تأثیر بقایای گیاهی به‌عنوان کود سبز بر معدنی شدن نیتروژن خاک در شرایط تنش خشکی

The incorporation of plant residues in soils of arid and semiarid regions is a major principle of sustainable agriculture. This study was conducted at the research farm of Urmia University (37° 32’N and 45° 5’ E), Urmia, Iran during the 2009 and 2010 growing seasons. Five green manure crops were grown in four replications arranged in a randomized complete block design. The treatments included white clover (T.repens), sainfoin (Onobrychis viciaefolia), pearl millet (Panicum miliaceum), sorghum (Sorghum bicolor) and turnip (Eruca sativa). Changes in soil nutrient elements and nitrogen mineralization were measured during different time periods after plant residues incorporation to soil. The plants were irrigated 50% of field capacity during growing period. The results showed that the total nitrogen and NH4-N were influenced by type of green manure in both years. The lignin and cellulose were the main factors controlling N mineralization and residue decomposition. In the first and second year, the results indicated that pearl millet green residues resulted in the highest amount of soil organic carbon. Nitrate-N content reached the highest amount in sainfoin and white clover. In conclusion, white clover and sainfoin due to increasing total and mineral nitrogen for subsequent plants could be introduced as a proper green manure in water deficit conditions.