To ensure grain production and increase crop yields, a crop rotation system can be implemented. The mechanism of crop rotation is a systematic process involving soil ecology, plant physiology, pest and disease control, and nutrient cycling, which promotes the sustainable development of agriculture. Its main functional mechanisms can be divided into the following aspects:

1. Breaking the Cycle of Pests, Diseases and Weeds

Pest and Disease Control: In continuous cropping systems, the persistent presence of host plants allows pathogen and pest populations to accumulate year after year. Crop rotation disrupts their life cycles by introducing non-host crops. For instance, rotating gramineous crops with leguminous crops can reduce the incidence of soil-borne diseases (such as Fusarium wilt) and the proliferation of host-specific pests.

Weed Suppression: Different crops vary in growth habits, planting densities and tillage methods, which can inhibit the growth of specific weed species. For example, rotating row crops (such as corn) with densely planted crops (such as wheat) alters the field microenvironment, thus curbing the spread of dominant weed species.

2. Improve Soil Structure and Fertility

Root Complementary Effect: Crop rotation between deep-rooted crops (such as cotton and sunflower) and shallow-rooted crops (such as rice and vegetables) allows for stratified utilization of soil nutrients and water, reducing nutrient loss from deeper layers and improving soil permeability.

Organic Matter and Microbial Diversity: Leguminous crops increase soil nitrogen through nitrogen fixation, while returning green manure or straw to the field increases organic matter content. Crop rotation also promotes soil microbial community diversity, enhances the activity of beneficial bacteria, and inhibits soil-borne pathogens.

3. Regulate Soil Nutrient Balance

Reduce Nutrient Imbalance: Different crops have different nutrient requirements. For example, leafy vegetables require more nitrogen, fruit vegetables require more phosphorus and potassium, and cereals require more silicon. Crop rotation avoids excessive consumption of a single nutrient and reduces the risk of soil salinization.

Biological Nitrogen Fixation and Nutrient Activation: Leguminous crops fix nitrogen symbiotically with rhizobia, providing a nitrogen source for subsequent crops; root exudates from some crops (such as rapeseed) can activate insoluble phosphorus in the soil, increasing phosphorus availability.

4. Reduced Dependence on Chemical Production Materials 

Crop rotation reduces reliance on chemical fertilizers and pesticides. For example, nitrogen provided by the preceding legume crop reduces nitrogen fertilizer usage in the subsequent crop; reduced pests and diseases lead to a corresponding decrease in pesticide use, aligning with sustainable agriculture.

5. Enhanced Stability of Agricultural Ecosystems

Increased Biodiversity: Crop rotation increases vegetation diversity in farmland, providing habitats for natural enemy insects (such as ladybugs and parasitic wasps), thus enhancing ecological pest control capabilities.

Improved Stress Resistance: Crop rotation can alleviate secondary soil salinization, acidification, and continuous cropping obstacles, improving the buffering capacity of farmland ecosystems against climate fluctuations and pests and diseases.