Effect of biological and chemical nitrogen sources on yield and yield components of corn (Zea mays L.)

One of the most important aspects of crop management is the supply of nutrients through the use of fertilizers to increase the quality and quantity of yield. Nitrogen is one of the most widely used chemical fertilizers and its deficiency limits the quality and quantity of plants yield more than other nutrients. In the past half century the consumption of chemical fertilizers increased the yield of many products, but due to the high consumption of fertilizers decreased environmental stability. In sustainable agriculture, attention to bio-fertilizers as an alternative to chemical fertilizers has been suggested as an approach to increase soil fertility. Azotobacter and Nitrokara are two bio-fertilizers containing many microorganisms. Therefore, considering the importance of biological and chemical nitrogen sources effects on yield and yield components of corn, this experiment was conducted to determine the effect of these sources on yield, yield components and qualitative yield of corn.

This experiment was carried out in a split plot arrangement in a randomized complete block design with three replications in summer 2017. The treatments consisted of chemical fertilizer nitrogen at three levels of zero, 60 and 120 kg.h-1 of pure nitrogen from urea source allocated to the main plots and three nitrogen bio-fertilizers including Azotobacter, Nitrokara and non-biofertilizer application were assigned to the sub plots. In this experiment, 30 ton.ha-1 sugarcane compost was used to supply some of the nutrients requied by the crop. 50 percent of chemical fertilizer nitrogen was applied at sowing and remaining nitrogen was applied at 4 to 6 leaf stages of crop growth. The first irrigation was done after seed sowing. Azotobacter biofertilizer from Green Biotechnology Company and Nitrokara from Kara Biotechnology Company were used as spraying on the seeds before planting. According to the recommendation of the producers, the amount of Nitrokara and Azotobacter biofertilizers were considered as 500 ml.ha-1 and 100 g.ha-1, respectively. The corn cultivar of S.C 703 was used in this study. The cultivation was under furrow and ridge method. Planting was done on top of ridges. The row to row spacing was 75cm, with plant spacing of 20 cm.

The results showed that chemical fertilizer had a significant effect at the probability level of 5% on number of rows per ear and on other studied traits including number of kernels per row, 1000- kernel weight, grain yield, biological yield, harvest index and protein percentage had a significant effect at the probability level of 1%. The effect of bio-fertilizers on all studied traits were significant at the 1% probability level. The effect of interaction between nitrogen bio-fertilizers and chemical fertilizer on 1000-kernel weight and protein percentage was significant at the 1% probability level and on grain yield was significant at the 5% probability level. However, it was not found to be significant on other traits. The average maximum grain yield (7228 kg.ha-1) and protein percentage (9.9%) were obtained from 120 kg.ha-1 nitrogen fertilizer and Nitrokara fertilizer, respectively, which show no statistically significant difference with those of the combined application of of 120 kg.ha-1 of chemical fertilizer nitrogen and bio-fertilizer of Azotobacter and the average minimum grain yield and protein percentage by 4726 kg.ha-1 and 7% were obtained under no consumption of chemical fertilizer nitrogen and bio-fertilizer (control), respectively.

In general, the results of this experiment showed that under application of sugarcane compost, either chemical or biological nitrogen, the quantitative and qualitative yields of maize were increased and the greatest effect was observed with the consumption of 120 kg.ha-1 nitrogen fertilizer in combination with Nitrokara fertilizer or Azotobacter fertilizer. This was probably due to the lack of nutrients in the soil and not enough time to decompose sugarcane compost for release and absorb the elements.