Monocropping in one field for many subsequent years will cause nutrient depletion in that field and lead to less productive returns. Crop Rotation is the process of planning the planting and harvesting of different crops planted on the same field over subsequent growing seasons, allowing less nutrient depletion and if applied effectively, increasing soil nutrients through nitrogen fixing etc. This farming practice also assists with weed control, prevents soil erosion, and is the most efficient and economical way to break the biological cycles of plant pests and diseases, mitigating the effects of pests/disease as they become more prevalent due to climate change and helping farmer diversify crop production. Research has shown that rotation between nitrogen consuming crops such as maize and nitrogen depositing plants such as soybeans can provide a healthy balance of nutrients. This farming practice is advantageous for smallholder farmers who are less able to leave fields fallow for extended periods of time, as well as for commercial farmers wanting to reduce pesticide use. It is seen as climate smart as it breaks pest and disease cycles, returning nutrients to the soil, thereby supporting more predictable yields in times of climate pressure, and locking more carbon in the soil.
An example of crop rotation is maize, followed by a legume. Grain SA has reported a 12 % increase in maize production following rotation with legumes such as cowpea. Furthermore, the legume yields often increase following rotation with the grain crop, and sometimes responding differently to the crop type. For example, soybean yield has been measured at 20 % higher following sorghum than maize. To effectively undertake crop rotation:
- Step 1: Determine which cereal crops and legumes are available in the area of interest.
- Step 2: Prepare land through clearing, weeding. No-tillage approaches are preferable (Technical Brief 12).
- Step 3: Plant a leafy cereal crop (maize or sorghum) and let the crop mature and harvest once ready. Once harvested, bend stalks over to increase biomass.
- Step 4: If possible, allow field to fallow for a short period. If this is not possible, practice cover cropping (Technical Brief 15).
- Step 5: Prepare land again, and sow second crop, usually a legume to improve soil structure and fertility. Harvest crop once ready.
- Step 6: Repeat process. It is possible to include more than two crops into crop rotation if desired.
It is advisable to carefully monitor yield for demonstration purposes, run test plots if necessary.
- The Food and Agriculture Organisation (FAO), 2010. Green manure/ cover crops rotation in Conversation Agriculture on small farms. Rome, Italy.
- FAO 1995. Sustainable dryland cropping in relation to soil productivity FAO soils bulletin 72 (Chapter 4 – sustainable crop rotations). Rome, Italy.
- Nel A. A. (2005) Crop rotation in the summer rainfall area of South Africa, South African Journal of Plant and Soil, 22:4, 274-278
Benefits
- Improved soil fertility and protect soil.
- Effect and cost-effective way to break pest/disease cycle.Food security/farm income increase.
- Food security/farm income increase.
- Nutrient fixing.
Drawbacks
- Time should be allowed between harvest and planting of different crops.
- Cultural shift away from traditional crops.
- Limited market opportunities for non-traditional crops.
