Effect of winter cover crops on the dynamics of soil mineral nitrogen and yield and quality of Sudan grass [Sorghum bicolor (L.) Moench].

The experiment was carried out in the Vojvodina province, Serbia between 2004-05 and 2005-06. The objectives of this study were to assess the effect of cover crops grown as green manure on the dynamics of NO3-N in the soil and on the yield and quality of Sudan grass. Three sole cover crops and one mixture were included in the experiment, namely wheat (Triticum aestivum L.), field pea (Pisum sativum L.), mixture of field pea and wheat and oilseed rape (Brassica napus L.), as well as mineral fertilization treatments, namely 40 kg N ha(-1) (N-1) and 80 kg N ha(-1) (N-2) and an unfertilized control. Cover crops and N treatment significantly affected the soil NO3-N content. In the treatments with field pea and its mixture with wheat, the contents of symbiotically fixed N were 140.97 and 53.9 kg N ha(-1), respectively. The highest nitrogen contribution was in the field pea (165.26 kg N ha(-1)), while the control and N-1 had negative N balances (-59.48 kg N ha(-1) and -25.40 kg N ha(-1), respectively). The yields of Sudan grass following the addition of N-2 and field pea cover crop were higher than the control, while they were on the same level as the control after cover crops of oilseed rape and the mixture of wheat-field pea. Wheat produced the lowest yield of Sudan grass, due to nitrogen deficiency after ploughing-in. The N-2 treatment had the highest crude protein content at the first cut and the lowest at the second cut.