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How to Improve Soil Fertility?

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How to Improve Soil Fertility?

Draganchuk M.

About the author:

Mikhail Ivanovich Draganchuk is the head of the peasant farm "Dragmi." (Crimea, Sakskiy region, Elizavetovo village).

The peasant farm was established in 1991 and it covered 3 ha then.

Since 2006, no-till farming was implemented on 367 ha. Currently, the farm size is 1430 ha, and the no-till technique is used all over the farmland. The farm is situated in the dryland, with rainfall of 220-300 mm per year. The following crops are grown on the farm (the average crop yield is given in parentheses): winter wheat (22 c/ha), winter barley (24 c/ha), flax (10 c/ha), chickpeas (11 c/ha), sunflower (15 c/ha).

Year by year, soil quality is deteriorating. People are exploiting land resources to obtain necessary products. Crop problems are attempted to be solved by applying different kind of tilling methods. Unfortunately, mechanical tillage leads to the destruction of soil biota, decline in organic matter, destruction of soil structure and erosion. And as a result, the soil loses its "health" and becomes less productive.

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M. Draganchuk demonstrates intercropping (double cropping) of sunflower and sainfoin on his field. Great biomass and "food" for the soil grows under sunflower plants.

In order to become profitable in agricultural business, the farmer has to solve a lot of problems:

  • reduction of labour costs and cycle time;
  • reduction of production costs;
  • savings on fuel;
  • increase in productivity of labour;
  • reduction of deterioration of equipment;
  • reduction of number of needed machinery;
  • and so on and so forth.

All these components are very important for business efficiency.

However, in modern agribusiness the main challenge is the preservation of the soil, which is the main capital of this business. The fertility of the soil will determine what we can get from our land, how much and of what quality. And it will definitely have an impact on the quality of life of farmers and of the society on the whole.

To preserve the soil it is necessary to:

  • stop soil erosion (wind and water);
  • reduce bulk density of soil,
  • improve its structure;
  • retain more soil water; and
  • increase organic matter in soil

How can it be achieved? Very easily! For this purpose farmer needs:

  • to stop mechanical tillage;
  • not to close up plant residues into the soil, but to mulch and leave them on its surface;
  • to keep any water that falls; and
  • to reduce the number of operations on the field, which will result in less soil compaction

The table below will help you to understand how each of these operations affects the solutions to the problems with soil.

Table N 1. The interdependence of the challenges and solutions to the problem of maintaining soil fertility

Soil conservation challenge

Solution

Cause and consequences

Control soil erosion (wind and water)

Stop mechanical tillage

Ploughing and other mechanical tillage contribute to disruption of the soil structure as a coherent whole, the soil becomes decomposed. This helps the wind to blow out the particles of soil and water to wash them off by watering and precipitations. Because of erosion each year about 24 billion tons of fertile soil is lost worldwide. The more we plough, the more soil is blown out and washed away.

Do not close up crop residues in the soil, but mulch them and leave them on the soil surface

Crop residues on the soil surface prevent wind and water erosion of the fertile layer of soil.

Reduce soil compaction

Stop mechanical tillage

Mechanical tillage does not reduce bulk soil density, but contributes to its increase. Ploughing is like a “drug” that temporarily relieves symptoms but does not address the cause of the soil compaction, which is small amount of organic matter in the soil, the loss of soil biota and, consequently, reduction of the content of humus in the soil.

Do not close up crop residues in the soil, but mulch them and leave them on the soil surface

Crop residues are food for the soil. The availability of the widest possible range of organic matter improves soil structure, improves its de-compaction and serves as food for soil microorganisms, which "loosen" the soil.

Reduce the number of operations on the field, that will reduce soil compaction

A greater amount of field traffic cause soil compaction. It is necessary to reduce to the field traffic to a minimum.

Improve soil structure

Do not close up crop residues in the soil, but mulch them and leave them on the soil surface

Crop residues are food for the soil. The availability of the widest possible range of organic matter improves soil structure and its de-compaction, and serves as food for soil microorganisms, which "loosen" the soil. It improves vertical flows of water and soil porosity.

Stop mechanical tillage

Mechanical tillage decomposes the soil and makes it prone to erosion. It disrupts biological, chemical and physical elements of the soil. Mechanical tillage lifts the layers of the soil, increases the soil's reaction with oxygen and thereby kills anaerobic soil biota {i.e. the one that lives in the soil without oxygen). Such microorganisms are important for improving soil structure. Their loss leads to deterioration of soil structure.

Reduce the number of operations on the field, that will reduce soil compaction

A greater level of field traffic cause soil compaction. It is necessary to reduce to the field traffic to a minimum.

Retain rainfall water

Optimum soil moisture should be maintained in the soil. Excessive desiccation of soils and subsequent excessive watering do not contribute to the preservation of the optimal level of moisture in the soil. The more optimal the soil moisture content is, the better microorganisms function, the better the soil structure becomes.

Retain more water

Stop mechanical tillage

Any tillage operation opens the soil. The wind blows out the moisture from the soil faster, and the sun dries the soil up faster.

Do not close up crop residues in the soil, but mulch them and leave them on the soil surface

Plant residues on the soil surface help to prevent moisture loss because of wind erosion and desiccation of the soil. The presence of plant residues helps to keep the moisture in the soil, reduces the amount of necessary watering on the irrigated lands and allows more crop yield due to the increased soil moisture on drylands.

Increase the amount of organic matter in the soil

Do not close up crop residues in the soil, but mulch them and leave them on the soil surface

At present, annually up to 1 t/ha of humus is depleted for cultivation of cotton from the arable layer of the soil. When applying 1 t of manure to the soil, only 90 kg of humus is formed. And when leaving on the field 1 t of straw, 170 kg of humus is formed. Thus, just to fill the annual losses, and to maintain the sustainable balance of humus, not less than 10 t/ha of manure should have been applied only to the arable layer of the soil, which is not the case. Crop residues are the best alternative to maintain the content of organic matter in the soil.

By implementing zero tillage farming, all these problems can be solved.

No-till farming is the abbreviated name of the zero tillage in horticulture, and it refers to the way of sowing seeds into the soil that has not been agitated by any tillage.

When the soil remains intact and covered with plant residues, the number of all types of soil organisms (from microbes and fungi to arthropods) increases. By increasing the amount of organic matter and improving infiltration, no-till farming improves the soil.

Reduction of the number of operations on soil by applying no-till technique leads to savings in time, labour, and fuel. No-till technique allows the farmer to work less, earn more and still maintain his precious land. That is why this technique has spread throughout the world over the past 20 years. Try to find at least one more technique that would prepare the soil more carefully! So, the zero tillage is the most effective way to stop soil degradation and to restore its productivity.

If in the first phase of implementation of this technique farmer face the challenge of protecting the soil from erosion and maintaining the existing level of soil fertility, then in the future the challenge of improving soil fertility becomes the new priority in their work.

Scientists around the world are paying attention to one of the main causes of the decreased soil fertility:

"Land productivity reduces dramatically because of soil erosion, salt accumulation and depletion of nutrients. Continuous soil tillage for a long period of time kills bacteria and micro-organisms that convert organic matter into nutrients”.

Professor Mary Scholes and associate professor Bob Scholes from the University of the Witwatersrand (South Africa).

Therefore, in order to effectively address the issue of soil fertility improvement, the central attention should be paid to the microorganisms living in the soil.

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Soil microorganisms convert organic matter into nutrients

Under no-till farming, we stop agitating the soil and leave all plant residues on the surface of the soil, thus favourable conditions for the development of soil biota are created, which facilitates soil remediation. But when we harvest cultivated crop, soil bacteria lose their source of nutrition, because they eat readily available carbon, which plant roots excrete in the process of photosynthesis. And the process of development of soil microorganisms is slowed down until the next year (until the following crop growing cycle).

If we want not just to save the current soil fertility, which in itself is a challenge no. 1 for many farmers, but also to increase its level at a faster pace, then we need to feed the soil biota, when commercial crops are not planted. What is necessary to do this?

It is necessary to always have plant roots in the soil, and permanent vegetation cover or, at least, mulch on the surface of the soil. To this end, every year after harvesting primary culture, it is necessary to plant cover crops. In the drylands crop residues should be shredded and left as green manure on the surface of the field.

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Cover crop residues in peasant farm "Dragmi", planted after harvesting winter barley

Cover crops have many important characteristics with regard to soil fertility. They are able to:

  • increase the content of organic matter in the soil, which contributes to the increase organic carbon content in soil;
  • increase the number and activity of beneficial soil organisms;
  • accumulate plant residues on the soil surface;
  • loosen and improve soil structure, improve air and water regimes;
  • increase water holding capacity of the soil;
  • add nitrogen by means of biological fixation (legumes);
  • control the growth of weeds;
  • protect the ground from soil erosion (water and wind) and overheating;
  • contribute to the circulation of nutrients in the soil;
  • retain snow and water;  and
  • reduce problems with pests and diseases.

They produce a large amount of green biomass and plant roots when the main commercial crop has already been harvested, which favour the increase in the number and activity of beneficial soil microorganisms. This is very important, because the growing number of bacteria in the soil leads to the improvement of soil fertility.

The surface of the soil should never be bare!

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Cover crop residues winter barley

Although cover crops (green manure) are just one of many elements of the no-till farming, but it should be a priority when considering the improvement of soil fertility. When working on it, the fastest results can be achieved, because growing cover crops will entail changes in the whole system of no-till farming. Such elements as "crop residues", "weed control", "soil water", "nutrients", and "crop rotation" will be improved, and the system itself will become more balanced and harmonious.

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There are two different ways to include cover crops in crop rotation: succession cropping[1] and double cropping[2]. Cover crops can be cultivated both in mono-culture and in combinations (the so-called "cocktails"), which is even better. And no matter what way of growing cover crops is chosen, the main principle should be respected: there should always be plant roots in the soil and permanent vegetation cover on the surface of the soil.

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Cross-section of top soil with cover crops

Planting cover crops between every commercial crops enables the soil to achieve the state as close to the natural as possible, and thus to dramatically accelerate the processes of soil formation, its preservation, and also to improve significantly the fertility of the soil.

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The No-till drill in use: it cuts crop residues with disc coulter and sows seeds right after.



[1]Succession cropping are crops that are sowed after harvesting annual main crops in order to get “green biomass”. Crop yield is harvested in autumn. Legumes, grains and their combinations can be used as green manure.

[2] Double cropping occurs when 2 crops are grown simultaneously on one field. For example, sunflower and alfalfa can be planted on one field. Alfalfa would cover the soil between the sunflower plants and would create the green biomass, which has its advantages, such as accumulation of organics in the soil, improvement of soil structure, water retention, accumulation of nitrogen in the soil for the future harvest, etc. 

 

Tags: soil fertility, humus, zero tillage, zero-seeding, land degradation, wind erosion, water erosion

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