Investigating the Possibility of Increasing Effectiveness of Different Levels of Nitrogen and Phosphorus Fertilizers by Changing the Planting Date of MungBean Green Manure in Autumn Wheat Cultivation

Although the use of green Fertilizers can supply nutrients and improve the soil but they are not able to meet all nutritional needs of plants. Therefore, it seems that the combination of such Fertilizers and the reduced amounts of mineral fertilizers not only meets the nutritional needs of plants but also increases the soil organic matter and improves its physical and chemical properties. Mung bean (Vigna Radiata) is a crop that belongs to the legumes family which is capable of biological nitrogen fixation and is cultivated as the green manure in some of tropical regions. The purpose of this study was to investigate the possibility of increasing the effectiveness of different levels of nitrogen and phosphorus fertilizers by changing the planting date of mung bean green Fertilizer on yield and yield components and the economic benefits of wheat cultivation.

For this purpose, an experiment was implemented in 3years in the north of Khuzestan in Iran as a factorial split plot design in a randomized complete block design with three replications. Chamran cultivar (wheat) as the main crop was planted with a pneumatic machine every year on December 6 and was harvested manually in the final ripening stage. Mung bean (Omrani cultivar) was used as green fertilizer. The mung bean was returned to a depth of 15 cm by a tractor rotator in the middle of the flowering stage (55days after planting). Two dates of mung bean planting (July12 and August19) along with fallow plot were contemplated as the main factor. Also (nitrogen fertilizer application) at three levels (0, 60, 120 kg/ha) and phosphorus fertilizer at three levels (0, 45, 90 kg/ha) were considered in sub-plots.Total nitrogen in seeds and straw was determined by Kjeldahl method, phosphorus by chlorometric method, potassium with Flam photometry. Heavy metal values were determined by the atomic absorption method in soil and plant samples by AAS1 device. Total nitrogen in soil samples was determined by Kjeldahl, phosphorus by Olsen method, potassium with FELIM photometer, pH by the potentiometer, electrical conductivity by Richards’s method, organic carbon with Mehlich method, Humus withValky-Balka, soil texture with the titration method, NO3- and NH4 +, by Thiurine-Cononova.

The results showed that the use of mung beans as a green fertilizer increases the amount of organic matter and minerals in the soil. The effect of green manure and interaction of treatments on grain yield was significant at 5% probability level and the effect of phosphorus and nitrogen treatments on this trait was significant at 1% probability level. Planting mung bean as green fertilizer on 12July due to increasing the number of seeds per unit and biological yield increased wheat grain yield compared to fallow conditions. Delay in the planting date of mung bean green reduced its beneficial effects on grain yield. The highest grain yield was obtained in the treatment of 120 kg nitrogen and 90 kg phosphorus from mung bean planting on 12July. The highest final economic benefit pertained to the treatment of 120 kg nitrogen + 90 kg phosphorus on planting on 12July.

The results showed that planting mung bean as green fertilizer increased wheat grain yield compared to fallow conditions. The use of mung bean on different dates as a green fertilizer is considered an important ecological factor in the process of increasing the content of organic matter and main nutrients (N,P2O5) in the soil, as well as reducing the types of moving heavy metals. It seems that using green and mineral fertilizers simultaneously increases the absorption of mineral fertilizers and also increases the use of wheat from the nutrients in green manures.