Abstract: The various relationships found between soil compaction and crop growth are discussed and the relation between soil compaction and soil structure considered. The factors which are relevent to crop growth and which are affected by compaction and the need for an index of soil structure are discussed. (Abstract retrieved from CAB Abstracts by CABI’s permission)

Abstract: FINITE element procedure was used to simulate multiple wheel loading and to predict its effect on soil compaction. Results of nonlinear analysis, conducted using an incremental loading procedure, show effects of tire size, soil type, and number of passes on soil compaction . The results of the study also demonstrate the potential use of the procedure in compaction related studies. However, experimental verification of the model is necessary before the procedure can be recommended for wider use. INTRODUCTION Effects of soil compaction on soil structure, texture and strength , and on plant development and crop yields have received considerable attention from researchers in the past (Klingbiel and O' Neal , 1952; Ingles, 1974; Fountaine, 1958; Negi et al. , 1980; Chancellor, 1971; Camp and Gill, 1969; Eavis and Payne, 1968; Rosenburg and Willits, 1962; Voorhees, 1977). In recent years , there has been a growing interest in machine-induced soil compaction, perhaps because of the steady increase in the size of field machines as well as increased use of conservation or no-tillage practices. During most agricultural and forestry operations, a significant portion of the site will be exposed to single or, at times, multiple passes of vehicles. The compaction which can result from this single or multiple loading will depend on factors such as soil and vehicle type, soil moisture level, number of passes, vehicle weight, contact pressure, etc. Most studies dealing with vehicle loading and soil compaction have been experimental. One disadvantage with the experimental procedure is that it is laborious, time consuming, and expensive. An alternative is to develop a mathematical model capable of describing the soil-tractive device interaction . Combined use of such a model and experimental procedure should be helpful to better understand the effects of various soil and vehicle parameters on soil compaction as well as the machanics of soil compaction . Therefore, the overall objective of this study was ·to develop a numerical procedure to predict the soil compaction from multiple wheel loadings. The specific objectives of the study were: 1. To develop a finite-element model to predict the The authors are: D. POLLOCK, JR. , Mechanical Engineer, Belvoir Research and Development Center, Fort Belvoir, VA; J. V. PERUMPRAL, Professor, Agricultural Engineering Dept., and T. KUPPUSAMY, Associate Professor, Civil Engineering Dept., Virginia Polytechnic Institute and State University, Blacksburg, VA . \"[ _.,_ lli so1 sur ace ...-::; ::r-

Abstract: Soil microorganism populations were measured 1 year after 4 years of compaction treatments on 0.07-ha plots in a mixed oak – red maple forest on loamy sand. Four treatments were imposed on two plots each: (i) control; (ii) soil compaction; (iii) mulch before compaction; (iv) 3-year compaction followed by mulch. Three selective agar media were used to isolate soil fungi and bacteria. Nematodes and macroarthropods were also sampled. Total fungi, bacteria, nematodes, and arthropods had significantly higher populations on control plots, usually with mulch treatments intermediate and compaction (no mulch) plots lowest. Fusarium sp. were most numerous on unmulched, compacted plots and only rarely isolated from the controls. Microorganism population differences associated with treatment were still detectable 2 years after compaction occurred, but not 5 years after compaction.

Abstract: In the autumn of 1983, five wheel-compaction treatments, including zero traffic, low-ground-pressure traffic, medium and heavy combine harvester traffic (maximum axle loads up to 13.2 t, maximum tyre inflation pressures up to 118 kPa) were applied to a silt loam soil before direct-drilling winter wheat. The soil had not been cultivated in the preceding 15 months and was at a water content between the lower plastic limit and field capacity when wheeled across the full width of the plots. Loss of porosity by wheel compaction depended on tyre inflation pressure; the largest maximum axle load decreased porosity to 50-cm depth. At 15-cm depth within the treatments, soil macroporosity ranged between 3 and 20% v/v and the cone resistance in the autumn between about 0.5 and 2.0 MPa. In this relatively dry and warm growing season, effects of these different soil conditions were more noticeable upon soil aeration than upon soil temperature. The soil structural differences between the treatments were diminished by the unusually heavy rains in May 1984, when the most heavily wheeled soil gained about 3% macroporosity and became weaker.

Abstract: Field experiments were conducted on a sandy loam soil (Aeric Tropaquent) during 1981 adn 1982 to assess the effects of compaction, puddling and no-till systems on soil physical properties and on rice growth and yield with and without supplementary irrigation. Soil compaction decreased macro- and micro-pores more than puddling or no-till treatments. The equilibrium infiltration rates were 0.12, 0.15 and 1.65 μm s −1 in compacted, ploughed and no-till treatments, respectively. The saturated hydraulic conductivity, void ratio and moisture content at −0.01 and −1.5 MPa water potential followed a similar trend. The mean weight diameters were 2.40, 2.36 and 2.09 mm for compacted, puddled and no-till treatments, respectively. The mean grain yields for 4 consecutive crops were 6.4, 5.1 and 4.9 Mg ha −1 , the compacted being significantly greater than the puddled and no-till treatments. Compared with both puddling and no-till treatments, soil compaction resulted in significant yield increases of about 20% under the rain-fed regime and from 34 to 40% in the flooded moisture regime. There was about 26% increase in rice grain yield by continuous flooding over the rain-fed treatments, with the rice producing greater dry matter and biological yields due to a higher uptake of P, Ca, Mg, K, Na, Mn, Fe and Zn.

Abstract: An experimental investigation was conducted to determine the change in engineering properties of a collapsible loess in Bulgaria resulting from dynamic compaction. The results of in situ tests conducted before and after compaction are described. A 13,605-kg (15-ton) circular concrete tamper was dropped from a height varying between 5 and 10 m (16 and 33 ft) to produce impact. Density measurements taken before and after compaction and in situ tests using dynamic cone and dilatometer, indicate that the effective depth influenced by the compaction was about 4 m (13 ft). The results suggest that the potential for collapse has been significantly reduced by dynamic compaction.

Abstract: The yield of direct-seeded and transplanted upland rice was investigated for seven tillage methods for an ultisol in a high rainfall region of southeastern Nigeria. The tillage methods were: two compaction passes of a 6-t roller with and without residue mulch; six compaction passes with mulch; ploughing with and without mulch and no-till with and without mulch. Soil compaction decreased seedling emergence and shoot and root growth. Residue mulching decreased seedling emergence by 35.6% in direct-seeded rice. There were more leaves, productive tillers and dry matter in the ploughed plots. Root densities at 10–20- and 20–30-cm depths were higher by 157 and 47%, respectively, in ploughed treatments. The highest grain yields of 6.3 and 6.1 Mg ha −1 in ploughed plots for the first and second seasons, respectively, were associated with greater uptake of P, Na, Fe and Zn at flowering and of N, Mg, K, Mn and Cu at both maximum tillering and flowering growth stages. The grain yield in the first season was 2.1 and 2.5 Mg ha −1 for two- and six-compaction pass mulched plots, respectively. In the second season, the yields of no-till and compacted treatments were identical and ranged from 1.5 to 2.4 Mg ha −1 . Mulching decreased grain yield by 43, 27 and 12% on compacted, no-till and ploughed plots, respectively, due to transient flooding and mechanical impedance to seedling emergence by the mulch cover. Within the unmulched treatments, ploughing increased rice yield by 71 and 35% over two compaction passes and the no-till treatments, respectively. The least bulk density and penetrometer resistance were also observed in ploughed plots.

Abstract: In an experiment designed to study the effect of soil compaction on growth of winter barley, different levels of compaction were induced by applying 0, 1 and 6 passes of a tractor to the entire area of the plots prior to drilling At the late tillering, booting and anthesis stages, root growth measurements were made, soil cone resistances were measured and tensiometer readings were taken With increasing number of tractor passes, cone resistance was found to increase at all depths, except for the third sampling in June, and root length decreased to depths of 03 m The exceptionally wet conditions during the spring of 1983 also had a major effect on root growth

Abstract: A stepwise simulation procedure was developed to assess soil compaction produced by machinery traffic on moist soil. Initial bulk density and water content distributions, soil compressibility and tractor wheel sizes, weight distributions and two or four wheel drive options were used as input data. The results obtained include draft, induced compacting stress and consequent soil bulk density distributions in the soil. The predicted results were compared with field measured data. It was found that the predicted bulk densities were always higher than the observed ones by 3–9% and 1–5% at depths of 5 and 25 cm, respectively. Nevertheless, the results obtained from the model used are of great importance in formulating recommendations and operational decisions for various field operations and for specific machinery and implement selection aimed at obtaining required tilth while maintaining low compactive hazard. The predicted compaction levels being higher than the observed ones suggest the uppermost limit of compaction attainable and indicate the direction to be taken to improve the model.

Abstract: The moisture characteristic of a swelling soil is the result of complex interaction between the soil water potential and imposed mechanical stresses. This can give rise to soil water profiles which cannot be interpreted by soil water theories for non-swelling soils. Agricultural soil physics has been concerned primarily with highly structured surface soils, and has developed simple theories for the effects of stress on soil water relations in swelling soils. These simple theories ignore the effect of lateral stress in the soil. Civil engineers, on the other hand, dealing mainly with less complex soils at depth, have developed more complex theories for the effect of three-dimensional stress states on soil water relations. This paper shows how the effect of three-dimensional stress can and should be included in soil water studies of swelling soils, and gives examples to demonstrate the possible magnitude of such effects.

Abstract: An experiment was conducted over three consecutive seasons during 1982 and 1983 to evaluate the effects of traffic-induced compaction on growth and yield of maize, cowpea and soya bean grown in a tropical Alfisol for no-tillage and ploughed systems. Compaction treatments of no, two and four passes of a 2-tonne roller were used on the sub-plots. The roller was 60 cm in diameter, 180 cm long, with a contact area of 0.1729 m2 and was pulled by a 33.6 kW tractor. The four-pass treatment reduced percentage emergence, plant height, leaf number, leaf area index, and dry matter yield of maize, cowpea and soya bean. These reductions were more marked on ploughed than on no-till plots. The two-and four-pass treatments significantly reduced root growth of maize, cowpea and soya bean in the 0–70 mm depth, but the reduction in root density was greater in ploughed than in no-tillage. The two-and four-pass compaction treatments reduced plant nutrient uptake and grain yield of maize, cowpea and soya bean. The four-pass treatment reduced maize grain yield by 48% in all seasons under no-tillage and by 53, 61 and 75% after ploughing in the first, second and third consecutive cropping seasons respectively, compared to the yield of the relevant non-compacted treatment. Cowpea yield was reduced by 38% in all seasons after no-tillage and by 39, 50 and 57% after ploughing during the first, second and third consecutive cropping season respectively. The response of soya bean to four-pass compaction resulted in yield reduction by 50,64 and 25% after no-tillage and by 47, 48 and 65% after ploughing in the first, second and third consecutive cropping season, respectively. Crop yields were found to be negatively correlated with soil bulk density, penetrometer resistance, and relative compaction, and positively correlated with infiltration rate, soil moisture content and specific volume. Multiple regression equations were also developed between crop yield and soil properties.

Abstract: Foundations for Units 1 and 2 of the first large steam power plant in Indonesia consist of concrete rafts supported on slender, end-bearing steel-cased concrete piles. Soil investigation established the presence of layers and/or lenses of locally loose silty fine sands at various depths. It was necessary to densify these materials to ensure that unacceptable differential settlement did not occur between separate shallow foundations and to reduce the potential for liquefaction of the looser zones in the event of seismic disturbance. A design peak horizontal ground acceleration of 0.3 g was calculated and compaction piles used to improve the soil under structures. The principle of compaction piling is to forcefully compact loose soil by introducing significant quantities of additional granular fill throughout the soil mass. This method introduces a far greater quantity of fill material into the soil mass than the sand piling method, which it superficially resembles.

Abstract: EXPERIMENTS were conducted to investigate the yield-loss effects of soil compaction due to machinery traffic on green peas. Using the estimated models and compaction area percentage for various tractor sizes, farm level yield losses were established. The total economic costs (loss plus cost) indicate that the optimum tractor size for a specialized pea farm is around 105 kW. The relationship between economic costs and number of passes implies that the management of field preparation in 4 instead of 5 passes will save about $28.25/ha. The results have implications for determining optimum size and use of machinery.

Abstract: Avoiding Costly Blunders Basics of Soil Compaction Curves: Laboratory Procedures Major Problems in Compacted Fill Technology: Proposed Solutions Applied Research and Development Fills and Fill Compaction Compaction Specifications Fill Control Procedures - Inspection Techonomics Update at Press Time References Index.

Abstract: A frame has a connecting part (3) and a vibrating part (4) which are connected to one another by flexible members (5) The connecting part (3) is provided with connecting members (9) by means of which it can be connected to members (1, 2) of a mobile machine The vibrating part (4) has an unbalanced mass (13), a motor (12) driving the unbalanced mass (13), and a levelling blade (16) so that the frame can be used for both soil compacting and levelling

Abstract: The sensitivity of spring barley (Hordeum vulgare, cv. Carnival), field beans (Vicia faba, ev. Maris Bead) and sugar beet (Beta vulgaris,cv. Monoire) to topsoil compaction induced by tractor wheelings, post sowing, on a coarse gravelly loam of the Arrow series was investigated in 1983 and 1984. The study revealed that in both years topsoil compaction increased the dry bulk density, vane shear strength and cone resistance of the soil. Although compaction reduced only the plant population of sugar beet in 1983 (by 35%) in 1984 it both delayed emergence and decreased the field bean, spring barley and sugar beet populations by 41%, 50% and 64% respectively. In 1983 the order of sensitivity of crop yield to soil compaction was spring barley < field beans