Effect of green manure on the soil organic matter and nitrogen

To investigate the effect of plant residues in increment of soil organic matter and nitrogen, a randomized complete block design (RBCD) with 4 replications using 10 different plant species was carried out in 2009. The studied plants belonged to three families including Gramineae (Sorghum bicolor, Panicum miliaceum and Avena sativa), Brasicaceae (Eruca sativa) and Leguminoseae (Trifolium pratense, T. repens, T. alexandrinum, Onobrychis viciaefolia, Vicia sativa and V. peregrine). According to the results, the highest increment in the organic carbon quantity (1.59%) has been derived by applying sorghum green residues. The total amount of soil nitrogen was significantly increased by applying all plants at the different sampling periods. The highest soil nitrogen content (0.23 %) was observed in white clover plant after five month incorporation. Incorporation of white clover and vetch residues showed considerable mineral nitrogen (N-NO3-) in corresponding soils which was high in white clover compared to vetch plots. In conclusion, white clover due to low soil C:N ratio, increasing of usable total and mineral nitrogen for subsequent plant, is introduced as proper green manure among studied plants.