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HISTORY AND OVERVIEW OF
CONSERVATION AGRICULTURE
Introduction
Latin America
North America
Australia
Asia
Europe
Africa
More and more people are starting to question the sustainability of the intensive production systems that characterize much of modern agriculture. Many of these systems require increased external inputs, such as expensive chemical fertilizers, heavy farm machinery and irrigation technologies, in order to obtain high agricultural yields. Yet the "more with more" approach also causes more environmental degradation, something many worry about when considering the future of agricultural production, particularly in fragile agroecosystems throughout much of the developing world. These harmful effects include widespread soil erosion and loss of soil organic matter (SOM), declining levels of soil fertility and soil aggregate stability, increased compaction from frequent tractor passes, falling water tables and increased levels of pollution in soil, air and water.
Conservation agriculture offers a more sustainable alternative to conventional production systems. As mentioned in the definitions section, the term "conservation agriculture" refers to a system of practices that seeks to improve overall soil quality by minimizing soil disruption and maintaining a permanent soil cover of diverse biota. The term itself gained much popularity during the 1980s, when international development programs such as the Food and Agriculture Organization (FAO) first began promoting soil conservation practices such as no-till (NT) among farmers in Latin America. In truth, however, farmers throughout the region had been practicing NT and other soil health management practices such as growing green manure cover crops (GMCCs) and rotating crops for decades, if not longer. The aim of promoting conservation agriculture among these farmers was to encourage them to implement the various soil conservation practices in unison in order to build healthier soils for enhanced crop production.
Subsequent efforts to promote conservation agriculture (CA) in other regions of the world, particularly in Africa and Central Asia, have been less successful in disseminating CA information and technology. Presently, it is estimated that 95% of the practical applications of CA in the world take place in the Americas. The United States, Brazil, and Argentina are the world leaders in NT cultivation, a key component in establishing sustainable CA systems. The following table illustrates worldwide NT adoption in 2003.
Table 1. Estimated global coverage of no-till (NT), 2003
| Country | Area planted million ha. | % of world total |
|---|---|---|
| United States | 22.4 |
31.1 |
| Brazil | 17.3 |
24.0 |
| Argentina | 14.5 |
20.1 |
| Australia | 9.0 |
12.5 |
| Canada | 4.1 |
5.7 |
| Paraguay | 1.3 |
1.8 |
| South Asia | 1.0 |
1.4 |
| Rest of world | 2.4 |
3.3 |
| Total | 72.0 |
100.0 |
People often wonder why North and South American farmers have been so successful in implementing NT farming practices. Yet widespread adoption among large commercial farmers in the US bears little resemblance to adoption in South American countries such as Brazil, Argentina, Paraguay and Uruguay (a.k.a. MERCOSUR). The four leaders in South America account for more than 33.4 million ha. under NT management, as compared to 22.4 million ha. in the US. Moreover, whereas approximately 90% of this area in South America is under permanent NT, the vast majority of North American NT area is under rotational tillage. MERCOSUR countries have experienced a 50 fold increase in area under NT, compared to a 5.5 fold increase in the US from 1997-2003.
Obviously, farmers in South America are adopting NT technologies on their farms more readily than in any other part of the world. Furthermore, widespread adoption of other conservation agriculture technologies in Latin America, such as growing green manure cover crops (GMCCs) and using crop rotations, has occurred without the aid of government subsidies. For many farmers in the region, adopting soil conservation measures on potentially erodible cropland is proving to be highly beneficial economically as well. In South America, widespread NT adoption was made possible by providing farmers with access to specialized NT technology, such as direct planters and improved chemical herbicides. From there, the technology has spread from farmer-to-farmer throughout the entire region, with the vast majority being small-scale producers.
In the United States and Canada, large-scale commercial farms account for most of the NT agriculture. Many farmers in the region turn to NT as part of their normal crop rotations and fallowing cycles. It is estimated that approximately 25% of the land under NT is permanently under this system; the remaining 75% being under various rotational tillage schemes. Unlike most of Latin America, NT is not the dominant form of conservation tillage in North America. Farmers in the US and Canada also rely on reduced (conservation) tillage and regular fallows to limit soil disturbance, though the majority continue to plough before every planting season. A growing body of scientific research on the effects of NT and other conservation agricultural practices is starting to convince more North American farmers to experiment with these technologies on their own farms.
Farmers in Australia are also adopting NT and other conservation agriculture practices for many of the same reasons as farmers throughout Latin America. Namely, much of the country's agricultural soils are subject to high levels of erosion and runoff and NT is effective at controlling nutrient losses while building up soil physical properties. The benefits of NT in increasing water use efficiency levels also is largely important in many of the country's dryland regions. Farmers also have access to NT planters and effective chemical herbicides for controlling weed problems, which heighten their chances for success in adopting NT and technologies important in conservation agriculture.
Zero tillage (as it is known throughout Asia and Africa) is among the fastest growing agricultural movements in South Asia, particularly in the Indo Gangetic Plains of India and Pakistan. From nearly nothing in the late 1990s, zero tillage (ZT) of wheat after rice now covers approximately 1.9 million ha. and this area is expected to double over the next few years. ZT offers several advantages over conventional tillage in rice-wheat systems, where sowing of the wheat crop is often delayed by tillage and weeding operations following the harvest of the rice crop. Farmers and researchers using ZT in the Indo Gangetic plains report higher wheat yields and reduced labor costs due to the absence of tillage operations on their farms and the timely planting of their primary wheat crop. Despite these advantages, ZT has yet to be widely adopted on the estimated 20 million ha. of rice-wheat systems throughout Asia.
Adoption of direct drilling (European term) and other important conservation agriculture technologies now accounts for less than 5 percent of the land under cultivation throughout Europe. This is somewhat surprising given the region's strong research initiative on direct drilling beginning in the 1950s. Much of the available research from European universities and scientists clearly illustrates many of the environmental advantages for direct drilling yet the majority of farmers continue to till their fields prior to each planting. The tillage tradition is perhaps stronger in Europe than anywhere else in the world, dating back to the end of the 18 th Century when the mouldboard plow proved the only tool effective at controlling quack grass (Agropyron repens) and thus staving off famine over much of the continent. Although direct drilling has been slow to catch on thus far, many European farmers have begun experimenting with minimum tillage, a development many hope will eventually lead to widespread adoption of direct drilling and other important soil conservation practices.
Reduced tillage is the primary form of soil preparation on small farms (1-2 ha.) in Africa. This involves tilling only a narrow strip of land with a hand held tool such as a hoe, and then planting seed into a small hole using a hand jab planter. Farmers in certain regions of Ghana and Zimbabwe have successfully adapted this practice to plant directly into crop residues without tilling the land. Yet permanent ZT is mostly limited to areas with higher rainfall or available irrigation. According to GTZ, traditional land tenure, uncontrolled or communal grazing and the lack of adequate soil cover as well as several socioeconomic factors are major obstacles in the diffusion of ZT technologies. Research and extension activities must work to effectively address these problems before ZT and other important conservation agriculture practices become a viable alternative for many small farmers throughout Africa.
References