Healthy soil and disease suppression

How to properly manage and conserve the soil, in order to maintain and stimulate its disease suppressive capacity, as well as preserve resilience to stress in a sustainable way.

The expression soil health It is used, in a broad sense, to indicate the capacity of the soil to function as a living system, sustain biological activity and maintain the health of plants and animals. In this sense, soil health has a positive correlation with productivity and system sustainability. In other words, healthy soils are more productive over time, because they have greater capacity to support stresses, such as those caused by agricultural activities. And among the symptoms of Weakness in soil health are soil diseases.

Soil diseases are those of plants caused by microorganisms (pathogens, in this case) that inhabit the earth. Control of these diseases is complex and to be successful you need to know the soil and act to restore your health. The soil is inhabited by countless microorganisms (fungi, bacteria, etc.), mostly unknown. Some scholars claim that the Most of what is not yet known about life on planet Earth is in the ground.

It is known, however, that the decomposition of debris in the soil (process reduction of carbon chains to release energy) is completely dependent on microorganisms. Microorganisms, therefore, are part of the soil and, more than that, they are truly responsible for the functioning of agricultural and natural ecosystems. These organisms are related to the beneficial functions of soil and ecosystem, including decomposition of organic material, cycling of nutrients, water storage, soil detoxification and suppression of organisms harmful and pathogenic.

Soils with high diversity and biological activity are more resilient to stresses and disease suppressants than soils with low biological activity. Per This means that control (maintenance of the state of equilibrium) biological disease is something that constantly occurs in soils agriculture, even if it is not observed. And the way you take care of your health Soil interferes with disease control, making it more or less suppressive.

A soil is considered disease suppressive when the pathogen and the plant host are present, and environmental conditions are favorable to occurrence of the disease, but the disease does not occur or occurs with less intensity. Physical and chemical characteristics of the soil can determine its suppressiveness to diseases. However, the management of the biological (health) characteristics of the soil tends to have a more marked effect on disease control, making the suppressive soil. Perhaps because soil health has, in many cases, been neglected, while the physical and chemical characteristics necessary for plant production have received greater attention in recent decades.

A soil can be naturally suppressive to diseases, that is, present physical, chemical and biological characteristics that, associated or not, suppress the occurrence of one or more diseases. However, soils that are not naturally suppressive drugs can suppress disease (induced suppressiveness) through cultural practices such as fertilization, decompression, addition of organic matter or application of microorganisms that establish themselves in the soil and act in the biological control of diseases. In this sense, the intensification of the use of the soil, through Integrated Agricultural Production Systems (SIPA), favors soil health and consequent disease suppression, as it includes, in its most varied arrangements, conservationist soil management practices and increased biodiversity.

Sustainable soil management strategies that maximize natural cycles and reduce dependence on non-renewable resources are fundamental to maintaining soil health. Furthermore, healthy soils constitute a most efficient substrate for the action of biological control agents that are applied (introduced) into the soil, as they present more favorable conditions for establishment of these bodies. On the other hand, monoculture, revolution of soil, application of chemical products and burning have deleterious effects on soil biota.

Among the sustainable soil management strategies it is possible to highlight those related to soil conservation, conservation of organic matter in the soil, stress mitigation and reduction in the use of toxic inputs.

Soil conservation can be achieved by reducing erosion and increase in vegetation cover. Conservation of soil organic matter includes the reduction of soil preparation, the application of organic fertilizers of plant origin or animal, the increase in species diversity and the growth in the supply of carbon to the soil. Mitigating stresses caused in the soil requires optimizing the soil preparation, reduce the traffic of machines, favor the maintenance of plant residues on the surface and water in the soil profile, and divide the use of chemicals over time, to avoid occasional stress. A reducing the use of inputs needed in farming includes integrated management of pests, diseases and weeds, the use of cultivars resistant to pests and diseases, crop rotation and the use of cover crops soil, with the aim of reducing the application of products that may present adverse effects on soil organisms.

Integrated Agricultural Production Systems (SIPAs), which cover different arrangements, including farming, livestock and cultivation of species forests, are more sustainable examples from a biological point of view. One growing number of studies demonstrate that this intensification of land use has a positive impact on the abundance and richness of specific groups of organisms soil and soil microbial diversity. Results available at scientific literature, for example, shows that the intensification of production through SIPAs can make the soil suppressive to diseases that cause tipping over of plants, reduce survival time and germination of sclerotia (survival structures) of pathogenic fungi, increase the microbial activity in the soil and the number of viable propagules of microorganisms commonly used in the biological control of diseases.

In summary, SIPAs are efficient ways of intensifying land use and include or facilitate the adoption of sustainable soil management strategies. This results in healthier soils, with greater resilience to stress and disease suppressiveness.

Alexandre Dinnys Roese, Embrapa Agropecuária Oeste

Article published in issue 229 of Cultivar Grandes Culturas, June 2018.