How managing water - soil - plant interaction can improve production response

Understanding production environments as production systems, which encompass not only each factor in isolation, but the integration of all system constituents, is a constant challenge. The plant can be understood as a production component that has a strong relationship with its genetics, developed according to the plant species, and with biotic and abiotic factors. However, it is understood that the soil must be an environment prepared to receive the seed that carries all these genetic impressions and that will result in a new plant, and provide chemical, physical and biological conditions for its development.

The term soil quality has some definitions. It can be defined as the ability of soil to function, within the limits of natural or managed ecosystems, to sustain plant and animal productivity, maintain or improve air and water quality, and support human health and housing (Doran & Parkin, 1994; Karlen et al., 1997).

The chemical, physical and biological components of the soil interact and directly interfere with the development, health and production of the plant. Soil quality has a direct influence on the maintenance and sustainability of production environments. In this way, quality indicators of the production system are used, so that it is possible to verify the evolution and performance of the management used in these environments, which will have an impact on crop productivity and the construction of the production system. The integration of soil quality indicators is necessary, as soil is a highly complex, dynamic and heterogeneous environment. The isolated observation of these indicators does not provide sufficient information to explain the potential loss or gain of crops on a given soil (Carneiro et al., 2009).

Physical soil indicators are frequently used, such as density, total porosity, and its divisions into macroporosity and microporosity, in addition to the assessment of resistance to penetration, which simulates the force exerted by the root system to develop. These assessments tell us how aerated the soil is, that is, its capacity to be occupied by water and gases, and provide an environment for the development of roots in depth and volume. When we have soil with high density and low porosity, consequently, we will have difficulty in root development and less infiltration and water retention in the soil.

With the scarcity or reduced storage of water in the soil, impacts will also be observed on chemical indicators: pH values, organic matter, phosphorus and potassium available in the soil solution, and base saturation in the soil. These properties may suffer interference linked to the physical structure of the soil and water levels. Root development is directly related to the amount of water and nutrients in the soil, as roots develop with the main purposes of supporting the plant, absorbing water and nutrients, and connecting with soil microorganisms and forming the rhizosphere.

Therefore, biological indicators are very important to demonstrate how active and functional soil biology is. The so-called soil bioindicators include assessments such as basal respiration, microbial biomass carbon, enzymatic activity of microorganisms, indices such as the metabolic quotient, Shannon diversity and even information related to the abundance and distribution of soil microbial populations. Some bioindicators related to macroorganisms (for example, earthworms) are also evaluated.

Microbial bioindicators are extremely sensitive to the management of the soil system, and are therefore used to check soil quality and indicate soil health. The relationship between biological indicators is direct with other indicators, physical and chemical. Since in an environment where root development and subsequent plant development is favored, consistency is noted in the indicators evaluated, resulting in efficient delivery of crop productivity.

The construction of the soil system, integrating the physical, chemical and biological components, results in a balanced production environment, availability of water and nutrients, favorable root development and provision of favorable conditions for plant development, with a consequent productive response.