Investigating the effect of deficit irrigation on yield and water productivity of silage maize under pulsed and continuous drip irrigation management

Using of drip irrigation systems in order to manage water consumption and increase irrigation water productivity is important in the absence of water resources. As water scarcity is a limiting factor in agricultural production, an accurate irrigation scheduling and management is necessary to increase water productivity and crop yield. Recently, a new technology called a pulsed management has been used in drip irrigation systems. Pulse irrigation management consists of a series of irrigation cycles with On-Off phases that these cycles will continue until the entire water required by the plant enters to the field. In order to investigate the effect of deficit irrigation on yield and water productivity of silage maize under pulsed and continuous management in a drip irrigation system, an experiment in the form of split strip plots based on a randomized complete block design with three replications was implemented in Varamin region in 2019. The aim of this study was to compare the water productivity and yield of silage maize under a surface drip irrigation system with pulsed and continuous flow.

Three irrigation levels include two deficit irrigation treatment and one full irrigation treatment were examined under two pulsed and continuous irrigation management. The main factor included three irrigation levels, applying 100, 80 and 60% of crop water requirement (W1, W2 and W3, respectively) and the sub-factor included two drip irrigation managements, pulsed (P) and continuous (C) in a drip irrigation system. The silage maize hybrid ZP 606 cultivar with a comparative maturity of 93 to 95 days was sowed at a depth of 5 cm with Pneumatic seeding machine. The replications were separated by 2 m to ensure that the treatments in plots were independent to each other. The linear plant density was 12.4 plants m-1, which is equivalent to 124,000 plants per ha. The space between plants was 11.5 cm. In full irrigation treatment, irrigation depth was determined based on bringing the soil moisture to the field capacity and other treatments received a coefficient of that treatment. The soil moisture content was measured using the PR2 profile probe instrument (Delta-T Devices, Cambridge, UK) that was calibrated in the field experiment. The access tubes of the profile probe installed in the middle of the maize twin rows beneath the emitter up to the 100 cm depth of the soil. The plant height, biological yield were measured at the end of the growing season and then water productivity was calculated. The statistical analysis of the results was done using SAS software to determine the best combination of factors for optimizing water productivity and crop yield.

The amount of irrigation water used in W1, W2 and W3 treatments was 405, 340, 275 mm, respectively. The results showed that the application of different irrigation levels had a significant effect on plant growth indicators, crop yield and water productivity. The effect of irrigation management on these parameters was also significant. Based on the obtained results, the highest biological yield of silage maize was related to PW1 treatment (25 ton/ha) and the highest irrigation water productivity was obtained in PW2 treatment (6.72 kg/m3) with a 25% and 35% increase compared to continuous full irrigation treatment, respectively. The application of pulsed management in W2 irrigation treatment (applying 80% of crop water requirement) compared to full irrigation treatment with continuous management, water productivity increased by 34.93%. The results also showed that in intensive deficit irrigation treatment, W3 (applying 60% of crop water requirement) applying pulsed management had an adverse effect on product growth and yield parameters, so that in this treatment, biological yield declined by 23.28% compared to continuous management treatment. The highest plant height was 285 cm related to PW1 treatment that has 4.5% increase compared to CW1 treatment. The overall results of this study showed that by applying pulsed management in deficit irrigation conditions, applying 80% of the crop water requirement while saving water consumption, the water productivity can be increased by about 35% without significant reduction in crop yield. The lowest plant height was 172 cm in PW3 treatment. According to the statistical analysis of irrigation water productivity, in areas with similar climatic condition and limited water resources in order to save 20% of irrigation water, PW2 treatment was recommended in silage maize planting.