Tuesday, 15 May 2012

Minimum Bewerking - No Till farming

What is no-till farming

                                                                                Author:  Stes de Necker

·        Background

Conventional crop production usually involves regular tilling with tractor-drawn implements that agitates the soil in various ways. Tilling is used to remove weeds, mix in soil amendments like fertilizers, shape the soil into rows for crop plants and furrows for irrigation, and prepare the surface for seeding. This can lead to unfavorable effects like soil compaction, loss of organic matter, degradation of soil aggregates, death or disruption of soil microbes, arthropods and earth worms, and soil erosion where top soil is blown or washed away. No-till farming avoids these unfavorable effects by reducing or excluding the use of conventional tilling.

Research has shown that repeated tillage destroys the soil resource base and causes adverse environmental impact. Tillage degrades the fertility of soils, causes air and water pollution, intensifies drought stress, consumes fuel, and contributes to global warming.  Farmers today are expected to produce food in ever greater quantities. This is becoming more difficult to do in view of declining soil quality which can be caused by soil tillage. It is becoming well known that no-till is an effective technique to reduce the degradation of soil. With this way of farming, crop residues or other organic matter are retained on the soil surface and planting and fertilizing is done with minimal soil disturbance.

Recently planted No-till field

A major obstacle that farmers often face when changing  to no-till is overcoming yield-limiting factors during the transition years, that is, the first years of no-till following a history of intensive conventional tillage. These factors are often poorly understood and are usually biologically driven. Some of the problems involve residue management and increased weed and disease infestations. Experience seems to indicate that many problems during the transition phase are temporary and become less important as the no-till system matures. The judicious use of crop rotations, cover crops and limited soil disturbance may help reduce agronomic risks during the transition years. Farmers switching to continues no-till must often seek new knowledge and develop new skills and techniques in order to achieve success with this different way of farming. Further research into these techniques is urgently needed to provide strategies for promoting no-till as a way to enhance agricultural stability in South Africa.

·        Effects on soil

In No-till farming the soil is left intact and crop residue is left on the field. Soil layers, and in turn soil biotics are therefore conserved in their natural state. Variations of the conservation tillage method may involve some working of the soil with attention paid to keeping soil compactation and carbon loss at a minimum. These variations include reduced tillage, i.e. strip-till, in which small strips may be tilled to allow space for planting seeds. Strip-tillage is primarily used in areas where the soil profile contains a natural hard pan that creates a barrier preventing plant roots from moving deeper into the soil profile to access water and nutrients. Strip-tillage also creates a more suitable seed bed for crops where the harvestable portion is produced below the surface such as peanuts.

Young maize plants flourishing in a No-till field

Young soybeans flourishing in a No-till field

·   Pros and cons

There are advantages and disadvantages to no-till and minimum tillage systems.

No-till has carbon retention potential through storage of soil organic matter in the soil of crop fields. Conventional methods cause the soil layers to invert, air mixes in, and soil microbial activity dramatically decreases. The result is that soil organic matter is broken down much more rapidly and carbon is lost in the form of carbon dioxide into the atmosphere. This, in addition to the emissions from the farm equipment itself increases carbon dioxide levels in the atmosphere.

Cropland soils are ideal for use as a carbon sink since it has been depleted of carbon in most areas. Conventional farming practices, that rely on tillage, have removed carbon from the soil ecosystem by removing crop residues such as left over maize stalks, and further through the addition of chemical fertilizers which also have the above mentioned effects on soil microbes.

By reducing tillage and leaving crop residues to decompose where they lay, field carbon loss can be slowed and eventually reversed.

·        Further benefits

Other benefits of no-till include increasing soil quality {soil function}, protecting the soil from erosion, evaporation of water, and structural breakdown. Crop residues left intact help both natural precipitation and irrigation water to infiltrate the soil where it can be used. The crop residue left on the soil surface also limits evaporation and conserving water for plant growth. The reduction in the number of times equipment move over the field helps prevents the compaction of soil.

Less tillage of the soil reduces labour and related fuel and machinery costs. Less soil ploughing means less airborne dust which is a serious pollutant in some agricultural areas. No-till fields often have more beneficial insects and annelids {earthworm}, a higher microbial content, and a greater amount of soil organic material.


·        Yield

Yields are often immediately impacted negatively by inexperienced no-till farmers. A combination of technique, equipment, pesticides, crop rotation, fertilization, and irrigation has to be found which is optimal for the area-particular conditions. However, excluding the need to till, and organize the soil into contours and drainage ditches is often sighted as increasing profit by reducing cost and labour, even with an initial diminished yield.

A problem that farmers may face is that in the spring the soil will take longer to warm and dry which may stall planting to a less ideal future date. One reason why the soil is slower to dry is that the field absorbs less solar energy as the residue covering the soil is a much lighter color than the soil which would be exposed in conventional tillage.

With no-till, residue from the previous year’s crops lying on the surface of the field, may have the potential of harboring pathogens. This may lead to a higher level of disease in the crop than that of an intensively tilled field.

·        Equipment

A primary disadvantage of no-till farming is the need for specialized planting equipment designed to plant seeds into undisturbed soil and crop residues. Fortunately today many types of no-till planters are readily available.

Having the right equipment

46 row John Deere planter

·        Chemicals

One of the purposes of tilling is to remove weeds. No-till farming changes weed composition drastically. Faster growing weeds may no longer be a problem in the face of increased competition, but shrubs and even trees may begin to grow eventually. This problem can however be solved by using a more aggressive herbicide such as Roundup and because of this, no-till is often associated with increased chemical use in comparison to traditional tillage based methods of crop production.

Crop rotation is also more important in no-till farming as soil conditions change. Some no-till farmers utilize a wide variety of crop cycles to exploit their particular soil condition and weed situation for maximum yields.

·        Erosion

While considerably less soil is displaced through no-till, drainage gullies that do form may get deeper every year instead of disappearing. This may necessitate either sod drain ways or permanent drain ways in extreme circumstances. Because no-till farming often causes a slight increase in soil bulk density there is a misconception that periodic tillage is necessary to “fluff” the soil back up. In countries like Brazil where millions of hectares of land have been no-tilled for over 20 years, water infiltration, biologic activity, soil aggregate stability, and productivity have all increased well beyond traditionally tilled land. No-till farming mimics the natural conditions under which most soils formed; more so than any other method of farming in that the soil is left undisturbed except to place the seed in a position to germinate.

Mobile sprayer

Trail sprayer

No-till sunflowers

As high as "an elephant's eye"

Anyone interested in obtaining more information on the practice of no-till can contact Stes de Necker at: or fax to email 0866125254

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·        Summary

Comparison between conventional and no-till systems summarized.

Conventional systems

1. Soil tillage is necessary to produce a crop
1. Tillage is not necessary for crop production
2. Burying of plant residues with tillage implements
2. Crop residues remain on the soil surface as mulch
3. Bare soil for weeks and months
3. Permanent soil cover
4. Soil heating because of direct solar radiation
4. Reduced soil temperatures
5. Burning crop residues allowed
5. Burning mulch prohibited
6. Strong emphasis on soil chemical process
6. Emphasis on soil biological processes
7. Chemical pest control first option
7. Biological pest control first option
8. Green manure cover crops and crop rotations are options
8. Green manure cover crops and crop rotations compulsory
9. Soil erosion is accepted as an un voidable process associated to farming on sloping land
9. Soil erosion is merely a symptom cause by soil mismanagement

Consequences of soil preparation and bare soil
Consequences of no-tillage and permanent soil cover

1. Wind and water erosion are unavoidable
1. Wind and water erosion near zero
2. Reduced water infiltration into the soil
2. Increased water infiltration into the soil
3. Less available soil moisture
3. More available soil moisture
4. Unavoidable reduction in the soil organic matter content thus reduction of soil quality
4. Maintenance or increase in the soil organic matter content [enhancement of soil quality
5. Soil carbon is lost as carbon dioxide into the atmosphere
5. carbon is retained in the soil enhancing its quality
6. Reduction of crop productivity
6. Crop productivity increase
7. Higher use of fertilizers and higher cost of production
7. Reduced use of fertilizers and lower production costs
8. Poverty, rural exodus increase of informal settlements and social conflict
8. Basic needs are satisfied, living standard and quality of life of farm families increased and depopulation of rural areas restricted and or even reversed

Off farm effects of soil erosion
Off farm effects of no-till

1. Sedimentation of rivers, reservoirs, dams and micro catchments
1. Reduction of sedimentation of rivers, reservoirs, dams and micro catchments
2. Reduced water quality
2. Enhanced water quality
3. Higher cost for government and for society due to the effects of soil erosion
3. Reduction of cost for government and society due to limited effects of soil erosion

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