1. Understanding CA
Module 3
Soil Cover

2. Soil cover
A good farmer gives her soil some cover to keep it healthy. Only a healthy soil can produce a good crop

3. The soil should always be covered

4. Types of soil cover There are two main types of soil cover
Living plant material
Crops and cover crops
Mulch or dead plant material
Crop residues and prunings from trees and shrubs

5. Cover crops
These are crops grown to cover the area between rows of commercial crops or to cover the whole field when no commercial crop is growing.
While commercial crops have a market value, cover crops are mainly grown for their effect on soil fertility or as livestock fodder.

6. Benefits and challenges of the use of cover crops
Protects the soil
Maintain N in organic form (less leaching)
Control weeds
Add OM to the soil
Can solve compaction problems
Increase porosity and internal drainage
Challenges
Some may require higher level of management
Decomposition of CC can lead to deficit of N at the beginning of the growing season

7. ‘Green manure crops’ vs ‘Cover crops’
Mainly legumes
Mainly for N addition to the soil
Incorporated into the soil at certain growth stages
Cover crops
Species from different plant families eg grasses, legumes etc
Grown for specific plant attribute
Grown to cover soil and feed soil organisms
Mostly no market value like commercial crops

8. Some common cover crops
Cajanus cajan – Pigeon pea
Canavalia ensiformis – Jack bean
-Dolichos lablab – Lablab bean
Mucuna pruriens – Velvet bean
Vigna unguiculata – Cowpea
List local ones

9. Considerations before choosing a CC
Multiple benefits
Compatibility with cropping system
Time of sowing and growth cycle
Ease of management
Water requirement – drought resistance
Possibility of becoming a weed

10. Residue management Properly managed Badly managed Adds OM to the soil
Retains C in the soil
Buffers soil pH & facilitates availability of nutrients
Captures rainfall
Reduces evaporation & increase soil moisture content
Badly managed
Provokes uneven drying of soil
Interferes with seeding &fertilizing activities
Hinders the emergence of crop seedlings
Allows weed species to emerge

11. Time of management of the CC
Important to know because
Most species can regenerate when interrupted prematurely
Mature seeds can germinate and cause problems as weeds
Most CC species at full flower = maximum accumulation of biomass
Legumes – 1st pod formed but not yet matured
Grains – milky stage
Woody species (eg. Cajanus) – just before flowering because of wood development

12. How to manage the CC For long term soil cover from dead mulch
Knife roller
Chain
Herbicide
For immediate decomposition to release nutrients
Slashing
Mowing

13. Time of sowing the commercial crop
Period between slashing/management of the CC and seeding of the commercial crop defines the production level of the crop. Related to allelopathy & N immobilization.
For direct seeding over the CC, allow
8 to 12 days for CC with low to medium C/N ratio (C/N of 12-22) eg. legumes
12 to 20 days for CC with high C/N ratio (C/N of >24) eg. grasses

14. Cover crop seed production
Initial source
Research institute, extension service, other farmers or from the wild
Produce just above 12-20% of the quantity needed.
Reserve a specific site on-farm for seed production only.
Produce more than one specie to spread risk

15. Challenges for maintaining soil cover
Semi-arid areas
Little rain so crops, shrubs,& trees produce less residue. Farmers also need them for feed, fuel wood or building.
May be impossible to maintain soil cover for the whole year. Best to depend on crop residue, and prunings from trees and shrubs as the main source of soil cover.
Diseases and pests
May attack the CC and may therefore require special attention. Farmers often use fire to destroy pests and diseases.
Rotate crops rather than burning to control pests and diseases. Consider using pesticides if necessary.

16. Challenges for maintaining soil cover
Rats
A dense CC may encourage rats which may attack the crop
Slash the live CC as close to the ground as possible before planting. Baits/traps can be used
Rotate crops to interrupt their food supply and disturb their living conditions
Termites
Many farmers report of soil cover attracting termites
Termites are important. They break plant material on the surface and carry it into the soil to add to soil OM. By so doing, they aerate the soil and improve infiltration
Most termites are beneficial. Only a few attack crops. They may eat the stem or damage the grain. This normally happens towards harvest time. Leave plant materials (mulch) on the surface so the termites attack this rather than the crop itself.

17. Challenges for maintaining soil cover
Fire
Bushfires or uncontrolled fires can spread into a CA field and destroy its soil cover.
Leave a buffer zone around the field. Once many farmers in the area begin to practice CA, burning will be minimized.
Education and bylaws are needed to reduce damage by uncontrolled fires.
Livestock
Uncontrolled grazing destroys soil cover
Prevent animals by planting living fences, spraying field boundaries with cattle urine or planting CC not eaten by cattle around the farm.
Fodder production and community agreed grazing area.

18. The value of mulch
Understanding CA = understanding the value of mulch

19. Understanding the CA system
Farmers that have not yet understood the importance of an adequate mulch cover have not yet understood the CA system