“Attention must be paid to temperature, sunlight exposure, and storage conditions…”
Christiane Paiva is a researcher at Embrapa Maize and Sorghum, focused on soil microbiology and bioproducts. Paiva has a degree in agronomy and a M.Sc. and doctorate from UFMG.
Christiane Paiva, Embrapa Maize and Sorghum
AgriBrasilis – What are the limitations of using inoculants?
Christiane Paiva – The main limitation is the lack of technical knowledge in handling. Inoculants are biological products, made from live microorganisms, and require different care than chemical products. Attention must be paid to temperature, sunlight exposure, and storage conditions. It is also necessary to know the correct way to inoculate the seed, using the appropriate dose.
Another challenge is compatibility with chemicals. Often, a farmer purchases seeds that have meanwhile been treated with pesticides and then wants to apply the inoculant. In this case, the effectiveness of the biological product may be compromised. The ideal approach is to first apply the chemical treatment, allow the seed to dry, and only then apply the inoculant.
In the field, it is recommended to use separate tanks for the application of chemicals and biologicals or, when this is not possible, to spray quickly, avoiding changes in pH and temperature. In summary, success depends on good management practices and the use of legitimate products registered and authorized by the Ministry of Agriculture, Livestock, and Food Supply.
AgriBrasilis – How do inoculants work to release phosphorus from the soil?
Christiane Paiva – Phosphate-solubilizing microorganisms act in the rhizosphere, near the roots of plants. In the case of the product developed by Embrapa, two bacteria act through different mechanisms that favor phosphorus absorption.
In Brazilian tropical soils, phosphorus is difficult to absorb due to the presence of minerals, clays, and oxides that retain the nutrient. It is estimated that almost 80% of the phosphorus applied via fertilizers ends up trapped in the soil. Thus, farmers invest heavily in phosphate fertilizers, but much of the element accumulates in the soil without being used.
The bacteria produce organic acids and enzymes that break the bonds between phosphorus and the soil, releasing phosphorus trapped in minerals and organic phosphorus present in organic matter, plant residues, and straw (in the case of no-till farming). In this way, the phosphate becomes soluble and available to plants.
AgriBrasilis – What is the cost-benefit of using inoculants for farmers?
Christiane Paiva – The cost is very low in relation to the potential return. Phosphorus inoculants can generate average gains of 5 to 6 bags of soybeans per hectare and up to 11 to 13 bags of corn, with an investment of less than half a bag/one bag of grain. It is, therefore, a highly profitable technology, which also allows for better use of the fertilizers applied and, in some cases, even a reduction in fertilizer doses.
“Microorganisms can increase the utilization of nutrients accumulated in the soil, but current efficiency is limited to a maximum of 20%”
AgriBrasilis – How efficient is phosphorus applied via traditional fertilization?
Christiane Paiva – It is quite low. In very clayey and weathered soils, common in Brazil, efficiency can be as low as 10%, meaning that 90% of the phosphorus applied is unavailable. In general, the average utilization in Brazilian soils does not exceed 20%.
AgriBrasilis – Can the inoculant completely replace phosphate fertilization?
Christiane Paiva – Definitely not. Unlike soybeans, where the inoculant replaces the use of nitrogen because this element is available in the air, phosphorus needs to be continuously replenished. Microorganisms can increase the utilization of nutrients accumulated in the soil, but current efficiency is limited to a maximum of 20%.
AgriBrasilis – Why is the use of inoculants more effective in no-till areas?
Christiane Paiva – No-till areas accumulate large amounts of organic phosphorus in straw and plant residues. This nutrient, which would not be naturally available, can be released by enzymes produced by microorganisms.
In addition, the no-till environment favors the microbiota: there is a higher content of organic matter, which serves as food for microorganisms, greater moisture tariff, and protection of the straw against sudden temperature changes. These conditions provide more biologically active soils, creating an ideal environment for the efficient action of inoculants.
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