ABSTRACT The application of sewage sludge (SS) in agriculture is a practice used worldwide, and it is commonly applied in sugarcane to supply nutrients, with beneficial effects on crop productivity and soil; but SS can increase sorption and decrease desorption of herbicides. However, in tropical soils such as in Brazil, there are no studies regarding the behavior of pre-emergent herbicides, mainly aminocyclopyrachlor and mesotrione, in SS-amended soil. The aim of the present study was to determine the effect of municipal SS applied in agriculture on the sorption–desorption of aminocyclopyrachlor and mesotrione in clay soil. Aminocyclopyrachlor (pyrimidine-2-14C-aminocyclopyrachlor) and mesotrione (cyclohexane-2-14C-mesotrione) sorption–desorption was evaluated using a batch equilibrium method. Soil was amended at 0% (control – unamended), 0.1%, 1%, and 10% (w∙w–1) of air-dried SS corresponding to 1.2, 12, and 120 t∙ha–1. The Freundlich Kf sorption values of aminocyclopyrachlor and mesotrione were similar for all treatments, ranging from 1.07 to 1.45 and 3.48 to 4.25 µmol (1–1/n) L1/n∙kg–1, respectively. Overall, the lowest Kd sorption value of these herbicides was reported for SS-amended soil (1%), while in the SS-amended soil (10%) it was higher than unamended soil. The H value for aminocyclopyrachlor was ~1 (no hysteresis) and for mesotrione was on average 0.4 (hysteresis occurring). In conclusion, the present study indicates that SS applied in any crop to supply nutrients can slightly affect the sorption–desorption of aminocyclopyrachlor and mesotrione, but this small difference does not affect the bioavailability of these herbicides for weed control.

ABSTRACT Microbial adaptation may occur in surface soils under agricultural uses exposed to herbicides. However, little is known about herbicide mixture effects in the soil, especially in tropical regions like Brazil. The aim of this study was to evaluate glucose mineralization in soils of contrasting textures (sandy clay and sandy loam) from areas cultivated with maize under application of S-metolachlor, terbuthylazine and mesotrione, alone and in a mixture. The methodology was established according to the soil microorganisms: carbon transformation test with 14C-glucose solution (D-[U-14C] glucose) in biometric flasks. After the addition of 14C-glucose, the amount of 14C in cumulative CO2 of microbial respiration was measured several times during the 28-day incubation. For unamended soil control (without herbicide), microbial activity followed a similar behavior to amended soil with herbicides in total 14CO2 released and accumulated, ranging from 23 to 27%. Overall, mineralization constant rate (k) values for all treatments were also similar, with an average value of 0.0038% CO2.d–1. Consequently, mineralization half-life times (MT50) were from 173 to 198 d. Microbial respiration for all treatments was slightly higher in the sandy clay compared with sandy loam soil; although soil samples with application of herbicides (alone and in a mixture) did not show decreased basal microbial respiration or mineralization rates of glucose. To corroborate these findings, additional research with different organic substrates and in cultures with different applications of herbicides are needed to prove the non interference of these herbicides on the microbial respiration in the soil.

Objetivou-se com este trabalho avaliar a eficiência do bispyribac-sodium como maturador químico na cultura de cana-de-açúcar variedade RB86-7515. O ensaio foi realizado no delineamento em blocos casualizados, esquema com parcelas subdivididas e 4 repetições. Os tratamentos principais (maturadores) foram compostos por testemunha T1 (sem aplicação), T2, T3, T4, T5, T6 (20; 22; 24; 26 e 28 g ha-1 de bispyribac-sodium, respectivamente), T7 (15 g ha-1 de sulfometuron-methyl) e T8 (200 g ha-1 de ethyl-trinexapac). Os tratamentos secundários (subparcelas) corresponderam às épocas de amostragens aos 15; 30; 45; 60 e 75 dias após a aplicação (DAA) dos maturadores. Foram considerados os parâmetros fitointoxicação, produtividade de colmos, brotações laterais, sólidos solúveis (%Brix), pol da cana (%Pol) e açúcares totais recuperáveis (ATR em kg t-1). Os maturadores foram seletivos, onde não foi constatado fitointoxicação, independente do tratamento. Para as variáveis produtividade de colmos, Brix e ATR, não houve diferença significativa entre os diferentes tratamentos químicos. Elevados índices de brotações laterais foram obtidos nos tratamentos com o bispyribac-sodium aos 60 e 75 DAA. Todos os tratamentos com maturadores apresentaram incrementos significativos nos índices de Brix e Pol, sem que houvesse decréscimo na produtividade e induziram ao aumento no teor de ATR aos 45; 60 e 75 DAA, em relação à testemunha. O bispyribac-sodium, assim como o sulfometuron-methyl e ethyl-trinexapac foram eficientes na melhoria da qualidade tecnológica e apresentam potenciais para serem utilizados como maturadores na cultura da cana-de-açúcar.

The aim of this work was to evaluate the efficiency of bispyribac-sodium as a chemical ripening agent in the cultivation of the sugarcane variety RB86-7515. The test was carried out in a randomised-block design, with split lots and four replications. The main treatments (ripening agents) were made up of the control T1 (with no application), T2, T3, T4, T5, T6 (20, 22, 24, 26 and 28 g ha-1bispyribac-sodium respectively), T7 (15 g ha-1 sulfometuron-methyl) and T8 (200 g ha-1 trinexapac-ethyl). The secondary treatments (sublots) corresponded to the sampling dates at 15, 30, 45, 60 and 75 days after application (DAA) of the ripening agents. The following parameters were considered: phytotoxicity, stalk productivity, lateral shoots, soluble solids (% Brix), pol of the cane (%Pol) and total recoverable sugars (ATR as kg t-1). The ripening agents were selective where no phytotoxicity was observed, regardless of treatment. For the variables of stalk productivity, Brix and ATR, there was no significant difference between the various chemical treatments. High rates for lateral shoots were obtained in treatments with bispyribac-sodium at 60 and 75 DAA. All the treatments with ripening agents demonstrated significant increases in Brix and Pol rates, with no decrease in productivity, and led to an increase in ATR levels at 45, 60 and 75 DAA, compared to the control. The bispyribac-sodium, as well as sulfometuron-methyl and trinexapac-ethyl, was effective in improving technological quality and all show potential for use as ripening agents in the cultivation of sugarcane.

Objetivou-se neste trabalho determinar os períodos de interferência de plantas daninhas na cultura do girassol. Foram realizados dois experimentos com o girassol híbrido Helio 250, sendo um conduzido no verão e o outro, no inverno. Para ambos, o delineamento experimental utilizado foi em blocos casualizados, com quatro repetições, e cada unidade experimental foi constituída de cinco linhas de plantas com 6,0 m de comprimento, espaçadas por 0,7 m. No experimento de verão foram avaliados oito períodos de convivência e controle de plantas daninhas: 10, 20, 30, 40, 50, 60, 70 e 88 dias após a emergência (dae). No experimento de inverno, os períodos foram: 7, 14, 21, 28, 38, 48, 58 e 82 dae. Avaliaram-se a massa da matéria seca e a área foliar das plantas de girassol, produtividade, massa de mil aquênios e massa da matéria seca de plantas daninhas. Estimaram-se os períodos anteriores à interferência (PAI), períodos críticos de prevenção à interferência (PCPI) e períodos totais de prevenção à interferência (PTPI). Considerando-se a produtividade de aquênios no verão, o PAI foi de 16 dae da cultura, o PTPI, de 39 dae e o PCPI abrangeu 23 dias do ciclo da cultura. No inverno, o PAI foi de 12 dae, o PTPI estendeu-se até os 34 dae, resultando em um PCPI de 22 dias.

The objective of this work was to determine the periods of weed interference in sunflower crops. Two experiments were done with the sunflower hybrid Helio 250, one in the summer and the other in the winter. For both experiments, a randomized block design with four repetitions was used and each experimental unit was composed of plants in five lines, 6.0 m in length, spaced 0.7 m apart. In the summer experiment eight periods of cohabitation and weedy plant control were evaluated: 10, 20, 30, 40, 50, 60, 70 and 88 days after emergence (dae). In the winter experiment, the periods were 7, 14, 21, 28, 38, 48, 58 and 82 dae. The dry matter mass, leaf area of sunflower plants, yield, thousand achenes mass and weedy plant dry matter mass were evaluated. The periods prior to interference (PPI), the critical periods of preventing interference (CPPI), and the total periods of preventing interference (TPPI) were estimated. Considering the yield of achenes in the summer, the PPI was 16 dae of the crop, the CPPI was 39 dae and the TPPI lasted 23 days of the crop cycle. In winter, the PPI was 12 dae and the CPPI lasted for 34 dae, resulting in a TPPI of 22 days.