Fertiláqua expert answers 12 fundamental questions about soil quality

Combining productivity, cost reduction and business and environmental sustainability is the math that works for the producer. Thinking about the positive balance of this account, Agronomist, PhD in Soils and Fertiláqua specialist, Dorotéia Alves Ferreira, explains why adequate soil management is fundamental and necessary, and tells what needs to be done (and left undone) for maintaining soil health, and to avoid the expansion of cultivated area and still see productivity grow. Follow: 

01 - Why is soil quality capable of interfering with the expansion of cultivated area?

Soil quality refers to the chemical, physical and biological properties of the soil, making it capable of providing better conditions for the development and production of crops. The balanced production environment helps the plant in its vegetative development, and provides conditions for it to express its productive potential. In this sense, plants grown in a quality soil system are more resilient and certainly deliver more productivity per hectare. The investment to ‘build soil’ is, without a doubt, something that is part of production environments that aim to produce more in a smaller cultivated area, that is, production with quality and sustainability. 

02 - What is the biggest challenge to be faced when it comes to soil health?

The production environment presents several challenges such as climate effects, biotic and abiotic stresses. However, one of the points that is raising doubts among producers is related to the insertion and integration of technologies and management that work with the soil's biological system. The functionality of soil biology has effects on the entire soil-plant system. In chemical aspects, it is related to nutritional cycling and availability of nutrients in the soil and in relation to soil physics, it acts strongly on the aggregation of particles, favoring porosity and consequent infiltration of water into the soil. In biological terms, the functionality of soil biology is linked to the protection of the root system, the biological balance of microbial populations and the induction of plant resistance. Therefore, the term soil health is quite complex, as it encompasses the entire soil system and has direct and indirect effects on the productive environment, making it quite challenging.

03 - How should management be carried out to guarantee the quality of the soil and its physical, chemical and biological components?

The management that can be used in the soil system is broad and variable in relation to the type of soil, climate, cultivated plants, investment required, among others. The insertion of carbon into the production system brings benefits to the soil properties and the production system, and organic carbon can be inserted in several ways, such as cover crops that have a high carbon/nitrogen ratio (C/N), sources of organic compounds arising from composting or not, and even a rotation or succession planting scheme with crops that leave vegetable remains in the soil to be transformed by biological activity, which promote nutrient cycling and stabilize carbon in the system. An important point to consider is the insertion of carbon into the soil through roots that develop in depth and volume in the soil. Plants release various carbon sources (enzymes, growth factors, organic acids, flavonoids, etc.) into the soil that stimulate microorganisms and promote the biological balance of the soil, reflecting biological activity, decomposition and mineralization of organic matter, in addition to their own roots form channels in the soil, promoting aeration and water infiltration. 

Therefore, the integration of plants that act as service providers to the soil system, the so-called cover plants and the insertion of biological technologies, are fundamental for the construction of a living, productive and sustainable soil system.

The practice of using different active ingredients in phytosanitary products and sources of mineral nutrients that are not fully soluble at the beginning of plant development are also important. These practices favor the diversity of microorganisms in the soil, as the environment becomes more heterogeneous from a management point of view, and consequently does not promote microbial selection. The biological diversity of the soil favors the soil-plant-environment system.

04 - How important is covering the soil with straw? What types of impacts can be avoided with this action?

Keeping the soil covered with plant material is fundamental for production environments, and this practice has effects on the physics, chemistry and biology of the soil. Covered soil is a basic premise of the Direct Planting system, as it prioritizes soil protection from solar rays, the force used by raindrops that cause so-called splashing, erosion and soil loss, in addition to stimulating biological activity. , promoting mineralization, mainly in the surface layer, in addition to protecting organic matter in the soil. 

05 - How can crop rotation and planting cover crops help improve the soil?

Plants that provide ecosystem services to the soil-plant system are included as cover crops or those used in off-season periods in rotation with cultivated plants. Among the aspects that are related to improving the soil system, we have some points to mention such as the insertion of plant residues (roots, aerial part dry matter and root exudates) different from the plant of economic interest, improving decomposition and consequent effective nutritional mineralization , due to different carbon sources that stimulate soil biology. In addition to the fact that it is often related to plant material with a C/N ratio that is also different from the cultivated plant and therefore reflects on soil coverage, construction and maintenance of organic matter.

In order to select the cover crops used in crop rotation, it is important to know some important points such as the allelopathy effect of some legumes (e.g. sunn hemp) in relation to some species of nematodes, also considering that they are plants with a lower C/N ratio and which, therefore, help decompose grass residues (e.g. brachiaria), which have a higher C/N ratio. The multiplier effect of soil microorganisms of a fasciculated root system, as observed with the use of grasses, mainly due to the greater amount of root environment for efficient rhizosphere formation and the high investment of carbon fixed via photosynthesis for root formation and release of carbon sources by roots (root exudates). Another important point is related to the occupation of the soil system by the mass of roots formed by grasses, for example, which, after decomposition, form channels in the soil that make it easier for the roots of cultivated plants to develop and are also related to water infiltration. on the ground. When we think about legume roots, which can be quite aggressive due to their pivoting morphology, it is possible to verify their ability to break through a compacted or dense layer of soil, depending on the level of resistance to penetration that the soil has.

Therefore, the benefits are the most distinct and it is important to evaluate the needs of the area, the availability of these plants, as well as their adaptability to the locations in which they will be inserted.

06 - What can we say about practices such as intensive and unnecessary soil disturbance?

Several management practices have caused degradation to the soil system, including the exposure of organic matter and the disruption of soil aggregates due to their disturbance. This practice is no longer widely adopted thanks to the various benefits provided to the soil and known through a constantly adopted management practice, which is the direct planting system. In this system, some basic premises must be adopted, such as the absence of soil disturbance, the continuous presence of vegetation cover on the soil and the rotation of crops planted in the area. In this sense, practices that can cause certain disturbance are adopted only in some situations, such as, for example, application of limestone, fertilizers and plaster, mainly when opening areas and in situations where the area requires mechanical intervention, due to compaction, with carrying out subsoiling. 

Turning promotes the exposure of the soil and organic matter that is constantly transformed in the soil by biological activity, causing oxidation and constant loss of carbon in gaseous forms, which results in losses of this carbon and environmental damage related to the greenhouse effect. 

07 - What are the damages of excessive fertilization?

Regarding the practice related to excessive fertilization, it is important to highlight that soil analysis is essential for carrying out this practice. Therefore, it is necessary to carry out fertilization compatible with the productive potential of the area, crop and cultivar, considering that we have two basic ways to build soil fertility, which are: construction fertilization and fertility maintenance, taking takes into account the export of nutrients by plants. Therefore, the excessive supply of soluble nutrients to plants leads to less interaction between them and biological groups, especially symbiotic ones, and can cause nutrient losses and environmental pollution due to the evaporation of some gaseous sources and silting of rivers due to surface runoff. of nutrients bound to soil particles. Nowadays, another important point is the scarcity of available fertilizers and their high costs.

08 - How can the use of fire and exposure without coverage harm the soil and how can this be reversed?

Fire is a practice adopted mainly in open areas or in situations where it happens accidentally. If it is used for a specific purpose, it is important to have control so that it does not spread in a disorderly manner. It is known that this practice in productive areas is very harmful to organic matter, due to its burning. The burning of organic matter causes loss of carbon from the soil, which is negative for the chemical, physical and biological components of the soil. A very important damage is reflected in physical issues of the soil, mainly related to the loss of water, as its evaporation occurs due to heat, which can result in lower soil porosity. It is important to insert management practices with cover crops and technologies focused on soil biology that aim to metabolize soil organic matter in order to recover the environment after this intervention in the system. 

09 - How can the use of nutrients help to effectively increase soil fertility?

Building soil fertility is essential for agriculture to have good results, as plant nutrition directly contributes to the development, growth and productivity of crops. For this reason, chemical analysis of soil for fertility purposes is essential so that fertilizer recommendations in relation to soil needs and crop production potential are made correctly.

However, in the scenario of modern and highly productive agriculture, in addition to the adequate supply of nutrients, the importance of adequate nutritional use has become evident. In this sense, it is important to think about building soil fertility, focusing on the chemical, physical and biological properties of the soil. It is noted that in a biologically active soil with a physical structure, the plant has the possibility of taking advantage of the nutrients that are constantly added and which, for some reasons, such as leaching or precipitation, may become unavailable.

In this aspect, the concept of soil fertility is broad and does not only aim to provide nutrients to the soil through the use of mineral fertilizers, but rather to improve aspects of the soil-plant system that aim to make better use of soil nutrients. 

10 - Can there be production systems without the capacity to increase productivity, despite chemical fertility? Why does it happen?

The development of soil science was extensively focused on soil chemistry, in this sense several works, methods and concepts were developed to improve this component of the soil system. However, properties related to soil physics, and more specifically soil biology, have not been much discussed and consequently implemented. 

When opening agricultural areas, mainly in the central region of the country, chemical management was extremely heavy. Mainly with high applications of limestone, in some cases gypsum, and nutritional sources based on phosphorus, potassium and nitrogen depending on the crop, in addition to micronutrients. In several of these regions, the soils had the characteristics of being deep and well drained, which is why attention was more focused on building chemical fertility.

However, after several years of cultivation, problems related to the loss of soil structure, causing compaction and imbalance in soil biology - generally due to the selection of microbial groups, tend to occur. While the frequent addition of fertilizers is always done, less attention is focused on the physical and biological aspects of the soil, meaning that the plant is unable to access the nutrients that are in the soil and pathogenic groups begin to dominate the soil's microbiological environment. Therefore, the result is areas with good chemical soil fertility, but which may not result in increased productivity due to the lack of integration of the soil system, not providing conditions for the plant to express its productive potential.

11 - How is it done and when is the best time to carry out soil analysis?

Soil chemical analysis for fertility purposes is generally carried out in the period after harvesting the planted crop. This occurs because the plant exports nutrients from the soil for its growth, development and production of grains or fruits. The plants' energy source would be photosynthesis itself and the nutritional source would be the soil, which is later converted into a drain, resulting in what is produced, which are grains or fruits. 

This is why soil analysis is so important, as it checks the chemical and nutritional situation of the soil, so that fertilizers can be applied to build soil fertility at the beginning of the use of a given area and, subsequently, maintain fertility. which takes into account what the plant exports to its drain. Furthermore, based on soil analysis, calculations are also carried out to obtain quantities of limestone and gypsum to carry out practices to correct the soil's active and potential acidity, providing greater nutrient availability. 

12 - In the state of Mato Grosso, soybean producer Mr. Nelson Kappes cultivates the so-called “giant soybean plant”, which is even in the record books. How is it possible for a soybean plant to grow and produce more than 21 thousand pods?

It is a plant grown under extremely controlled conditions and with everything it needs, including artificial light at night. These factors mean that the plant is metabolically active at all times, which promotes great use of energy from photosynthesis and as the plant is grown in a pit, nutrients are highly available. Another interesting point is the vertical staking that is done so that the plant develops vegetatively.

It really is a plant built to break records, which means that its utilization is extremely high considering the production of pods. This scenario does not apply in normal field production conditions, since production is carried out on a large scale and, as we routinely say, we are in an “open-air laboratory”, with several positive and negative points for growth, development and productivity. of plants.