15 Slices
Medium 9781780646862

9: Conservation Agriculture

Finley, S. CABI PDF

9

Conservation Agriculture

‘Conservation agriculture’, also known as ‘conservation farming’ or ‘no-till farming’, is a farming style that bucks against long-held understandings of the importance of tillage for land preparation. Conservation farming is an integrated set of practices that seeks instead to minimize soil disturbance, while promoting the continuous recycling of organic matter and nutrients through the plant–soil system. When effectively adopted, these practices have the potential to increase crop yields with respect to conventional farming, all while requiring less work.1 By supporting the natural cycles of soil regeneration in parallel with crop production, conservation agriculture also promotes the long-term health of the farm ecosystem. It is promoted as a form of sustainable land management.2

Conservation agriculture (commonly abbreviated as CA) has expanded rapidly over the past 20–30 years, with the strongest growth in Brazil and throughout South America.3 It is practiced across humid, sub-humid, and semiarid climate zones. Though still relatively uncommon in sub-Saharan Africa, some countries in the dry tropics of East and Southern Africa have seen an expansion in the number of farms converting to conservation farming over the past two decades.4 As the benefits of CA become visible, governments, international organizations and farmers’ groups are now moving to promote conservation agriculture among poor farmers struggling with poor soil health and excessive erosion.

See All Chapters
Medium 9781780646862

5: Climate Outlook

Finley, S. CABI PDF

5

Climate Outlook

The earth’s climate is changing. Farmers, especially those working on rainfed projects in the drier parts of the world, have likely already felt the effects of global climate change, in the form of shifted rainy seasons, heavier storms, or extended dry periods during the growing season. In fact, smallholder farmers and laborers working on rainfed farms in the developing world are among those most directly affected by global climate change. At the same time, the ingenuity and traditional environmental knowledge that small farmers possess will be a key tool for adaptation to new climate realities.

Changes in water availability – in the form of rainfall patterns, green water storage, surface water flows, and water quality – are some of the most visible effects of climate change. Because the unpredictability of these resources is only expected to increase in as time goes by, it is important to learn to anticipate and adapt to new conditions before their effects become too pronounced.

See All Chapters
Medium 9781780646862

Summary of Key Points

Finley, S. CABI PDF

Summary of Key Points

 Dry spells during the growing season, and not total rainfall deficits or droughts, are the principal cause of water deficit on most rainfed farms.

 The impact of dry spells on crop yields can be mitigated by adopting soil and water conservation practices, harvesting rainfall, applying supplemental irrigation, and/or practicing conservation agriculture.

 In many dryland areas, over half of the rain that falls is not captured by the soil but is lost as runoff, evaporation, deep percolation, and evaporation.

 The capacity of field soils to hold water is closely related to organic matter content and soil type.

 Soil organic matter content can be enhanced by providing soil cover, recycling plant residues into the soil, and planting several varieties of crop.

 Cover crops and green manures cover the soil while acting as natural fertilizer.

 Rainwater runoff can be beneficially harvested to provide additional water inputs.

See All Chapters
Medium 9781780646862

3: Soil and Water

Finley, S. CABI PDF

3

Soil and Water

More than anything else, the key to enhancing resilience and promoting water availability for crop growth lies in the proper care of farm soils. In fertile regions, the native soil underlying forests, brush or grasslands tends to be naturally ‘healthy’, that is, rich in nutrients with good structure and organic matter content. When land is cleared for farming, soil can quickly lose its ‘healthy’ qualities, especially if farming practices employed do not encourage its regeneration. Without proper management, agricultural soils can become completely depleted in as little as a few decades or even a few years after clearing, depending on the nature of the land and its use.1

Some negative effects that agriculture can have on the soil include:

nutrient mining (continual removal of nutrients without renewal); breakdown of organic matter; loss of water holding capacity; compaction; erosion; surface sealing (crusting); and deterioration of natural habitat for soil organisms (microorganisms, insects, and worms).

See All Chapters
Medium 9781780646862

Preamble to Part 3

Finley, S. CABI PDF

Preamble to Part 3

What is Irrigation?

Irrigation is the term used to describe any type of water application to agricultural fields that is administered by artificial means (as opposed to natural means such as rain, floods, and runoff). Irrigation exists in many forms, and involves widely varying levels of technology. On small farms in developing countries, irrigation is primarily human-, or animal-powered, and systems are designed around locally available resources. On larger commercial farms, mechanical irrigation is used to reduce the labor required to apply water to large plots. These installations carry a high capital cost but are often more efficient and easier to calibrate than simpler methods.

Full irrigation is the practice of applying water to the field at regular intervals throughout the growing season in order to maintain a desired level of available soil water. Supplemental irrigation, as introduced in Chapter 7, is the selective application of water to primarily rainfed fields when rainfall is insufficient to protect the plants against water stress. Application methods for supplemental irrigation are much the same as full irrigation methods, though they generally lie toward the low end of the technology spectrum. On smallholder farms in the semi-arid tropics, supplemental irrigation is usually applied using low-cost surface irrigation.1 Supplemental irrigation is a useful complement to the soil and water management practices outlined in Part 2, and significant productivity improvements have been observed in cases where these strategies are implemented together.2 Because water is only applied when needed, the efficiency of crop water use under supplemental irrigation is much higher than it is for fully irrigated crops.3

See All Chapters

See All Slices