The Effect of Nitrogen Fertilizer and Faba Bean Density in Rotation, on Maize Nitrogen Use Efficiency under No-till System

Introduction

Sustainable agriculture is necessary to tackling environment pollutions whilst protecting food security and reducing dependence to fossil fuels. Conservative agriculture is a sustainable system for crop production which improves crops production. No-till system is one of the methods of Conservative agriculture which decreases greenhouse gas emissions and soil erosion. Mulching is also one of the other methods of conservation agriculture which covers the soil surface with varied covering materials and decreases moisture losses and increases crops yield. Nitrogen is an essential element for plant and its deficiency causes plants growth and yield reduction. Grain legumes are a great source of protein for humans and livestock and recommended in areas under common agricultural systems within ecological focus. These crops have also the ability of biological nitrogen fixation through symbiotic bacteria with their roots, finally, produced nitrogen returns to the soil and reduces the nitrogen fertilizer demand for subsequent plants. However, only a fraction of nitrogen in their biomass will be available for the following crop. It is estimated that 41 to 50% of nitrogen fertilizer applied to Maize (Zea mays L.) has been lost to the environment. Thus, this experiment was conducted to evaluate the effects of faba bean cover crop-rotation on forage corn.Materials and MethodsIn order to study the effects of faba bean in rotation with corn, a field experiment was conducted in two growing seasons (2018-2019) at the research farm of the Agriculture and Natural Resources Faculty, University of Mohaghegh Ardabili, located in Babolan village, Ardebil, Iran. Experimental treatments included faba bean densities (25, 35, 40, and 80 plants per square meter) and different levels of nitrogen fertilizer in forage corn (0, 100, 200 and 300 kg ha-1). A local small-seeded variety of faba bean was used in this experiment and 80000 plants ha-1 -of corn- Single cross hybrid (201). Nitrogen fertilizer was applied as urea at the V5 stage of corn development by top dressing (in three stages). At maturity stage of faba bean, samples were taken by 0.5 × 0.5m quadrat for each plot. Grain yield was determined by harvesting seeds and dried in oven 65°C for 48 h and weighted by digital scale (0.01 g). Three plant of corn were cut randomly in each plot, thereafter were weighed to determine fresh forage yield. Shoot were dried in oven 75°C for 72 h and weighted for dry matter calculation (data converted to hectare). Statistical analysis of the data was performed by using of SAS software (version 9.4). Also, significant difference between the treatment means were tested with Duncan's Multiple Range Test at P<0.05.

Results indicated significant effects of faba bean plant densities on most of the traits. The maximum fresh and dry grain weight were obtained from densities of 80 and 40 plant per m2. Also, the maximum grain nitrogen and grain crude protein were observed from 25 plants per m2. 40 plant of faba bean per m2 had the highest amount of seed dry matter, protein yield, protein harvest index, and productivity effort. Also, results of interaction effects showed that various densities of faba bean and different levels of nitrogen fertilizer had significant effect on forage corn. So that, the maximum dry matter yield and production efficiency was obtained from 40 plant of faba bean per m2 and application of 200 kg niterogen per ha-1. 35 plant of faba bean per m2 without application of nitrogen fertilizer had the highest amount of nitrogen utilization efficiency.

Totally, results showed that faba bean rotation with corn could be a suitable alternative method for mono-cropped maize with high utilization of nitrogen fertilizer (density of 40 plant per m2 of faba bean and application of 200 kg nitrogen per ha is recommended).