Interferência de plantas daninhas no acúmulo de nutrientes em folhas de mandioca sob plantio direto ou plantio convencional

The objective of this work was to evaluate the effect of weed competition on the accumulation of nitrogen and phosphorus in the leaves and on the dry weight of the roots of cassava (Manihot esculenta) in the conventional and no-tillage systems, in two crop cycles. The experiments were carried out in a randomized complete block design, with split-split plots and four replicates. The plots consisted of conventional tillage or no-tillage; the split plots, of the competition or not with weeds; and the split-split plots, of the evaluation periods (0, 25, 50, 75, 100, 125, 150, 175, 200, and 225 days after planting/pruning). In the first cycle, weed competition reduced the accumulation of nitrogen in 82.6 and 81.3% and of phosphorus in 65.7 and 85.3% under conventional tillage and no-tillage, respectively. In the second cycle, the reductions in the accumulation of nitrogen were of 41.1 and 52.4% and of phosphorus of 44.1 and 52.6%, in conventional tillage and no-tillage, respectively. The root dry weight of cassava grown with weed competition showed reductions of 15.8 and 11.2% under conventional tillage and no-tillage, respectively, only in the second cycle. Weed competition reduces the accumulation of nitrogen and phosphorus in the leaves of cassava in the conventional and no-tillage systems in both crop cycles, but reduces the dry matter of cassava roots only in the second cycle.O objetivo deste trabalho foi avaliar o efeito da competição de plantas daninhas sobre o acúmulo de nitrogênio e fósforo nas folhas e sobre a massa seca das raízes de mandioca (Manihot esculenta), nos sistemas convencional e direto, em dois ciclos de cultivo. Os experimentos foram realizados em delineamento de blocos ao acaso, com parcelas subsubdivididas e quatro repetições. As parcelas consistiram do plantio convencional ou do plantio direto; as subparcelas, da competição ou não com plantas daninhas; e as subsubparcelas, dos períodos de avaliação (0, 25, 50, 75, 100, 125, 150, 175, 200 e 225 dias após o plantio/poda). No primeiro ciclo, a competição com plantas daninhas reduziu o acúmulo de nitrogênio em 82,6 e 81,3% e o de fósforo em 65,7 e 85,3%, no plantio convencional e no plantio direto, respectivamente. No segundo ciclo, as reduções no acúmulo de nitrogênio foram de 41,1 e 52,4% e, no de fósforo, de 44,1 e 52,6%, no plantio convencional e no plantio direto, respectivamente. A massa seca das raízes de mandioca cultivada sob competição de plantas daninhas apresentou reduções de 15,8 e 11,2% no plantio convencional e no plantio direto, respectivamente, apenas no segundo ciclo. A competição de plantas daninhas reduz o acúmulo de nitrogênio e fósforo nas folhas de mandioca, nos sistemas convencional e plantio direto, em ambos os ciclos de cultivo, mas reduz a matéria seca das raízes de mandioca apenas no segundo ciclo

Weed interference in cassava in different cycles and cropping systems

The study aimed to determine the interference periods of weeds in cassava ‘IAC 90’ cultivated in different cycles and cropping systems. An experiment was conducted in the period 2014/15 (1st cycle) and another was conducted from the pruning of cassava plants in the period 2015/16 (2nd cycle). The experimental design was a randomized block design with split-split plots and four replicates. The plots represented the cropping systems (conventional and no-tillage) and the split-split plots corresponded to the periods with and without coexistence with weeds (0, 25, 50, 75, 100, 125, 150, 175, 200 and 225 days after planting or pruning - DAP/DAPr). In the 1st cycle, there was no interaction between the cropping systems and the coexistence periods and, therefore, based on the acceptable losses of 5% in the root and starch yield of 'IAC 90' cassava, the PCPI was estimated between 20 and 212 DAP and 14 to 214 DAP, respectively. In the 2nd cycle, the CPPWI ranged from 17 to 176 DAPr and 30 to 216 DAPr based on the root and starch yield obtained in the conventional method, respectively. While in no-tillage, the estimated CPPWI ranged from 18 to 198 DAPr and 9 to 218 DAPr based on root and starch yield, respectively. In general, the data indicate that conventional weed management should be carried out in a more intensified way than in no-tillage. In addition, CPPWI based on starch losses can avoid losses in root production

ESTABILIDADE DE AGREGADOS EM ÁREA DE CULTIVO ORGÂNICO COM DIFERENTES MANEJOS E CONVENCIONAL

O objetivo desse trabalho foi avaliar as propriedades físicas do solo em áreas com diferentes manejos do sistema de cultivo orgânico e cultivo convencional. O experimento foi conduzido na Estação Experimental Professor Alcibíades Luiz Orlando, localizada no município de Entre Rios do Oeste. O solo da região é classificado como Latossolo Vermelho Eutroférrico, o delineamento experimental foi inteiramente casualizado (DIC), onde em cada área em estudo foram demarcados seis pontos de amostragem, sendo cada ponto representante de uma repetição dentro da área. Os talhões em estudo e seus respectivos manejos foram considerados os tratamentos e o talhão convencional foi considerado a testemunha. Para determinação da estabilidade coletou-se monólitos de solo na camada de 0-0,10 e 0,10 a 0,20 m. Os resultados demonstraram que a melhor estabilidade dos agregados avaliadas pelo diâmetro médio ponderado e geométrico foi no sistema de rotação: Soja/ trigo mourisco/ aveia preta + nabo/ milho/ aveia preita + nabo/ lab-lab + feijão-guandu; onde houve a maior diversidade de plantas de cobertura. O talhão cultivado no sistema plantio direto, mas manejado convencionalmente obteve menor qualidade estrutural

Evaluation of glyphosate and paraquat in management of Brachiaria ruziziensis

O objetivo deste trabalho foi o de avaliar o efeito de doses do paraquat e do glyphosate na dessecação da forrageira Brachiaria ruziziensis. O delineamento experimental foi de blocos casualizados com quatro repetições. As doses do do glyphosate foram 0, 90, 180, 360, 720 e 1440 g ha-1 e do paraquat foram 0, 50, 100, 200, 400 e 800 g ha-1. Com base nos resultados obtidos pode-se concluir que o paraquat foi ineficiente na dessecação da B. ruziziensis e que o glyphosate foi eficiente apenas nas doses de 720 e 1440 g ha-1. Não houve emissão de novos perfilhos após a dessecação das plantas da forrageira que permitisse utilização prática para manejo no sistema agricultura-pecuária.The objective of this study was to evaluate the effect of doses of paraquat and glyphosate on desiccation Brachiaria ruziziensis. The experimental design was randomized blocks with four replications. The rates glyphosate were 0, 90, 180, 360, 720 and 1440 g ha-1 and paraquat were 0, 50, 100, 200, 400 and 800 g ha-1. Based on the results obtained it can be concluded that paraquat was ineffective in desiccation B. ruziziensis and the glyphosate was only effective at rates of 720 and 1440g ha-1. There was no issuance of new tillers after desiccation of forage plants to allow practical use for management in crop-livestock system

Flat-spectrum symmetric objects with ~1 kpc sizes I. The candidates

In order to understand the origin and evolution of radio galaxies, searches for the youngest such sources have been conducted. Compact-medium symmetric objects (CSO-MSOs) are thought to be the earliest stages of radio sources, with possible ages of <10^3 yrs for CSOs (<1 kpc in size) and 10^4-10^5 yrs for MSOs (1-15 kpc). From a literature selection in heterogeneous surveys, we have established a sample of 37 confirmed CSOs. In addition, we only found three confirmed flat-spectrum MSOs in the literature. The typical CSO resides on a z<0.5 galaxy, has a flat radio spectrum (a_thin<0.5; S_v proportional to v^-a), is <0.3 kpc in size, has an arm length ratio <2, and well-aligned (theta<20 deg) opposite lobes with a flux density ratio <10. In order to populate the 0.3-1 kpc size range (large CSOs) and also in order to find more flat-spectrum MSOs, we have built a sample of 157 radio sources with a_{1.40}^{4.85}<0.5 that were resolved with the VLA-A 8.4 GHz. As first results, we have 'rediscovered' nine of the known CSO/MSOs while identifying two new ~14 kpc MSOs and two candidate CSO/MSOs (which only lack redshifts for final classification). We were able to reject 61 of the remaining 144 objects from literature information alone. In the series of papers that starts with this one we plan to classify the remaining 83 CSO/MSO candidates (thanks to radio and optical observations) as well as characterize the physical properties of the (likely) many 0.3-15 kpc flat-spectrum CSO/MSOs to be found.Comment: 19 pages, 14 figures, 6 tables (note that Table 2, in landscape format, has a separate file); accepted by MNRA