Yields rose 79% from sustainable agriculture in South
By Lim Li Ching
(South-North Development Monitor #5967 Thursday 16 February 2006)
A study published in Wednesday’s issue of the journal ‘Environmental Science & technology’ suggests that poor farmers in developing countries can increase agricultural productivity by adopting "resource-conserving" or sustainable agriculture.
An international study team found that farmers in 286 projects in 57 countries have improved food crop productivity since the early to mid 1990s, while simultaneously increasing water use efficiency and carbon sequestration, and reducing pesticide use.
Thus, the researchers found that in addition to increasing yields (by an average of 79%), resource-conserving agriculture also reduces adverse effects on the environment and contributes to important environmental goods and services (e. g., climate change mitigation).
The 286 projects involved some 12.6 million farmers engaged in transitions towards agricultural sustainability, farming over 37 million hectares of land and making use of a variety of packages of resource-conserving technologies and practices. These include the following:
( 1) Integrated pest management, which relies on ecosystem resilience and diversity for pest, disease, and weed control. Pesticides are only used when other options are ineffective.
( 2) Integrated nutrient management, which balances the need to fix nitrogen within farm systems with the need to import inorganic and organic sources of nutrients, while reducing nutrient losses through erosion control.
( 3) Conservation tillage, which reduces the amount of tillage, sometimes to zero, so that soil can be conserved and available moisture used more efficiently.
( 4) Agroforestry, which incorporates trees into agricultural systems, and includes collective management of nearby forest resources.
( 5) Aquaculture, which incorporates fish, shrimps, and other aquatic resources into farm systems, such as into irrigated rice fields and fish ponds. This leads to increases in protein production.
( 6) Water harvesting in dryland areas, which can mean that formerly abandoned and degraded lands can be cultivated. Furthermore, additional crops can be grown on small patches of irrigated land due to better rainwater retention.
( 7) Livestock integration into farming systems, such as dairy cattle and poultry.
The researchers, led by Professor Jules Pretty from the University of Essex, United Kingdom, used questionnaires and published reports to assess the adoption of sustainable agriculture and changes over time. The data were triangulated from several sources, and cross-checked by external reviewers and regional experts.
The work builds on earlier research, published in 2003, which assessed 208 sustainable agriculture projects. The earlier research found that for 89 projects for which there was reliable yield data, farmers had, by adopting sustainable agriculture practices, achieved substantial increases in per hectare food production The yield increases were 50-100% for rain-fed crops, though considerably greater in a number of cases, and 5-10% for irrigated crops.
This time, for the 360 reliable yield comparisons from 198 projects that the researchers had, they found that the average relative yield increase was 79% across a wide variety of systems and crop types. However, because of the wide spread in results (25% of projects reported relative yields increasing by 100% while half of the projects had yield increases of between 18% and 100%), the geometric average is a better indicator, and this shows a still substantial 64% increase in yield.
In nearly all cases, there was an increase in yield after a sustainable agriculture project was adopted. While the yield increase in rice and cotton was small, soybean and groundnut showed average yield increases of about 50%.
Maize, millet and sorghum, potatoes, and other legumes (beans, pigeon peas, cowpea, and chickpea) all showed average yield increases of more than 100%. For most of the main field crops that are well represented in the survey, those with low yields before intervention often showed larger relative improvements.
Although many technologies and practices were used in these projects, the researchers broadly identified three types of technical improvements that were likely to have played substantial roles in food production increases:
( i) more efficient water use in both dryland and irrigated farming;
( ii) improvements in organic matter accumulation in soils and carbon sequestration; and
( iii) pest, weed, and disease control emphasizing in-field bio-diversity and reduced pesticide (insecticide, herbicide, and fungicide) use.
As sustainable farming practices demand less water, increases in food production are possible while maintaining water-related ecosystem services. This rests on the capacity to increase water productivity, i. e., by realizing more kg of food per unit of water.
The research results demonstrated that the greatest opportunity for improvement in water productivity lies with rain-fed agriculture. Although chronic low productivity and crop failure are characteristic of many rain-fed systems, this situation can be avoided by better farm management, including ensuring that there is supplemental irrigation and fertility
management.
A key issue facing the world today is climate change and the need to reduce carbon emissions. Carbon sequestration is defined as the capture and secure storage of carbon that would otherwise be emitted to or remain in the atmosphere. Farmers can play an important role in this, by increasing carbon sinks in soil organic matter and above-ground biomass.
The researchers calculated the potential annual contributions being made in these 286 projects to carbon sink increases in soils and trees, using established carbon audit methods. They found that the sustainable agriculture projects were potentially sequestering 11.4 Mt C per year on 37 million hectares.
Furthermore, integrated pest management (IPM) programs are beginning to show how pesticide use can be reduced and modified without yield penalties. The researchers analysed the 62 IPM initiatives in 21 developing countries in the data-set and found that in most cases, pesticide use declined (by 70.8%) while yields increased (by 41.6%).
While pesticide reduction is to be expected in IPM projects, the cause of yield increases induced by IPM is more complex. The researchers felt that it was likely that farmers who receive good quality field training would not only improve their pest management skills but would also become more efficient in other agronomic and ecological management practices. The farmers were also likely to invest cash saved from not spending on
pesticides in other inputs such as higher quality seeds and fertilizers.
The study concluded that while it is not certain whether these techniques can meet all the future food needs of developing countries, given increasing population growth, urbanization and increasing consumption of meat, it was poor households that have the most to gain from adopting sustainable agriculture practices.
One big challenge that the researchers identified is the need to improve all farmers’ access to these resource-conserving technologies and practices. Thus, the critical priority is to ensure that international, national, and local policy and institutional reforms are supportive of sustainable agriculture.