Paulo Fabrício Sachet Massoni

Arroz tolerante a imidazolinonas: controle do arroz-vermelho, fluxo gênico e efeito residual do herbicida em culturas sucessoras não-tolerantes

After several decades searching for tools to control red rice, imidazolinone tolerant rice was developed to selectively control red rice. To better understand this technology An experiment was conducted in 2004/2005, in Santa Maria, Rio Grande do Sul, Brazil to evaluate: 1) red rice control by imidazolinone herbicides in Clearfield™ rice; 2) evaluate the imidazolinone herbicide carryover effect on rygrass and non-tolerant rice (IRGA 417) and 3) evaluate the outcrossing rates between Clearfield rice and red rice. The experimental design was a randomized block design, with 3 treatments and 12 replications. To determine the outcrossing rates between Clearfield rice and red rice, virtually all the red rice panicle was collected and analyzed in the area. The carryover effect was tested using ryegrass and a non-tolerant rice cultivar (IRGA 417). The herbicides tested controlled red rice. Although injury to Clearfield rice was observed, the herbicide did not affect yield. Herbicide carry-over to non-tolerant rice was observed, reducing plant stand on rice seeded 361 days after herbicide application. Natural out-crossing occurred between Clearfield rice and red rice, at rates of 0.065%.

Controle de arroz-vermelho em dois genótipos de arroz (Oryza sativa) tolerantes a herbicidas do grupo das imidazolinonas

Red rice (Oryza spp.) is one of the main limiting factors to rice (O. sativa) yield. An experiment was carried out to evaluate red rice control and the behavior of two rice genotypes tolerant to the imidazolinone herbicides in response to imazethapyr (75 g L-1 ) + imazapic (25 g L1 ) application rates and timing. The experiment was conducted in Santa Maria-RS, Brazil in 2004/2005 and was arranged in a factorial scheme, in a randomized block design, with four replications. Factor A included the two rice genotypes tolerant to the imidazolinones, a cultivar (IRGA 422 CL) and a hybrid (Tuno CL); and factor D included the treatments for red rice control, which was a combination of rates and herbicide application timing. The hybrid was found to be more tolerant to the herbicide only than the cultivar. Application rates up to 200% on the hybrid genotype could be done without affecting rice yield. It is important to state that increasing the rate of herbicide application can create carryover problems to non-tolerant crops. Red rice control was total with split application of imazethapyr + imazapic in PRE and POST emergence with the total rate above 125%. The most efficient treatment was application of 75% in PRE followed by 50% in POST, which was the lowest rate promoting 100% control, with relatively low toxicity to the cultivar and without affecting rice yield.

Persistence of the herbicides imazethapyr and imazapic in irrigated rice soil

The mixture of herbicides imazethapyr and imazapic is used to control red rice in irrigated rice crops. However, such herbicides might persist on the soil for a long period causing phytotoxicity on susceptible rice grown in succession. The objective of this work was to determine the effect of different soil tillage systems during the off-season on the residual phytotoxicity of imazethapyr and imazapic on non tolerant rice. Herbicide residues caused phytotoxicity on susceptible rice with the highest values being registered 25 days after emergence and decreasing after this period until almost disappearing 60 days after emergence. Herbicide residues affected plant stand, number of stems per m2, number of panicles per m2 and plant height, but did not affect grain yield. Soil movement decreased herbicide activity on the superficial soil layer (0-3 cm).

Controle químico de arroz-vermelho na cultura do arroz irrigado

Red rice (Oryza spp.) reduces rice (Oryza sativa L.) grain yield and quality. A field study was conducted to compare two red rice control tools, the first using the Clearfield™ system and the second using high rates of clomazone and rice seeds treated with safener to suppress red rice emergence. The treatments included: check control without herbicide application, three treatments for the formulated herbicide mixture (imazethapyr 75 g i.a. L-1 + imazapic 25 g i.a. L-1) under the Clearfield system, and three clomazone treatments (clomazone 500 g i.a. L-1). The most efficient treatment for red rice control was the formulated mixture of imazethapyr + imazapic (0.7 L ha-1 PRE followed by 0.7 L ha-1 POST). This treatment promoted 100% red rice control, without affecting plant stand and promoting high grain yield.

Carryover of Imazethapyr and Imazapic to Nontolerant Rice

Abstract The present work aimed to evaluate plant injury caused by residues in the soil of the formulated mixture of imazethapyr and imazapic to a nontolerant genotype of rice (IRGA 417) drilled at 371 and 705 d after herbicide application (DAA). Herbicide carryover reduced up to 55% of the grain yield of the IRGA 417 drilled at 371 DAA, and plant injury was still evident at 705 DAA but without grain yield reduction. Nomenclature: Imazethapyr; imazapic; rice, Oryza sativa L. ‘IRGA 417’

Lixiviação do imazethapyr em solo de várzea sob dois sistemas de manejo

Imazethapyr has been widely used in Rio Grande do Sul since the development of Clearfield TechnologyTM(CL) on rice, in a formulated mixture of imazethapyr + imazapic (75 + 25g L-1). However, the use of such technology raised the problem of herbicide carryover, which might affect non-tolerant crops in rotation with different intensities. The plant injury is related, among other factors, with the herbicide position in the soil profile. The present work had the objective of determining the depth positioning of imazethapyr on a lowland soil cultivated with rice in two soil tillage system: conventional system (CS) and no till system (NT), in an area where CL rice had been cultivated for two years followed by non tolerant rice in the third year. Herbicide concentration in soil samples was analyzed by HPLC-DAD. There is a higher concentration of imazethapyr in the topsoil (0-5cm) on the CS, when compared to the NT, while it leached until 20cm in both systems. In the CS, imazethapyr were uniformly distributed in the first 15 cm of soil, whereas in NT, imazethapyr were accumulated in 5-10 and 10-15cm layers.

Manejo da irrigação em cultivares de arroz no sistema pré-germinado

In the pre-germinate system, the rice field is flooded before sowing and about three days later, the initial drainage takeplace in order to promote the plants initial growth but there occurs loss of nutrients and water. Then, three irrigation managements have been evaluated: water removal three days after sowing, water removal 30 days after sowing and without water removal, associating three rice cultivars with the objective to measuring rice grains yield, and loos nutrients with water removal. The water managements evaluated have not influenced the rice plant parameters. The grains yield varied according to the year, with an average 5,100, 9,565 and 7,078kg ha-1 ha in the years 2002/03, 2003/04 and 2004/05, respectively. Only in 2003/04, the grains yield was different among the rice cultivars. In 2002/03 and 2003/04, the phosphorous nutrient was similar among treatments, but in 2004/05 a great loss occurred when water removed three days after sowing. Concerning potassium, the highest concentrations were observed in water when it was removed three days after sowing. Results demonstrate that a continuous water sheet should be kept to preserve the nutrients within the field since it does not affect the crop yield and reduce the environmental impact of the water bodies.

Arroz tolerante a imidazolinonas: banco de sementes de arroz-vermelho e fluxo gênico

The objective of this study was to evaluate the rotation of the irrigated rice Clear field® system with the conventional system in the evolution of the seed bank and the emergence of red rice biotypes resistant to the imidazolinone chemical group. The experiment was arranged in a randomized block design in a factorial scheme (2 x 4) with 4 replications. The first factor was constituted of the management systems used (Clearfield®x conventional) which consisted of the succession/rotation between the rice not tolerant to imidazoline, variety IRGA 417 (conventional), and the rice tolerant to imidazolinone, variety IRGA 422 CL (Clearfield®). The D factor was consti tuted by the variation between the conventional and the Clearfield®systems, over time. The use of the Clearfield®system provides a reduction of the seed bank after three years of use; however, it does not remove all the red rice seeds from the soil. The crossing between red rice and cultivated rice increases with the increase of infestation, reaching 2.9% after four crops.

Resposta do arroz irrigado ao uso de inibidor de urease em plantio direto e convencional

O objetivo do presente trabalho foi avaliar a volatilizacao de N-NH3 e a resposta do arroz irrigado ao uso de ureia com inibidor de urease em dois sistemas de cultivo, direto e convencional. Para tanto, desenvolveu-se um experimento em campo, no ano agricola 2008/09, na UFSM em Santa Maria/RS. O delineamento utilizado foi de blocos ao acaso em esquema bifatorial (2x5), sendo o fator A constituido por ureia e ureia revestida com B e Cu (inibidor de urease) e o fator B composto por diferentes intervalos de entrada de agua (0, 3, 6, 9, 12 dias) apos a aplicacao das fontes de nitrogenio (N). Os resultados demonstram que o inibidor de urease retarda e diminui a conversao de N para NH3, reduzindo as perdas por volatilizacao, comparativamente a ureia sem inibidor. Entre os sistemas, as perdas sao potencializadas no sistema plantio direto. O inibidor de urease nao traz beneficios a produtividade em qualquer um dos sistemas de cultivo utilizados e o estresse causado na planta de arroz pelo atraso no inicio da irrigacao e mais prejudicial do que as perdas causadas pela volatilizacao de N-NH3.

Produtividade, fitotoxicidade e controle de arroz-vermelho na sucessão de cultivo de arroz irrigado no Sistema CLEARFIELD®

The objective of this study was to evaluate the CLEARFIELD ® system regarding the control of red rice, influences on productivity, as well as the possible phytotoxicity caused by carryover soil formulated mixture of imazethapyr and imazapic in tolerant rice genotype (IRGA 422CL) and non-tolerant (IRGA 417), which served as indicator plants. The experimental design was randomized blocks in a factorial scheme (4x3) with subplots, the main plots represented by rotating tolerant rice (IRGA 422CL) and rice not tolerant to imidazolinone (IRGA 417). In sub-plot treatments were applied to control red rice in different stages of the post-emergence (V4), pre + post emergence (day of seeding V4). Phytotoxicity was characterized based on the color of the leaves, width, growth and development of the leaf. It was observed that phytotoxicity was greater when the herbicide was applied post-emergence, effects remaining until 383 days after application. The control of red rice is not efficient with the use of only one agricultural year of CLEARFIELD® system and the best level of control and yield was obtained after two or three consecutive years of this system.