Effect of biofertilizers and chemical fertilizers on yield and seed quality of corn under normal irrigation and drought stress conditions

Introduction The area, production and productivity of maize have increased several-fold over the last five decades. In Asia, maize has recorded the fastest annual growth (around 4%), as compared to other cereals. In 2015 with about five million tons of corn, Iran was world’s fifth largest corn importer. Maize is one of the main crops for poultry and livestock feed in Iran. Maize is the number three crop after wheat and rice in terms of area and production and number two, only after wheat in terms of productivity. The average of area in Kermanshah province in recent years has been more than 45,000 hectares. But in 2015 this amount has decreased by 30 thousand hectares, 15580 hectares, which is the main reason for water scarcity in the region. On the other hand application of chemical fertilizers in conventional agriculture severe environmental problems, increased production costs and negative effects on biological cycles causes. The objective of this study was to determine the effect of biofertilizers and chemical fertilizers on yield and yield components of Maize under normal and deficit irrigation condition in western Iran region and looking for the best biological treatments could be applied to the maize to get a high yield in addition to keep our environment clean and safe. Materials and methods Field experiments were conducted for two years (2014 – 2015) at the agricultural research farm, Agricultural and Natural Resources Research Centre in Kermanshah, Iran. In this research, effects of vermicompost and Azotobacter as a boifertilizers and chemical fertilizers on yield and yield components of Maize under normal and deficit irrigation was investigated in two sites. Sites included normal irrigation and deficient irrigation (65% optimum water requirement) and each site was conducted as the factorial split plot in a randomized complete block design with three replications and three factors. Treatments included Azotobacter in the main plots (non-inoculation and inoculation), vermicompost (consuming 0, 2, 4 and 6 ton/ha) and chemical fertilizers included N,P,K in tree levels (100% recommendation based on soil test, 50% recommendation and no fertilizer) in the sub plots. Irrigations were done at 7 day intervals. Irrigation treatments (deficit and adequate irrigation) in the middle phase of growth stage (approximately V6) began. Beginning on these dates, water was applied at weekly intervals based on the amount of evapotranspiration for the previous week as determined by the on-site weather station using a modified version of the Penman FAO equation. Statistical analysis included analysis of variance to compare mean by least significant difference (LSD) by SAS statistical software and graphs were performed by EXCEL. Results The yield of maize was significantly influenced by deficient irrigation; Results showed that during the both research years, grain yield was decreased from 8.2 ton/ha to 4.4 ton/ha by deficient irrigation. Although, application of vermicompost led to increase in grain yield, the highest grain yield was related to integrated treatments 6 ton/h vermicompost and 100% chemical fertilizers recommendation based on soil test. Results also indicated that the use of 6 ton/ha vermicompost and Azotobacter in soil, 50% of the maize fertilizer supplied. The results showed that combined use of bio-fertilizers with chemical fertilizers increased the grain yield. Therefore the uses of biological fertilizers significantly reduce the consumption of chemical fertilizers and reduce the adverse environmental effects. On the other hand from this experiment, application of vermicompost in combination with chemical fertilizers showed better performance than only chemical fertilizers, even in 100% recommendation based on soil test treatments. It can be stated that the increase in growth parameters of maize are due to greater availability of nitrogen in full organic and integrated treatments. In full chemical treatments most of nitrogen would be leached from the soil profile. In addition, high porosity and water holding capacity of vermicompost that helps in better aeration and drainage. Moreover use of 6 ton/ha vermicompost and Azotobacter in treatments with no chemical fertilizers produced 7 and 4.4 ton/ha grain yield in normal and deficit irrigation respectively.