Effect of different types of drip irrigation tapes and different levels of irrigation on yield components of forage maize

The arable land in Iran is about 11 million hectares, and maize production is the second largest after wheat production. Agricultural studies in Iran lands reveal that the water use efficiency of irrigation is between 22.5% and 85.5% with an average of 56%. Drip irrigation is one of the best methods that by applying appropriate management can be used for agriculture in high salinity soils, with saline irrigating water and dry conditions, especially for maize crops. Sprinkler irrigation system has a positive effect on improving irrigation efficiency in Iran, but the main problem of this system is the water loss related to evaporation and wind. Usually, drip irrigation plan is implemented in combination with sprinkler or low-pressure irrigation plan, so that it is possible to change the irrigation network and make an optimal use of the system according to the needs of the cultivation pattern. In the most previous studies, drip irrigation tape was generally used, depending on the type of crop and the growing conditions. Also, limited studies have been conducted on the comparison of irrigation tape types, hence comprehensive studies are needed. Also, study on the interactions of different types of tapes and irrigation levels is needed. The aim of this study was to evaluate the performance and yield components of forage maize under moisture stress. A pilot project was conducted in form of factorial experiment of randomized complete blocks, during one year in Isfahan province. There were 6 treatments consist of emitter tape systems of 15, 20, and 30 cm, and drip tape of 10, 20, and 30 cm with distance of 0.7 m. The treatments of irrigation included 5 levels of 100, 90, 80, 70 and 60% of soil moisture depletion, with 3 replications. The cultivated maize cultivar was Single Cross 704, which was cultivated at 0.7 m intervals. For each treatment repetition of three rows of the same irrigation strip with the length of 50 m was performed. The crops were harvested from the middle row. During the growing season, irrigation was carried out for 22 times based on the measurement of moisture in the root zone and the supply of moisture deficiency to the level of crop capacity in terms of programmed water shortage. For each treatment-repetition, amounts of total product weight, total weight of maize, average plant height, average height of maize, product productivity index and maize productivity index per hectare were calculated at the end of the cultivation season after sampling. The results showed that the main and interaction effects of irrigation tape type and irrigation rate on yield components were significant at 1% probability level. Based on the performance indicators, the best treatment was the emitter tape strip with the 20 cm nozzle-distance, the total crop yield and maize yield of 70112 and 14593 kg/ha, respectively. According to the product performance index, the emitter tape with the diameter of 30 cm and the drip-tape of 30 cm, were the weakest treatments in terms of maize's performance. Wetting widths in heavy-textured soils are wider than in the light-textured soils. Despite the relatively heavy texture in this study, the 30-cm distance between the nozzles in the irrigation strip did not provide adequate overlap in the development of moisture within the plant root zone. Therefore, the irrigation tape with the nozzle distance of 30 cm is not recommended for the cultivation of forage maize in similar conditions of the present field. In terms of irrigation levels, the best result obtained in the treatment of 100% depletion of the moisture capacity of the root area with crop yield and maize yield was 66.5 tons per hectare and 11.3 tons per hectare, respectively. According to the two indicators of plant and maize height, the drip-tape irrigation strip next to the seam with the nozzle distance of 20 cm (with plant and maize height of 19.15 and 19.4 cm, respectively) as well as the 15-cm emitter tape were in the top group. The weakest treatment according to these two indicators was the 30-cm drip tape and then the 30-cm emitter tape treatment. A comparison based on irrigation levels showed that the treatment supply of 100% depletion of moisture capacity of root zone was the superior treatment with the plant and maize height of 179.3 and 15.3 cm, respectively. Also, in terms of maize's height, there is no significant difference between the treatments of 80%, 90% and 100. In terms of water efficiency indicators, the 20-cm drip tape was the best option with crop and crop water productivity of 13.4 and 2.8 kg/m3, respectively. The highest water productivity for the total product and maize occurred in the treatment of 100% and the lowest in the treatment of 60%. Based on the interaction of irrigation tape types and irrigation levels, the superior treatments was that in which the drip tape by 20 cm was applied, 100% of soil moisture was provided, forage yield and water productivity of 81279 kg / ha and 14.2 kg / m3 were obtained, respectively.