Wheat (Triticum aestivum L.) is the main winter crop in the Southern region of Brazil, which is the region that produces the most wheat grains nationally. Furthermore, considering the growth of the soybean sown area in the country in recent decades, including the Southern region, there are situations where these two crops compete in terms of planting time. This occurs because the end of the wheat cycle can coincide with the beginning of the soybean cycle.
Given this scenario, pre-harvest desiccation in wheat crops can partially reduce this temporal competition. According to the literature, studies indicate that desiccation can advance the wheat harvest by up to six days. This advancement occurs because desiccation involves the application of a herbicide at the end of the crop cycle, promoting the uniform maturation of the grains. In this context, desiccation accelerates the drying of plant tissues, bringing forward the harvest.
However, despite the operational benefits that pre-harvest desiccation can generate, producers are still apprehensive about using this practice, especially regarding potential productivity losses. This concern is associated with the fact that inadequate pre-harvest herbicide application can, in fact, cause losses. Generally, such losses occur when application is carried out at inappropriate stages or with high dosages.
Therefore, in the present study, different doses of glufosinate ammonium, a herbicide used in desiccation, were applied at stage 87 (hard dough stage) of the Zadoks scale, in order to evaluate its effects on wheat productivity.
The experiment was conducted during the 2023 growing season in the city of Canguçu (RS). The experimental design adopted was randomized blocks, with the herbicide doses being the factor studied. The doses used were 0 ml/ha, 100 ml/ha, 200 ml/ha, and 300 ml/ha of glufosinate-ammonium (Glufosinate-Ammonium 200g/L SL), with four replications per treatment.
The doses were defined according to the product label, as follows: 0 ml/ha, control (no application); 100 ml/ha, dose lower than recommended; 200 ml/ha, recommended dose; and 300 ml/ha, dose higher than recommended.
Agronomic management was carried out according to crop recommendations. The plants were harvested manually, and subsequently, the grains were dried until they reached 13% moisture. Then, the grains were weighed to determine the productivity of each treatment.
The data were subjected to analysis of variance and, when significant by the F-test at 5% probability, to comparison of means by the Scott-Knott test (5%) and regression analysis.
Application at doses of 100 ml/ha (lower) and 200 ml/ha (recommended) did not result in productivity losses, remaining equivalent to the control treatment (no application). These results indicate that the use of glufosinate ammonium in pre-harvest desiccation can be safely carried out at these doses, allowing for earlier harvesting without compromising productivity. It should be noted that the herbicide was applied at stage 87 of the Zadoks scale; therefore, the data refer specifically to that stage. Applications at different stages may present different results regarding productivity.
On the other hand, the 300 ml/ha dose resulted in a productivity reduction of 20,2%, 20,9%, and 21,9% compared to the doses of 0 ml/ha, 100 ml/ha, and 200 ml/ha, respectively (Figure 1). This reduction may be associated with the interruption of the final remobilization of assimilates from the stalk to the grains. The application was carried out at stage Z87, the phase of maximum dry matter accumulation; however, vegetative reserves may still contribute in the following days. Thus, the application of the highest dose promoted accelerated tissue desiccation, limiting the final flow of assimilates and negatively impacting production. Also, under such circumstances, high doses can intensify oxidative stress and cell degradation, reducing grain weight and, consequently, productivity.
Doses of 100 ml/ha and 200 ml/ha of glufosinate ammonium applied at the Z87 stage do not interfere with wheat grain production. On the other hand, the dose of 300 ml/ha causes a reduction in productivity, as observed in this study.
By Benhur Schwartz Barbosa, Bianca Schwartz Barbosa (UFPel); Emanuela Garbin Martinazzo Aumonde (Furg); Tiago Zanatta Aumonde, Tiago Pedó (UFPel)
* Article published in issue 321 of Cultivar Grandes Culturas Magazine
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