Image by Rachel Meiergerd

Soil management practices in crop production

As described in a Conscious Club Article, soil is described as “earth’s fragile skin, supporting all life“. It comprises countless species which create a dynamic ecosystem.

As large scale and commercial agriculture practices developed soil diversity have narrowed. Cultivated crops can also not hold on to the soil like natural vegetation does and cause the loss of large amounts of topsoil because of erosion. Some form of degradation affects over 24% of the world’s land area. Given this, soil management is a key agricultural component to manage to ensure world-class yields and production.

Agriculture causes soil degradation

A variety of factors cause soil degradation, most of which are a direct effect of formal agriculture:

  • Water erosion
  • Wind erosion
  • Build-up of salt
  • Loss of organic matter
  • Fertility decline
  • Increased soil acidity
  • Structural decline

Soil supports 95% of global food production. As population levels increase across the globe, the demand for more food is also increasing. It is, therefore, even more important for the global community to protect soil against degradation.

Farmers must deal with many variables such as the climate, soil quality, varietal performance, and the market price of produce. Of these, the farmer can influence the most important – soil quality. A farm can have the best product variety on the market, but if he/she does not look after the soil, that variety will not perform to its full potential.

Good soil management practices

With soil management, the principle stays the same, irrespective of the crop one is dealing with. Action taken may, of course, differ due to varying nutrient or seedbed requirements. When applying good soil management practices, the following considerations are important:

  1. Polyculturing (alternating between crops)
  2. Soil nutrient management
  3. Effective cultivation practices
  4. Organic matter management
  5. Weed control

1.      Polyculturing

In the past, most farmers stuck to planting only one crop continuously, which is a very detrimental practice for the soil. This type of planting is known as monocropping. From the perspective of biological activity within the soil, the main issue with monocropping is removing the advantage of soil organism diversity. Every crop has its own nutritional requirements, so if certain nutrients are not replenished constantly, the soil is stripped of those elements. If farming practices do not replace nutrients comprehensively enough, the soil profile degrades over time. Crops affect the soil’s physical structure in different ways, which may influence soil structure irreversibly.

It is thus extremely important for a farmer to adopt polyculturing by alternating crop production, or at the least planting a cover crop during the off-season periods. A good example is to alternate a grass (monocot) crop with a legume. The legume will act as green manure to help build up the soil and replace certain lost elements within the soil. The most important aspect when taking this action is to alternate the principal crop with a crop from a different grouping to prevent soil degradation.

2.     Soil nutrient management

Managing soil nutrition is one of the most important aspects of any crop production. If there is not enough nutrition within the soil, then harvest results will be lower than expected. As mentioned previously, each crop has nutrient requirements which it needs to perform optimally. If these elements are not available in the right amounts and at the correct time, the crop will not achieve an optimum yield. To manage this, a farmer applies fertiliser that provides the relevant nutrients a plant needs to grow. Under-applying fertiliser can be detrimental not only to the yield but can also eventually affect the soil.

When a plant does not receive sufficient fertiliser, it still extracts what remains in the soil and over time completely strips the soil of all its nutritional value. On the other side of the spectrum, applying too much fertiliser can also lead to the degradation of the soil. Too much fertiliser can either cause an increase in the acidity or alkalinity of the soil, and no crop will thrive in one of these extremes. Balance is thus extremely important and can only be achieved by applying the correct amount of nutrients.

Fertiliser with a high salt index can also increase the salinity of the soil, and if large amounts of this are applied constantly, then the salt content will continue to increase within the soil, affecting the sustainability of agriculture and affecting the structure of the soil. Farmers can achieve the critical balance by testing soil as often as possible to ensure correct fertiliser application.

Soil Sampling provides control of the pH of the soil by liming (adding lime), which minimises any acidity/ alkalinity issues. Managing the nutrient content of soil is also crucial in crops like sugarcane, which is ratooned on a commercial scale. Every 18-month cycle extracts many nutrients from the soil and to ensure that the following year’s crop is just as successful sugarcane farmers must ensure they replace all nutrients that were extracted.

3.      Effective cultivation practices

Cultivation affects the physical structure of the soil. In agriculture, this is initially important as it loosens the soil and allows for effective aeration which improves crop production. Excessive cultivation, however, is not a sustainable practice as it leaves an opening for erosion which permanently degrades the quality of the soil. In recent years, more farmers are looking at no-till farming, where they do not till the soil before planting. Not everyone agrees on this approach, favouring rather a ‘minimal till ’ practice where the soil is tilled every four to five years, compared with traditional farming methods which see annual soil tilling. This option reduces erosion of the soil and will also allow the soil to keep a more uniform structure. In the long run, this will reduce degradation drastically.

When preparing a seedbed, farmers should ensure that the fields are as level as possible, especially those with a natural slope. Correct contouring can also be effective in minimising topsoil loss due to water erosion. Besides erosion, a seedbed that is not level and uniform can cause spots of water build-up within the field. These spots have low levels of pH and high levels of salt content. The lowering of the pH is due to an increase in the soil’s water level. Acidic compounds from the subsoil surface to the topsoil, leading to lower pH levels. All these actions degrade the soil and could, eventually, be irreversible.

4.      Organic Matter Management

Normal agricultural practices usually remove the entire plant with no organic matter left in or returned to the soil. A soil that is left barren with no follow-up crop speeds up the disintegration of organic matter, further decreasing the organic content of the soil. When soils are excessively tilled, the plant matter is usually buried deep in the soil as it is turned over, with little being left in the topsoil.

As noted earlier, it is important to keep some sort of vegetation in the field to minimise erosion and provide organic matter for the soil by leaving stubble on the field and tilling the soil less. By increasing the organic matter content of the soil, one can improve its water-holding capacity, which helps a crop during drier periods. Higher organic matter content also:

  1. improves the temperature profile of the soil; and
  2. influences the diversity of soil organisms.

The more diverse the soil is, the more nutrients naturally become available and act as a buffer against pathogens.

5.      Weed control

Farmers sometimes choose to let their field during the off-season become overgrown with weeds. These weeds are often invasive and can cause much damage to the soil. Weeds have an extremely high-water demand and reduce the amount of water within the soil profile. In most cases, weeds harbour different crop pathogens and these can suppress a crop’s growth.

BY correctly managing resources like soil, farmers can produce more on smaller parcels of land which increases profitability and sustainability.

Unitrans Africa encourages agricultural practices which make the best use of the parcel of soil at their disposal. The company follows a strong partnership approach to delivering tailored end-to-end agricultural solutions. They assist farmers by bringing innovation and implementing Best Practices like soil management to key farming activities; delivering customised solutions to solve production issues; introducing new methodologies to drive efficiencies and supporting all parties in the achievement of goals.

Find out more about Unitrans Africa’s values of innovation, honesty, excellence, unity, safety and constancy, as well as their ability to provide comprehensive contributions to farming operations by contacting them via email.

Image: Rachel Meiergerd / Pexels