Reaction forces of lightweight mouldboard ploughs at slow speeds of tillage in Nitosol, Vertisol and Ferralsol soils under two moisture conditions

The mouldboard plough is the standard tillage implement used with animal power in Kenya. Various designs are currently used indiscriminately in varied soil types and conditions of operation. Their draught characteristics and comparative ability to achieve or maintain desired depths of operation under inherent edaphic conditions are unknown. The significance of variation in working speeds, when different species of draught animals are used, is also unknown. This study was therefore aimed at rating the performance of some common ploughs in order to advise farmers on optimisation of their use. Draught and vertical reaction (suction) on a per-tool basis were measured for four ploughs commonly used in the region; the Victory^®, the Rumpstad winding-body^® and two types of Rumpstad cylindrical-body^® ploughs, using an instrumented rig. The experiments were in Pellic Vertisol, Ferralsol and Nitosol soils under two soil moisture conditions. Draught increased significantly with depth for all four ploughs, hence, regulation of tillage depth is paramount to avoidance of drastic fluctuations. Similarly, vertical reaction increased with depth of ploughing, which implies a more stable operation, hence, when draught can be sustained over an acceptable work duration, it is desirable to set the ploughs to work deeply. Significant speed–depth interactions were also recorded, and these imply that speed is important when operating depth is stochastic as is the case in the dynamics of these ploughs. Overall, the Victory plough had the lowest draught requirement (0.32–1.02 kN) under dry and moist soil conditions, hence, was the best option for use in areas represented by the three soil types in Kenya. Soil-type had a significant effect on mean draught and vertical reaction in the order (Draught, Vertical reaction); Vertisol (1.65 kN, 0.70 kN) > Ferralsol (0.66 kN, 0.44 kN) > Nitosol (0.64 kN, 0.01 kN), and Ferralsol (1.17 kN, 0.71) > Vertisol (1.09 kN, 0.23 kN) > Nitosol (0.49 kN, 0.11 kN) under moist and dry conditions, respectively. These results suggest that the duration of continuous work periods with draught animals should be based on soil-type.     

Specific draught for mouldboard plough, chisel plough and disc harrow at different water contents

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-m² 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.     

Cultivation effects on the dynamics of a Johnson grass seed population in the soil profile

The effect of maize and wheat cultivation on a Johnson grass (Sorghum halepense (L.) Pers.) seed population, and its vertical distribution in a 20-cm soil profile was evaluated from autumn to early spring. The experiment was carried out in plots with 2 different types of seed-banks:

1. (A) with 1 generation of seeds distributed on the surface of the soil;

2. (B) with 2 generations of seeds, 1 buried and the other distributed on the surface of the soil.

The wheat system had one tilling operation in April with a mouldboard plough and rotary cultivator and another one in August, before sowing, with the rotary cultivator only. The maize system had 2 tilling-operations with a mouldboard plough and rotary cultivator; the first one in April and the second one in October, before sowing.

Treatments were a combination of cultivation systems and seed-bank types.

A significant seed loss was detected only in those plots under the maize cultivation system with 2 generations of Johnson grass seeds.

Tilling with the mouldboard plough and rotary cultivator significantly changed the vertical pattern of seed distribution. No appreciable modification was observed after cultivation with the rotary cultivator alone.

The mouldboard plough appeared to be more efficient at burying seeds (ca. 80%) than at bringing them to the surface (ca. 38%).

In the maize crop system, after sowing, there was a significantly greater number of full florets (25%) in the 0–4-cm layer, in relation to the total in the soil profile, than in the wheat crop system (7%).

Ecological implications of these cultivation methods on Johnson grass seed dynamics are discussed.     

Ergebnisse zur bodenverlagerung durch bearbeitungserosion in der jungmoränenlandschaft Nordostdeutschlands: Investigations of soil movement by tillage as a type of soil erosion in the young moraine soil landscape of Northeast Germany

Soil translocation by soil tillage can have a considerable importance on arable land. These results were published in the international literature. The aim of the experiments is to quantify the translocation of soil due to tillage with different typical tools. A mouldboard plough and a disc harrow were tested in field experiments on a slope (4° inclination) with sandy soil. The average movement of soil particles of the top soil was determined about the changed tracer concentration. The tracer coloured gravels were most suitable of all tested tracer. The comparison of the tools showed more soil translocation caused by mouldboard plough (145?kg) than by disc harrow (12?kg). The transport was also different: plough 0.50?m and disc harrow 0.11?m average distance.     

Implement and soil condition effects on tillage-induced erosion

Water, wind, or tillage-induced soil erosion can significantly degrade soil quality. Therefore, understanding soil displacement through tillage translocation is an important step toward developing tillage practices that do not degrade soil resources. Our primary objective was to determine the effects of soil condition (i.e. grassland stubble versus previously tilled soil), opening angle, and harrow speed on soil translocation. A second field study also conducted on a Lixisol but only in the stubble field, quantified displacement effects of mouldboard ploughing. The field studies were located 12 km South of Évora, Portugal. Soil displacement or translocation after each tillage operation in both studies was measured using aluminium cubes with a side length of 15 mm as ‘tracers’. Offset angles for the harrow disk were 20°, 44° and 59°; tractor velocities ranged from 1.9 to 7.0 km h⁻¹ and tillage depth ranged from 4 to 11 cm. The depth of mouldboard ploughing was approximately 40 cm with a wheel speed of 3.7 km h⁻¹. The translocation coefficients for the two implements were very different averaging 770 kg m⁻¹ for the mouldboard plough and ranging from 9 to 333 kg m⁻¹ for the harrow disk. This shows that the mouldboard plough was more erosive than the harrow disk in these studies. All three variables (soil condition, opening angle, and tillage velocity) were critical factors affecting the translocation coefficient for the harrow disk. Displacement distances were the largest for compacted soils (stubble field), with higher opening or offset angles, and at higher velocities. The results also showed significant correlation for (a) mean soil displacement in the direction of tillage and the slope gradient and (b) soil transport coefficient and the opening angle. Our results can be used to predict the transport coefficient (a potential soil quality indicator for tillage erosion) for the harrow disk, provided tillage depth, opening angle, and tool operating speed are known.     

Effect of tillage intensity on weed infestation in organic farming

Conservation tillage is not yet widely accepted by organic farmers because inversion tillage is considered to be necessary for weed control. Three long-term experiments were established with combinations of reduced and conventional plough tillage and stubble tillage to determine weed infestation levels in organic farming, i.e. herbicide application being excluded. Experiment 1 (with very low stocking density of perennial weeds) showed that in presence of primary tillage by mouldboard ploughing the number of annual weeds was nearly unaffected by the mode of stubble tillage. In experiment 2, however, with Canada thistle (Cirsium arvense) being artificially established, thistle density was significantly affected by stubble tillage and by a perennial grass–clover forage crop. Experiment 3 combined two levels of stubble tillage (skimmer plough, no stubble tillage = control) with four implements of primary tillage in the order of decreasing operation depth (deep mouldboard plough, double-layer plough, shallow mouldboard plough or chisel plough). Primary tillage by chisel plough resulted in significantly highest annual weed density compared to all other treatments. The natural C. arvense infestation in experiment 3 showed highest shoot density in the “skimmer plough/chisel plough” treatment compared to the lowest infestation in the “skimmer plough/double-layer plough” treatment. The poor capacity of the chisel plough for weed control was also reflected by the soil seed bank (5500 m⁻² C. arvense seeds for chisel plough, <300 seeds for all other primary tillage). A reduced operation depth of the mouldboard plough (“shallow mouldboard plough”) seemed to have an insufficient effect in controlling C. arvense infestation as well. Stubble tillage by the skimmer plough in addition to nearly any primary tillage operation largely reduced both annual weeds and thistle shoots. Most effective in controlling C. arvense was also a biennial grass–clover mixture as part of the crop rotation.Double-layer ploughing is a compromise between soil inversion and soil loosening/cutting and can be regarded as a step towards conservation tillage. In terms of controlling annual weeds and C. arvense, the double-layer plough was not inferior to a deep mouldboard plough and seems to be suitable for weed control in organic farming. Tilling the stubble shallowly after harvest can support weed control in organic farming remarkably, particularly in reducing C. arvense. If no noxious, perennial weeds occur and primary tillage is done by soil inversion, an omission of stubble tillage can be taken into consideration.     

横坡和顺坡耕作对紫色土土壤团聚体稳定性的影响

通过径流小区试验,分析探讨了紫色土横坡和顺坡两种耕作模式下表层(0~20 cm)土壤水稳性团聚体及有机碳含量的特征,为紫色土区坡耕地的有效改造和综合利用提供科学依据。试验结果表明,横坡耕作下土壤水稳性指数K值比顺坡耕作高38.99%,而土壤分散性D值为顺坡耕作的1.64倍,横坡耕作抗蚀性大于顺坡耕作。横坡耕作>0.25 mm水稳性团聚体含量比顺坡耕作增加3.62%,>5 mm、5~3 mm、3~2 mm水稳性团聚体含量横坡耕作均高于顺坡耕作,横坡耕作显著提高>2 mm水稳性团聚体含量。横坡耕作下团聚体结构体破坏率较顺坡耕作减少3.05%,团聚体平均重量直径为顺坡耕作的1.39倍。2种耕作模式下0.5~2 mm团聚体有机碳含量均最高,>0.25 mm不同粒级团聚体有机碳含量百分数均随粒径的减小而减小,均在0.5~0.25 mm粒级下达到最小。横坡和顺坡耕作模式下2~1 mm团聚体有机碳含量无显著差异。横坡耕作较顺坡耕作能够显著增加紫色土>2 mm水稳性团聚体含量,且对有机碳的固持作用更好,有利于土壤结构的改善。     

复式耕整机耕深与耕宽稳定性分析与试验

针对设计的复式耕整机出现的耕作稳定性问题,结合复式耕整机整体结构及工作原理,从牵引、水平面内受力、机器振动3个角度分析影响耕作稳定性因素,确定影响耕作稳定性关键因素为牵引角、犁体配置斜角、旋耕刀升角。以牵引角、犁体配置斜角、旋耕刀升角为试验因素,以工况耕深稳定系数和工况耕宽稳定系数为性能评价指标进行二次正交旋转组合试验。正交试验结果表明:试验因素对评价指标影响程度从高到低皆为:犁体配置斜角、牵引角、旋耕升角,当各影响因素分别取值为17.3°、27.8°、72.6°时,工况耕深稳定系数和工况耕宽稳定系数分别为91.8%、93.4%。以影响因素最优参数组合为基础进行的验证试验结果表明:试验后工况耕深稳定系数和工况耕宽稳定系数为91.5%、93.1%,与软件分析结果基本一致,且其他耕作指标均达到农艺要求。该研究可为复式整地机械的耕作稳定性研究提供技术参考。     

Effects of rake angle of chisel plough on soil cutting factors and power requirements: A computer simulation

A computer simulation was conducted to predict the effects of rake angle of a chisel plough and soil bulk density on angle of soil failure plane, rupture distance, width of side crescent, frictional, overburden, cohesion and adhesion soil cutting factors, draft forces and drawbar power requirements. The experimental work was carried out in two locations. Soil of the first location was sandy clay with the soil bulk densities of 1.75 and 1.70 g/cm³ for firm and loose soil conditions, respectively, with an angle of internal friction of 30° and a surface friction angle of 20°, cohesion of 2.5 kN/m² and adhesion of 1.2 kN/m². Soil of the second location was clay loam with the soil bulk densities of 1.65 and 1.50 g/cm³ for firm and loose soil conditions, respectively, with an angle of internal friction of 34° and a surface friction angle of 23°, cohesion of 2.4 kN/m² and adhesion of 1.14 kN/m². The prediction showed that the angle of failure plane found to decrease with the rake angle. The rupture distance decreased with the rake angle from 15° to 55° and then increased as the rake angle increased over 55°. The width of the side crescent increased as the rake angle increased and the maximum value and the minimum value were recorded at 75° and at 15°. Values of frictional and overburden factors decreased as rake angle increased. The maximum and minimum values were recorded at 15° and 75°, respectively. The values of cohesion factor increased as rake angle increased. The maximum value was recorded at rake angle of 75° and the minimum value was recorded at rake angle of 15°. Adhesion factor was found to change inversely with the rake angle from 15° to 55° and then to change directly with the rake angle over 55°. The draft force decreased with the rake angle and reached its minimum value at 45° rake angle. Over 45°, the draft force increased and reached its maximum value at 75° rake angle. The draft increased with soil bulk density. The power required for moving the plough recorded the maximum value at rake angle of 15°, while the minimum value was recorded at 55° rake angle. The values of power increased with decrease of soil bulk density. The predicted values demonstrated some deviations from the experimental values of the draft force and the drawbar power.     

Long-term tillage system effects under moist cool conditions in Switzerland

How do different soil tillage systems influence soil quality over the years? Under moist cool conditions is it possible in the long term to reduce dramatically soil tillage intensity without experiencing reductions in yield or other problems? In 1987, the Swiss Federal Research Station for Agricultural Economics and Engineering in Tänikon initiated a long-term soil tillage trial to clarify these questions. The trial compared mouldboard plough, chisel, paraplow, shallow tillage and no-tillage systems on a well-drained Orthic Luvisol with 160 g kg⁻¹ clay, 310 g kg⁻¹ silt, and under a climate that has a mean annual precipitation of 1180 mm. The tillage treatment effects were evaluated by measuring several biological, chemical, and physical soil quality indicators. Reduced soil tillage increased earthworm populations, reduced Pseudocercosporella herpotrichoides infection in wheat (Triticum aestivum) and increased plant colonisation by arbuscular mycorrhizal fungi. Yields for no-tillage and other ploughless cultivation techniques were on par with those obtained by ploughing. An exception was direct-drilled maize (Zea mays), where no-tillage decreased yield by more than 10% over the course of 14 years. In the first 7 years of the trial, the level of soil organic carbon in all the tillage regimes was approximately 40% lower than natural grassland (initial situation 1987=75 Mg SOC ha⁻¹). The no-tillage method did not differ from the others in respect of bulk density, but it showed an increased preconsolidation stress and hence better trafficability. Under Switzerland’s moist cool climatic conditions, it is possible to reduce soil tillage intensity without substantial reductions in yield, and at the same time improve soil quality.     

Impacts of long-term and recently imposed tillage practices on the vertical distribution of soil organic carbon

Although many studies suggest that no-tillage (NT) increases soil organic carbon (SOC) within the soil profile relative to mouldboard ploughing, other studies indicate that no net change occurs. The latter studies suggest that NT only stratifies the SOC, where a near-surface increase in SOC is offset by a concomitant decrease in the subsurface. We examined the SOC distribution and stocks in a cool, humid Brookston clay (Typic Argiaquoll) soil under four soil management systems with a corn–soybean rotation. The objectives of this study were to compare the profile distribution and total amount of SOC under long-term (21 years) NT and mouldboard plough (MP) tillage with the changes that occur over 8 years when 13-years continuous NT is converted to MP, and when 13-years continuous MP is converted to NT. In the top 5 cm of soil, the long-term NT management accumulated greater SOC compared with the long-term MP treatment. However, this near-surface increase was offset by lower SOC concentrations in the 10–20 cm depth, resulting in similar total amounts of SOC stored in 0–20 cm for both long-term NT and MP. The SOC stratification that existed after 13 years of NT management was eliminated with one mouldboard ploughing operation, however the total SOC content in the plough layer of the new-MP treatment remained relatively constant over the subsequent 8 years. Soil organic carbon stratification was evident in the new no-tillage treatment 3 years after the cessation of tillage. The continuous build-up of SOC in the surface of new-NT soils was associated with no change in the total amount of SOC in the plough layer relative to long-term NT. This implies that the diminution of SOC in the 10–20 cm depth was at the same rate as the accumulation of SOC in the 0–5 cm depth. Although there was no net effect of tillage on total carbon stocks in this fine-textured soil, SOC stratification required several years to build-up after adoption of NT, but only a single year to destroy under MP.     

Computer Aided Analysis of Forces Applied to Semi-mounted Plough

半悬挂犁工作幅宽大，作业效率高，非常适应大农业生产的要求，为了合理地进行半悬挂犁与拖拉机机组的配套设计和使用，减少耕作过程中的功率消耗，提高机组效率，就必须要对半悬挂犁进行受力和结构参数分析，传统的分析方法是利用图解法。本文从理论上分析了采用图解法进行半悬挂犁受力分析所存在的问题，建立了半悬挂犁受力的矩阵方程组，利用计算机辅助分析，预测了半悬挂犁机组各结构参数变化对机组受力工况的影响，从而为半悬挂犁机组的合理配置、强度计算和优化设计提供了理论依据。     

Optimized soil inversion in the headlands with a novel section-controlled mouldboard ploughing system

In inversion tillage systems, the mouldboard plough is fundamental for producing a desirable seedbed. The desired ploughing quality is achieved when the plough layer is inverted homogeneously. This is, however, difficult to obtain in the main-headland intersection zone where the plough is lowered and elevated, as ploughed and unploughed triangles are formed. This results in zones where the soil is inverted twice, which may result in poor residue and weed incorporation and a poor seedbed quality. The design of the three-point linkage-attached mouldboard plough has not changed since the 1950s, but the number of furrows has increased, which has increased the size of the aforementioned triangles. A novel ploughing system was introduced to meet these headland challenges, where each plough section can be lowered and elevated independently. The aim of this study was to evaluate the effects of using a section-controlled mouldboard plough. Two similarly designed, randomized, field plot experiments were conducted on two different soil types (sandy loam and loamy sand) on a stubble field and grass field. The study showed that the section-controlled plough reduced the main-headland overlap area by ~98%. The results of a range of soil physical properties measurements and seedbed quality analyses showed that the section-controlled plough created a homogeneous loosened seedbed quality, improving the incorporation of crop residues and leaving fewer residues on the soil surface. Furthermore, the section-controlled plough showed additional benefits, for example wedge operations and visual line marking.     

Performance of low-draft tillage implements on a hard setting Alfisol of the SAT in India

Abstract. Four bullock-drawn tillage implements (mouldboard plough, chisel plough, sweeps, and shovels) were evaluated on a hard-setting Alfisol. Measurements included draft requirement, bulk density, cone index, soil crust strength, water content of the plough-layer and crop yield. Changes in bulk density and cone index due to tillage decreased with time and were negligible by the end of the growing season. After tillage with a mouldboard plough the crust was stronger than after tillage with other implements. The shovel cultivator enabled the soil to store more water, and required least draft per unit effective area of cut.     

Soil management by shallow mouldboard ploughing in The Netherlands

The structure of the soil in the arable layer is controlled by tillage, soil biota activities and weathering, whereas the structure below this layer is mainly the result of the activities of soil biota. Organic farmers tend to minimise the depth of the main tillage operation to encourage soil biota to create a soil structure with continuous biopores and a well crumbled topsoil. The best main tillage operation for preventive weed control, especially important in organic farming, is mouldboard ploughing. The shallow ploughing experiments described in this paper were conducted to ascertain the minimum ploughing depth for an ecologically accountable, sustainable tillage system with good weed control, good land qualities (in terms of workable days, aeration and soil moisture conditions) and finally with good yields. The “ecoplough” used for shallow ploughing was developed by Rumptstad Industries to meet the requirements of relatively shallow ploughing with good soil inversion for weed control. The plough has seven or eight bottoms for ploughing depths of 0.12–0.20 m, a working width of 2.1 m and a working speed of 1.7 m s⁻¹. Its width is such that the tractor with wide low-pressure tyres runs on top of the land.

After using the plough for 6 years on Luvisols (>200 gkg⁻¹<2 μm) in the IJsselmeer polders and on Luvisols (120–160 gkg⁻¹<2 μm) in polders near the northern coast of The Netherlands, it was found that compared with conventional ploughing, shallow ploughing required less energy and labour and produced a relatively smooth surface. The latter facilitates the preparation of a seedbed consisting of relatively fine, strong, stable and moist aggregates. Organic matter, soil biota and nutrients were concentrated higher in the profile, influencing the workability of the soil, the growth of weeds and the growth of crops. Most of the yields were similar to yields after conventional ploughing, but weed populations increased when ploughing depth was <0.2 m. It was concluded that for organic farming on “active” soils (soils subject to shrink/swell with >200 g kg⁻¹<2 μm), shallow ploughing seems to be the best reduced tillage system. It has several advantages. The main factor determining the minimum ploughing depth is control of weeds, especially of perennials.     

Measurement and modelling of the effects of initial soil conditions and slope gradient on soil translocation by tillage

Tillage erosion studies have mainly focused on the effect of topography and cultivation practices on soil translocation during tillage. However, the possible effect of initial soil conditions on soil displacement and soil erosion during tillage have not been considered. This study aims at investigating the effect of the initial soil conditions on net soil displacement and the associated erosion rates by a given tillage operation of a stony loam soil. Tillage erosion experiments were carried out with a mouldboard plough on a freshly ploughed (pre-tilled) soil and a soil under grass fallow in the Alentejo region (Southern Portugal).

The experimental results show that both the downslope displacement of soil material and the rate of increase of the downslope displacement with slope gradient are greater when the soil is initially in a loose condition. This was attributed to: (i) a greater tillage depth on the pre-tilled soil and (ii) a reduced internal cohesion of the pre-tilled soil, allowing clods to roll and/or slide down the plough furrow after being overturned by the mouldboard plough.

An analysis of additional available data on soil translocation by mouldboard tillage showed that downslope displacement distances were only significantly related to the slope gradient when tillage is carried out in the downslope direction. When tillage is carried out in the upslope direction, the effect of slope gradient on upslope displacement distances was not significant. This has important implications for the estimation of the tillage transport coefficient, which is a measure for the intensity of tillage erosion, from experimental data. For our experiments, estimated values of the tillage transport coefficient were 70 and 254 kg m⁻¹ per tillage operation for grass fallow and pre-tilled conditions, respectively, corresponding to local maximum erosion rates of ca. 8 and 35 Mg ha⁻¹ per tillage operation and local maximum deposition rates of ca. 33 and 109 Mg ha⁻¹ per tillage operation.     

犁旋一体机自动调平系统设计与试验

为了解决犁旋一体机作业过程中调节机具问题,设计了一种犁旋一体机自动调平系统,该系统包括执行机构、控制系统、液压系统。根据犁旋一体机自身的特点,提出了一种确定调平角度范围的方法,并根据实际田间作业情况,运用EDEM仿真软件进行田间作业的虚拟仿真,仿真结果表明:地表平整度小于2 cm,满足农艺要求。在设计和仿真的基础上,进行田间试验,将手动调平的犁旋一体机的作业情况和自动调平的犁旋一体机的作业情况进行对照,分析了作业过程中机具的角度变化和作业后的耕深及其稳定性,地表平整度。结果表明:自动调平犁旋一体机相对于手动调平犁旋一体机,在耕深的稳定性和耕后地表平整度上有较为明显的提高,前者耕深稳定系数达到87.31%,后者为84.76%。前者地表平整度为1.97 cm,后者为2.56 cm。     

红壤坡耕地耕层土壤质量特征及障碍因素研究

为探究红壤坡耕地耕层质量特征及其障碍因素,通过野外调查、资料查阅及室内土壤理化性质分析等综合性研究手段,对江西红壤坡耕地耕层土壤质量统计特征、演变特征及主要障碍因素进行分析。结果表明:(1)红壤坡耕地田面坡度主要分布在2~16°之间,耕层平均厚度13.40 cm,有效土层厚度平均88.30 cm,土壤容重平均为1.17 g/cm~3;耕层土壤有机质平均含量19.37 g/kg,土壤pH值平均5.36。(2)红壤坡耕地耕层质量近20年有明显提高,田面坡度从6°降至4°,耕层厚度从13.68 cm增至16.42 cm;耕层土壤有机质含量24.63 g/kg,提高33.93%,全氮、有效磷和速效钾含量分别增加10.53%、230.98%、44.18%。(3)红壤坡耕地低产耕层土壤质量的主要障碍因素是土壤养分贫瘠化、粘重化和酸化;花生和木薯低产耕层的土壤容重和粘粒含量均大于高产耕层,而土壤孔隙度、田间持水量、有机质含量及pH值均小于高产耕层,表明高产坡耕地耕层土壤质量优于低产坡耕地。研究结果可为江西红壤坡耕地耕层质量改善和合理耕层构建提供科学参考。     

Effects of tillage depth on organic carbon content and physical properties in five Swedish soils

The soil tillage system affects incorporation of crop residues and may influence organic matter dynamics. A study was carried out in five 15–20 year old tillage experiments on soils with a clay content ranging from 72 to 521 g kg⁻¹. The main objective was to quantify the influence of tillage depth on total content of soil organic carbon and its distribution by depth. Some soil physical properties were also determined. The experiments were part of a series of field experiments all over Sweden with the objective of producing a basis to advise farmers on optimal depths and methods of primary tillage under various conditions. Before the experimental period, all sites had been mouldboard ploughed annually for many years to a depth of 23–25 cm. Treatments included primary tillage to 24–29 cm depth by mouldboard plough (deep tillage) and to 12–15 cm by field cultivator or mouldboard plough (shallow tillage). Dry bulk density, degree of compactness and penetration resistance profiles clearly reflected the depth of primary tillage and substantially increased below that depth. Compared to deep tillage, shallow tillage increased the concentration of organic carbon in the surface layer but decreased it in deeper layers. Total quantity of soil organic carbon and carbon–nitrogen ratio were unaffected by the tillage depth. Thus, a reduction of the tillage depth from about 25 cm to half of that depth would appear to have no significant effect on the global carbon cycle.     

Traffic and seasonal influences on the energy required for cultivation and on the subsequent tilth

Two similar experiments were conducted over a 3 year period on a clay soil to compare the effects of different intensities of traffic, ranging from 0 to 124 t km ha⁻¹ (1.24 MN km ha⁻¹) on the energy required for ploughing and secondary cultivation. The tilths produced by these operations were measured by sieving and, in one year, by image analysis of sections cut from large blocks of resin-impregnated soil.

Both energy required for cultivation and mean aggregate size after ploughing were related to the intensity of wheeling and the soil water content at ploughing. In the absence of wheeling, energy for ploughing was reduced by between 17 and 45%, and mean aggregate size was reduced to 20–70% of that resulting from a conventional tractor and plough-based system.

Specific draught in the driest soil conditions was almost twice that in the wettest conditions. The geometric mean diameter of aggregates produced by the mouldboard plough ranged from 7 mm in a wetter year and with no traffic to 140 mm in the driest year with a year-round tractor traffic system.

Scanning sections of large impregnated blocks with an image analyser provided more detailed information on aggregate size distributions within the plough layer than did sieving, and it also provided information on pore size distributions. This technique served to illustrate large differences in soil macrostructure between a conventional tractor and plough cultivation system compared with an untrafficked but ploughed soil.