Lesson 2: Conservation Tillage Methods

Conservation tillage leaves the previous year’s crop residue, such as maize stalks, on the fields when planting the next crop. This helps to control soil erosion and improves the infiltration of water. Conservation tillage methods include no-till, strip-till, ridge-till, and mulch-till. These methods may require different types of specialised or modified equipment and adaptations in management. 

No-till and strip-till practices involve the planting of crops directly where there are crop residues. No-till agriculture is planting into the residues of untilled fields. Strip-till agriculture is planting into narrow tilled strips between crop residues. 

Ridge-till agriculture is planting row crops on permanent ridges about 10 to 12 centimetres high. The previous crop’s residues are cleared off ridge tops into the furrows between the ridges to make way for the new crop. Ridges must be well maintained using modified or specialised equipment. 

Mulch-till agriculture is another reduced tillage system that leaves at least one third of the soil surface covered with crop residue mulch.

The Benefits of Conservation Tillage

Conservation tillage reduces soil erosion by as much as 60% to 90%, depending on the method. Crop residues protect the soil from rain and wind until new plants produce a protective canopy over the soil.

Second, conservation tillage improves soil quality (fertility, soil texture, and structure) by adding organic matter through the decomposition of crop residues. The result is an open soil structure that reduces runoff and allows water to run into the soil more easily. 

Last, conservation tillage improves soil structure, enhancing crop growth in dry periods or drought conditions.

Crop Rotation

Crop rotation is the rotation of crops from one field to another. Rotating crops helps interrupt the breeding of pest hosts and prevents the build-up of pests, weeds, and pathogens. Crops with different root depths and different nutrient requirements are chosen in cycles to help the soil recover and regenerate. The benefits associated with good crop rotations include:

• Maintaining good physical condition and organic matter levels in soil.

• Improving the distribution of crop nutrients in the soil by choosing crops with different root depths.

• Improving soil fertility with nitrogen-fixing legume crops such as groundnuts and soya beans. This can improve crop quality and increase yields by 10-15%.

• Helping control weeds, some crop diseases and insect pests, reducing the need for natural herbicides, insecticides and fertilisers.

• Reducing soil erosion.

• Increasing flora, fauna, and wildlife diversity.

Examples of crop rotation systems can be found in many books. Farmers can design their own systems by: 

• Making a list of all the vegetable types and number of crops they want to plant. 

• Grouping crops in botanical families and planting crops from the same family in the same planting area. 

• Drawing a plan of the growing area. For a four-year crop rotation system, four separate sections are needed.

• Keeping records of what actually happens. This information should be used when planning for the following year.