Leandro Galon

Residual activity of (imazethapyr+imazapic) on ryegrass (Lolium multiflorum), following clearfield® rice

The aim of this study was to evaluate the residual activity of the prepackage mix of the herbicide Only (imazethapyr+imazapic) in a Clearfield (CL) rice production system during one, two or three rice seasons. The study was carried out in the field at Centro Agropecuario da Palma/Universidade Federal de Pelotas, Rio Grande do Sul, southern Brazil. Ryegrass (Lolium multiflorum) was planted after CL rice, cv. IRGA 422 CL. CL rice was considered as the main crop (summer) and ryegrass was planted following CL rice. The experimental design was a randomized complete block, with four replications. The treatments were arranged as a factorial: factor A, during the same season, compared herbicide residues during one, two or three years of CL rice and factorxa0B, for herbicide rates. Herbicide (imazethapyr+imazapic) was applied at (0; 25+75; 37,5+112,5; 50+150) g ha-1 with surfactant Dash being added at 0.5% v/v. The results showed interaction between CL rice seasons and the herbicide rate for the variables plant height and biomass. All variables tested were affected by herbicide (imazethapyr+imazapic) residue and the effect was more severe at higher rates. Grain weight and germination percentage were only affected by the herbicide rates. The results showed also that the residue of herbicides (imazethapyr+imazapic) applied to CL rice may stay in the soil and affect ryegrass plants cultivated following CL rice. CLxa0rice production system with herbicides (imazethapyr+imazapic) requires periods longer than 180 days for planting ryegrass as a successional crop.

Anatomical characters of Brachiaria brizantha submitted to Trinexapac-Ethyl application

The objective of this work was to evaluate changes in the anatomical and morphological characters of leaf (sheath and mesophyll), and stem of Brachiaria brizantha when treated with the plant growth regulator trinexapac-ethyl. The experimental design was completely randomized, with two doses of trinexapac-ethyl (0.00, 0.75 kg ha-1) and five repetitions. Fifty days after treatment application, samples from the middle third of the sheath, blade of the second fully expanded leaf and stem internode below the leaf sheath insertion were collected for the determination of morphological characteristics, such as plant height, internode length and diameter, sheath length and leaf length and width. For evaluation of the anatomical features, transverse cuts of leaves, stem and sheath and longitudinal cuts of the stem were made, in table microtome and stained with fuchsin and astra blue and prepared into semi-permanent slides. The images obtained were scanned using a light microscope coupled to a digital camera and connected to a computer. To obtain area and linear measures, the software Image Pro-Plus was used. The data were subjected to statistical analysis, using the Fxa0test at 10% probability. The growth regulator reduced the length of tho the leaf blade, internode and sheath and also plant height. On the other hand, trinexapac-ethyl increased leaf blade thickness sheath cell and mesophyll areas, providing anatomical and morphological changes in B. brizantha.

Disponibilidade de macronutrientes em cultivares de cana-de-açúcar submetidas à competição com Brachiaria brizantha

Objetivou-se com o trabalho verificar os teores foliares dos macronutrientes e o desenvolvimento das cultivares de cana-acucar RB72454, RB867515 e SP801816 em competicao com populacoes de Brachiaria brizantha. Os tratamentos utilizados foram: 1) cultivar de cana-de-acucar RB72454 e populacao de B. brizantha de 0, 1, 3, 7, 15, 32, 40, 32, 64, 92, 88 e 112; 2) RB867515 e 0, 1, 4, 14, 10, 18, 28, 30, 36, 54, 52 e 72; 3) SP801816 e 0, 1, 3, 6, 14, 20, 24, 26, 26, 32, 46 e 56 plantas m-2. Aos 120 dias apos a emergencia da cultura, foi quantificada a massa seca (MS) da parte aerea da cana-de-acucar e da B. brizantha. Aos 290 dias apos a emergencia (DAE), foram coletadas amostras das folhas +3 (terceira folha a partir do apice das plantas), nas quais foram avaliadas as concentracoes de nitrogenio total, fosforo, potassio, magnesio e calcio. Com o aumento da populacao de B. brizantha, observou-se reducao da MS somente na cultivar RB72454. O aumento na populacao de B. brizantha reduziu a concentracao de fosforo em todas as cultivares, nitrogenio em RB72454 e SP801816, potassio e magnesio para RB72454. Nas populacoes mais elevadas de B. brizantha, houve maior competicao pelos nutrientes disponiveis no meio, sendo o fosforo o mais limitante. A cultivar RB72454 foi a menos competitiva pelos nutrientes no solo. As cultivares apresentaram reducao media de 76% na produtividade de colmos na densidade maxima de B. brizantha.

Effect of dose and application site on quinclorac absorption by barnyardgrass biotypes

This work aimed to evaluate the uptake and translocation of quinclorac in function of application sites (shoot or roots) by Echinochloa crusgalli biotypes resistant and susceptible to this herbicide. The treatments consisted of quinclorac doses (0; 0.5; 1; 2; 4; 16 and 64xa0ppm), applied on the shoot or roots of seedlings of barnyardgrass biotypes. The experimental units consisted of plastic cups containing 250 cm3 of sand. The treatments were applied 10 days after emergence, when barnyardgrass plants reached a 2- to 3- leaf growth stage. The barnyardgrass biotypes were irrigated with nutritive solution weekly and maintained for 40 days after emergence, when length, fresh and dry matter of shoot and roots were evaluated. Variance analysis was carried out using the F test at 5% probability, and in case of significance, a non-linear regression analysis was also carried out using a three-parameter logistic model. In the susceptible biotype, quinclorac was more absorbed by the roots than by the shoot. Comparing dry mass production of the different plant parts of the susceptible biotype per application site, it was verified that quinclorac action is higher when applied to the plant roots. However, for the resistant biotype, it was not possible to determine the dose causing 50% reduction in dry mass accumulation (GR50) and in the resistance index (RI) between both biotypes, due to its high resistance to quinclorac (128 times the recommended dosage). The results showed that quinclorac resistance by the evaluated biotype is not due to differences in the absorption site, strongly suggesting that the resistance acquired by the biotype may result from alteration in the target site.

Milho (Zea mays) como espécie bioindicadora da atividade residual de (imazethapyr+imazapic)

The objective of this study was to evaluate the residual soil activity of herbicide (imazethapyr+imazapic), labeled for the Clearfield (CL) system and using corn, cv. Biomatrix 2202, as a bioindicator. The study was carried out in a greenhouse, at the Universidade Federal de Pelotas, in southern Brazil. Rice, cv. IRGA 422 CL, was planted in boxes (60 x 40 x 20 cm). At the 3-4 leaf stage, the herbicide Only (imazethapyr+imazapic) was sprayed at 0; 25+75; 37.5+112.5 and 50+150 g ha-1. After harvesting the rice, boxes were kept without flooding for 45 days. Black oat (Avena strigosa) was planted to keep the soil covered during the winter. In the spring, oat was harvested and 360 or 540 days after herbicide aplication (DAA), the soil from the boxes was transferred to two sets of pots labeled as experiment 1 (main corn crop) and experiment 2 (minor corn crop), respectively. The soil for experiment 2 was kept drained during the time period between seeding the two studies (360 to 540 DAA). Corn was planted in both studies and harvested at the 4-5 leaf stages. The variables evaluated were shoot and root biomass, plant height and leaf area index (for experiment 2). The data from both studies were analyzed using ANOVA (<0.05), and tested as polynomial models, when significant. A significant reduction was observed in shoot and root biomass, plant height and leaf area index planted up to 540 days after (imazethapyr+imazapic) aplication to CL rice. Corn cv. Biomatrix 2202 showed to be a good bioindicator of soil residual activity for the herbicide (imazethapyr+imazapic) in the CL system.

Interferência de plantas daninhas na cultura do sorgo sacarino

This work aimed to carry out a phytosociological study and to determine the critical period of weed interference on sweet sorghum crop. The experimental design adopted was randomized blocks with three replications. Treatments consisted by increasing periods of control or coexistence of weeds in different phenological stages of crop growth: 0-3 (V3), 0-5 (V5), 0-7 (V7), 0-9 (V9), 0-11(V11) fully expanded leaves and 0-R5 (harvest). The weed community was evaluated based on number the number of individuals and their correspondent dry mass accumulation, for each weed population in different periods of coexistence. Sweet sorghum was harvested at 101 days after emergence, when was measured plant height, culm diameter, total soluble solids (°Brix) in function of coexistence periods between crop and weeds, besides the yield of culms. Commelina benghalensis e Panicum maximum were the two species of higher relative importance at the crop harvested. The lack of weed control, during the crop cycle, caused an increase in total soluble solids (°Brix) and reduction of, respectively, 9 and 25% in plant height and culms diameter when compared with the hoed control during all cycle. Accepting losses of 5% in culm yield, was observed that the critical period of weed interference corresponded to the period of time between the phenological growth stage V3 to V11.

Métodos de manejo de Cyperus esculentus na lavoura de arroz irrigado

The Cyperaceae family include the most important weeds found in the state of Rio Grande do Sul rice fields. The objective of this work was to evaluate Cyperus esculentus control and rice cv. Qualimax 1 selectivity and grain yield in function of the irrigation starting times, application times and penoxsulam rates. The trial was set up under field conditions in the agricultural year of 2005/2006 and was arranged in a completely randomized block design with split plots and four replications. Treatments were in a factorial scheme (2 x 3 x 5) and consisted of two herbicide application times (early and late), three irrigation starting times (1, 15 and 30 days after treatment), and herbicide rates (0, 24, 36, 48 and 60 g ha-1 ). The herbicide penoxsulam showed selectivity to the rice culture regardless of the association between the evaluated treatments. The application of penoxsulam, combined with irrigation starting 15 days after herbicide application promoted efficient control of C. esculentus. Highest grain yield was obtained by applying penoxsulam at the rates of 36 g ha-1 or above, regardless of the application time, and when early irrigation was carried out.

Water use by hybrid and conventional rice plants

The objective of this work was to evaluate the characteristics associated to water use efficiency in hybrid or conventional rice plants. The trial was installed under greenhouse conditions, in a completely randomized block design and factorial scheme 2xa0xxa06, with four replications. The treatments consisted of one hybrid (Inov) or conventional (BRS Pelota) rice plant at the center of the plot surrounded by 0, 1, 2, 3, 4, or 5 conventional (BRS Pelota) plants. Fifty days after emergence, shoot dry mass, stomatal conductance of water vapor, leaf temperature and transpiration rates were evaluated, as well as water use efficiency through the relation between the photosynthesis and transpiration rates. Hybrid rice plants were superior to, or did not differ from, the conventional plants in relation to water use efficiency.

MULTIPLE RESISTANCE OF Sagittaria montevidensis BIOTYPES TO ACETOLACTATE SYNTHASE AND PHOTOSYSTEM II INHIBITING HERBICIDES

The objective of this research was to evaluate the occurance of multiple resistance of Sagittaria montevidensis (SAGMO) biotypes to acetolactate synthase (ALS) and photosystem II (PSII) inhibiting herbicides through dose-response experiments. The experiment was conducted in a greenhouse from October 2012 to March 2013, in Pelotas, RS. The experimental design was completely randomized, with four replications. Treatments were arranged in a triple factorial design: two biotypes of S. montevidensis(SAGMO 35 - susceptible to herbicides and SAGMO 32 - suspected to be multiple resistance to ALS and PSII inhibiting herbicides), four herbicides (penoxsulam, (imazethapyr+imazapic), bentazon and saflufenacil) and 8 rates of these herbicides (1/32x, 1/16x, 1/8x, 1/4x, 1/2x, 0x, 1x, 2x, 4x, 8x, 16x, 32x and 64x). SAGMO 32 biotype presented high levels of resistance to penoxsulam, (imazethapyr+imazapic) and bentazon. For a 50% reduction in dry matter of the resistant biotype rate of 138 and 2.46 times higher than the label required for the susceptible biotype of the herbicides (imazethapyr+imazapic) and bentazon, respectively, are required. Saflufenacil may be used successfully to controlSagittaria montevidensis resistant in irrigated rice.

Meia-vida do diuron em solos com diferentes atributos físicos e químicos

The distribution and dissipation of herbicides on soils are dynamic and unique processes for each soil-herbicide relation. In this research, the half-life of diuron was determined in five soils (Red-Yellow Latosol, Red Latosol, and Yellow Latosol), with different pH values. Diuron concentrations were determined in samples of each soil collected at eight different times (1, 8, 15, 22, 36, 66, 96 and 156 days after herbicide application at 3.0kg ha-1). Part of each soil sample was used to quantify diuron by high performance liquid chromatography. The other part of soil sample was used to do biological tests in order to confirm the results of chromatographic analysis. It was found that the persistence of diuron is dependent on the physical and chemical soil attributes. However, the correction of soil pH favored only herbicide degradation in sandy soils with low organic matter content. The half-life of diuron in soils ranged from 40 to 91 after its application and it was higher in soil with higher organic matter content. The biological tests confirmed these results and they were efficient and complementary to the chromatographic analysis.