Harrow

Abstract: The influence of agricultural production systems on greenhouse gas generation and emission is of interest as it may affect potential global climate change. Agricultural ecosystems can play a significant role in production and consumption of greenhouse gases, specifically, carbon dioxide. Information is needed on the mechanism and magnitude of gas generation and emission from agricultural soils with specific emphasis on tillage mechanisms. This work evaluated four different tillage methods on the short-term CO2 and water vapor flux from a clay loam soil in the Northern Cornbelt of the USA. The four tillage methods were moldboard plow only, moldboard plow plus disk harrow twice, disk harrow and chisel plow using standard tillage equipment following a wheat (Triticum aestivum L.) crop compared with no tillage. The CO2 flux was measured with a large portable chamber commonly used to measure crop canopy gas exchange initiated within 5 minutes after tillage and continued intermittently for 19 days. The moldboard plow treatment buried nearly all of the residue and left the soil in a rough, loose, open condition and resulted in maximum CO2 loss. The carbon released as CO2 during the 19 days following the moldboard plow, moldboard plow plus disk harrow, disk harrow, chisel plow and not tilled treatments would account for 134%, 70%, 58%, 54% and 27% respectively of the carbon in the current year's crop residue. The short-term carbon dioxide losses 5 hours after four conservation tillage tools was only 31% of that of the moldboard plow. The moldboard plow lost 13.8 times as much CO2 as the soil area not tilled while different conservation tillage tools lost only 4.3 times. The smaller CO2 loss following conservation tillage tools is significant and suggests progress in developing conservation tillage tools that can enhance soil carbon management. Conservation tillage reduces the extent, frequency and magnitude of mechanical disturbance caused by the moldboard plow and reduces the air-filled macropores and slows the rate of carbon oxidation. Any effort to decrease tillage intensity and maximize residue return should result in carbon sequestration for enhanced environmental quality.

Abstract: Mechanized agriculture is increasing rapidly in the Cerrado region of Brazil, causing concerns about water quality, off-site impacts, and sustainability. Our objective was to determine the impact of tillage on soil biological activity and aggregate stability in an Oxisol typical to the region. Three different tillage practices common to the Cerrado region (no-till, disk harrow, and disk plow) and an area under native vegetation were examined. Five different soil enzyme activities, C- and N-mineralization, organic C, total N, and aggregate distribution were determined. Total N, acid phosphatase, arylamidase, and C- and N-mineralization were the most sensitive to changes in tillage management. For each of these analyses, the no-till system had greater concentrations or activities (18–186%) than disk plow in the 0–5 cm layer. Significant differences observed in the 0–5 cm depth did not necessarily translate into total profile differences to a depth of 30 cm. No-till had significantly greater levels of total N, and C- and N-mineralization (20– 127%) than the disk harrow system. Total N ranged from 1.8 to 2.2 kg m � 3 ; C- and N-mineralization (24-day incubation) ranged from 2.8 to 6.8 and 0.04 to 0.10 kg m � 3 , respectively, among tillage systems and soil depths. Enzyme activities in all treatments were more strongly correlated with total soil N than with soil organic C (SOC), contrary to the norm in temperate soils where the stronger correlation is with SOC. Mean weight diameter of water stable aggregates was related to SOC (r = 0.73) and total N (r = 0.92), indicating that soil organic matter does play a significant role in stabilizing aggregates in Oxisols. Results indicated the importance of reducing tillage as a means of increasing soil biological activity of the topsoil in the Cerrado region of Brazil. By understanding the effects of tillage on soil biological properties, management systems can be implemented that improve natural nutrient cycling processes and soil structure, resulting in increased agricultural sustainability of tropical ecosystems. Published by Elsevier B.V.

Abstract: This study, covering 12 cultivations, was carried out at Embrapa Rice & Beans Research Center, Santo Antonio de Goias, Goias, Brazil, in an Oxisol, under center pivot, for six consecutive years. The effects of four soil tillage systems and six crop rotations on bulk density and soil porosity were evaluated. The experiment was conducted in a completely randomized design, using a splitplot arrangement, with three replications. The tillage treatments were: moldboard plough/harrow disc, moldboard plough, harrow disc, and no-tillage. Tillage treatments constituted the main plots and rotation treatments, the subplots. The crop rotations were: (a) upland rice-common bean, (b) corn-common bean, (c) soybean-wheat, (d) soybean-wheat-soybean-common bean-upland rice-common bean, (e) upland rice associated to calopogonium-common bean, and (f) corn-common bean-corn-common bean-upland rice-common bean. Crop rotations a, b, c, and e were annuals and d and f were of three years'duration. The soil under no-tillage at the surface layer (0-10 cm) showed the highest bulk density value and the lowest total porosity and macroporosity values. Whereas the soil under harrow treatment showed the lowest bulk density and the highest total porosity values. Under moldboard plough, the 10-20 and 20-30 cm soil layers had the lowest bulk density values and the highest total porosity and macroporosity values. On the surface layer, crop rotations composed by soybean and wheat showed the highest bulk density and microporosity values and the lowest macroporosity values while the crop rotation composed by upland rice associated to calopogonium and common bean showed the highest macroporosity value and the lowest microporosity value .

Abstract: The objective of the present study was to measure the specific draught (force per cross-sectional area of worked soil) and energy use for soil fragmentation for different tillage implements and soil conditions. Draught was calculated from measurements of fuel consumption and speed during tillage with a mouldboard plough and a chisel plough set to working depths of 13, 17 and 21 cm, and a disc harrow. Tillage was carried out at three different water contents (“Wet”, “Moist” and “Dry”) on two sites. The average working depth was calculated from weighing the loose soil within a 0.25-m 2 frame. Specific area of the soil was determined by sieving. Soil strength was measured in situ using a shear vane and a penetrometer. Average working depth was much less than the set working depth for the chisel plough. Specific draught was generally the lowest for the mouldboard plough and the highest for the chisel plough, and increased with decreasing soil water content. The specific draught was strongly correlated to soil cohesion, but not to penetration resistance. The proportion of coarse aggregates after tillage was the highest for the mouldboard plough and the lowest for the moist soil. The energy use for soil fragmentation was in most cases the lowest for the disc harrow, while there were small differences between the chisel and the mouldboard ploughs. The results show that the mouldboard plough is energy efficient for loosening soil, while the disc harrow is energy efficient for soil fragmentation during primary tillage. Tillage at an intermediate water content, close to the plastic limit, gave the largest proportion of small aggregates and consequently the lowest energy use for soil fragmentation.