Francisco Cláudio Lopes de Freitas

Photosynthetic efficiency and water use in eucalyptus plants sprayed with glyphosate

Objetivou-se com este trabalho avaliar a eficiencia fotossintetica e o uso da agua por plantas de clones de eucalipto submetidas ao herbicida glyphosate. O experimento foi realizado em esquema fatorial 4 x 5, com quatro clones de eucalipto (57, 386, 1203 e 1213) e quatro doses de glyphosate (43,2; 86,2; 129,6; e 172,8 g ha-1) e uma testemunha sem herbicida, considerada dose zero, com quatro repeticoes. Aos 7, 14, 21 e 28 dias apos aplicacao do herbicida (DAA) foi avaliada a intoxicacao das plantas, e aos 7 e 21 DAA, o fluxo de gases pelos estomatos (U - mmol s-1), a atividade fotossintetica (A - mmol m-2 s-1), a condutância estomatica (Gs - mol m-1 s-1), a transpiracao (E - mol H2O m-2 s-1) e a eficiencia do uso da agua (QUE - mol CO2 mol H2O-1). Aos 50 DAA, as plantas de eucalipto foram coletadas e colocadas em estufa de ventilacao forcada a 70 oC ate atingirem massa constante. Aos 21 DAA, o clone 1203 comportou-se como mais sensivel ao herbicida. Nao houve diferenca entre clones para as variaveis fisiologicas avaliadas. Aos 21 DAA constatou-se que, com o incremento da dose de glyphosate, houve reducao na condutância estomatica, na taxa de fluxo de gases pelos estomatos, na taxa fotossintetica e na eficiencia do uso da agua. Plantas dos clones 1213 e 1203 apresentaram maior acumulo de massa seca. O aumento da dose do glyphosate promoveu menor acumulo de massa seca das plantas de eucalipto. O glyphosate afetou negativamente o crescimento e a eficiencia fotossintetica e de uso da agua dos clones estudados.

Crescimento de pimentão em diferentes arranjos espaciais

The objective of this work was to evaluate the growth of green pepper cv. Atlantis under different spatial arrangements. Three spacing arrangements between double and simple planting rows (1.5x0.5 m, 1.6x0.4 m and 1.7x0.3 m) and four spacing distances between plants in the rows (0.2, 0.3, 0.4 and 0.5 m) combined in factorial scheme were evaluated. A randomized block design in split-plots divided in time with three replicates was used. The growth assessment was done in nine occasions, 14 days apart, and the first one was performed 14 days after transplanting (DAT). Leaf area (LA), leaf area index (LAI), dry masses of leaves (LDM), stem (SDM), fruit (FrDM) and total shoot (TDM); absolute growth rate (AGR), rates of net assimilation (NAR) and relative growth (RGR); and leaf area (LAR) and leaf mass (LWR) ratios were evaluated until 126 DAT. The changes in LA, RGR, LWR and LAR did not depend on row spacing, but spacing influenced LDM, SDM, FrDM and TDM, LAI and AGR. The increase in spacing reduces LAI and LAR, and increases LA, LDM, SDM, FrDM, TDM, AGR and NAR, but does not influence RGR and LWR.

Qualidade de cenouras em diferentes densidades populacionais

Foi objetivo avaliar os efeitos de diferentes espacamentos de plantio sobre a qualidade de raizes de tres cultivares de cenoura nas condicoes de Mossoro, Rio Grande do Norte. O delineamento experimental utilizado foi em blocos casualizados, em esquema fatorial 6 x 3, com tres repeticoes, sendo o primeiro fator constituido pelos espacamentos: 20 x 4, 20 x 6, 20 x 8, 15 x 4, 15 x 6 e 15 x 8 cm e o segundo, pelos cultivares: Brasilia, Alvorada e Esplanada. As caracteristicas avaliadas nas raizes de cenoura foram: comprimento da raiz, diâmetro da raiz, comprimento do xilema, diâmetro do xilema, solidos soluveis (SS), acucares totais, acidez total (AT), vitamina C, relacao SS/AT e pH. Nao houve interacao significativa entre cultivares e espacamentos de plantio em qualquer das caracteristicas avaliadas. Os espacamentos influenciaram o comprimento e diâmetro da raiz e o comprimento e diâmetro do xilema. O cultivar Alvorada sobressaiuse nos solidos soluveis, acucares soluveis totais e relacao SS/AT.

Manejo de plantas daninhas na cultura da melancia nos sistemas de plantio direto e convencional

We evaluated strategies for weed management on the production of watermelon in no-tillage and conventional systems, in successive cultivation to the melon crop. The research was carried out in split plots, distributed in the experimental design of randomized blocks. Two cropping systems were evaluated in the plots (no-tillage and conventional tillage) and in the sub-plots were evaluated nine strategies of weed management [covered with polyethylene film, with weeding at 14 days after transplanting (DAT); 14 and 28 DAT, 14 and 42 DAT; 14, 28 and 42 DAT; 28 DAT, 28 and 42 DAT; 42 DAT and control without weeding]. Before the implantation of the experiment, the area was cultivated with melon in the respective cropping systems, the straw mulch being used again in the treatments with no-tillage system, as well as polyethylene film in the treatments with use of this material in two cropping systems. At 14, 28 and 42 DAT and at harvest of watermelon (80 DAT), were assessed the density and dry mass of weeds. The weeds were cut at ground level, separated by species, counted and put into oven with forced air at 65°C until constant weight to determine dry mass. From the watermelon crop were evaluated the number of marketable fruits, total number of fruits, average mass of marketable fruits per plant and average fruit mass (total) per plant and marketable and total yield. The no-tillage system reduced the density and dry mass of weeds, requiring only one weeding between 14 and 42 DAT, whereas in the conventional tillage system two weedings were needed, at 14 and 28 DAT. When the crop was maintained without weeding throughout the cycle, there was a reduction of 100 and 35.7% in marketable fruit yields in conventional and no-tillage systems, respectively. The no-tillage and polyethylene film in conventional tillage system enabled the cultivation of watermelon in succession to the melon crop, reducing weed interference and providing satisfactory productivity.

Mobilidade do ametryn em solos da região semiárida do Rio Grande do Norte

This work aimed to evaluate ametryn mobility in four types of soils, three from the semiarid region of the state of Rio Grande do Norte (Cambisol ; Fluvic Neosol; Latosolic Dystrophic Red-Yellow Argisol) and one from the state of Minas Gerais (Red-Yellow Latosol). Ametryn mobility was evaluated using PVC columns of 10 cm in diameter and 50 cm long. The experiment was conducted in a split-plot in a completely randomized design with four replications. The plots were composed by the columns, filled with the four types of soils and the subplots by 10 depths at intervals of 5 cm (0-5, 5-10, 10-15, 15-20, 20-25, 25-30 , 30-35, 35-40, 40-45 and 45-50 cm). Ametryn was applied on top of the columns (4 kg ha-1) and, 12 hours later, rainfall was simulated at the intensity of 60 mm. After 72 hours of simulated rain, the columns were placed in a horizontal position and opened longitudinally, divided into sections of 5.0 cm. At the center of each section, soil samples were collected for subsequent herbicide extraction and quantification through analysis by liquid chromatography (HPLC). Five seeds of cucumber (Cucumis sativus) were sown as bio-indicators of the presence of the herbicide. Ametryn mobility at the columns was influenced by the physical and chemical characteristics of the soil,(soil texture, organic matter, and pH). The Rio Grande do Norte semiarid region soils had higher ametryn mobility potential, being detected at up to 25, 20, and 15 cm depth in Latosolic Dystrophic Red- Yellow Argisol, Cambisol, and Fluvic Neosol, respectively. Ametryn mobility was restricted to 5 cm depth in the Red Yellow Latosol, with higher organic matter content and pH 4.7. The bioassay method was more efficient to confirm ametryn leaching than liquid chromatography.

Production and efficiency of water usage in capsicum crops under notillage and conventional planting systems.

This study aimed to evaluate the effect of no-tillage and conventional planting systems, and of weed- management strategies on water-usage efficiency in capsicum crops. The experiment was carried out at the Universidade Federal Rural do Semi-Arido in Mossoro, Rio Grande do Norte, using a split-plot layout in a randomized block design with four replications. The tillage systems were evaluated in the plots, and three weed-management strategies evaluated in the subplots (soil cover with polyethylene film, and with and without weeds). The density and dry mass of the weeds, the commercial and total productivity, and the daily water consumption were all evaluated. It was found that the no-tillage system reduced the density and dry mass of the weeds in comparison to conventional systems, and the interference of these plants reduced commercial productivity under both planting systems. The strategy of weeds under a no-tillage system, despite a higher water consumption, showed a productivity and efficiency of water usage superior to those of the strategies of polyethylene film both under no-tillage and conventional systems, and of weeds under a conventional tillage system.