Tips for assessing soil quality in the farm

Soil quality is one of the influential factors in the productivity and quality of a crop – and there is a reason for that! Soil is much more than just a substrate: it is also responsible for bringing water and nutrients to crops, recycling organic matter, filtering pollutants, and keeping pests under control. It is therefore natural that growers seek to know more about how we can maintain soil quality.

A fertile, balanced, and correctly handled soil makes all the difference in the results of the harvest. To measure this quality, you have to analyse a number of indicators – physical, chemical, and biological –, as well as their interrelation and interdependence.

How to evaluate soil quality in farming?

To learn more about how to measure soil quality in your field and apply proper management and conservation techniques, check out the 4 tips we have listed below!

1. Consider the physical indicators

The physical indicators of soil fertility are directly linked to how the soil particles are arranged and distributed. If they are too compacted, for example, soil porosity drops considerably, which ends up influencing the substrate’s density and water retention capacity.

Thus, it is essential to consider the physical factors when evaluating the quality of the soil in your plantation. The main ones are:

• porosity;
• density;
• stability of aggregates;
• texture;
• superficial crusting;
• compaction;
• hydraulic conductivity;
• available water storage capacity.

Physical factors, when unbalanced, significantly affect crop productivity, because they limit root growth and seedling emergence.

In addition, the infiltration capacity and the movement of water between soil profiles may be damaged, decreasing the flow of water to crops.

2. Learn some chemistry

If you want to evaluate the quality of your farm’s soil with mastery, you will need to learn a little chemistry, even if it was not your favourite subject in high school. Chemical indicators are essential for understanding how fertile the soil at your farm is.

The chemical characteristics of the soil directly influence its relationship with the crops. They also affect the quality and quantity of water and nutrients available to the plants and other organisms responsible for balancing the ecosystem.

The mobility of contaminants/pollutants and the buffering power are also very important factors of chemical nature, and are decisive in the quality of agricultural substrates.

Furthermore, the chemical characteristics of the soil are intrinsically linked to the physical aspects, affected by them in a direct way, such as the tendency to compaction and the formation of surface crusts.

Some chemical indicators of soil quality are usually examined. Examples are:

• pH;
• salinity;
• cation exchange capacity (CEC)
• capacity to supply nutrients to plants;
• concentration of potentially contaminating elements (mercury, arsenic, other heavy metals and radioactive elements);
• concentration of micro and macro-nutrients.

3. Get to know the bioindicators

As we have already mentioned, soil is not an inert substrate. It is estimated that in one gram, there may be up to 100 million microorganisms of the most distinct species, which perform their specific biological functions in a delicate balance.

Thus, the soil can be considered a living ecosystem. As in any ecosystem, changes in its quality directly affect the populations that coexist there.

This is why the so-called bioindicators are critical when determining soil quality. They are considered a reliable way to identify possible negative changes in the substrate in time to reverse them. This is because biological elements react much more quickly to changes in management and planting techniques than those of a physical and chemical nature.

For example, measuring the amount of ergosterol per gram of soil can give excellent indications of its health. Ergosterol is a product of fungal origin that plays a fundamental role in the formation of aggregates, including the maintenance of their stability.

So, if there is not enough ergosterol, your crop could be in trouble.

Other equally important bioindicators for analysing the quality of the soil include:

• quantity of organic matter;
• diversity of animal species and microbiology;
• microbial biomass;
• level of respiration;
• quantification and qualification of enzymes present;
• quantity of earthworms and nematodes;
• speed of decomposition.

4. Take it to the laboratory

At this point, you should already be aware of the large number of indicators that must be taken into consideration when determining soil quality. More than that: it is extremely important to know how each of these indicators (physical, chemical, and biological) relate to and influence each other.

If the water holding capacity is low, for example, this will radically affect the transport of nutrients to the plants as well as the local microbiota, especially fungi. This means that the quality of the soil as a whole is shaken from the imbalance of just one indicator, in a very damaging chain reaction.

How is it possible to evaluate, quantify and interpret so many indicators at the same time? The best thing to do, without doubt, is to collect soil samples from your properties and send them to a laboratory specialised in this type of analysis.

These places have a wide range of equipment and machines exclusively designed to accurately examine each soil quality indicator. Armed with these results, you can design management strategies aimed at restoring soil health and equilibrium. The outcome? Increased productivity, savings in inputs, and long-term fertility.

The situation is not the best. So what now?

OK, you have thoroughly analysed all the indicators necessary to certify the quality of your soils, and the result is not the most encouraging. Now what? What to do next? 

Before you go out buying tons of supplies and fertilisers, know that it is not necessary to spend a fortune to make your crop soil fertile again. In many cases, adding fertiliser in the wrong way can even make the situation worse!

In fact, most of the time, a change in the way of handling is the key element when the objective is to improve the quality of the soil. No-till techniques, crop rotation and more efficient fertilisation are excellent examples of methodologies that tend to improve the situation.

How to maintain soil quality?

We will now see how the techniques and others that help maintain soil quality work.

Preparing the planting area

If you want to know how to maintain the quality of the soil, understand that the first necessary step is to prepare the growing area. This preparation begins with choosing the most suitable location – which includes paying attention to factors such as light and the availability of water for irrigation. From there, you can prepare the soil to increase the chances of successful farming, taking into account its physical, chemical, and biological needs.

There are several recommended practices which are capable of correcting the soil, improving its attributes, and ensuring that it contains the essential nutrients for the healthy development of the plants.

No-till farming

No-till farming is a management technique that proposes covering the soil in order to maintain its nutrients. Straw and plant remains are kept in the soil, preventing the occurrence of harmful processes such as erosion and desertification.

In this type of management, the soil is only handled during the planting process, when the farmer uses a specific sowing machine to open the furrows and deposit the fertilisers and seeds. After that, there is no more soil manipulation. The farmer then begins to take Integrated Pest Management (IPM) and weed management actions. In this way, the straw remains intact before and after cultivation.

The advantages of this technique include:

• thermal balance of the soil;
• increased organic matter in the soil;
• more availability of nutrients and water;
• control of erosion processes;
• increased productivity;
• more protection against contamination;
• less machinery activity and, consequently, savings in fuel consumption;
• less release of carbon from the soil into the atmosphere, which is one of the processes that contributes to the greenhouse effect.

Despite the advantages, it is important to pay attention to some necessary precautions. For example, having some technical knowledge is essential. Besides this, weed control and soil compaction also need extra care. Therefore, always count on the technical guidance of a specialist to avoid losses.

Another recommendation is that the farmer focus on crops that are best adapted to the region. No-till farming generally adopts forage species, since their roots and the straw they provide can also be adopted in the production of milk and meat.

Crop rotation

Monoculture can be detrimental to soil quality. Over time, it promotes alterations such as chemical, physical and biological degradation. As a result, crop productivity is compromised, and it becomes necessary to use other varieties in a rotation system.

Crop rotation consists of alternating different plant species in a certain area from time to time. The recommendation is to use plants with different root systems so that each crop leaves a residual inheritance in the soil to be used by the next planting.

The main advantages of this technique include:

• reduction in the incidence of pests, as it breaks the pathogens’ development cycle;
• diversification of income by having new crops;
• Increase of carbon and organic matter in the soil;
• reduction of the erosion process;
• reduction of the compaction process due to the diversity of root systems;
• recycling of nutrients in the soil;
• increase of soil fertility;
• reduction in the emission of gases that cause the greenhouse effect.

Plastering

A study carried out in corn plantations by the Federal University of Goiás, Brazil, has shown that the addition of gypsum and lime to crops can increase corn crop productivity by 9.3%, and soybean productivity by 11.3%. This occurs because gypsum modifies the chemical and biological properties of the soil.

The main objective of gypsum is to increase soil fertility by reducing Al+3 in depth. Gypsum (CaSO4, or calcium sulphate) reacts with aluminium, reducing its toxicity for plants. In addition to this neutralisation, the sulphate gives the soil calcium and sulphur, which act as follows.

Calcium

It has a function in the plant’s structure, forming compounds that are part of its cell walls.

Sulphur

It strengthens the plant in its defence against pests and diseases, acting in the hormonal control for the plant to develop in a healthy manner.

Liming

Liming is the application of lime to the soil to control its acidity as well as supplying nutrients such as calcium and magnesium. Unlike plastering, liming alters the pH of the soil. It is very common, especially in regions with a subtropical and tropical climate.

In those regions, much of the arable land has a low pH, besides high concentrations of Al+3. Liming increases the pH and reduces the concentrations of aluminium.

Since the reaction of lime is slow in the soil, it is necessary to perform liming uniformly and at least 3 months before fertilisation.

Fertilisation of special nutrients

Fertilisation is an indispensable practice for the insertion of micro and macronutrients important for plant growth. These include:

• nitrogen;
• phosphorous
• potassium
• calcium
• magnesium;
• sulphur;
• boron;
• chlorine;
• iron;
• manganese;
• zinc;
• copper;
• molybdenum;
• nickel.

Mineral correction should be carried out with the support of an agronomist, since each crop will have its specific needs, and inadequate doses will also harm the quality of the soil.

With tests and analyses, it is possible to arrive at a diagnosis that indicates the properties of the soil and its nutritional needs. Thus, it is possible to define the types of fertilisation, correction, and techniques that you should adopt to obtain more satisfactory results.

Earthworm culture

Earthworm culture can be considered a type of organic fertilisation, as it uses worms to ensure the presence of nutrients in the soil. The technique can be applied in two ways:

Tunnels

The worms dig their way through the soil and leave these empty spaces, which aerate the soil and contribute to the drainage of rainwater and irrigation.

Humus

The faeces left behind by earthworms are made up of plant and animal waste, giving rise to organic matter with nutrients that are essential to the quality of the soil.

The production of earthworm humus results in an organic fertiliser rich in nutrients, and guarantees a great improvement in the physical attributes of the soil.

In this article, you have better understood how we can maintain soil quality. The result of obtaining a balanced soil through the practices listed here you can check in practice: more productivity and fertility, plus less pest infestation!

Want to learn more about how technology can help increase productivity and improve your management in the field? Be sure to check out our article on precision agriculture.