How should the crop rotation sequence be arranged?

1. Corn. Corn is a crop with a relatively high fertilizer requirement; it is not strict about the previous crop, but bean stubble is best. At the same time, corn tolerates short-term continuous cropping, but in order to obtain a relatively high yield, the amount of fertilizer applied when planting corn must be increased. Corn fields have few weeds, so corn is a good previous crop for many crops.

2. Sorghum. The sorghum root system goes very deep into the soil and can absorb nutrients and water from deep soil layers. For its previous crop, bean stubble is best, but it is not suitable for continuous cropping or alternating cropping. Sorghum stubble can be followed by corn or soybeans.

3. Millet. Millet is a shallow-rooted crop, but its root system is relatively well developed, and its ability to absorb fertilizer and water is very strong. In addition, it grows slowly during the seedling stage and is prone to weed damage. Therefore, for the previous crop, it is best to choose soybeans or corn stubble with fertile soil and few weeds, but it cannot be continuously cropped or alternated, so as to avoid seedling failure and reduced yield. Millet stubble land is hard and low in fertility, and generally can be followed by soybeans or corn and other crops.

4. Wheat. For wheat, corn and soybeans are best as the previous crop, and continuous cropping can also be practiced, but it cannot be planted on millet stubble to prevent weed infestation.

5. Soybeans. The soybean root system goes relatively deep into the soil and also absorbs nutrients and water from deep soil layers. It can increase nitrogen in the soil, improve soil structure, and restore and raise soil fertility. Soybean fields have few weeds and high fertility, and are a good previous crop for many crops. Soybeans are not suitable for continuous cropping. As the saying goes: oil after oil brings three years of worry. Therefore, a rotation system of more than three years should be implemented for soybeans.

6. Sugar beets. The sugar beet root system is extremely large and goes deep into the soil, and it absorbs more nutrients and water than other crops. It has strict requirements for the previous crop. Usually, stubble of crops such as wheat, corn, and soybeans is suitable, but continuous cropping is not allowed. Generally, a rotation system of four to five years or more can be implemented. Sugar beet stubble has low fertility and is cold and heavy, so on the basis of increasing manure application, crops such as wheat and corn can be planted.

7. Sunflowers. Sunflowers are an oil crop with tall plants and a well-developed root system. They need large amounts of nutrients and water, and their nutrient requirements are one to two times greater than those of cereal crops. For their previous crop, corn, sorghum, or millet is suitable, and continuous cropping is not appropriate. Generally, a five- to six-year rotation system should be implemented. Liu Tong