Sustainable Agriculture Part 16



EARTHSCAN          2005




Perspective 27: Reducing Food Poverty by Increasing Agricultural Sustainability in Developing Countries by Jules Pretty, James Morison and Rachel Hine (Cont)

Improvements in soil health and fertility

  • Soil health is fundamental for agricultural sustainability, yet is under widespread threat from degradation processes.
  • Agricultural sustainability starts with the soil by seeking both to reduce soil erosion and to make improvements to soil physical structure, organic matter content, water-holding capacity and nutrient balances.
  • Soil health is improved through the use of legumes, green manures and cover crops, incorporation of plants with the capacity to release phosphate from the soil into rotations, use of composts and animal manures, adoption of zero-tillage, and use of inorganic fertilizers where needed.
  • In projects in Central America, the incorporation of nitrogen-fixing legumes into agroecosystems has substantially affected productivity, particularly the velvetbean (Muuna pruriens).
  • This grows rapidly, fixes 150-200kg N per hectare, suppresses weeds, and can produce 35-50 tonnes of biomass per hectare per year.
  • Addition of the biomass to soils substantially improves soil organic matter content, and has helped to increase cereal productivity for some 45,000 families in Guatemala, Honduras and Nicaragua.
  • In the past decade, Latin American farmers have found that eliminating tillage can be highly beneficial for soils.
  • The Cerrado area of Brazil is a vast area of formerly unproductive lands colonized for farming in the past two decades. These lands needed lime and phosphorus before they could become productive, and now zero-tillage is being widely adopted.
  • Farmers are now adapting technologies – organic matter levels have sufficiently improved that fertilizer use has been reduced and rainfall infiltration improved, such that some farmers are removing contour terraces.
  • Other side-effects of zero-tillage include reduced siltation of reservoirs, less flooding, higher aquifer recharge, lowered costs of water treatment, cleaner rivers, and more winter feed for wild biodiversity.
  • There is still controversy over zero-tillage, as some feel the use of herbicides to control weeds, or of genetically-modified crops, means we cannot call these systems sustainable.
  • However, the environmental benefits are substantial, and new research is showing that farmers have some effective alternatives, particularly if they use cover crops for green manures to raise organic matter levels.
  • Using 20 species of cover crops and green manures, Petersen and colleagues have shown how small farmers can adopt zero-tillage systems without herbicides.
  • A public good is also being created when soil health is improved with increased organic matter. Soil organic matter contains carbon, and soils with above-ground biomass can act as ‘carbon sinks’ or sites for carbon sequestration.
  • Conservation tillage systems and those using legumes and/or cover crops  contribute to organic matter and carbon accumulation in the soil.

In the Sahelian countries of Africa, the major constraints to food production are also related to soils, most of which are sandy and low in organic matter. In Senegal, where soil erosion and degradation threaten large areas of agricultural land, the Rodale Institute Regenerative Agricultural Resource Center works closely with farmers’ associations and government researchers to improve the quality of soils. The primary cropping system of the region is a millet-groundnut rotation. Fields are cleared by burning, and then cultivated with shallow tillage using animals. But fallow periods have decreased dramatically, and inorganic fertilizers do not return high yields unless there are concurrent improvements in organic matter, which helps to retain moisture. The Center collaborates with 2000 farmers organized into 59 groups on improving soil quality by integrating stall-fed livestock into crop systems, adding legumes and green manures, increasing the use of manures, composts and rock phosphate, and developing water-harvesting systems. The result has been a 75% to 190% improvement in millet and ground-nut yields – from about 300 to 600-900kg per hectare. Yields are also less variable year on year, with consequent improvements in household food security.

Thus if the soil is improved, the whole agricultural system’s health improves. Even if this is done on a very small scale, people can benefit substantially. In Kenya, the Association for Better Land Husbandry found that farmers who constructed double-dug beds in their gardens could produce enough vegetables to see them through the hungry dry season. These raised beds are improved with composts, and green and animal manures. A considerable investment in labour is required, but the better water holding capacity and higher organic matter means that these beds are both more productive and better able to sustain vegetable growth through the dry season. Once this investment has been made, little more has to be done for the next two to three years. Women in particular are cultivating many vegetable and fruit crops, including kale, onion, tomato, cabbage, passion fruit, pigeon pea, spinach, pepper, green bean and soya. According to one review of 26 communities, 75% of participating households are now free from hunger during the year, and the proportion having to buy vegetables had fallen from 85% to 11%. For too long, agriculturalists have been sceptical about these organic conservation methods. They say they need too much labour, are too traditional, and have no impact on the rest of the farm. Yet the spin-off benefits are substantial, as giving women the means to improve their food production means that food gets into the mouths of children. They suffer fewer months of hunger, and so are less likely to miss school.

Pest control with minimal or zero-pesticide use

Modern farmers have come to depend on a great variety of insecticides, herbicides and fungicides to control pests, weeds and diseases, and each year, some 5 billion kg of pesticide active ingredients are applied to farms. But farmers in these projects have found many effective and more sustainable alternatives. In some crops, it may mean the end of pesticides altogether, as cheaper and more environmentally benign practices are found to be effective.

  • Many projects in our survey reported large reductions in pesticide use in irrigated rice systems.
  • Following the discovery that pest attacks on rice was proportional to pesticide use, Farmer Field Schools were later developed to teach farmers the benefits of agrobiodiversity.
  • In Vietnam, two million farmers have cut pesticide use from more than 3 sprays to 1 per season.
  • In no case has reduced pesticide use led to lower rice yields.
  • If pesticides are removed, then fish can be reintroduced.
  • In Kenya, intercropping of local legumes and grasses with maize has been found to reduce stem borer attack through interactions with parasitic wasps.
  • More than 2000 farmers in western Kenya have adopted maize, grass-strip and legume-intercropping systems, and have increased maize yields by 60% – 70%.

Another project in Yunnan, China has shown the value of mixtures of rice, both in reducing disease incidence and increasing yields. Researchers working in ten townships on 5350 hectares encouraged farmers to switch from growing monocultures of sticky rice to alternating rows of sticky rice with hybrids. The sticky rice brings a higher price, but is susceptible to rice blast, which is generally controlled through applications of fungicides. But planting mixtures in the same field reduced blast incidence by 94% and increased total yields by 89%. By the end of two years, it was concluded that fungicides were no longer required.

Impacts on rural livelihoods and economies

Rural people’s livelihoods rely for their success on the value of services flowing from the total stock of natural, social, human, physical and financial capital. A number of examples can be extracted from the dataset to show that agricultural sustainability projects and initiatives have been able to contribute to the accumulation of locally valuable assets. A selection of the impacts reported in these sustainable agriculture projects and initiatives include:

v  Improvements to natural capital, including increased water retention in soils, improvements in water table (with more drinking water in the dry season), reduced soil erosion combined with improved organic matter in soils, leading to better carbon sequestration, and increased agrobiodiversity.

v  Improvements to social capital, including more and stronger social organizations at local level, new rules and norms for managing collective natural resources, and better connectedness to external policy institutions.

v  Improvements to human capital, including more local capacity to experiment and solve own problems; reduced incidence of malaria in rice-fish zones, increased self-esteem in formerly marginalized groups, increased status of women, better child health and nutrition, especially in dry seasons, and reversed migration and more local employment.

The empirical evidence indicates that some improvements in agricultural sustainability have had positive effects on regional economies. In the Ansokia Valley, Ethiopia, one project increased annual food production from 5600 to 8370 tonnes in six years, at the same time as the population increased from 36,000 to 45,000. The project turned around an annual food regional deficit of –2106 tonnes to a surplus of 372 tonnes per year. In Bushenyi, Uganda, formerly experiencing substantial food shortages during the months of October to December, one project so increased banana and cattle production that the region could sell 330 tonnes of bananas and 2.7 tonnes of meat each week. In En Nahud, Sudan, the 10,000 tonnes of additional food produced by 15,000 households were consumed by local people. None found its way into national statistics.

There is also evidence that productivity can increase over time as natural and human capital assets increase. If agricultural systems are low in capital assets (either intrinsically low, or have become low because of degradation), then a sudden switch to ‘more sustainable’ practices that have to rely on these assets will not be immediately successful. In Cuba, for example, urban organic gardens produced 4200 tonnes of food in 1994. By 1999, they had greatly increased in per area productivity – rising from 1.6kg per square meter to 19.6kg per square meter. Increasing productivity over time has also been noted in fish-ponds in Malawi. These are typically some 200-500 square meters in size. Researchers compared the performance of 35 fishponds over six years: in 1990 yields were 800kg per hectare, but rose steadily to 1450kg per hectare by 1996. This is because fish ponds are integrated into a farm so that they recycle wastes from other agricultural and household enterprises, leading to steadily increasing productivity over time as farmers themselves gain understanding.

Confounding factors and trade-offs

What we do not yet know is whether moving to more sustainable systems, delivering greater benefits at the scale occurring in these projects, will result in enough food to meet the current food needs in developing countries, let alone the future needs after continued population growth and adoption of more urban and meat-rich diets. But what we are seeing should be cause for cautious optimism, particularly as evidence indicates that productivity can grow over time if natural, social and human assets are accumulated.


Scaling up through appropriate policies

Three things are now clear from this data set about spreading agricultural sustainability:

  1. some technologies and social processes for local adoption of more sustainable agricultural practices are well-tested and established;
  2. the social and institutional conditions for spread are less well-known, but have been established in several contexts, leading to very rapid spread in the 1990s;
  3. the political conditions for the emergence of supportive policies are least well established, with only a very few examples of real progress.
  • Only two countries, Cuba and Switzerland, have given explicit national support for a transition towards sustainable agriculture – putting it at the centre of agricultural development policy and integrating policies accordingly.

A good example of a carefully designed and integrated programme comes from China. In March 1994, the government published a White Paper to set out its plan for implementation of Agenda 21, and put forward ecological farming, known as Shengtai Nongye or agroecological engineering, as the approach to achieve sustainability in agriculture. Pilot projects have been established in 2000 townships and villages across 150 counties. Policy for these ‘eco-counties’ is organized through a cross-ministry partnership, which uses a variety of incentives to encourage adoption of diverse production systems to replace monocultures. These include subsidies and loans, technical assistance, tax exemptions and deductions, security of land tenure, marketing services and linkages to research organizations. These eco-counties contain some 12 million hectares of land, about half of which is cropland, and though only covering a relatively small part of China’s total agricultural land, do illustrate what is possible when a policy is appropriately coordinated.


This empirical study shows that there have been promising advances in the adoption and spread of more sustainable agriculture. The 208 projects/initiatives show increases in food production over some 29 million hectares, with nearly 9 million households benefiting from increased food production and consumption. These increases are not yet making a significant mark on national statistics, as we believe there is a significant elasticity of food consumption in many poor rural households. They are eating the increased food produced, or marketing small surpluses to other local people. We cannot, therefore, yet say whether a transition to more sustainable agriculture, delivering increasing benefits at the scale occurring in these projects, will result in enough food to meet the current food needs of developing countries, the future basic needs after continued population growth, or the potential demand following adoption of more meat-rich diets. Even the substantial increases reported here may not be enough. There should be cautious optimism, as the evidence indicates that productivity can increase steadily over time if natural, social and human capital assets are a accumulated.

Increased agricultural sustainability can also be complementary to improvements in rural people’s livelihoods. It can deliver increases in food production at relatively low cost, plus contribute to other important functions. Were these approaches to be widely adopted, they would make a significant impact on rural people’s livelihoods, as well as on local and regional food security. But there are clearly major constraints to overcome. There will be losers along with winners, and some of the losers are currently powerful players. And yet, social organization and mobilization in a number of contexts is already leading to new informal and formal alliances that are protecting existing progress and developing the conditions for greater spread. Improving agricultural sustainability clearly will not bring all the solutions, but promising progress has been made in recent years. With further explicit support, particularly through international, national and local policy reforms, these benefits to food security and attendant improvements to natural, social and human capital could spread to much larger numbers of farmers and rural people in the coming decades.

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