The effect of superabsorbent and iron and zinc foliar application on antioxidant enzyme activity and yield maize (S.C.704) (Zea mays L.) under irrigation regimes

Maize (Zea mays L.) is one of the most important cereal grains that is cultivated in more than 180 million hectares, and its production is over 1000 million tons. The occurrence of water stress causes metabolic disorders in plant cells, such as the increase in the production of active forms of oxygen such as radical superoxide, hydrogen peroxide and radical hydroxyl as one of the major factors in metabolic abnormalities in the cell. Plants against oxidative stress induced, efficient defense system that can destroy or neutralize free radicals. This defense system includes superoxide dismutase, catalase and ascorbate peroxidase. Correct management practices and the application of advanced techniques to maintain moisture storage and increase water holding capacity are effective measures to increase the efficiency of irrigation and thus improve the utilization of water resources. One of the new methods for increasing irrigation efficiency is the use of superabsorbents. Superabsorbent polymers can absorb large amounts of water or aqueous solutions and swell. These water storage tanks, when placed in the soil, absorb irrigation water and rainfall and prevent it from quenching. After the environment is dry, the water inside the polymer is gradually evacuated, and thus the soil for a period of Long and no need to re-irrigate, it's moisturizing, it also increases the impact of plant and nutrients, and, on average, reduces phosphorus losses by 84 percent, reducing nitrogen to 83 percent. Therefore, the purpose of this study was to investigate the effect of iron, zinc, and superabsorbent application of water deficit stress on quantitative yield and corn antioxidant enzymes activity in Shushtar climate.

This research was carried out in two years between 2016-2017 and 2017-2018 in a farm located in Shushtar with a longitude 48 degrees and 49 minutes east and a latitude 32 degrees and 14 minutes north and a height of 110 meters from the sea level. The experiment was carried out as split split plot in a randomized complete block design with three replications. The main factor was irrigation regime with three levels (irrigation after 30, 40 and 50% field capacity depletion, respectively). Sub-factor was composed of twolevels of polyurethane foam (super-adsorbent, 0 and 200 kg ha-1) and sub-subplots including spraying of nutrients with four levels [control (water), iron spraying, zinc spraying and spraying Iron + zinc].

Combined analysis of variance showed that the effect of water deficit and superabsorbent stress on grain yield, 1000 grain weight, number of grain per ear, catalase enzyme and supraoxydisodium were significant. In dehydration conditions, grain yield, number of seeds per ear and ascorbate peroxidase decreased, but the activity of catalase and superoxide dismutase enzymes increased. On the other hand interaction of dehydration and superabsorbent stress was significant on grain yield. The highest grain yield (8530.6 kg ha-1) was attributed to irrigation after 40% capacity utilization and application of 200 kg/ha superabsorbent. Spray application of iron and zinc resulted in increased grain yield, number of seeds per ear, catalase and superoxide dismutase.

Overall, the results showed that foliar application of micronutrients and superabsorbent important role in the growth and development of corn plants as well as the fact that the highest values of grain yield and activities of antioxidant enzymes of fertilizer zinc and iron from micro-nutrients are, It can be concluded that using such fertilizers can provide the best conditions for obtaining maximum yield and biochemical traits in corn. On the other hand, iron and zinc micronutrient spraying caused a decrease of 45% damage caused by water deficit stress on grain yield. The superabsorbent effect is also more pronounced in lower moisture content. The application of superabsorbent hydrogels in the soil increased plant yield and saved water consumption, therefore the use of this substance in less water can be effective in increasing the yield and reducing the adverse effects of stress in conditions of water shortage. Therefore, according to the results obtained in irrigation conditions after discharge of 40% of the crop capacity, the application of polyester absorbent and micronutrient application of iron and zinc improved seed yield and biochemical traits of corn.