Effect of bio and chemical fertilizers on some physiological traits of maize (Zea mays L.) under drought stress

Introduction Water deficit stress is an abiotic stress that seriously affects crop production in more parts of the world. Drought stress affects growth and yield of plants in different ways. A wide range of molecular disorders stress can result from the production of reactive and destructive oxygen species (ROS) that lead to physiological damage to plants under drought. These radicals lead to the reactions that destroy the DNA, fat peroxidation, membrane proteins and Macro proteins including photosynthetic pigments and enzymes. The activity of the anti-oxidant enzymes in plant cells is often increased when the plant is encountered with environmental stress, and from this way the plants would be to reduce the damages due to oxygen free radical production. Considering the increasing drought stress in arid and semi-arid regions and with regard to the importance of providing the food need of the growing population of the world, finding the ways to reduce the effects of drought stress on plant growth and yield is very important. Proper nutrition and supply of required nutrients of the plant through the use of bio-fertilizers along with the chemical fertilizers application, would reduce the use of chemical fertilizers and environmental impacts caused by the excessive use of these fertilizers, because the positive effects of microorganisms in biological fertilizers can be considered as a strategy to reduce the effects of stress on growth and yield of crops. This research was conducted, in order to study the effect of bio and chemical fertilizers application on some physiological traits and grain yield in maize in order to reduce of drought stress effects on grain yield of maize and reduce the chemical fertilizers. Materials and methods This experiment was conducted in research farm of university of Kurdistan in 2012. The research was arranged in split-plot based on a randomized complete block design with three replications. In this experiment, irrigation levels including full irrigation and drought stress in flowering stage allocated to main plots, and fertilizer levels (100% chemical fertilizer, 100% chemical fertilizer + micronutrients, biosuperphosphate + nitroxin, biosuperphosphate + nitroxin + micronutrients, 50% chemical fertilizer + biosuperphosphate, 50% chemical fertilizer + biosopperphosphate + nitroxin and control without fertilizer) were assigned to sub plots. In this study, the Mv500 corn hybrid was sown. The traits studied in present study were: chlorophyll content of leaf, hydrogen peroxide (H2O2), membrane lipid peroxidation, proline content, activity of catalase and peroxidase enzymes. The content of leaf chlorophyll was measured by the Arnon (1949) method, and the amount of hydrogen peroxide was determined by the Loreto and Velikova (2001) method. Measurement of malondialdehyde was performed using the Cakmak and Horst (1991) Method. Proline content was measured by the Bates et al. (1973) method, and the activity of catalase enzyme was determined using the Chance and Maehly (1995) method. The activity of peroxidase enzyme was also measured by the Mac Adam et al. (1992) method. For analyzing variance of data and means comparison, MSTAT-C software was used and the means comparison was done by the Duncan test procedure. Also the charts were drawn using Excel software.  Results and discussion The study results showed that water deficit stress increased antioxidant enzymes activities, while bio-fertilizers and micronutrients elements reduced the enzymes activities. Water deficit stress reduced the leaf chlorophyll content, but the proline concentration, malondialdehyde (MDA) and hydrogen peroxide were significantly increased in response to the stress. Application of bio and chemical fertilizers partly prevented from decreasing leaf chlorophyll content and increasing hydrogen peroxide induced by drought stress and could largely moderated the effects of drought stress on grain yield of corn. The lowest grain yield was obtained in non-fertilized condition, which was significantly less than other fertilizer treatments. Consumption of fertilizers caused a significant increase in grain yield in drought stress condition, and although the highest grain yield (7840 kg ha-1) was obtained in corn treated with 100% chemical fertilizer + micronutrient, which significantly had more yield than other treatments, but using bio fertilizers alone or along with 50% chemical fertilizers, significantly increased grain yield under drought stress condition. Conclusion Application of bio and chemical fertilizers could increased resistance of corn plant to drought stress and recovered its yield through supply of nutrients required by the plant. Therefore the correct using fertilizers can be considered as a way for decreasing and moderating the drought stress effects on crop yield.