Role of soil physicochemical properties in quantifying the fate of diuron, hexazinone, and metribuzin.

The physicochemical properties of soil are fundamental to quantification of the fate of herbicides. Thus, the aim of this research was to evaluate the fate of diuron, hexazinone, and metribuzin in five soils (Clay-1, Clay-2, Loam-1, Loam-2, and Sand), presenting variation in clay content, cation exchange capacity (CEC), pH, and organic carbon (OC). Herbicides radiolabeled with 14C were applied, and the 14C-CO2 released from mineralization was trapped in 0.2 mol L-1 sodium hydroxide solution. The degradation ratio, as well as herbicide-bound residues (non-extractable), transformation products, and residues extractable from soil, was also evaluated. Average 14C-CO2 evolution accumulated for diuron mineralization was higher (22.24%) than hexazinone (7.73%) and metribuzin (3.20%). The degradation time half-life (DT50) values for hexazinone correlated with soil OC content. Although no correlation between soil properties and DT50 values was found for metribuzin, the degradation rate and total degree of mineralization were low in sand soil for metribuzin. Regarding diuron, OC content and CEC value appear to be related to mineralization and degradation rate, respectively. Differences in soil properties can influence the persistence and fate of herbicides, affecting their impact on the environment, weed control, and possible effects on subsequent crops.

Influência do glifosato na eficiência nutricional do nitrogênio, manganês, ferro, cobre e zinco em soja resistente ao glifosato / Glyphosate influence on nitrogen, manganese, iron, copper and zinc nutritional efficiency in glyphosate resistant soybean

Com o desenvolvimento da soja resistente ao glifosato, Roundup Ready (RR), observa-se um aumento considerável no uso desse herbicida, com aplicações de três a quatro vezes durante o ciclo da cultura. Dessa forma, essas aplicações podem estar influenciando a nutrição mineral da cultura. Objetivou-se realizar este experimento para avaliar a influência do glifosato na eficiência nutricional de N, Mn, Cu, Zn e Fe pela soja transgênica cv. 'P98R31 RR'. O experimento foi realizado em casa de vegetação, na ESALQ/USP, Piracicaba (SP), em 2009. A unidade experimental foi constituída por vaso contendo 11kg de substrato (NITOSSOLO VERMELHO Eutroférrico latossólico), com duas plantas por vaso. Os tratamentos foram arranjados em um esquema fatorial 5X5, com cinco níveis do fator Mn (0, 20, 40, 60 e 80mg dm-3) e cinco de glifosato (0; 0,648; 1,296; 1,944 e 2,592kg i.a. ha-1), sendo que o Mn foi fornecido a partir do sulfato de manganês (MnSO4.H2O). O delineamento experimental foi em blocos casualizados, com quatro repetições. Não houve influência na resposta das plantas com relação ao fator Mn. A aplicação de glifosato interferiu de forma negativa na eficiência nutricional da planta e nos teores totais de N, Mn, Cu, Zn e Fe. A utilização de glifosato causou redução ao número de nódulos e redução na produção de massa seca.

After development of glyphosate-resistant (GR) soybean, there is a considerable raise in the use of this herbicide, with three to four applications during the culture cycle. Thus, these applications may be influencing the mineral nutrition of the crop. So, the aim of this research was evaluate the glyphosate influence on uptake, translocation and use efficiency of N, Mn, Cu, Zn and Fe by (GR) soybean 'P98R31' cultivar. The experiment was conducted in the greenhouse at ESALQ/USP, Piracicaba, State of São Paulo, Brazil, in 2009. The experimental unit was formed by 11kg vase-1 of soil (Rhodic Paleudult) with two plants in each vase. The treatments have been arranged in a factorial pathway 5X5, with five levels of the factor Mn (0, 20, 40, 60 and 80mg dm-3) and five of glyphosate drifts (0; 0,648; 1,296; 1,944 e 2,592kg e.a. ha-1) and the Mn was supplied by the manganese sulfate (MnSO4.H2O). The experimental design was randomized blocks, with four repetitions. There was no influence on response from plants concerning the levels of Mn used into the experiment. The application of glyphosate interfered on mineral nutrition of soybean and the total contents of N, Mn, Cu, Zn and Fe. The use of glyphosate has caused reduction of the nodules number and reduced the output of dry mass.

Vernalização em cinco cultivares de morangueiro / Vernalization on five cultivars of strawberry

A produção de morango é sazonal, e os melhores preços dos frutos são obtidos fora da estação. Buscando obter frutos fora da estação, o objetivo deste trabalho foi avaliar o efeito da vernalização em mudas de cinco cultivares de morangueiro. As mudas foram produzidas no sistema de vasos suspensos. O delineamento experimental utilizado foi blocos ao acaso em fatorial 5x2x4, com cinco cultivares ("IAC-Campinas", "Dover", "Sweet Charlie", "Cartuno" e "Oso Grande"), dois tratamentos (com e sem vernalização das mudas) e quatro tempos, com quatro repetições. Para vernalização, as mudas foram levadas para câmara fria à temperatura de 10+2°C e fotoperíodo de 8h de luz dia-1 durante 28 dias, e em seguida transplantadas. Foram avaliadas as percentagens de sobrevivência, florescimento, frutificação, emissão de estolhos, a massa e o número de frutos produzidos por planta. A sobrevivência de mudas não foi afetada pela vernalização. Houve efeito significativo no florescimento e na frutificação das plantas vernalizadas. O estolonamento de plantas foi mais precoce nas mudas vernalizadas. Para todas as cultivares e tratamentos, a produção de frutos foi insignificante e comercialmente inviável.

The strawberry production is seasonal, and the best fruit prices are obtained during the off season. Seeking to get fruits off season, this research was aimed at evaluating the effect of the seedling vernalization of five strawberry cultivars. The strawberry seedling were produced in suspended pot system. The experimental design was is completely randomized blocks with the factorial design 5x2x4, with five strawberry cultivars (IAC-Campinas, Dover, Sweet Charlie, Cartuno and Oso Grande), two treatments (with and without strawberry runners vernalization) and four times. For vernalization, the strawberry seedling was taken to cold chamber at 10±2°C, and photoperiod of 8h of light day-1 for 28 days, after this they were transplanted. The parameters evaluation were survival percentages, flower blooming, fructification, stolons emission, the weight and the number of fruits produced. The strawberry seedling survival was not affected by the vernalization. The results showed statistic differences among this treatments only on flower appearance and fructification of the vernalized plants. The runner emitions were earlier in the vernalized seedlings. For all strawberry cultivars and treatments the production of fruits was very low and the produced fruits were unsuitable for commercialization.

Alternative herbicides to manage Italian ryegrass (Lolium multiflorum lam) resistant to glyphosate at different phenological stages.

During the growing season of 2002--2003, field and greenhouse experiments were conducted with the objective of evaluating the influence of Italian ryegrass phenological stages and management alternatives on the control of resistant biotypes to glyphosate. Three field experiments were conducted in Lagoa Vermelha, RS, Brazil and glyphosate was applied alone and in combinations with alternative herbicides. Two greenhouse experiments were also conducted at the Department of Crop Science, ESALQ/USP, Piracicaba, SP, Brazil. The Italian ryegrass resistant population was collected from Lagoa Vermelha, RS, Brazil. From the results it was possible to conclude that: (i) the more advanced the phenological stage of application, the more difficult the control of resistant Italian ryegrass by glyphosate, mainly by the rate of 960 g a.i. ha(-1); however, this rate applied at earlier phenological stage (five tillers), the control was higher than 90%; (ii) with the increment of glyphosate rate, it significant response was observed on the control at all stages of application; (iii) the mixture of glyphosate + clethodim (1440 + 72 g a.i. ha(-1)), paraquat + diuron (500 + 250 g a.i. ha(-1)), at all stages of application and clethodim (96 g a.i. ha(-1)) and paraquat + diuron (300 + 150 g a.i. ha(-1)) at the initial stages until pre-flowering were excellent alternatives for management of these populations; and (iv) the response of control was much faster for the mixture of glyphosate + clethodim, independently of growth stage.