Growth, Nutrient Accumulation, and Nutritional Efficiency of a Clonal Eucalyptus Hybrid in Competition with Grasses

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The occurrence of weeds in eucalyptus plantations can cause losses in productivity. Chemical control is widely used, but the efficiency of herbicides depends on management and environmental factors. This study aims to evaluate the efficiency of S-metolachlor + glyphosate in the control of grasses in different densities of eucalyptus straw and with simulated rainfall after application of the product. The experiment was conducted in a randomized block design, factorial, with four replications. The first factor represented 0; 1.06 + 0.79 e 2.12 + 1.59 kg i.a. ha−1 of the commercial dose of S-metolachlor + glyphosate, the second 0; 5 and 10 tons ha−1 of straw and, the third 25 and 50 mm of water depth applied in soil with a mix of grasses previously sowed. The evaluations carried out were fresh mass, dry mass, and visual analysis of the control percentage. The fresh and dry mass and the grasses’ dry mass/water ratio decreased with increasing herbicide dosage and straw density. The treatments without straw and with the herbicide application had the highest percentages of control, the highest in the dosage of 2.12 + 1.59 kg i.a. ha−1 of S-metolachlor + glyphosate. Applying different water depths (25 mm or 50 mm) did not influence the control. In conclusion, it was observed that the isolated straw promoted the control of grasses. However, in treatments that included straw and herbicide, there was a decrease in the efficiency of the product, which suggests an antagonism between the vegetation cover and S-metolachlor + glyphosate.

Section: Introductionmentioning

confidence: 99%

Efficacy of S-metolachlor + glyphosate for Weed Control in Different Levels of Eucalyptus Straw

Duque,

Oliveira,

Souza

et al. 2023

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Sensitivity of Eucalyptus Clones to Herbicides Associated with Foliar Fertilizers

Barroso

Carvalho

Custódio

et al. 2022

Postemergence application of herbicides can cause phytotoxicity problems in eucalyptus seedlings. Foliar fertilization can improve seedling development and mitigate the effects of herbicides on eucalyptus. Thus, the objective of this work was to evaluate the sensitivity of eucalyptus clones subjected to herbicides applied postemergence and associated with the application of foliar fertilizer. For this, a field experiment was carried out with the application of the products indaziflam, clomazone, glyphosate + S-metolachlor, sulfentrazone, and diuron + sulfentrazone, plus the application of an additional foliar fertilizer (composition in g/L of 78, 13, 40.3, 1.17, 0.78, 16.9, 13, 14.3, 0.52, and 29.9, respectively, for C, N, S, B, Co, Fe, Cu, Mn, Mo, and Zn). Height, stem diameter, shoot dry mass, chlorophyll content, and visual intoxication were the analyzed variables. The herbicides indaziflam and glyphosate + S-metolachlor were the most harmful to the tested eucalyptus clones, interfering with the growth variables. Among the evaluated clones, Clone AEC 144 had more significant changes in the analyzed variables in treatments with herbicides and foliar fertilizer application. The eucalyptus seedlings were generally more sensitive to indaziflam and glyphosate + S-metolachlor herbicides. Foliar fertilization reduced the intoxication caused by indaziflam in Clone AEC 056. The fertilizer intensified treatment symptoms with clomazone and diuron + sulfentrazone in Clone AEC 144 and with sulfentrazone and diuron + sulfentrazone in Clone AEC 2034.

Weed Coexistence in Eucalyptus Hybrid Stands Decreases Biomass and Nutritional Efficiency Mid-Rotation

Momolli,

Schumacher,

Ludvichak

et al. 2023

Determining the period of weed coexistence with eucalyptus stands assists in the integrated management of weed competition, which reduces the application of herbicides, economic costs, and environmental damage. Therefore, the objectives of the present study were to evaluate the impact of a hybrid stand of Eucalyptus grandis × Eucalyptus urophylla trees on biomass production, the concentration and stock of macro and micronutrients, and the efficiency of nutrient utilization under different periods of coexistence with weeds. Our study is the first to report the impacts of weed management on the biomass and nutrients present in the leaves, branches, stembark, and stemwood at the time of mid-rotation (4.5 years old). The experiment was carried out in southern Brazil in the Pampa biome and followed a randomized block design, with three replications. The treatments consisted of increasing periods of coexistence with or control of weeds. The total biomass in the coexistence up to 378 days treatment was 53.7 Mg ha−1, and in the control treatment up to 168 days, it was 81.4 Mg ha−1, differing statistically. This reduction was in the order of 34%. The continuous presence of weeds led to a significant reduction in the production of wood and total biomass. The highest nutrient utilization efficiency (NUE) was observed for wood. The control of weeds for up to 168 days promoted greater productivity than controlling weeds for 378 days. This recommendation can be adopted by plantation managers for this region, reducing the amount of herbicide applied on the stand.