Offset Disc Harrow Research Articles

AI-based engine performance prediction cum advisory system to maximise fuel efficiency and field performance of the tractor for optimum tillage

Tractor engine performance is critical for optimizing energy efficiency in tillage operations across various soil conditions. This study introduces an artificial neural network (ANN) based novel approach for predicting and optimizing specific fuel consumption (SFC) and fuel consumption per tilled area (FCA), during tillage operations. Field tests were conducted to collect the data on rear axle torque, forward velocity, fuel consumption, throttle position, engine speed, and depth of operation under soft, medium, and hard soil conditions while using a reversible MB plough, offset disc harrow, and rigid tyne cultivator. Tractor engine performance was predicted using ANN and optimized by matching the required rear axle power with the available rear axle power. Optimal operating parameters for three distinct tillage implements, each associated with varying soil types and tillage depths, were determined based on minimizing SFC and FCA. An integrated ANN-based user advisory system was developed to provide tractor engine performance predictions and recommendations for optimal operating parameters to maximize fuel efficiency. The recommendations were validated with actual field data, resulting in Mean Absolute Percentage Errors of 7.56% and 8.98% for MB plough, 11.19% and 9.36% for offset disc Harrow, and 10.90% and 10.57% for cultivator, respectively, for SFC and FCA. Highlights ANN-based novel approach is proposed to optimize fuel efficiency during tillage Advisory system is developed to recommend parameters for optimum tillage Suggestions for minimum SFC and FCA are provided in soft, medium and hard soil The accuracy and reliability of advisory system are proven by field validation

Effects of Tillage Depth and Tractor Speed on Implement Speed for Three Tillage Implements on a Clay Loam Soil

The utilization of agricultural machinery represents the main aspect contributing to the total energy input in the agricultural system. The trials were achieved using five tractor speeds(3.6, 5.4, 7.2, 9.0 and 10.8 km/hr) and five tillage depths(10, 15, 20, 25 and 30 cm) to determine implement speed at different tillage depths for 3-bottom disc plough, spring tine cultivator and offset disc harrow on a clay loam soil. The design of the experiment used were two factors, five levels factorial of Central Composite Rotatable Design of Response Surface Method. The implement speed for 3-bottom disc plough, spring tine cultivator and offset disc harrow ranged from 0.78 to 1.95, 0.67 to 2.19 and 0.70 to 2.11 m/s, respectively. The effects of tillage depths and tractor speeds on implement speed for the three tillage implements were assessed. The results indicated that increasing the tillage depth decreased the implement speed for all the tested implements but increasing the tractor speed increased the implement speed. The tractor speed had more pronounced effect on the implement speed than the tillage depth. This study therefore recommends that the availability of time and implement width should be used in determining the speed required to finish the work on time.

Optimizacija performansi sile vuče i zahtevaza snagu neke opreme u obradi ilovastog zemljišta - pristup prema osobinama površine zemljišta

Tillage is the basic operation in agriculture and its energy requirements represent a considerable portion of the energy utilized in crop production. A field experimental data were optimized using central composite rotatable design of response surface method for draft and power requirement for 3-bottom disc plough, spring tine cultivator and offset disc harrow in a loamy soil. Optimum draft for 3-bottomdisc plough, spring tine cultivator and offset disc harrow on a loamy soil were 2.80; 0.20 and 1.82kN, respectively while optimum power requirements for 3-bottom disc plough, spring tine cultivator and offset disc harrow were 3.93; 0.30 and 2.42 kW, respectively. Optimum tillage depth and tractor speed for 3-bottom disc plough, spring tine cultivator and offset disc harrow were 22.03 cm and 10.84 km/hr, 14.07 cm and 10.80 km/hr, 17.70 cm and 10.24 km/hr, respectively. It is therefore recommended that tillage operation should be carried out at the specified optimum values at the study location in order to increase the efficiency of the operation.

Qualidade da operação de preparo do solo em três velocidades de deslocamento

O uso da mecanização agrícola permitiu a realização de práticas de cultivo mais eficientes nas lavouras. Objetivou-se avaliar a qualidade da operação de preparo do solo com grade aradora em três velocidades de deslocamento utilizando o Controle Estatístico de Processos (CEP). As velocidades utilizadas foram 3, 4 e 5 km h-1. O trator utilizado foi da marca New Holland, modelo 7630, com potência de 80 kW (108 cv) no motor, acoplado a grade aradora. Foram avaliadas a capacidade de campo operacional e o rendimento de campo efetivo como indicadores de qualidade da operação de preparo do solo. A capacidade de campo operacional obteve processo estável em todas as velocidades. Já o rendimento de campo efetivo obteve instabilidade de processo quando trabalhado com 3 km h-1. A aplicação do Controle Estatístico de Processo na operação preparo do solo permitiu identificação de pontos instáveis no rendimento de campo efetivo para a velocidade de 3 km h-1. A existência de variabilidade no rendimento de campo efetivo não compromete a estabilidade da operação de preparo do solo com grade aradora nas três velocidades. A capacidade de campo operacional e o rendimento de campo efetivo apresentam menor variabilidade na velocidade de 3 km h-1.

Modeliranje operativnih parametara obrade za plan potrebne snage za tri radna tela u obradi ilovastog zemljišta

Tillage is the basic operation in agriculture and its energy requirements represent a considerable portion of the energy utilized in crop production. The trials were achieved using five tractor speeds (3.6, 5.4, 7.2, 9.0 and 10.8 km/hr) and five tillage depths (10, 15, 20, 25 and 30 cm) to determine implement speed at different tillage depths for 3-bottom disc plough, spring tine cultivator and offset disc harrow on loamy soil. The design of the experiment used were two factors, five levels factorial of Central Composite Rotatable Design of Response Surface Method. Selected models were analyzed using ANOVA at ao. 05 and also validated. The high values of the coefficient of determination for all the selected models and the reasonable agreement between the predicted and actual values of draft and power requirement for all the tested implements show that the generated model equations can be used for predictive purposes for draft and power requirement.

Effect of Three Soil Tillage Practices on Soil Organic Matter and Nutrient in Any Semi-Arid Area in Tunisia

The distribution of soil organic matter (SOM), nitrogen (N), potassium (K), total calcium carbonate (CaCO3) and pH was studied in relation to three soil tillage practices: conventional (CT) using mouldboad plough followed by three crossing of off-set disc harrow, tooth harrow and seed drill, Reduced (RT) using a chisel, and no-till (NT) using direct driller and 2 plant species: Vicia faba and Durum wheat, grown in a clayey soil of the semi-arid region of Kef (North western Tunisia) during three years 2009-2011.
 Results showed that, under NT, Vicia faba increased SOM and N in the first fifteen centimeters by 20% and 84% respectively as compared to the CT, and reduced soil pH by 0.1 unit. Indeed, Vicia faba benefited from the residues of the Durum wheat. In contrast, CT buried the residues of the previous crop increasing the rate of SOM and N in the subsoil (30-45 cm depth). This made clear that NT, had the benefit of improving top-soil fertility and putting soil nutrients at the reach of the Vicia faba plant roots. Moreover, NT increased the concentration of K in the top-soil which helped seedlings and young plants resisting biotic and non biotic stresses imposed by the semi-arid environment.

Comparative assessment of energy requirement and tillage effectiveness of combined (active-passive) and conventional offset disc harrows

The combination of active and passive tillage tools has been acknowledged as an effective way of dealing with the soil compaction, due to reduced field trips required for preparing seedbed compared to conventional practices. A comparative analysis was carried out between an active-passive configuration of combined offset disc harrow (CODH) and conventional passively-driven mode of offset disc harrow (ODH) in sandy clay loam soil to achieve maximum tillage quality with a minimum expenditure of power. The test parameters consisted of: forward speeds (3.46, 4.55, and 6.82 km h−1), rotational speeds of front gang axle (95, 133, and 150 rpm), and working depths (80, 120, and 145 mm). Better penetration ability and uniformity in tilling depth was observed with CODH compared to passively-driven ODH. The soil pulverizing ability, stubble cutting, and crop residue burial efficiency (CRBE) was observed to be better with CODH compared to passively-driven ODH. The CODH exhibited best tillage performance index at rotational speed of 133 rpm, at which draught requirement and the corresponding driving wheel slip were witnessed to be reduced by 50.73–55.01% and 68.70–79.55%, respectively as compared to free rolling ODH, whereas, fuel consumption per tilled area and specific energy were increased by 0.06–25.53% and 4.07–37.11%, respectively. Furthermore, the soil cone index (CI) and clod size were reduced by 14.29–46.90% and 14.88–43.73%, respectively and the CRBE was increased by 11.36–100%. The results indicate that the active-passive CODH outperformed the conventional passively-driven ODH with respect to both energy consumption and quality of soil tilth.

Effect of velocity ratio on performance characteristics of an active-passive combination tillage implement

A study was conducted to investigate the effect of velocity ratio (ratio of peripheral velocity to the forward velocity of tillage tool) on the performance of an active-passive combined offset disc harrow. This implement unites the benefits of powered discs and combination tillage to reduce draft requirements, wheel slip, and gross fuel consumption. The test parameters consisted of forward velocities (3.46, 4.55, and 6.82 km h−1) and rotational velocities of front gang axle, NFGA (95, 133, and 150 rpm) to ultimately vary the velocity ratio from 1.48 to 4.59. Tests were conducted in freshly harvested paddy fields with sandy clay loam soil having moisture content and cone index of 11 ± 0.75% (dry basis) and 975 ± 50 kPa, respectively. The results indicate that increase in velocity ratio from 1.48 to 3.49 helped to reduce both draught and torque requirement with negligible reduction observed when velocity ratio was increased beyond 3.49. At a velocity ratio of 2.91, the specific energy consumption was minimum. Attempts were made to select a suitable velocity ratio based on tillage performance index considering both fuel energy input and tillage effectiveness parameters such as crop residue burial efficiency and soil pulverization. It is suggested to operate this type of implement at velocity ratio of 3.09 (forward velocity 4.55 km h−1, NFGA 133 rpm) and 4.06 (forward velocity 3.46 km h−1, NFGA 133 rpm) during the first pass and the second pass, respectively to obtain maximum tillage performance with minimum energy consumption.

Specific draft estimation model for offset disc harrows

Predicting draft requirements of tillage implements is essential from the viewpoint of proper tractor-implement matching and machinery design. It was hypothesized that draft requirement of offset disc harrow (ODH), a widely used tillage implement depends mainly on four major soil and working parameters, i.e. soil cone index (CI), forward speed, working depth and front gang angle (FGA), which could be used to develop a reasonable regression model for estimating its specific draft. To test this hypothesis, investigations were carried out on the draft requirement of ODH in an indoor soil bin available at Indian Institute of Technology, Kharagpur (22°19′ N, 87°19′ E), India during the months of November 2016 to May 2017. The soil available in the soil bin was acid lateritic sandy clay loam and taxonomically grouped under order Alfisol (Oxyaquic haplustalf). The experimental design was completely randomized with draft measured using S-type load cell (2-tonne capacity) at four levels each of FGA and forward speed, three levels each of working depth and soil CI using a 3 × 3 ODH (i.e. 3 discs in each of the two gangs) with the objective to acquire data on the draft force requirement of ODH at various soil and working parameters. The forward speed, working depth, and soil CI were measured with the help of a magnetic-type proximity switch, rotary potentiometer, and hydraulic cone penetrometer, respectively and were found to have a significant effect (p ≤ 0.01) on the draft with CI having highest influence followed by working depth, speed, and FGA. Multiple regression analysis was carried out to develop a model for estimating specific draft for ODH. The efficiency of specific draft model, was assessed by various performance indices such as mean error (ME), value account for (VAF), root mean square error (RMSE), coefficient of determination (R2), and mean absolute percentage error (MAPE) and their values were found to be -3.22, 92.77%, 4.82, 0.90 and 14.75, respectively. A major advantage of the developed specific draft model compared to other researchers’ model is the inclusion of all parameters that affect draft especially FGA and CI which would increase its applicability. A good general agreement between measured and estimated specific draft was found with the data obtained from the soil bin with an average absolute variation (AAV) of 10.76%. Verification of the model was also carried out by comparing its outputs with the model outputs of previous researchers to check its applicability for other soil types and working conditions, and the results were found to be fairly good (Al-Janobi and Al-Suhaibani, 1998 (R2 = 0.87, AAV = 14.33%), Kheiralla et al., 2004 (R2 = 0.93, AAV = 11.95%), and Roul, 2014 (R2 = 0.94, AAV = 23.05%) except the ASABE draft model (R2 = 0.66, AAV = 50.18%). Therefore, the developed model in this research could be used to predict draft requirements of ODH’s with reasonable accuracy.

Soil mixing and redistribution by strategic deep tillage in a sandy soil

Strategic deep tillage (SDT) is proposed as a single or occasional practice to help sustain the long-term productivity of the no-till system. Soil water repellence, herbicide resistant weeds, subsoil acidity and compaction are constraints that can evolve in long-term no-till systems and SDT may provide an effective solution for these. While the effect of SDT on the lateral and vertical movement of soil is understood, soil heterogeneity and mixing caused by SDT is not. Soil mixing may be an important factor for the availability of soil nutrients after SDT or for the effectiveness of soil amendments. Soil mixing and redistribution were quantified using coloured soil tracers and digital image analysis. Trenches of synthetic coloured soil were installed at four depths at a field site and four tillage treatments were applied; offset disc harrow and deep ripping (DHDR), disc plough (DP), mouldboard plough (MP) and rotary spader (RS). Digital images were acquired for soil pit faces at 5 cm intervals to capture the location of the coloured soil after SDT, these images were segmented and the 3-dimensional distribution of the coloured soil tracers was reconstructed. The mixing indices for the tillage treatments were low level (0.04–0.12). The vertical movement of soil differed between treatments; approximately 80, 60, 60 and 10% of soil from 0 to 10 cm was redistributed to deeper soil layers by MP, DP, RS and DHDR respectively. The soil profiles after the SDT treatments were composed of layered, or rotated soil that had been translocated within the working depth of the implement; however, there was some mixing at the interface between layers, or seams of soil that originated from different depths. The impact of a change in the spatial distribution of soil nutrients created by SDT on crop growth is an important knowledge gap.

A draught force estimator for disc harrow using the laws of classical soil mechanics

The disc harrow is a tillage implement that can be used to perform both the conventional and conservation tillage practices; therefore, it is important to have an accurate understanding of draught force and power requirements of it. The main objective of this study was to develop and validate a theoretical equation for the estimation of draught force of a disc harrow in a range of tillage practices and configurations. The model considers soil cutting, clod break up, soil displacement, and disc blade rolling resistance processes. According to the results of this study, in all cases of operation of a tandem and an offset disc harrow, the output values of the estimator were within the acceptable range obtained from the ASAE standard. In addition, the error of the estimator in predicting experimental data obtained from various published sources was lower than 20%. Finally, measured draught forces of a 28-blade tandem disc harrow on a silty clay loam soil varied in the range of 14 kN to 42 kN for primary, and 15 kN to 20 kN for secondary disc harrowing. In addition, errors of the estimator to predict the experimental data obtained in this study for primary and secondary disc harrowing were lower than 8%, and 6%, respectively. Therefore, the overall conclusion of the present study is that the developed estimator will be able to predict the draught force requirements of a disc harrow.

Performance of combined offset disc harrow (front active and rear passive set configuration) in soil bin

Soil bin investigations were initiated with combined offset disc harrow (CODH) which unites the benefits of powered discs and combination tillage together through a front active-rear passive set configuration. The proposed configuration may help to achieve timeliness in sowing, better crop residue handling with reduced tillage passes and improved engine power utilization of tractor. The effects of speed ratio (u/v), front gang angle (α), operating depth and cone index (CI) on its draft, torque and power requirement were studied and compared with its traditional passively driven mode at an average soil moisture of 9–10% (db) in sandy-clay loam soil. Optimum system settings were found out before further performance evaluation in the field. The substantially reduced draft requirement with CODH might help to reduce the wheel slippage and improve field productivity while increased power requirement might prevent the under-loading of tractor engine. Tillage quality was assessed considering CI values and found to be far superior compared to traditional mode. Optimum system settings were found at α of 35° and u/v ratio of 3.6 in terms of lowest power expenditure and better work quality with torque power expenditure of 60–70% in total power indicating improved utilization of engine power if operated with tractor power take-off (PTO).

Draft Prediction of Commonly Used Tillage Implements for Sandy Clay Loam Soil in India

Draft requirements for prototypes of mouldboard plough, cultivator and offset disc harrow with different widths of cut or number of tools were measured at four levels of depth and four levels of forward speed in three soil compaction levels in a soil bin with sandy clay loam soil at an average soil moisture content of 9.58% (d.b.). Effect of depth was more significant on draft of mouldboard plough and offset disc harrow, whereas number of tynes was the most significant factor for cultivator. Rate of increase of draft with respect to depth was higher as compared to forward speed, cone index and width of cut for all implements tested. Draft values predicted by ASABE model were compared with those obtained from soil bin tests at three compaction levels. Quite often, the measured draft values were found to be about 2.9, 1.7 and 1.65 times more than the ASABE predicted values for mouldboard plough, cultivator and offset disk harrow, respectively. An equation similar to the ASABE model incorporating cone index was developed using stepwise regression analyses to model the draft of tillage implements for the range of soil and operating condition tested. Field tests with commercial models of these implements were conducted to acquire data for draft by developing appropriate instrumentation to validate the developed draft equation. The average absolute variations between the predicted and measured values of draft were within 5.5 % and 11.6% for all the implements tested, and thus validated the developed draft prediction equation.

Performance Study of Moldboard Plow with Two Types of Disc Harrows and Their Effect on Some Soil Properties Under Different Operating Conditions

A field experiment was conducted in two different locations at Agricultural Research Station of Garmat Ali in Basrah-Iraq. The aim of this investigation is to evaluate the effective field capacity, field efficiency, draft force, pulverization index (PI), soil bulk density and soil porosity for moldboard plow (primary tillage), mounted disk harrow and offset disk harrow (secondary tillage) under different operating speed (2.54 (S1), 3.84 (S2) and 5.77 (S3) km hr-1) in two different soil textures (silty loam soil and clay soil). The design of the experiment was complete randomized blocks design in factorial experiment. The results showed that the moldboard plow had high values of draft force, pulverization index (PI) and soil porosity and lower soil bulk density, effective field capacity and field efficiency than that of mounted disk harrow and offset disk harrow in both soils. The operating speed and the interaction between operating speed and implements tillage type had significantly affect (p < 0.05) on all the studied parameters. The silty loam soil achieved higher effective field capacity, field efficiency, soil porosity (low bulk density) and considerable pulverization of soil clods than that of clay soil. The results also showed that the optimal operation conditions of implements tillage were associated with high operating speed of 5.77 km hr-1 in silty loam soil especially with using the disks harrow.

Computer simulation for predicting tractor engine overloading for tillage operations

The primary purpose of agricultural tractors, especially those in the middle to high power range, is to perform field work. Tractor manufacturer needs prediction of tractor field performance data in the tractor design stage itself so that they can optimize the transmission with the engine to give better performance. Engine speed prediction model was developed using Budni tractor test data. Developed engine speed prediction model for 10 engine model was compared with actual data of engine speed, it was found that for all engine models R 2 (co-efficient of determination) between predicted and actual engine speed was greater than 0.98. So developed empirical equations can be used in software for predicting engine speed. The field experiments were conducted using a tractor with three different implements viz., 3-bottom mould board plough, 11-tyne cultivator and offset disc harrow. For each operation, the performance parameters such as draft, slip, depth, engine speed and fuel consumption were measured at different combinations of gear and throttle positions. Software in visual basic was developed to predict tractor engine overloading (engine speed drop) for field operations (MB plough, cultivator and disc harrow). The developed software was validated using field data collected in Kanchipuram, Tamil Nadu. For field operation with 2 WD tractor equipped with bias-ply tires and attached with cultivator the deviation of software predicted engine speed (rpm) drop was -16.47 to 26.92 per cent and for draft was -11.07 to 4.65 per cent. For field test with offset disc harrow the deviation of software predicted engine speed (rpm) drop was -17.44 to 15.38 per cent and for draft was -10.98 to 4.76 per cent. For field operation with MB Plough the deviation of software predicted engine speed (rpm) drop was 18.48 to 21.52 per cent and for draft -12.01 to -3.75 per cent.

Measurement of weight transfer in two wheel drive tractor by developed ring transducer

Weight transfer or weight shift is, in fact, reaction transfer or change in the reactions of front and rear wheels of the tractor. Weight transfer because of drawbar loading decreases soil reaction against the front wheels and increases reaction against the rear wheels. A study was done to measure the dynamic front wheel reaction of the tractor and thereby the weight transfer from front to the rear wheel. Developed ring transducer was attached below the tractor's front axle to measure the front wheel reaction. Field experiments were conducted using Ford-3630 tractor with three different implements viz., 3-bottom mould board plough, 9-tyne cultivator and offset disc harrow. For each operation, the parameters such as dynamic front wheel reaction, draft, slip and depth were measured. The instrumented link forces were used to calculate implement draft. Slip was calculated by measuring actual speed in the field at different depths and theoretical speed on a concrete surface in the same gear and throttle position. The dynamic front wheel reaction was measured by using the developed ring transducer and thus, the weight transfer from front to rear was calculated. Also the weight transfer for a given draft was calculated theoretically and compared with the experimentally determined weight transfer. The data indicated that weight transfer increased with increase in draft. The maximum variation between theoretical and experimental values of weight transfer was found to be 12.62 per cent. This variation may be due to some assumptions made in theoretical calculation as well as due to vibration of the front axle while operating the tractor in the field.

Umidade e temperatura de argissolo amarelo em sistemas de preparo e estádios de desenvolvimento do milho

RESUMO Os sistemas de preparo do solo afetam a quantidade de resíduo vegetal sobre a superfície do solo e, consequentemente, sua umidade e temperatura. Objetivou-se avaliar a temperatura e a umidade do Argissolo Amarelo em estádios de desenvolvimento da cultura do milho sob sistemas de preparo mecanizado. O experimento foi conduzido no delineamento em blocos inteiramente casualizados, com quatro repetições, em Petrolina - PE. Os sistemas de preparo do solo foram: sem preparo primário, grade off-set de discos de 0,56 m, grade off-set de discos de 0,61 m, escarificador e arado de aivecas. As leituras de umidade e temperatura foram realizadas ao longo do dia, nos horários de 6; 9; 12; 15 e 18 h, nos estádios de desenvolvimento V3, V8, R3 e R6 do milho. A umidade do solo foi avaliada na camada de 0,00-0,05 m utilizando-se do método gravimétrico, e a temperatura do solo na superfície, utilizando-se de termômetro infravermelho. Os sistemas de preparo do solo e os horários de leitura influenciaram na umidade e na temperatura do solo. Os maiores valores de umidade ocorreram no período da manhã, enquanto a maior temperatura do solo ocorreu na parte da tarde.

VARIÁVEIS FÍSICAS DE ARGISSOLO AMARELO DO SEMIÁRIDO NORDESTINO EM FUNÇÃO DAS OPERAÇÕES DE PREPARO PERIÓDICO

A realização de operações de preparo afeta as propriedades físicas do solo, podendo levar com o tempo a uma redução da sua qualidade. Parâmetros relacionados à estrutura do solo tais como agregação, densidade e porosidade, são comumente utilizados para inferir sobre a qualidade física dos solos agrícolas. Assim, objetivou-se avaliar o estado de agregação, o índice de floculação, a densidade e a porosidade total de Argissolo Amarelo do semiárido nordestino em função dos sistemas de preparo e do número de operações. O experimento foi desenvolvido em área pertencente à Universidade Federal do Vale do São Francisco – UNIVASF, sendo os tratamentos compostos pela combinação de diferentes tipos de preparo e intensidades de operação, os quais foram, respectivamente: sem preparo, preparo com escarificador, com grade leve em “tandem”, grade leve “off-set” (discos de 0,56 m de diâmetro) e, grade leve “off-set” (discos de 0,61 m de diâmetro); uma, duas e três operações. Utilizou-se o delineamento em blocos casualizados com quatro repetições, com os tratamentos dispostos em esquema de parcelas subdivididas, sendo os sistemas de preparo dispostos nas parcelas e o número de operação nas subparcelas. Foram coletadas amostras deformadas e indeformadas de solo para avaliação da estabilidade dos agregados do solo, densidade do solo, porosidade total e índice de floculação. Não foram obtidas diferenças significativas para os parâmetros Diâmetro Médio Geométrico (DMG), Diâmetro Médio Ponderado (DMP) e Índice de Estabilidade de Agregados (IEA) quando comparados os sistemas de preparo utilizados. A densidade e a porosidade total do solo também não foram significativamente afetadas pelos sistemas de preparo e o número de operações.

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.

Nível de ruído emitido por conjuntos mecanizados em função da velocidade e da condição do solo

The noise generated by agricultural mechanization has brought side effects, and one of them is the damage to the hearing of agricultural machinery operators. According to NR-15, which establishes the tolerance limits for continuous noise, the exposure to noise levels above 115 dB (A) for individuals who are not adequately protected is not permitted, given that the maximum tolerable limit, considering an 8-hour working day, is 85 dB (A). The objective of this work was to study the influence of the travel speed and soil condition on the determination of sound power levels emitted by the tractor in several agricultural operations. The study was conducted at the Campus of Agricultural Sciences of Universidade Federal do Vale do São Francisco, Petrolina, Pernambuco, Brazil, using a Valtra tractor model 785 TDA without cabin and a noise level meter. The sound power level of the tractor was evaluated in five speeds (0.83; 1.39; 2.42; 2.97 and 3.61 m s-1) on prepared soil and soil covered with weeds, with the machinery: tractor (control), off-set disk harrow, chisel plow and rotary mower. Data were analyzed by polynomial regression when significant at least 5% probability by the F test. The most significant values were found in the tractor and plowing, observing that the need for higher engine power increased the sound power level. The other operations had noise values above the sound power established by the NR-15, considering the 8-hour working day.