An annual rotation model of alfalfa and corn in Yangtze River area

To explore new cultivation methods for the production of alfalfa (Medicago sativa) and to establish an annual rotation model for alfalfa and maize (Zea mays) in the Yangtze River area, techniques of alfalfa cultivation in winter fallow fields and maize cultivation rotated with alfalfa were studied in the Yangtze River area. Two applications of an NPK fertilizer were undertaken in an alfalfa field, and three applications of alfalfa green manure were undertaken in a corn field, which were addition alfalfa green manure (3000 kg·ha⁻¹ in dry weight) in local sites (alfalfa growing sites), in contrast land (unplanted alfalfa sites), and the non-addition of alfalfa green manure which was as control. The results showed that alfalfa planted in autumn could be harvested twice, first in early April and then, in the middle of the May of next year, in which NPK fertilizer addition significantly increased alfalfa growth and the nitrogen content of its leaves (P < 0.05). The accumulated alfalfa yields increased by 22.7% (10897 kg·ha⁻¹) compared with the control. In comparison to fallow plots, planting alfalfa significantly increased total nitrogen, available phosphorus, and the organic matter of the soil to a depth of 30 cm (P < 0.05). The yields of whole corn plants significantly increased by the addition of alfalfa green manure in both local (40%) and contrast (16.7%) sites compared with the control (P < 0.05). The total nitrogen content and available potassium in soil upto a depth of 20 cm, and the available phosphorus and organic matter in the soil at a depth range of 10 − 20 cm were significantly higher after the application of alfalfa green manure in the local sites (P < 0.05). These results indicate that the annual rotation of alfalfa and corn is an effective and sustainable model in the Yangtze River area, which can not only produce high yields of both alfalfa and corn, but also improve soil quality.