High potential hillsides - Soil conservation and recuperation in Mesoamerica
A major movement of soil improvement has sprung into life on the hillsides of Meso-America during the last 30 years. The following article describes the SC and SR techniques that have made this movement possible in Meso-America (the area from Central Mexico through Nicaragua). It includes descriptions of the practices, how they have changed over time, analyses of their economic costs and benefits, and data on their sustained adoption or abandonment by small farmers.
ILEIA Newsletter • 14 nº 2-3 • September 1998
High potential hillsides
Soil conservation and recuperation in Meso-America
IntroductionA major movement of soil improvement has sprung into life on the hillsides of Meso-America during the last 30 years. Basically, this movement has come to life because of a convergence of three factors:
• an increasing realisation among villager farmers that population pressures
are forcing them to intensify their land use - that traditional slash and burn
systems must be intensified or changed.
• a growing effort among development organisations, mostly NGOs, to develop and spread soil conservation and soil recuperation (SC and SR) techniques, using primarily farmer-led, or farmer protagonist, methods of research and extension.
• the existence of widespread traditional systems of intercropping different species of beans with maize.
The following article describes the SC and SR techniques that have made this movement possible in Meso-America (the area from Central Mexico through Nicaragua). It includes descriptions of the practices, how they have changed over time, analyses of their economic costs and benefits, and data on their sustained adoption or abandonment by small farmers.
Soil ConservationSC refers here to techniques used to reduce water run-off and erosion on hillsides, whereas SR refers to those that increase medium- to long-term soil fertility, usually through the application of organic matter. The major SC practices used in Meso-America are contour hedgerows ("live barriers"), contour rock barriers, contour or drainage ditches, and in-row tillage (known also as "minimum tillage").
Contour hedgerows consist of vegetation that is planted along contours spaced 1.5 to 3 vertical metres down a hillside. The hedgerow serves to interrupt run-off, thereby trapping soil and gradually forming a bench terrace.
Hedgerows were first popularised among small farmers in Meso-America in the late 1960s when the NGO World Neighbors learned of the technology from Marcos Orozco and began spreading it around Central Guatemala. At that time, hedgerows invariably consisted of Napier grass (Pennisetum purpureum), and were planted every 1.5 metres of vertical distance down the hillside. From Guatemala, the World Neighbors introduced the hedgerows to Mexico and Honduras, and to the Campesino a Campesino programme in Nicaragua.
The distance between hedgerows also varies from 1.5 to 3.5 vertical metres, depending on soil type, rainfall and the existence of other SC practices such as cover crops, in-row tillage and/or micro-terraces between the hedgerows (Lopez et al 1995).
The economics of hedgerows vary widely depending on the slope, the species used and the value of the crops between them (Ellis-Jones et al 1995). Thus, the labour costs of establishing grass hedgerows in Honduras range from about US$11 per hectare for a 15 percent slope to US$37 per hectare for a 50 percent slope (Almendares et al 1995; Mejia 1993) making them one of the cheapest technologies available. Farmers usually do not reap the benefits of increased soil fertility the first few years, but the food or fodder produced by the hedgerows often pay back the costs within a year or two. Long-term benefits, such as increased land values, reduced risk, and higher productivity make the practice very attractive. In fact, the most important long-term benefit is that it makes possible all the other SC and SR measures, because they will no longer be destroyed or washed down the hillside.
Hedgerow adoption rates show how much farmers appreciate these benefits. A rough estimate would put present sustained adoption at between 50,000 and 75,000 farmers. A study done five to fifteen years after programme termination shows adoption varied from 90 to 135 percent of original adopters five years after the program ended. Fifteen years after termination, adoption rates had doubled (Bunch and Lopez 1995). It should be noted, however, that in areas where projects used artificial incentives to motivate "adoption," the technology was still being maintained by only 5 to 10 percent of the farmers just two years after termination (Lopez 1992).
Contour rock walls
Rock walls replace hedgerows where rocks are so common as to disturb farming operations. The walls are built on a contour every 1.5 to 3.0 vertical meter down a hillside. Costs, however, are high, from US$125.00 of labour per hectare for a 15 percent slope up to US$410.00 on a 50 percent slope), and the wall itself provides few additional benefits (Almendares 1995; Mejia 1993). Many NGOs have now moved to just pushing the rocks out of the row in in-row tillage, or forming small piles of rocks about every third row, thus reducing labour costs considerably. Cost also becomes difficult to assess because the work is combined with other operations and is often done gradually over several years.
Contour or drainage ditches
This technology consists of a ditch just beneath the hedgerow, either on a contour or at a 1 or 2 percent slope. The purpose is to stop run-off and either hold the water or, if on a slope, drain the water out of the field. Nevertheless, even though we previously promoted such ditches widely, with positive long-term results, we now see them as requiring too much labour. Drainage ditches are still recommended at times, but only when poor drainage obviously limits productivity.
In-row tillage consists of tilling the soil only in the crop row, leaving the soil between the rows untilled. This often adds productivity just by itself to no-till traditional systems. Over a period of three or four years, it also forms a microterrace, that reduces erosion and concentrates water in the root zone. The practice also allows organic matter to be incorporated into the soil, concentrating it in the root zone of crops, and allowing its residual effect to be used by crops year after year, since the row remains in the same place. Because of these and many other advantages, in-row tillage, along with contour hedgerows, is one of the two most widely used SC. practices in Meso-America today.
In-row tillage, a variation of the "strip tillage" used in the United States, was first practised in Meso-America by Elias Sanchez on his demonstration farm in Honduras in the early 1980s, and then was popularised by World Neighbors and other NGOs. The most common change farmers have made in this practice is that of varying the width of the tilled strip. Usually for basic grains planted in rows about 1 meter apart (for example maize, cassava, and potatoes), farmers till an area about 35 centimetres in width, whereas for beans they till a strip 50 to 60 centimetres wide to allow for a double row. For vegetables they may widen the cultivated row to 80 cms. In a few villages, where farmers produce high-value vegetables, they actually build micro-terraces right from the start, investing additional labour in order to have the micro-terraces formed immediately.
The cost of in-row tillage varies tremendously depending on soil type, slope, the presence of rocks, the width of the row, and whether it is done by hand or by animal traction. In-row tillage done by hand will cost an average of about US$130 per hectare to establish, US$65 per hectare to redo the second year, and US$45 hectare per year thereafter. However, using a mule (which is generally possible only on slopes of less than 45 percent), it will cost about US$30 per hectare to establish and $20 hectare per year to maintain. Benefits will also depend on the soil type, the amount of organic matter. incorporated, and the crops grown. The greatest advantage may well be that after four or five years, farmers using in-row tillage and incorporating large amounts of organic matter may well be able to move to high-productivity zero tillage with surface applications of organic matter, thereby reducing costs further while maintaining yields.
A study in Honduras indicates that hand-built in-row tillage was sustained only where farmers could use it for irrigated vegetables (Arellanes 1994). However, the experience of other programmes indicates that in-row tillage done by animal traction is being adopted spontaneously by maize farmers with no irrigation, and that farmers using animal traction to make in-row tillage dedicate larger areas of land to this practice. Thus, even though this innovation is too recent for post-programme studies, experience would indicate that hand-built in-row tillage is profitable and sustainable only for higher-value crops, whereas in-row tillage done with animals is widely competitive even for basic grains.
Of course, along with contour barriers and in-row tillage, farmers have also adopted strip farming and planting in contour rows, and have quit burning. These practices require virtually no additional costs, while their advantages are also relatively small, though enough to make them widely and sustainably adopted.
Soil recuperationGreen manure/cover crops
The addition of major quantities of organic matter to the soil has proven to be the most important and easiest way for small farmers to maintain or boost the natural productivity of their soils, even those soils so depleted they have been abandoned. This practice of reviving deteriorated soils through heavy organic matter applications (the benefits to productivity of which are highly underestimated by most agronomists) is now called "soil recuperation". Although many sources of organic matter may be used, including animal manure, coffee pulp, sugarcane pulp and compost, the least expensive and most widely used in Central America is green manure or cover crops.
In Latin America, green manure or cover crops are utilised in such a way that they do not use land that has an opportunity cost; do not require any out-of-pocket expenses; do not require major amounts of additional labour, and finally, provide benefits other than merely improving the soil (Bunch 1995). Thus they can be grown during the dry season or in periods of frost, under fruit trees, on fallowed land or intercropped with traditional crops, such that the land they occupy cannot otherwise be used. In Meso-America, intercropping them with maize or growing them under fruit or coffee trees has been the most popular approach, although farmers are experimenting many other uses (Anon 1997). Green manure or cover crops should thus be developed to produce high-protein human food, to produce feed or fodder for animals, or for weed, disease or pest control, in addition to soil improvement (Bunch 1997).
While many green manure or cover crops in Meso-America are traditional, the velvet bean has been introduced over the last 60 years, and has spread spontaneously among tens of thousands of farmers in Mexico, Guatemala, and Honduras. Systematic extension of green manure and cover crops began, so far as we know, with two independent efforts: the work of Drs. Steve Gliessman and Roberto Garcia in Tabasco State, Mexico, and that of this author, working with World Neighbors in Guatemala, both in the mid-1970s.
The systems used in Meso-America vary tremendously. Traditional systems include the intercropping of maize with scarlet runner bean (Phaseolus vulgaris), cowpeas (Vigna unguiculata), the lablab bean (Dolichos lablab) and rice bean (Vigna umbellata). Introduced systems include intercropping maize, sorghum, and/or cassava with velvet bean (Mucuna sp.), jackbean (Canavalia ensiformis), sweet clover (Melilotus albus) and a variety of vignas, as well as planting any of these or some perennial legume under perennial crops (Anon 1997).
Most of these systems were developed and adapted almost totally by villagers. Even in the case of introduced systems, programmes brought seed into the area, but villagers adapted the planting dates, seeding rates, crop associations and management regimes to their own specific needs. During this process, farmers have tended to move toward added diversity, reduced labour requirements, and a maximisation of uses for the green manure or cover crop species (for example, additional ways of cooking them or feeding them to animals).
The few scientific studies done so far on the benefits of these practices have yielded varying results. A study of the economics of a maize-velvet bean system in Honduras showed that the cost per ton of maize produced was 30 percent less than in a nearby high-input maize system (Flores 1992). A second study of a different maize-velvet bean system also showed it to be economically advantageous (Ellis-Jones et al 1995) while a third study showed negative benefits (SILSOE 1998). This apparent discrepancy is probably due to the third system’s incorporation of the green manure cover crop in a warm, lowland climate some five months before subsequent planting. Most of the organic matter and nitrogen were most likely burned out. None of these studies took into account any uses of the green manure or cover crops other than for increased soil fertility, and all assumed subsequent maize production (a relatively low-value crop).
Whether these systems are presently spreading or contracting is debatable in many cases. The most heavily studied system, the velvet bean-maize system in Northern Honduras, seems to be contracting rapidly in the areas it has been used the longest, because of encroaching cattle farmers, recently changed tenure laws, and nearby alternative sources of employment (the area planted in maize is dropping about as fast as is that in velvet bean) (Neil undated). On the other hand, very similar systems are spreading spontaneously to new areas of colonisation in Honduras, as well as into Belize, the Guatemalan Peten, and Chiapas and Tabasco States in Mexico.
Several of the other traditional systems are probably being gradually abandoned, such as the scarlet runner bean in Mexico and Honduras, and the vignas in El Salvador, while the introduced systems, really just getting started, have a mixed record so far, though evidence of spontaneous adoption exists in cases where green manure and cover crops have multiple uses. As farmers are taught additional uses for many of these beans, adoption trends will likely improve. Also, if petroleum prices increase substantially (quite likely sometime within the next 10 to 15 years, as world petroleum production peaks), green manure and cover crops will be able to compete even better with chemical fertilisers (MacKenzie 1996).
Coffee pulp, sugarcane pulp, and other sources of organic matter
The use of these often locally available resources (not generally practised traditionally), has become very popular. Especially where vegetables or fruit are grown, they often provide strikingly favourable cost-benefit ratios.
Can they compete with high-external-input techniquesTens of thousands of farmers using low-input SC or SR techniques maintain or increase their yields each year, rather than suffering decreasing yields, as before. Costs are often lower than for high-input agriculture, with similar yields. At the same time, these same farmers no longer have to leave their land fallow or burn forests in search of new land. Farmers who previously had to migrate in search of new land every two to four years have now used the same land for 15 to 25 years.
A study of 12 villages in Guatemala and Honduras using many of these technologies shows that average maize yields have increased from 0.5 tons per hectare to 3.4 tons per hectare over 22 years, temporary outmigration has almost been eliminated, permanent outmigraton to city slums has been reversed, wage levels have increased, land values have shot up, educational levels have improved, and village organisation has advanced. Farmers in the four Guatemalan villages in this study are now producing an average of 4.4 tons per hectare of maize, while farmers in neighbouring villages using approximately three times more chemical fertiliser per hectare but no SC or SR techniques are harvesting only about 1.4 ton per hectare (Bunch and Lopez 1995).
Closer, more scientific comparisons between specific high- and low-input systems would be desirable, but may well be difficult to carry out. Robert Chambers has described villager farmers as having "complex, diverse" farming systems (Chambers 1994). In Meso-America, farmers using SC or SR not only have complex and diverse systems, but rapidly changing ones, too. They know that only through rapid change can a farming system remain profitable over time.
Furthermore, the benefits of any SC or SR technology depend very much on the rest of the farming system. The benefits from hedgerows and in-row tillage depend heavily on the value of the crop planted between or in them. The major benefit of in-row tillage comes from being able to incorporate organic matter from green manure or cover crops and eventually being able to forego tillage altogether. The green manure or cover crop species, and the costs and benefits of that species, will vary from one crop or crop rotation to the next, and the value of the improved soil will depend on what crop follows the green manure or cover crops and when, as well as the cost of alternative sources of organic matter for the system.
It is virtually impossible to compare complex, diverse, rapidly changing low-input systems with high-technology systems that are also complex and rapidly changing, even if somewhat less diverse. Even when achieved, such a comparison may be largely irrelevant because it would only apply to those few farmers using a similar system, and even they will likely modify their systems within a few years. Furthermore, frequently there are no high-input systems with which these low-input systems can be compared. The velvet bean-maize study mentioned earlier, for instance, had to compare a velvet bean-maize system on a 35 percent hillside with a high-input maize system on flat land, because the high-input system will not function on a hillside (Flores 1992).
Another study analysed ten different "improved systems" of production in southern Honduras, each combining several of the above SC and SR technologies, plus a few others. All ten systems were more profitable than the traditional system. Nevertheless, they varied from being just slightly more profitable (a system using only hedgerows and contour ditches) to one in which added income was over six times that of the added costs (a system including hedgerows, in-row tillage, green manure or cover crops and some chemical fertiliser) (Almendares 1995). But no unirrigated high-input systems existed that could be compared with these systems, probably because the risk of losing one’s considerable investment to drought is too high. Furthermore, local irrigated systems do not produce maize, beans and millet, the low-value subsistence crops that dominate the traditional systems. And the irrigated systems only function on flat land. Thus comparison would be largely useless.
Therefore, this author would see widespread adoption or abandonment of technologies as a more useful measure of economic feasibility than scientific studies. Given the now well-substantiated fact that villager farmers largely behave in economically rational ways, the spontaneous, non-subsidised adoption or abandonment of a given technology over large areas of a nation should logically indicate a technology’s ability to compete economically. Thus, the fact that many low-input technologies are being sustained or are spreading in Meso-America, even years after outside intervention, would seem to be the best proof we will probably ever have that certain low-input SC or SR technologies are economically viable under these farmers’ complex and diverse conditions. Using this measure, technologies such as multi-purpose contour hedgerows, animal-traction in-row tillage, and a good number of multi-purpose green manure and cover crops have definitely proven themselves competitive with competing high-input technologies.
Even though we now have good evidence of the economic feasibility of these technologies, if they are to continue to compete we must continue to improve them, both in quality and quantity. We must find more ways, and more efficient ways, to use green manure and cover crops as food and fodder. We must do a good deal more research on integrated pest management (IPM), especially for small-scale commercial vegetable growers. And we must research ways that allow individual small-scale farmers to harvest rainwater, to better use their improved soils and to make both SC and SR and low-input agriculture in general, more attractive in semi-arid areas.
Recommendations for other areas• Multi-purpose contour hedgerows and animal-traction in-row tillage have been well validated for use by hillside farmers, and should be widely taught to hillside farmers in much of the tropics.
• Green manure and cover crop technologies should also be widely adaptable for use in the tropics. In this case, the one major exception would be intensive, high-value systems such as irrigated vegetables, where purchased organ matter and compost, for example, become competitive because of the high opportunity cost of any land dedicated to green manures and cover crops.
• Artificial incentives, including subsidies, give-aways, and food-for-work, should not be used for promoting SC and SR technologies. Programmes should choose and/or design technologies such that full payback in increased productivity comes within the first year, thereby making artificial incentives unnecessary.
• More research is urgently needed on micro-scale water harvesting and IPM.
• All further research for villager farmers should take full advantage of participatory technology development (see Veldhuizen et al 1997).
• Extension of these technologies should use farmer-led or farmer protagonist methodologies. (See, for instance, Bunch, 1982, and FAO)