Choice and use of bioinputs in winter crops

Current agriculture faces the challenge of increasing agricultural productivity, with economic, environmental and social sustainability, reducing impacts on established biomes and the use of chemical inputs. The use of microorganisms to promote growth, fix nitrogen, solubilize nutrients and control pests and diseases is yet another contribution of microbiology to agriculture. Research in this area is growing exponentially, generating registrations, patents and products used in various sectors, mainly in agriculture. The Ministry of Agriculture and Livestock (Mapa) defines as bioinputs products of biological origin (vegetable, animal, microbial and mineral) used in agriculture to combat pests and diseases, improve soil fertility and increase the availability of nutrients for plants.

Furthermore, the multifunctionality of microorganisms provides several functions in the environment, but they are often assigned only one main function. The scientific nomenclature of microorganisms is made up of genus, species and, more recently, strains are gaining prominence, as this allows for greater specificity in the function attributed to them. If, on the one hand, there is greater scientific precision, on the other hand, rural producers find it difficult to recognize the functions of different microorganisms. Therefore, this text intends to present management options for winter crops based on information generated by the Research Group Sustainable Management of Large Highland Crops (Coxilha-UFSM).

Considering winter crops (focusing on wheat, barley, oats and vetch), microorganisms capable of assisting producers and technicians in decision-making to solve the most common crop problems are being presented. It is noteworthy that the concentration of the microorganism, viability and management of its application are also fundamental for its effective action on plants. Table 1 exemplifies a proposal for using microorganisms. It should be considered that there are several alternatives, but in general this is how microorganisms are used in the experimental teaching area at Coxilha-UFSM. And they present promising results in the research carried out. Other variations are possible when considering microorganisms, strains and cultures.

Inoculation via seeds

Some details that make a difference in inoculation are worth highlighting. When inoculation is via seed, mixing the bioinput with fungicides and insecticides should be avoided. After carrying out the chemical treatment of the seeds, wait for them to completely dry and then carry out the biological treatment. The doses of microorganisms must be established to obtain a high concentration of colony forming units (CFUs) per seed. This information is not available for many microorganisms, cultures or purposes of use.

According to Hungary, inoculants must have a minimum concentration of 108 Azospirillum cells per gram (g) (peat inoculant) or per milliliter (ml) (liquid inoculant). Application with liquid inoculant at the highlighted concentration can be carried out with 150 ml/50 kg of corn seeds and 200 ml/50 kg of wheat seeds. Therefore, the theoretical estimate of CFUs is 270.000 CFUs/seed (corn) and 36.000 CFUs/seed (wheat). For soybeans, there must be at least 1.200.000 CFUs/seed. A strategy when the values ​​for culture or microorganisms are not scientifically established: the usual one for soybean seeds and Bradyrhizobium sp. can be considered in a similar way. (1,2 x 10⁶ CFUs per seed).

Based on this, the minimum number of UFCs/seed must be multiplied by the number of seeds that will be used in the area (Figure 1). Therefore, the number of CFUs needed to cover all the seeds must be divided by the concentration of CFUs that the bioinput to be used has. Let's look at an example for wheat cultivation. 350 seeds will be used per m² (350 seeds x 10.000 m² = 3.500.000 seeds/ha). Now, the number of seeds per hectare must be multiplied by 36.000 UFCs/seed = 1,26 x 1011. So, we will have to apply 1,26 x 1011 UFC per hectare (3.500.000 seeds).

As it is not possible to count each microorganism at the time of application, the concentration of the commercial product must be observed and divided by this value to obtain the volume to be applied. Considering a commercial product that is 2 x 10⁹, the volume of bioinputs to be applied is 63 ml in 3.500.000 seeds. Note: the bio-input must be diluted in water to be able to form a syrup. The volume of syrup can vary from 300 ml to 500 ml/50 kg of seeds. Other points that must be considered are that if the commercial product has the exponent 10⁸ and not 10⁹, the volume to be applied must be 630 ml per 50 kg of seeds. And this would not be suitable for treating wheat seeds due to the dilution of the chemical seed treatment, runoff and lack of the appropriate number of CFUs per seed. Therefore, an alternative is to use inoculation via spraying in the sowing furrow.

Inoculation via furrow

For spraying via the sowing furrow, it must be considered that the jet must reach the seeds and that part of the spray will cover the furrow walls. In this sense, at least 50 L/ha of spray must be used and the bioinput dose must be 3x the recommended dose per seed.

Airborne spraying

This form of application should generally be carried out at times of the day with mild temperatures and without or with a low presence of solar radiation, ideally in the late afternoon and early evening, thus improving the efficiency of the interaction of microorganisms with the plants. When this indication is not followed, the percentage of CFUs drops drastically and the effective number of CFUs may not be efficient to provide the expected response. The volumes of bioinputs applied via foliar tend to be larger, as the objective is to have a high density of CFUs per area on the leaf.

In Figure 2, root growth can be observed due to the use of bioinputs via seeds when sowing vetch. The use of vetch increased root length by 193%, surface area by 175% and root volume by 160%, when bioinputs were applied.

The use in white oat (Figure 3) increased the contrasts in relation to the control without application of bioinputs. There was a 294% increase in root length, a 315% increase in surface area and a 337% increase in root volume with the use of bioinputs. But we must always consider what problem we want to solve in the crop of interest to define the strategy for using bioinputs.

Last thoughts

Currently, there is a wide range of bioinputs available to help farmers, whether through on-farm production or commercially by industries. This diversity puts pressure on producers who, initially, must know the problem they want to solve. From this, microorganisms and their strains must be chosen appropriately, based on scientific criteria and characteristics that guarantee the quality of the products such as concentration, validity and application methodology.

By Thomas NewtonMartin, Anderson Cesar Ramos Marques, Edgar Salis Brasil Neto, Fernando Sintra Fulaneti, Janaina de Fatima Spanevello e Laís by Paula Ribeiro (Federal University of Santa Maria); Rosana Taschetto Vey (Inoculate Agricultural Solutions); Tânia Maria Bayer da Silva (Three of May Educational Society); Vitor Sauzem Rumpel e Yago Muller Alves (Federal University of Santa Maria). Published in issue 295 of Revista Cultivar Grandes Culturas