全部

1·Over centuries the landscape changed to open chalk downland.

几百年后，这片土地变成了白垩丘陵地带。

2·The main factors influencing the wheat yield in downland were initial nitrogenous dressing, the amount of nitrogenous fertilizer applied for different leaf age and close fertilization.

对模型进行解析，找出了影响五区小麦产量较大的因子是氮基肥、不同叶龄追施氮肥和密度。