Molecular Soil Biology 2025, Vol.16, No.3, 137-149 http://bioscipublisher.com/index.php/msb 140 organic matter will be reduced, nutrients will be unbalanced, and yields will decrease (Liu et al., 2023; Yang et al., 2024). In northwest China, experiments have found that rotating potatoes with corn, flax, broad beans, etc. not only makes the plants taller, produces more dry matter, improves soil quality, saves water, and improves water use efficiency and income (Liu et al., 2023). With one rotation per year, the number of tubers per potato plant increased by 38.24%, the income increased by 9.7%, the water use efficiency increased by 41.86%, and the soil became fertile. In the Mediterranean, rotating potatoes with durum wheat, adding organic fertilizers and conservation tillage, can increase soil organic carbon, reduce carbon dioxide emissions, and use less fertilizer and energy (Mancinelli et al., 2023). If there are leguminous crops in the rotation, it can also improve the activity and health of microorganisms in the soil (Yang et al., 2024). 3.3 Contribution to nutrient cycling and organic matter input Potatoes are also useful in nutrient cycling and increasing soil organic matter, especially when planted or rotated with legumes. Planting potatoes alone for a long time can cause soil organic matter and microbial activity to deteriorate, but rotation and intercropping can improve this situation (Nyawade et al., 2019a). In the experiment conducted in the highlands of Kenya, intercropping potato and leguminous crops increased light group organic matter in the soil by 12 to 28%, dissolved organic matter by 7 to 21%, microbial biomass by 15 to 38%, and soil enzyme activity and microbial respiration were enhanced. These systems also promote nutrient transformation and cycling because there are more plant residues, so there is more organic matter in the soil, which is food for microorganisms (Nyawade et al., 2019a). In the North China Plain, the rotation of potatoes with sweet potatoes, peanuts, and soybeans has also increased equivalent yields and farmers' incomes, increased soil carbon by 8%, and improved soil health index by 45% (Yang et al., 2024) (Figure 2). Figure 2 Schematic illustration of system integration from issues to outcomes (Adopted from Yang et al., 2024) Image caption: In the North China Plain—the case study area, traditional cereal monoculture (such as wheat–maize double-cropping, i.e., two cereal crops per year) requires inputs of synthetic agrichemicals and irrigation in food production, causing large greenhouse gas (GHG) emissions; in contrast, rotation systems diversified with cash and legume crops can maintain crop yields, increase farmers’income, and reduce GHG emissions due to the biological N2 fixation by legumes partly substituting for synthetic N inputs. Legume-included rotations can also enhance soil health by stimulating soil microbial activities, increasing carbon sequestration, and enhancing nutrient cycles (Adopted from Yang et al., 2024) Returning potato residues to the field and adding organic fertilizers can also help improve soil structure and carbon and nitrogen cycle efficiency, and reduce nutrient loss and pollution (Mancinelli et al., 2023).
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