Investigation the Effect of Water Stress, Different Levels of Nitrogen Fertilizer and Plant Density on Grain Yield and Water Productivity of Proso Millet for Arid Climate of Kashmar

Millet (Pennisetum glaucum L.) is one the conventional cereals in arid and semi-arid areas of tropical regions. Environmental stresses such as drought stress is one of the important factors restricting the plant growth in the most regions of the world and preventing from obtaining the potential yield of crop plants. Deficit irrigation is a suitable method for achieving economic and acceptable yield using the consumption of minimum volume of irrigation water. Nitrogen is one the most important nutrients for production systems of crop plants. Some studies reveal that the higher water productivity can be obtained by fertilizer consumption. According to the shortage of water resources in arid region of Kashmar and to attention of this point that many people in this region are occupied to agriculture and livestock, the necessity of appropriate water resources management in planting of millet is not avoidable. To this purpose, the objective of this study was to investigate the grain yield and water productivity of proso millet under deficit irrigation conditions and consumption of different levels of nitrogen fertilizer. A field experiment including four irrigation regimes, three nitrogen fertilizer levels and two plant densities, was conducted based on completely randomized block design as split-split plot with three replications in Agricultural Research and Natural Resources Center of Kashmar, during 2018. The irrigation treatments were full irrigation providing 100% irrigation water requirement and deficit irrigation treatments providing 40, 60 and 80% irrigation water requirement as main plots; fertilizer treatments including 0, 50 and 100 kg/hanet nitrogen as sub plots; and plant density treatments including 10 and 20 plant/m2 as sub-sub plots. Each plot including six rows plant sowing had 5 m length and 50 cm spacing. There were two rows no sowing as spacing between sub main plots. A 3 m distance was considered as space between main plots. For computing of crop water requirement, moisture changes in root zone was used. The soil water content was measured daily, using TDR. The net irrigation requirement for full irrigation was determined by following relation: ( ) Where, In: net irrigation requirement (mm), θ Fc water content at field capacity, θi: soil water content before irrigation event, and Dr: root development depth (mm). The irrigation water volume for each plot was measured using counter. There was no effective rainfall during the growth period. The plant height, yield and yield components including grain yield and 1000-grain weight were measured and results’ analysis was done by SPSS software.Variance analysis of results showed that interaction among irrigation regimes, different levels of nitrogen fertilizer and plant density was significant at the level of 1% on plant height, 1000-grain yield, grain yield, harvest index and water productivity. The results showed that applying deficit irrigation caused a significant decrease in plant height, 1000-grain weight, grain yield and water productivity at 1% probability level. The grain yield for full irrigation treatment compared to 80, 60 and 40% irrigation water requirement was 17, 31.6 and 47.8% higher, respectively. In all irrigation treatments, the consumption of 100 kg/ha nitrogen fertilizer increased the grain yield significantly in comparison with the same treatments with no use of nitrogen fertilizer. The maximum amount of grain yield was 2259 kg/ha for full irrigation, 100 kg/ha nitrogen fertilizer and 10 plant/m2 treatment. For 80 and 40% irrigation water requirement treatments and 100 kg/ha nitrogen fertilizer level, increasing the plant density from 10 to 20 plant/m2 , decreased the grain yield 5.6 and 6.3%, respectively. The minimum and maximum amounts of water productivity were 0.56 and 0.8 kg/m3, in 40 and 100% water irrigation requirement treatment, respectively. The consumption of 100 kg/ha nitrogen fertilizer increased the water productivity significantly in all irrigation treatments in contrast to no use of nitrogen fertilizer. The amount of increase in water productivity for 100 and 80, 60 and 40% water irrigation requirement treatments was 16.2, 5.8, 6.2 and 8.4%, respectively. The harvest index for irrigation treatments of 100, 80 and 60% irrigation water requirement had no significant difference at the level of 5%. The maximum and minimum harvest indices were determined in 100 and 40% irrigation water requirement treatments, respectively. Based on the results obtained from this research, it can be stated that providing 100% irrigation water requirement, consumption of 100 kg/ha nitrogen fertilizer and plant density of 10 plant/m2 is recommended for Proso millet in Kashmar region.