 881.6 kg.ha-1 in both seasons respectively. The treatment of K3 achieved the highest values of yield and its components for the two seasons. 5. Irrigation treatments I1 and I2 showed the superiority in the absorption amount of potassium by plant and seeds without significant difference between them for the two seasons. The treatment of K3 was better than other treatments concerning absorption amount of potassium by plant and seeds for the two seasons. 6. Proline content in leaves was decreased to 0.98 and 1.03 ml mol.gm-1 in the I1 treatment, but it was increased to reach 1.27 and 1.87 ml mol.gm-1 in the I4 treatment for two seasons respectively, while it was significantly decreased from 1.15 and 1.66 ml mol.gm-1 for control (K0) to 1.04 and 1.22 ml mol.gm-1 for K3 treatment. 7. Irrigation treatments I1 and I2 was characterized by the highest protein yield in mungbean seed without significant difference between them (218.20 and 174.30 kg.ha-1) in I1 treatment and (214.70 and 171.90 kg.ha-1) in I2 treatment for the two seasons respectively. K3 treatment significantly gave the highest protein yield (194.30 and 153.50 kg.ha-1) for both seasons. 8. Interaction of treatments I1K3, I2K3 and I1K2 showed their superiority in for all studied traits without significant differences among them except the proline content in leaves and protein percentage, which were superior in treatment I4K0 (for proline content) and I3K3 (for protein percentage).