Soil Conservation Aids Soybean Production

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Fanya juu terraces Type 3 offer a way of achieving level terraces by limited input of labour over a period of time Figure 4. Contour bunds may be useful because of the dual purpose of conserving both soil and water, Figure 4. There may also be circumstances where a combination of shallow soils with limited storage capacity, and heavy rain, results in frequent surface run-off which calls for a system of graded channel terraces, either without storage Type 6 or with some storage and a designed overflow.

The problem is that any such system is likely to be expensive in relation to the productivity of the land, and it is difficult to maintain grassed waterways as disposal channels when rainfall is limited and unreliable. Level terraces for dryland farming Type 2 have been extensively used in the past, for example Ethiopia Plate 4.

Most were built in the past and nowadays are increasingly not maintained or abandoned as the maintenance becomes uneconomic or impossible because of labour shortages. Until recently Haraz has been one of the most densely populated high-mountain regions in the world, with virtually all slopes being terraced or used as rainwater collection areas. Mainly since the end of , large areas of this man-made ecosystem have been abandoned. In this district it is esti- mated that males have migrated from the Yemen Arab Republic to jobs in the nearby oil states out of a population of between 5 and 7 million.

Several similar examples are recorded on the north coast of Africa where the migration has been across the Mediterranean to Europe. We have seen that in semi-arid conditions it is seldom appropriate to divert surface run-off from arable lands, and the same arguments largely apply to cut-offs or diversion drains put in at the top edge of arable land in order to protect it from surface run-off from uncultivated higher land.

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There could be special circumstances, such as a shallow saturated soil which would be less damaged if water coming down from above could be diverted. The difficulty is that the drain may also divert run-off during gentle storms which might have been usefully absorbed by the arable land.

The use of diversions will therefore be limited to cases where there is uncontrolled flood run-off in a channel or gully which will be wasted unless it is diverted to some useful purpose. This is discussed under run- off farming in Chapter 5. When there is a risk that any structure intended to gather run-off may be overtopped in heavy storms, it is important to deliberately provide planned overspills which can act as safety valves and make sure that the run-off is discharged in places where it will do least damage.

The discussion of terracing and conventional conservation works clearly points to the use of simple and easily applied measures. The first of these should always be farming on the contour. This alone can reduce soil loss to approximately half of what it would be with cultivation up and down the slope. We have already seen that although rainfall in semi-arid areas will be less in total, it can still include very damaging storms, and so it will usually be beneficial to have some form of structure which will slow down the surface run-off, encourage the deposition of suspended mater- ial, and reduce the concentration of surface run-off in minor depressions.

Structures on the contour are simpler and cheaper than graded channel terraces for three reasons. First there is no need to set them out on a precise gradient. They should be more or less on a level contour, but small errors are not as important as in the case of graded channel terra- ces. Secondly, where water is to be led off the land, then the spacing between the terraces has to be calculated, because each channel terrace has to handle the water from a given area.

There is no point in using the design formulas when structures are either on a level contour, or are not intended to discharge run-off. If the object of structures on the contour is to store the total run-off then they must be designed to do this, as in the case with fanya juu terraces in Kenya Thomas et al. If the structures are perme- able or can be overtopped safely in heavy storms, then the distance between them is immaterial.

Thirdly, since there is no attempt to lead water along the structure, there is no problem of trying to handle the discharge in drains or waterways. However, care is needed to avoid the danger of one level contour bank overtopping, and causing a progressive failure of all the lower banks, with the risk of starting gullies. A general term for simple structures on the contour is 'stop-wash lines' which correctly defines their purpose. The form of such lines will depend on what materials are available.

On stony ground, using the stones to build rock lines serves the dual purpose of clearing them from the field as well as building the stop-wash lines. Where stones are not available, lines can be formed by piling up crop residues, perhaps with a few shovels of soil, and progressively built up later by adding weeds from hand hoeing. An example is shown from Ethiopia in Plate 4. No design is necessary, but the general principle is that there is not much point in building large or high structures, particularly if built from stone, since they will be very permeable, and in general a larger number of small barriers will be more effective than a small number of large structures.

Catalog Record: Your nursery and soil conservation | Hathi Trust Digital Library

Grass strips can also be used as stop-wash lines, and this was the basis of a national conservation programme in Swaziland. In the s the king issued a royal edict that strips of the indigenous grass were to be left on all ploughed land, 2 m wide at 2 m vertical interval. The rule was rigorously enforced and almost all arable land has grass strips today as shown in Plate 4. For lack of sufficient field advisors many of the strips were off-grade, and others were on land which is too steep for erosion to be halted by this method, as shown in Photo 4.

In Kenya live hedges are sometimes planted for the same purpose, often sisal, euphorbia, or other drought-resistant species Photos 4. In areas with higher rainfall, grass may be densely planted to cut for fodder and cause a terracing effect Photo 4. When stop-wash lines are intended to divert water out of small channels, it is desirable to reduce the permeability at this point. This is done using the principle of the reverse filter. The main structure is composed of large stones, then on the upstream side smaller stones are packed, but large enough so that they cannot be washed through the gaps in the large stones.

Upstream of the small stones a layer of gravel is added. Water will still flow through the structure, but slowly, and it will build up in the depression and flow out on either side eventually finding a way through the rock barrier and continuing its path down the slope. This same principle can be used on a larger scale for gully control structures. Some applications of stone lines have the primary objective of water harvesting rather than soil conservation. Run-off from uncropped land hig- her up the slope runs down onto the cropland, and is spread by the perme- able stone lines along with the run-off which starts on the cropland.

When this is the objective there will not be a diversion drain at the upper edge of the cropland, and the stone lines should not use the reverse filter. Where the object is to trap and hold sediment behind the stone bunds, and reduce the slope by developing terraces, the reverse filter effect is desirable along the whole length of the bunds if stones of different sizes are available.

This demonstrates the principle that it is always important to be quite clear about the desired objective. Even a simple device like stone lines can be built to help them to remain permeable, or to silt up as quickly as possible, or to silt up in the depressions only -according to the objective. There are many examples of inappropriate and unsuccessful attempts to use graded channel terraces in semi-arid conditions Heusch ; Roose and Piot There are also a number of examples of the successful use of small low-cost structures.

An example is the Mossi plateau in Burkina Faso where the recommended solution is to build frequent low barriers cm high at m spacing, built of a basic structure of laterite blocks and stabilized with grass Roose and Piot Another project in Burkina Faso used similar stone lines as illustrated in Plate 4. Bench terraces built in a single operation Figure 4.

Progressive reduction of slope fanya juu Figure 4. Absorb some rain with emergency overflow contour bund Figure 4. Controlled reduced run-off -ridging, Plate 4. Soil loss through erosion or run-off hurts agricultural production with depletion of organic matter and fertility. It also has environmental implications. Some parts of this site work best with JavaScript enabled. Menu Share This Page.

Crop Residue and High-Carbon Char: Potential Soil Conservation Tools May 8, Soil is the single most important resource on which our agriculture depends. Rye cover crop termination date and corn residue removal study at Rogers Memorial Farm near Lincoln. February 12, Researchers examined the effect of a rye cover crop on reducing soil erosion from wind in fields where a large amount of the crop residue had been removed.

A study led by Ken Olson of University of Illinois concluded that this differing result occurs in part because tested soil samples need to include the full depth of rooting, 1—2 meters. Also, there has not been a uniform definition of soil organic carbon sequestration among researchers. No-till farming improves soil quality soil function , carbon, organic matter, aggregates, [24] protecting from erosion , [25] evaporation of water, [26] and structural breakdown.

Reducing of tillage reduces compaction of soil. This can help reduce soil erosion almost to soil production rates.

Soil Conservation | CropWatch

Recently, researchers at the Agricultural Research Service of the United States Department of Agriculture found that no-till farming makes soil much more stable than plowed soil. Their conclusions draw from over 19 years of collaborated tillage studies. No-till stores more carbon in the soil and carbon in the form of organic matter is a key factor in holding soil particles together.

The first inch of no-till soil is two to seven times less vulnerable than that of plowed soil. The practice of no-till farming is especially beneficial to Great Plains farmers because of its avoidance of erosion. Crop residues left intact help both natural precipitation and irrigation water to infiltrate the soil. Residue also limits evaporation , conserving water for plant growth.

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No-till farming leaves soil intact and crop residue on the field. Soil layers and soil biota, remain in their natural state. No-tilled fields often have more beneficial insects and annelids , [29] more organic material and microbial content, and variety of wildlife.

Tillage lowers the albedo of croplands. The potential for global cooling as a result of decreased Albedo in no till croplands is similar in magnitude to the biogeochemical carbon sequestration potential. Tilling regularly damages ancient structures under the soil such as long barrows.

No-till farming

In the UK, half of the long barrows in Gloucestershire and almost all the burial mounds in Essex have been damaged. According to English Heritage modern tillage techniques have done as much damage in the last six decades as traditional tilling did in the previous six centuries. By using no-till methods these structures can be preserved and can be properly investigated instead. No-till farming requires specialized seeding equipment such as seed drills , to plant seeds into undisturbed crop residues and soil.

The cost can be offset by selling plows and tractors, but farmers often keep their old equipment while trying out no-till farming. This would result in more money being invested into equipment in the short term until old equipment is sold off. If a soil has poor drainage, it may need drainage tiles or other devices to remove excess water under no-till.

Water infiltration improves after years of no-till farming, so farmers may want to wait before investing in such an expensive system. Gullies can be a problem in the long-term. While much less soil is displaced by no-till farming, any drainage gulleys that do form deepen each year since they are not smoothed out by plowing. Gully formation can be avoided entirely with proper water management practices, including the creation of swales on contour. One of the purposes of tilling is to remove weeds.

No-till farming does change weed composition drastically. Faster growing weeds may no longer be a problem in the face of increased competition , but shrubs and trees may begin to grow eventually. However, there are many agroecological alternatives to increased chemical use, such as winter cover crops and the mulch cover they provide, soil solarization or burning.

No-till farming requires some different skills than conventional farming. As with any production system, if done incorrectly, yields can drop. A combination of technique, equipment, pesticides, crop rotation , fertilization, and irrigation have to be used for local conditions. In no-till occasionally uses cover crops to help control weeds and increase nutrients in the soil by using legumes [35] or by using plants with long roots to pull mobile nutrients to the surface from lower layers of the soil.

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Cover crops then need to be killed so that the newly planted crops can get enough light, water, nutrients, etc. With no-till farming, residue from the previous years crops lie on the surface of the field, cooling it and increasing the moisture. This can increase or decrease disease or cause it to vary [39] compared to tillage farming.

Planting different crops year after year denies a pest or pathogen population a supply of whatever food it is adapted to consume. Some farmers who practice organic management often place ordinary, non-dyed corrugated cardboard on seed-beds and vegetable areas. Used correctly, cardboard placed on a specific area can. Plant residues left over plant matter originating from cover crops, grass clippings, original plant life etc. This rotting attracts worms and other beneficial microorganisms to the site of decomposition, and over a few seasons usually Spring to Fall or Fall to Spring and up to a few years, creates a layer of rich topsoil.

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