Evaluation of the effect of low irrigation levels on the quantitative and qualitative traits of different maize hybrids forage in the climatic conditions of Gorgan

Maize cultivation is rapidly expanding in the world due to its high adaptability to different weather conditions, and it is an exceptional product that can be effectively used as feed and forage products to meet the ever-increasing needs of livestock. Low irrigation is an approach to increase water productivity with the view of increasing production per unit of water consumption. The research results show that water stress has a significant effect on the quantity and quality of forage. Lack of water is one of the important factors in reducing the level of corn, so this experiment was conducted in order to check the possibility of saving water consumption by using low irrigation method and choosing the best hybrid in low irrigation conditions.

In order to investigate the effects of low irrigation and different maize hybrids on the quantitative and qualitative traits of maize forage in the Gorgan region, an experiment was conducted in split plots arranged in a randomized complete block design with three replications in the Iraqi station of the Gorgan. Low irrigation was implemented in four levels in the main plots (100, 75, 50% and 25% of water requirement) and subplots in four levels (including hybrids SC703, SC704, ZP548 and BK50). To determine the amount of water consumption three days after each irrigation, the amount of moisture was determined by sampling the soil and immediately after reaching 40 to 60% usable moisture, irrigation was done. Irrigation was done as a drip using tapes, the distance between the nozzles was 20 cm and the amount of water output per nozzle was 2 liters per hour. Harvesting was done from the two middle lines by removing half a meter at the beginning of the row and weighed separately (leaf, stem, cob) in a separate laboratory, and their fresh weight was recorded and then placed in an oven with a temperature of 65 degrees Celsius for 72 hours, Then the dry weight was calculated. The samples of dry forage were sent to the laboratory of Forests and Ranges Organization (Tehran) and the amount of protein, fiber and other quality attributes of forage were measured by infrared spectrometry with PertenInformatic 8620. The data were analyzed using SAS 9.1.3 statistical software and the means were compared with the LSD test at the 5% probability level.

The results of analysis of variance showed that low irrigation effect was significant on all studied traits. Also, the effect of the studied hybrids on all the traits was significant except for insoluble fibers in acidic detergent and water-soluble carbohydrates. Also, the interaction effect of hybrid × low irrigation was significant only on forage yield (Total biomass, ear fresh weight, stem and leaf fresh weight, and total dry weight). The results of means comparison showed that the highest biomass yield was observed in the 100% water demand treatment, which was 7.2, 49, and 79.7% higher than the 75, 50, and 25% irrigation treatments, respectively. However, the highest water consumption efficiency with a significant difference compared to other levels was observed in the treatment of 75% water requirement (5.99 kg m-3). Also, with the increase of irrigation levels, the amount of crude protein, crude fiber, water-soluble carbohydrates and insoluble fibers in the neutral environment increased significantly, and among the studied hybrids, the SC703 hybrid had the highest forage yield (43692.4 kg ha-1).

Considering the shortage and high economic value of water, the reduction in rainfall and the occurrence of successive droughts in recent years, optimum use of water can allocate more land to irrigated cultivation in addition to achieving appropriate and economic performance. The results showed that the lack of water reduces all quantitative traits. Among the studied hybrids, SC703 had the highest forage yield per unit area. On the other hand, low irrigation treatment at the level of 75% of the total water requirement is recommended to achieve the highest water consumption efficiency in Gorgan region.