Afonso Lopes

Avaliação de semeadora-adubadora de precisão trabalhando em três sistemas de preparo do solo

The performance of a precision seeder with four lines in the culture of maize (Zea mays L.) working in Latossolo Vermelho Escuro Eutrofico, moderate A, argillaceous texture was evaluated. The experimental parcels were disposed in casualized blocks with four repetitions, according to a factorial scheme 3 x 3, totalizing 36 observations. The factors had been given by the systems of tillage (conventional, no tillage and reduced) and by the gears of the tractor (3rd reduced high, 4th reduced low and 4th reduced high). The variables analyzed were: displacement speed, speed reduction, traction force and drawbar pull, fuel consumption, motor rotation and medium slipping wheels of the tractor. The results showed that the sowing operation in soil under reduced tillage presented larger fuel consumption, smaller displacement speed, smaller effective field capacity and larger slipping.

Produtividade de híbridos de milho em função da velocidade de semeadura

The present work was lead in the experimental area of the Laboratory of Machines and Agricultural Mechanization of the Sao Paulo State University, Jaboticabal, Brazil, in a soil classified as Haplustox, in conventional tillage. It had been evaluated the development and the components of production of two hybrids of corn (DKB 390, simple and DKB 435, double) in function of three speeds of the set tractor-seeder-fertilizer (5.4; 6.8 and 9.8 km h-1), totalizing six treatments with four repetitions in a randomized block-type design, factorial 2 x 3. The results had evidenced that the increase of the speed of the tractor-seeder-fertilizer set, reduced the productivity of grains for the simple hybrid and did not interfered with the productivity of the double hybrid. But in the lower speed the simple hybrid presented greater productivity of grains when compared with the double hybrid. The increase of the speed in the operation of seeding reduced the percentage of normal spacing between the seeds, independent of the studied hybrid.

Temporal variability of soil CO2 emission after conventional and reduced tillage described by an exponential decay in time model

A quantificacao do impacto das praticas de preparo sobre as perdas de carbono do solo e dependente da habilidade de se descrever a variabilidade temporal da emissao de CO2 do solo apos preparo. Tem sido sugerido que as grandes quantidades de CO2 emitido apos o preparo do solo podem servir como um indicador das modificacoes nos estoques de carbono do solo em longo termo. Neste trabalho e apresentado um modelo de duas partes baseado na temperatura e na umidade do solo e que inclui um termo exponencial decrescente do tempo que e eficiente no ajuste das emissoes intermediarias apos preparo: arado de disco seguido de uma passagem com a grade niveladora (convencional) e escarificador de arrasto seguido da passagem com rolo destorroador (reduzido). As emissoes apos o preparo do solo sao descritas utilizando-se estimativa nao linear com um coeficiente de determinacao (R2) tao alto quanto 0.98 apos preparo reduzido. Os resultados indicam que nas previsoes da emissao de CO2 apos o preparo do solo e importante considerar um termo exponencial decrescente no tempo apos preparo.

First-order decay models to describe soil C-CO2 Loss after rotary tillage

To further understand the impact of tillage on CO2 emission, the applicability of two conceptual models was tested, which describe the CO2 emission after tillage as a function of the non-tilled emission plus a correction due to the tillage disturbance. Models assume that C in readily decomposable organic matter follows a first-order reaction kinetics equation as: dCsoil (t) / dt = -k Csoil (t), and that soil C-CO2 emission is proportional to the C decay rate in soil, where Csoil(t) is the available labile soil C (g m-2) at any time (t) and k is the decay constant (time-1). Two possible assumptions were tested to determine the tilled (FT) fluxes: the decay constants (k) of labile soil C before and after tillage are different (Model 1) or not (Model 2). Accordingly, C flux relationships between non-tilled (FNT) and tilled (FT) conditions are given by: FT = FNT + a1 e-a2t (model 1) and FT = a3 FNT e-a4t (model 2), where t is time after tillage. Predicted and observed CO2 fluxes presented good agreement based on the coefficient of determination (R2 = 0.91). Model comparison revealed a slightly improved statistical fit of model 2, where all C pools are assigned with the same k constant. Rotary speed was related to increases in the amount of labile C available and to changes of the mean resident labile C pool available after tillage. This approach allows describing the temporal variability of tillage-induced emissions by a simple analytical function, including non-tilled emission plus an exponential term modulated by tillage and environmentally dependent parameters.

Biodiesel de mamona no diesel interior e metropolitano em trator agrícola

The demand for energy resources by production systems allied to scarcity of fossil fuels has driven the production of Biodiesel, a fuel produced from renewable sources. The purpose of this study was realize two tests, the first dynamics to assess the operational performance as a parameter of consumption of fuel, the second static to measure the smoke opacity (particulate material) from an engine of a farm tractor, operating with interior and metropolitan diesel mixed with castor beans Biodiesel in seven proportions. The tests were conducted in the Rural Engineering Department of UNESP/Jaboticabal - SP. The results showed that the kind of diesel influenced the consumption of fuel and smoke opacity, and the metropolitan diesel showed better quality, it was observed as well that as biodiesel proportion increased, consumption of fuel increased too, however, the opacity of smoke decreased with an increase of Biodiesel by B75.A demanda de recursos energeticos pelos sistemas de producao, aliada a escassez dos combustiveis fosseis, tem motivado a producao do Biodiesel, que e um combustivel obtido de fontes renovaveis. O objetivo deste trabalho foi realizar dois ensaios: o primeiro dinâmico, para avaliar o desempenho operacional utilizando como parâmetro o consumo de combustivel, e o segundo, estatico, para mensurar a opacidade da fumaca (material particulado) do motor de um trator agricola, operando com diesel metropolitano e interior misturados ao Biodiesel de mamona, em sete proporcoes. O trabalho foi conduzido no Departamento de Engenharia Rural da UNESP/Jaboticabal - SP. Os resultados mostraram que o tipo de diesel influenciou no consumo de combustivel e na opacidade da fumaca, sendo o diesel metropolitano de melhor qualidade; observou-se, tambem, que a medida que a proporcao de Biodiesel aumentou, o mesmo ocorreu para o consumo de combustivel; entretanto, a opacidade da fumaca reduziu com o acrescimo de Biodiesel ate B75.

Soil and crop residue CO2-C emission under tillage systems in sugarcane-producing areas of southern Brazil

Appropriate management of agricultural crop residues could result in increases on soil organic carbon (SOC) and help to mitigate gas effect. To distinguish the contributions of SOC and sugarcane (Saccharum spp.) residues to the short-term CO2-C loss, we studied the influence of several tillage systems: heavy offset disk harrow (HO), chisel plow (CP), rotary tiller (RT), and sugarcane mill tiller (SM) in 2008, and CP, RT, SM, moldboard (MP), and subsoiler (SUB) in 2009, with and without sugarcane residues relative to no-till (NT) in the sugarcane producing region of Brazil. Soil CO2-C emissions were measured daily for two weeks after tillage using portable soil respiration systems. Daily CO2-C emissions declined after tillage regardless of tillage system. In 2008, total CO2-C from SOC and/or residue decomposition was greater for RT and lowest for CP. In 2009, emission was greatest for MP and CP with residues, and smallest for NT. SOC and residue contributed 47 % and 41 %, respectively, to total CO2-C emissions. Regarding the estimated emissions from sugarcane residue and SOC decomposition within the measurement period, CO2-C factor was similar to sugarcane residue and soil organic carbon decomposition, depending on the tillage system applied. Our approach may define new emission factors that are associated to tillage operations on bare or sugarcane-residue-covered soils to estimate the total carbon loss.

Consumo de combustível de um trator em função do tipo de pneu, da lastragem e da velocidade de trabalho

The objective of this study was to compare the consumption of fuel of the FWD agricultural tractor, equipped with three types of tyres (bias ply, radial and low pressure), with and without tyre water ballasting, operating in four forward speeds. The research was carried out at FCAV/UNESP, SP, Brazil, The soil was tilled using a chisel plow. A tractor with 89 kW (121 HP) engine power equipped with FWD was used in the experiment, and the tyres used had the following characteristics: radial (front: 14.9R26 and rear: 620/75R30), bias ply (front: 14.9-26 and rear: 23.1-30) and low pressure (front: 500/60-26.5 and rear: 700/55-34). The experiment was conducted in a completely randomized block design (3x2x4), with a total of 24 treatments and three replications. The results evidenced advantages for the tractor equipped with radial tyres. The ballasting condition with water in the tyres showed lower specific consumption. It was also observed that the increase of the forward speed reduced the specific consumption.

Efeito da profundidade de semeadura e de rodas compactadoras submetidas a cargas verticais na temperatura e no teor de água do solo durante a germinação de sementes de milho

As rodas compactadoras das semadoras-adubadoras tem como principal funcao, propiciar o bom contato entre o solo e a semente para garantir a germinacao das sementes e a emergencia das plântulas. Objetivou-se, neste trabalho, estudar a influencia de tres modelos de rodas compactadoras, tres profundidades de semeadura e tres niveis de carga sobre a roda compactadora sob a temperatura e o teor de agua do solo. O trabalho foi desenvolvido na pista de ensaios de semeadura, localiza em Uberaba, MG, em Latossolo Vermelho distrofico, utilizando-se o delineamento experimental de parcelas sub-subdivididas, com 27 tratamentos e quatro repeticoes. As rodas com maior area de contato com o solo proporcionaram maiores valores do teor medio de agua e da temperatura do solo. O nivel de carga sobre a roda compactadora nao afetou a temperatura e o teor de agua do solo.

Desempenho operacional do conjunto trator-recolhedora de feijão

Mechanized harvesting of beans has a high cost. On the other hand, the botanical characteristics and the high tendency for lodging of bean planting make the combined use of harvesters difficult. This paper aimed to evaluate the operational performance of the pull-type bean combine and to quantify losses in bean harvest. The experiment was carried out in the experimental field of the Sao Paulo State University in the city of Jaboticabal, SP, Brazil. The field trial was in randomized blocks, in a 2 x 3 factorial scheme, combining two soil tillage systems (conventional and no-tillage) and three theoretical working speeds (V1, V2 and V3, respectively 4.0, 4.9 and 5.8km h-1). Four repetitions of the scheme totaled up 24 observations. The analyzed factors (tillage systems and working speeds) did not affect noise level, volume and weight of fuel consumption, machine feeding flow, dry matter and straw density, losses at the harvester platform and total losses. The losses with threshing, separation and cleaning were lesser in the 4.9km h-1 speed.

Distribuição longitudinal de sementes de soja e características físicas do solo no plantio direto

The techniques of the no tillage are complemental to the current techniques of conservation of the soil, which involve smaller mobilization and larger amount of vegetable covering in the surface of the soil. The work was accomplished in UNESP - Jaboticabal, Brazil, of November from 2003 to march of 2004 and had as objective evaluates the effect of cultures, handlings and marches of the set tractor-seeder in the sowing of the soybean in no tillage. The used experimental for installation was randomized block design in split-split-plot, with four replications. It was analyzed: initial stand, seed spacing uniformity, resistance to penetration, bulk density and soil moisture. The initial stand was not influenced by the treatments. The seed spacing uniformity was affected by the march of the tractor-seeder. The resistance to penetration suffered effect just in the layer from 0.20 to 0.25 m in the interaction cultures, handlings and marches of the tractor. The interaction cultures and handlings in the layer from 0.10 to 0.20 m for bulk density indicated the presence of compacted layer than 0 to 0.10 m and 0.20 to 0.30 m. The soil moisture was smaller in the superficial layers of the soil influenced by the handlings.