[:is]Soil is a non-renewable natural resource on a human time scale. (Albaladejo and Diaz, 1990). That is why it is essential to take measures for its conservation and renewal. These measures include prevention of erosion, improvement of vegetation cover, and replacement of nutrients taken up by crops from the soil.
Soil performs three fundamental functionsOn the one hand, it is the environment where plants grow, but it also acts as a regulator of water flow in the environment and mitigates the harmful effects of pollutants through physical, chemical and biological processes.
For these reasons, at Ideagro we believe that we must promote actions that maximize their productivity while promoting their conservation. That said, the objective has to be not only to minimize soil degradation, but also to adopt crop management measures that tend to maintain soil fertility.
The soil is a complex system, which is in a dynamic balance where the living beings that inhabit it have a fundamental role in its fertility. A healthy soil contains a large number of living organisms that form complex and diverse communities. These communities are made up of a large number of microorganisms such as bacteria and fungi, even organisms such as worms and insects. Plant roots can also be considered soil organisms in view of their symbiotic relationships and numerous interactions with other soil components. All these various organisms interact with each other in the soil ecosystem, forming a complex web of biological activity.
Soil is a heterogeneous, discontinuous, and structured environment dominated by a solid phase where microorganisms form discrete micro-habitats within the soil. These microorganisms have a very important role in the dynamics of the soil ecosystem and the enzymatic activity associated with them is an indicator of the different functions they fulfill in the soil. All soils contain a group of intracellular and extracellular enzymes with different origins that can be synthesized by plants, animals and microorganisms (Gianfreda et al., 1996; Verdoucq et al., 2003). Intracellular enzymes can be found in various parts of living proliferating cells (Nannipieri et al., 1998). However, living cells produce and secrete extracellular enzymes that function outside of the progenitor cells as free enzymes in a soil solution or as enzymes that are still associated with the outer surface of the epidermal root or microbial cell wall (Gianfreda, 2015). These enzymes are not only available in dead cells, but can also be absorbed into clays or integrated into humic substances. This means that soil enzymes play a crucial role in the movement of nutrients from the soil, since they transform the substances contained in the soil into simpler compounds, thus releasing nutrients that can be used by plants through the roots or by the numerous organisms that inhabit the soil. That is, if this enzymatic activity did not occur in the soil, the movement of nutrients towards the plant and in the soil ecosystem itself would be extremely low.
Enzymes play a vital role in agriculture and in nutrient cycling, in particular, since they are constantly synthesized, accumulated, inactivated, and decomposed in the soil (Balota and Chaves, 2010).
The enzymatic activity of the soil is responsible for the formation of stable organic molecules that contribute to the stability of the soil ecosystem, and are involved in the cycles of the elements. such as nitrogen (urease and protease), phosphorus (phosphatase) and carbon (B-glucosidase). For example, the total activity of soil microorganisms can be estimated by measuring the activity of the enzyme dehydrogenase. This enzyme plays an important role in respiration. Therefore, knowing the dehydrogenase activity of a soil will give us a global idea of the amount of energy in motion that is in the soil. On the other hand, phosphatase activates the transformation of organic phosphorus into inorganic phosphorus that can be assimilated by the crop.
Since soil quality depends on the physical, chemical, biological and biochemical properties of the soil, changes in these properties must be taken into account when evaluating changes in soil quality (Klein et al., 1985; Yakovchenko et al., 1996). However, as changes in some soil properties may occur very slowly or may only occur when the soil undergoes drastic changes, such properties are not suitable for estimating soil quality (Filip, 2002), and properties that respond quickly to environmental stress should be used (Dalal, 1998). The biological and biochemical properties of the soil respond rapidly to environmental stress or changes in soil management. (Klein et al., 1985; Nannipieri et al., 1990). In addition, they include properties that are directly related to the number and activity of the soil microbiota (microbial biomass, basal respiration, etc.) as well as properties associated with the decomposition of organic compounds present in soils and the release of nutrients, that is, the activity of hydrolytic enzymes (Visser and Parkinson, 1992; Gil-Sotres et al. 2005). Since enzymatic activity is highly sensitive to external agents, the measurement of the activity of numerous hydrolytic enzymes has been widely used in recent years to study the effect of changes in land use on processes that affect the cycle of bio-elements such as carbon, nitrogen, phosphorus, and sulfur (Bandick and Dick, 1999; Dick et al., 1994; Kandeler and Eder, 1993).
Microorganisms exert a great influence on numerous oxidation, hydrolysis and degradation reactions of organic matter. This in turn has a crucial role in the cycles of elements such as carbon, nitrogen, phosphorus and other elements necessary for the development of the crop. Bearing in mind the importance of soil in agriculture and the benefits of healthy soils indicated by the FAO, at Ideagro we have developed a test protocol that contemplates the enzymatic activity of the soil since it "Measuring the enzymatic activity of the soil is more important as an indicator of the fertilizing action of a microorganism than calculating its quantity."
These data allow us to corroborate the effects of the tested products not only on the health of the soil but also on the flow of nutrients from the soil. In addition, correlations can be established between the state of the crop and the state of the soil before and after the application of the product. With which, the determination of the enzymatic activity of the soil can be an adequate tool to incorporate in the development of new fertilizers based on microorganisms (RD 999/2017).
On the other hand, it must be taken into account that the data obtained from the enzymatic activities of a soil are not easy to interpret and there are no reference values, since these results are highly variable depending on the pH, the organic matter content of the soil, etc. At the Ideagro facilities we have carried out more than 12,000 enzymatic determinations of soils in Spain, Portugal and Italy and in 46 different crops.
This important number of analyzes It has allowed us to establish correlations through an algorithm between the observed enzymatic activities and the physical and chemical properties of the soil studied, thus laying the foundations for the interpretation of the results of future analyzes through a new indicator of soil biological fertility.
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