【英语时差8,16】玉米大豆种植模式效益更好？2（在线收听）

 These bacteria split the nitrogen atoms apart and combine them with other molecules, making the nitrogen available to the plants that the bacteria are living on. In exchange, sugars produced by the plant’s photosynthesis fuel the process of nitrogen-fixation and enable the bacteria to grow. These bacteria not only help the plants they live on, but release useable nitrogen into the soil which is taken up by other plants, and in turn passed on to animals that eat those plants. The Maya knew that corn and beans grow well together, just as in this country some farmers rotate their crops, planting alfalfa or beans every few years to replenish the soil’s nitrogen.