Impact of water deficit at different stages of soybean development
By Solange Rocha Monteiro de Andrade, Embrapa Cerrados
The Biological Project is a work aimed at studying the importance and technical-economic viability of biological tools applied to the management of pests and diseases in the production system. It is developed by the Mato Grosso Agricultural Research Support Foundation (MT Foundation) with support from partner companies.
The project began in the 2022/23 soybean harvest and was developed in the municipality of Sapezal (MT), a region strongly characterized by the soybean-cotton production system. The management carried out in cotton cultivation began with seed treatment, continuing with foliar applications to control pests and diseases, depending on each treatment:
1 – Witness: no chemical or biological management actions were carried out in this environment.
2 – Chemical standard: the products used in seed treatment and application against pests and diseases were exclusively chemical, without any use of biological products.
3 – Replacement (less chemical and more biological): in this treatment, chemical fungicides and insecticides were reduced in at least two applications.
4 – Addition: biological products were added to the fungicide and insecticide programs, without any replacement of chemical molecules.
In the 2022/23 harvest, the project had the support of three important companies currently operating in the biological segment, namely Lallemand, Biocontrol - Nitro and Biotrop. Each positioned its biological products, bioinsecticides, biofungicides and bionematicides, according to the structure of the "substitution" and "addition" treatments. However, for presentation purposes in this article, the results of the three management proposals were analyzed using joint statistical analysis, and the results presented in a summarized form.
Each treatment comprised an area of 0,56 hectares (112 x 50 m), in which all cultural treatments and fertilization, planting, applications and harvesting operations were carried out mechanized, in accordance with technical recommendations for crop cultivation. cotton. Biological products were applied together with chemicals when their compatibility was met. Otherwise, they were applied alternately, with safe intervals of five days. The treatments were maintained in place after soybean cultivation, only changing the crop, which in this case was cotton. In Figure 1 it is possible to observe the dimensions of the project.
The 2023 cotton harvest took place with good environmental conditions for plant development, with regular rainfall during the critical phenological phases of the crop. Such conditions also favored the occurrence of pathogenic microorganisms and biocontrol agents. In relation to initial diseases, there was an incidence of fallen plants, caused by soil fungi, with less stand loss in places with application of seed treatment or sowing furrow (Figure 2).
For foliar diseases, the incidence of target spot and ramularia spot were verified. The target spot severity averages were relatively low, and were not influenced by treatments. In controlling ramularia spot, it was found that the two treatments with application of biofungicides presented the best disease control averages (Figure 3). The "replacement" and "addition" treatments clearly demonstrated that the integrated management of chemicals and biologicals was synergistic, reducing the progression of the disease and presenting better control efficacy than exclusively chemical management.
In addition to the direct effects of biocontrol agents on pathogens, it was also found that the plants present in the two treatments with biological application, the plants apparently suffered less stress with the application batteries for boll weevil control and low air temperatures. This is possibly due to the indirect effects that biocontrol agents can cause on cotton plants, such as growth promotion, production of phytohormones, and other physiological effects.
For the incidence of pests, the presence of caterpillars of the genus spodoptera spp., whitefly, aphid and spider mite. All of these species had relatively low incidence during the cotton crop cycle. For the population of spodoptera spp. and whitefly, it was observed that all treatments showed control for these species, in relation to the control without application (Figure 4 and Figure 5). It is worth highlighting that the control efficiency was slightly higher in treatments with biological products, especially in the "replacement" treatment.
It is expected that, over time, depending on the pest infestation, the results may be more evident, as microorganisms become established in the area (Figure 7 and Figure 8). In this way, this work shows the importance of continuing the project, so that more assertive and robust responses can be obtained over time, considering that pest infestations and disease severity can fluctuate according to the scenario of each harvest and the system. of cultivation, which can directly impact the efficiency of products used in different management programs, especially biological ones.
In addition to contributing to the management of pests and diseases in cotton crops, programs using biological products also had positive effects on crop productivity. The results of lint productivity (seed cotton) demonstrated that in the "addition" and "replacement" treatments, productivity averages were as good as those observed in the treatment with exclusively chemical management (Figure 8).
Finally, it was possible to see that the integrated management of chemical and biological fungicides and insecticides showed promising results in reducing the evolution of diseases and pest populations, as well as positive impacts on cotton productivity. Both strategies, when well positioned, and preferably integrated, can contribute to a more balanced management of pests and diseases in the production system, whose crops can suffer severe yield damage. Biocontrol agents can also, in addition to direct action, indirectly contribute to the more vigorous development of cotton plants. This project is one initiative, among several others, that Fundação MT has been developing. In this 2022/23 harvest, it had the support of partner companies Lallemand, Biocontrol – Nitro and Biotrop. The plan is to expand in size and agricultural scenario, to also encompass the soybean and corn production system.
By John Paulo Ascari e Mariana ortega, MT Foundation
Article published in issue 295 of Cultivar Grandes Culturas Magazine
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