Showing papers on "Lime published in 2003"

Lability of Cd, Cu, and Zn in Polluted Soils Treated with Lime, Beringite, and Red Mud and Identification of a Non-Labile Colloidal Fraction of Metals Using Isotopic Techniques

Abstract: The use of soil amendments has been proposed as a low input alternative for the remediation of metal polluted soils. However, little information is available concerning the stability, and therefore the longevity, of the remediation treatments when important soil parameters change. In this paper we investigate the effect of pH changes on the lability of heavy metals in soils treated with lime, beringite, and red mud using a modified isotopic dilution technique in combination with a stepwise acidification procedure. Significant amounts of nonlabile (fixed) Cu and Zn were found to be associated with colloids <0.2 μm in the solution phase. The results obtained indicated that the mobility of fixed colloidal metals is significant and increases with soil pH. This must be considered because most of the soil amendments are alkaline and increase soil pH. All the soil amendments significantly decreased the lability of Cd, Zn, and Cu in the soils as a whole. However, when the soils were re-acidified, the labile pool ...

Heavy metal bioavailability in a soil affected by mineral sulphides contamination following the mine spillage at Aznalcóllar (Spain).

Abstract: A field experiment, lasting 14 months, was carried out in order to assess the effect of organic amendment and lime addition on the bioavailability of heavy metals in contaminated soils. The experiment took place in a soil affected by acid, highly toxic pyritic waste from the Aznalcollar mine (Seville, Spain) in April 1998. The following treatments were applied (3 plots per treatment): cow manure, a mature compost, lime (to plots having pH < 4), and control without amendment. During the study two crops of Brassica juncea were grown, with two additions of each organic amendment. Throughout the study, the evolution of soil pH, total and available (DTPA-extractable) heavy metals content (Zn, Cu, Mn, Fe, Pb and Cd), electrical conductivity (EC), soluble sulphates and plant growth and heavy metal uptake were followed. The study indicates that: (1) soil acidification, due to the oxidation of metallic sulphides in the soil, increased heavy metal bioavailability; (2) liming succeeded in controlling the soil acidification; and (3) the organic materials generally promoted fixation of heavy metals in non-available soil fractions, with Cu bioavailability being particularly affected by the organic treatments.

Alterações químicas do solo e resposta da soja ao calcário e gesso aplicados na implantação do sistema plantio direto

Abstract: There has been an increasing interest to search alternatives for the establishment of crops under no-tillage systems in the southern region of Brazil, opening up new areas without soil disturbance. A field trial was carried out on a dystrophic Clay Rhodic Hapludox in Ponta Grossa, Parana State, Brazil, from 1998 to 2001, with the aim to evaluate changes in chemical soil characteristics, as well as the soybean response to lime and gypsum applications in a no-tillage system. A completely randomized block design with three replications in a split-plot experiment was used. The main plots received dolomitic limestone treatments (no lime, total rate of 4.5 t ha-1 of lime, 1/3 of this dosage during three years, as surface application and incorporated into the soil) and the subplots, the gypsum rates (0, 3, 6, and 9 t ha-1). Liming, whether surface applied or incorporated into the soil, provided a more accentuated soil acidity correction in the superficial layer (0-5 cm), but there was a stronger reaction in the 5-10 and 10-20 cm layers when lime was incorporated into the soil. The beneficial effects of lime for subsoil acidity correction were not very pronounced and more evident where lime was incorporated. Gypsum improved the subsoil, increasing the pH (CaCl2 0.01 mol L-1), Ca, and S-SO42- concentrations, P concentrations in the superficial soil layer (0-5 cm) and in soybean leaves, and decreased Mg concentrations in the soil and soybean leaves. Results showed no soybean response, in three years, to lime and gypsum treatments. It was concluded that gypsum, whether applied as superficial or incorporated liming, did not present an interesting strategy for the installation of soybean crop in a no-tillage system, since no improvement in grain yields could be observed.

Cyanobacterial inoculation of heated soils: effect on microorganisms of C and N cycles and on chemical composition in soil surface.

Abstract: Physiological groups of soil microorganisms, total C and N and available nutrients were investigated in four heated (350 °C, 1 h) soils (one Ortic Podsol over sandstone and three Humic Cambisol over granite, schist or limestone) inoculated (1.5 μg chlorophyll a g −1 soil or 3.0 μg chlorophyll a g −1 soil) with four cyanobacterial strains of the genus Oscillatoria , Nostoc or Scytonema and a mixture of them. Cyanobacterial inoculation promoted the formation of microbiotic crusts which contained a relatively high number of NH 4 + -producers (7.4×10 9 g −1 crust), starch-mineralizing microbes (1.7×10 8 g −1 crust), cellulose-mineralizing microbes (1.4×10 6 g −1 crust) and NO 2 − and NO 3 − producers (6.9×10 4 and 7.3×10 3 g −1 crust, respectively). These crusts showed a wide range of C and N contents with an average of 293 g C kg −1 crust and 50 g N kg −1 crust, respectively. In general, Ca was the most abundant available nutrient (804 mg kg −1 crust), followed by Mg (269 mg kg −1 crust), K (173 mg kg −1 crust), Na (164 mg kg −1 crust) and P (129 mg kg −1 crust). There were close positive correlations among all the biotic and abiotic components of the crusts. Biofertilization with cyanobacteria induced great microbial proliferation as well as high increases in organic matter and nutrients in the surface of the heated soils. In general, cellulolytics were increased by four logarithmic units, amylolytics and ammonifiers by three logarithmic units and nitrifiers by more than two logarithmic units. C and N contents rose an average of 275 g C kg −1 soil and 50 g N kg −1 soil while the C:N ratio decreased up to 7 units. Among the available nutrients the highest increase was for Ca (315 mg kg −1 soil) followed by Mg (189 mg kg −1 soil), K (111 mg kg −1 soil), Na (109 mg kg −1 soil) and P (89 mg kg −1 soil). Fluctuations of the microbial groups as well as those of organic matter and nutrients were positively correlated. The efficacy of inoculation depended on both the type of soil and the class of inoculum. The best treatment was the mixture of the four strains and, whatever the inoculum used, the soil over lime showed the most developed crust followed by the soils over schist, granite and sandstone. In the medium term there were not significant differences between the two inocula amounts tested. These results showed that inoculation of burned soils with alien N 2 -fixing cyanobacteria may be a biotechnological means of promoting microbiotic crust formation, enhancing C and N cycling microorganisms and increasing organic matter and nutrient contents in heated soils.

Engineering Behavior of Stabilized Soils

Abstract: Stabilization of soils is an effective method for improving soil properties and pavement system performance. For many soils, more than one stabilization agent may be effective, and financial considerations or availability may be the determining factor on which to use. A series of tests was conducted to evaluate the relative performance of lime, cement, Class C fly ash, and an enzymatic stabilizer. These products were combined with a total of seven different soils with Unified Soil Classification System classifications of CH, CL, ML, and SM. Durability testing procedures included freeze-thaw, wet-dry, and leach testing. Atterberg limits and strength tests also were conducted before and after selected durability tests. Changes in pH were monitored during leaching. Relative values of soil stiffness were tracked over a 28-day curing period using the soil stiffness gauge. Lime- and cement-stabilized soils showed the most improvement in soil performance for multiple soils, with fly ash-treated soils showing substantial improvement. The results showed that for many soils, more than one stabilization option may be effective for the construction of durable subgrades. The enzymatic stabilizer did not perform as well as the other stabilization alternatives.

Microstructural investigation of a silica fume–cement–lime mortar

Abstract: Several additions, minerals and organic, are used in mortars, such as pozzolanic materials, cementicious materials and polymers. Literature about the use of additions in masonry mortars (cement/lime/sand mixes) is scarce; usually, studies are about concrete mortars. The purpose of this work is to study the microstructural effects of the substitution of 10% of Portland cement by silica fume in a 1:1:6 (cement/lime/sand mix proportion by volume) masonry mortar. Scanning electron microscopy with energy dispersive X-rays analysis (SEM/EDX) shows that, with silica fume, the C–S–H formed is type III at early ages and that type III and type I coexist at later ages. Silica fume lowers the total porosity and increases compressive strength only at later age and, as expected, the pore structure of mortar with silica fume is found to be finer than of non-silica fume mortar.

Reduction of arsenic uptake by lettuce with ferrous sulfate applied to contaminated soil.

Abstract: Soil contamination by arsenic (As) presents a hazard in many countries and there is a need for techniques to minimize As uptake by plants. A proposed in situ remediation method was tested by growing lettuce (Lactuca sativa L. cv. Kermit) in a greenhouse pot experiment on soil that contained 577 mg As kg(-1), taken from a former As smelter site. All combinations of iron (Fe) oxides, at concentrations of 0.00, 0.22, 0.54, and 1.09% (w/w), and lime, at concentrations of 0.00, 0.27, 0.68, and 1.36% (w/w), were tested in a factorial design. To create the treatments, field-moist soil, commercial-grade FeSO4, and ground agricultural lime were mixed and stored for one week, allowing Fe oxides to precipitate. Iron oxides gave highly significant (P < 0.001) reductions in lettuce As concentrations, down to 11% of the lettuce As concentration for untreated soil. For the Fe oxides and lime treatment combinations where soil pH was maintained nearly constant, the lettuce As concentration declined in an exponential relationship with increasing FeSO4 application rate and lettuce yield was almost unchanged. Iron oxides applied at a concentration of 1.09% did not give significantly lower lettuce As concentrations than the 0.54% treatment. Simultaneous addition of lime with FeSO4 was essential. Ferrous sulfate with insufficient lime lowered soil pH and caused mobilization of Al, Ba, Co, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, Pb, Sr, and Zn. At the highest Fe oxide to lime ratios, Mn toxicity caused severe yield loss.

Efficacy and phytotoxicity of lime sulphur in organic apple production

Abstract: Curative and preventive efficacy and phytotoxicity of lime sulphur spray schedules, based on a warning system, were evaluated in the Netherlands during two growing seasons under field conditions. In most cases, lime sulphur treatments applied either curatively or preventively resulted in significantly lower scab damage on both the leaves and fruits compared to wettable sulphur treatments. However, all lime sulphur treatments showed high phytotoxicity values, reduced leaf size and had a tendency to a reduced yield quality compared to all other treatments. For curative schedules of lime sulphur on scab control, phytotoxicity and yield did not differ significantly from preventive schedules of lime sulphur. However, the use of a warning system combined with curative schedules of lime sulphur saved one and two lime sulphur sprays in 2000 and 2001, respectively, compared to the preventive treatments of lime sulphur. Our results demonstrated that a curative spray programme with lime sulphur at 0.75-2%, applied 35-45 h after predicted infection periods, can provide effective primary apple scab control, but no benefit in either yield or fruit quality was reached under organic growing conditions. Moreover, research herein clearly showed that organic growers are forced to find a balance between good efficacy and phytotoxic effects of lime sulphur.

An integrated limestone/lime process for partial sulphate removal

Abstract: This paper will focus on two topics, namely (1) an innovative process for the neutralization and partial sulphate removal of acid streams produced during coal mining and processing and (2) optimization of this integrated neutralization process by adding small amounts of synthetic organic polymers. The integrated lime and limestone process has been developed to neutralize acid mine water and to remove sulphate (to less than 1 200 mg/l), magnesium and metals. Limestone and lime treatment is the most cost-effective technology for neutralization and partial sulphate removal of acidic/sulphate-rich water to sulphate levels of less than 1 500 mg/l due to precipitation of magnesium and removal of the associated sulphate fraction (through gypsum crystallization). Neutralized mine water of this quality may be suitable for irrigation. The process consists of the following stages: 1. Limestone (CaCO3) neutralization to raise the pH to 7 and CO2-production. 2. Lime (Ca(OH)2) treatment to pH 12 for Mg(OH)2 precipitation and gypsum (CaSO4.2H2O) crystallization. 3. pH adjustment with CO2 recovered from stage 1 and CaCO3 precipitation. Retention times of 1 hour, 4 hours and 1/2 an hour were required by stages 1, 2, and 3 respectively. The sulphate level was reduced to 1 094 mg/l, which is less than the original aim of 1 200 mg/l. Chemical costs associated with neutralization, using limestone instead of lime, are reduced by 69% in the integrated limestone/lime process. The overflow water from the clarifier of each of the above stages generally contains a wide variety of colloidal impurities that may cause the water to appear turbid or may impart colour. This results in very slow sludge settling rates that cause overflow water with a high degree of turbidity and colour. There are a number of successive or simultaneous stages involved in the agglomeration of particles. To get optimum neutralisation of the acid water and partial sulphate removal to below the saturation level of gypsum (i.e. 1 500 mg/l), maximum sludge recovery is needed. The higher the concentration of seed crystals, the larger the surface area. Therefore, effective removal of suspended and colloidal matter from the overflow of each stage is required and can be achieved by coagulation and flocculation. The polymers PAC6 and 3095 were effectively used as coagulant and flocculant respectively. The addition of these polymers resulted in a clear overflow in each of the above stages with a very low turbidity.

Stabilising effects of different binders in some Swedish soils

Abstract: In Sweden, lime and lime–cement have been used for several decades as stabilising agents in deep stabilisation of soft soils. More recently, other types of binder have come into use, but so far only to a limited extent. In order to gather experience about the effect of various binders, laboratory tests have been performed on different types of soil stabilised with a range of binders. Lime, cement, fly ash and blast furnace slag in different combinations together with different admixtures, such as gypsum, silica fume and calcium chloride, have been used in the investigations. The variation in strength with type of binder has been studied, and comparisons have also been made with results from some previous investigations using different binders. The tests showed that there is no optimal, universal binder for stabilisation of the soils. Whereas some binders are robust, yielding good results in most types of soil, there are also binders that produce very good results in certain soils but poor results in other...

Amelioration of acidity with time by limestone under contrasting tillage

Abstract: Farmers in south-eastern Australia have been advised, on one hand, to sow by direct drilling so as to conserve soil structure. On the other hand, farmers have been advised to thoroughly incorporate limestone into the soil so as to ameliorate acidity and obtain an economic return on the expense of liming. To help to resolve this conflict we investigated lime movement on a long term cropping trial, which included treatments that had been under 12 years of direct drilling. It was hypothesised that there would be a relatively rapid movement of surface applied limestone into the soil under the direct drilled treatments and hence a minimal time delay in amelioration compared with incorporation by various intensities of tillage. However, it took between 2 and 4 years after liming (1.5 t ha −1 ) before there was no statistically significant difference in pH at 5–10 cm depth between surface applied limestone and limestone incorporated with offset discs (and retained stubble). Thus, the acidity constraint at 5–10 cm depth was amended slowly by surface application compared with incorporation of the limestone by discs. Where incorporation of limestone was by scarifier (and stubble burnt), the lag period for surface applied limestone to match the soil amelioration was unclear in that the pH and exchangeable Al data gave different apparent findings, but the increase in pH at 5–10 cm was small compared with incorporation by discing. In a wheat–clover rotation where scarifying took place every second year (before wheat) there was no significant pH difference between cultivated and surface applied limestone below 0–5 cm depth during the 8 years. Surface application of limestone allowed an acidic, high Al ex layer to remain in the subsurface soil. We propose two compromise courses of action to enable the effective use of limestone in conjunction with direct drilling: (a) apply limestone at a higher rate than calculated or measured for where limestone is incorporated, so as to drive the leaching of bicarbonate; (b) apply the limestone earlier than under conventional tillage, so that the lime movement might precede the appearance of exchangeable Al at depth.

Effects of acidification and its mitigation with lime and wood ash on forest soil processes: a review

Abstract: Anthropogenic acid deposition causes forest soil acidification and perturbation of the soil forming processes. The impact of soil acidification on tree growth is discussed in view of the role of mycorrhizal fungi in weathering and nutrient uptake. A review has been carried out of experiments involving treatments of forest soil by lime and wood ash, where soil properties and soil solution composition have been investigated. Results from these experiments in Europe and North America are summarized. In general, the content of C in the mor layer decreased as a result of treatment due to higher microbial activity and soil respiration as well as increased leakage of DOC. In addition, the content of N in the mor layer, in general, decreased after treatment and there are occasional peaks of high NO3concentrations in soil solution. In nearly all reviewed investigations the pH of the deep mineral soil solution decreased and Al, SO4and NO3concentrations increased after treatment. These effects are probably due to the high ionic strength and increased microbial activity as a consequence of the treatments. In the soil, pH, CEC and base saturation increased in the upper horizons, but decreases in the upper mineral soil are also reported. In general, there was no increase in tree growth as a result of these treatments. The positive effects of the treatments on soil processes and tree growth are therefore questionable. In view of these conclusions, an investigation was carried out on the soil and soil solution chemistry and the role of mycorrhizal fungi in a spruce stand treated with two doses of lime and another treated with lime/ash in southern Sweden. The results of this investigation is reported in this volume.

Experimental evaluations of stabilisation methods for sulphate-rich expansive soils

Abstract: In this paper, Class F fly ash, sulphate-resistant cement, ground granulated blast furnace slag (GGBFS) and lime mixed with fibres are evaluated as potential stabilisers in enhancing the strength and volume change properties of soft, expansive and sulphate-rich soils. As part of the research evaluation, a comprehensive laboratory experimental programme was designed and conducted on four different subgrade soils. Two dosage levels of each stabiliser and three curing periods were investigated. Strength and volume change behavioural tests, including unconfined compressive strength, vertical swell, linear shrinkage and Atterberg tests, were conducted on both control and stabilised soils. Test results showed that the sulphate-resistant cement and lime mixed with fibres provided the most effective stabilisation on all four soils. Both fly ash and GGBFS stabilisation methods provided average-to-moderate improvements in soil properties. Statistical ANOVA analysis of variance on all test results indicated that the...

Sulfate resistance of high-performance concrete

Abstract: High-performance concrete mixes containing various proportions of natural pozzolan and silica fume (up to 15% by weight of cement) were prepared and stored in sodium and magnesium sulfate solutions, in Dead Sea and Red Sea waters. The progressive deterioration and the relative sulfate resistance of these mixes were evaluated through visual observations, ultrasonic pulse velocity measurements, and relative strength determinations. The investigation indicated that the concrete mix containing 15% natural pozzolan, and 15% silica fume showed the best protection in sulfates solutions and sea waters. It retained more than 65% of its strength after one year of storage in sulfates solutions and sea waters. The superior resistance of that mix against sulfate attack is attributed to the pore refinement process and further densification of the transition zone occurring due to the conversion of lime forming from the hydration of cement into additional binding material through lime-pozzolan reaction. This investigation recommends the use of silica fume in combination with natural pozzolan for better performance in severe sulfate environments.

Stabilization of fuel oil contaminated soil—A case study

Abstract: Fuel oil contamination brings adverse effect on basic geotechnical properties of foundation soil. The present study pertains to one such case, from the petrochemical complex near Vadodara City in Gujarat State, India. Here, the fuel oil contaminated soil samples exhibit drastic changes in their geotechnical parameters. Noteworthy among such deleterious changes are: decrease in maximum dry density (−4%), cohesion (−66%), angle of internal friction (−23%) and unconfined compressive strength (UCS) (−35%) and increase in liquid limit (+11%). An attempt has been made to stabilize the contaminated soil using various additives viz., lime, fly ash and cement independently as well as an admixture of different combinations. It is apparent from the test results that the stabilization agents improved the geo-technical properties of the soil by way of cation exchange, agglomeration, and pozzuolanic actions. The best results were observed when a combination of 10% lime, 5% fly ash and 5% cement was added to the contaminated soil. The improvement in unconfined compressive strength (UCS), cohesion and angle of internal friction can be attributed to neo-formations such as Calcium Silicate Hydrates (CSH, CSH-1) that coats and binds the soil particles. Formation of stable complex between oil and metallic cations, results in reduction of leachableoil.

Evaluation of industrial by‐products as soil acidity amendments: chemical and mineralogical implications

Abstract: Summary Lime, mined gypsum and some gypsum-like by-products have been frequently applied to soil to counter acidity We have examined the changes in the chemical and mineralogical properties of three acid soils resulting from the application of three industrial by-products (phosphogypsum, red gypsum and sugar foam) We did so in laboratory experiments on suspensions of soil in saturated solutions of the by-products A sizeable fraction of the Al released by exchange with Ca of the amendments remained on the mineral surfaces as Al polymers, as suggested by changes in the CuCl2-, oxalic–oxalate- and DTPA-extractable Al contents Polymerization of Al was promoted by corresponding neutral and basic pH of red gypsum and sugar foam saturated solutions, respectively Sorption of these Al polymers was particularly favourable in those horizons with more clay fraction and variable-charge clay minerals On the other hand, in most cases there was little or no detectable sorption of sulphate, thus excluding precipitation of crystalline or amorphous basic Al sulphates to alleviate Al toxicity Based on the reduction of the Al saturation of the exchange complex in the soils, as well as on the small contents of heavy metals and natural radionuclides of the three by-products, these can be considered effective alternatives to mined gypsum and lime for alleviating soil acidity and reducing toxic concentrations of Al in agricultural, acid soils

Economic and Environmental Evaluation of Variable Rate Nitrogen and Lime Application for Claypan Soil Fields

Abstract: Variable Rate Technology (VRT) has the potential to increase crop yields and improve water quality relative to Uniform Rate Technology (URT). The effects on profitability and water quality of adopting VRT for nitrogen (N) and lime were evaluated for corn production on four claypan soil fields in north central Missouri under average to better than average weather conditions. Variable N and lime rates were based on measured topsoil depth and soil pH, respectively. VRT rates were compared to two different uniform N applications (URT-Nl based on the topsoil depth within these claypan soil fields, and URT-N2 based on a typical N rate for corn production in this area). Expected corn yield was predicted based on topsoil depth, soil pH, N rate, and lime rate. Water quality benefits of VRT relative to URT were evaluated based on potential leachable N. Sensitivity analyses were performed using simulated topsoil data for topsoil depth and soil pH. Results showed that VRT was more profitable than URT in the four sample fields under URT-N1, and in two of the four fields under URT-N2. Greater variation in topsoil depth and soil pH resulted in higher profitability and greater water quality benefits with VRT. Results support adoption of VRT for N and lime application for other claypan soil fields with characteristics similar to those in the fields used in this study.

Liming and Cultivars Affect Root Growth, Nodulation, Leaf to Stem Ratio, Herbage Yield, and Elemental Composition of Alfalfa on an Acid Soil

Abstract: Soil acidity is one of the limiting factors affecting the production and sustainability of pastures and crops in many parts of the world. An on‐farm experiment was conducted in Australia to investigate the cultivar variation in alfalfa (lucerne) (Medicago sativa L.) with respect to soil acidity and response to applied lime. The experimental site was a brown sandy clay loam with a soil pH of 4.8 (1:5 calcium chloride). Ten cultivars (Hunter River, Hunterfield, Sceptre, Aurora, Genesis, Aquarius, Venus, PL90, PL55, and breeding line Y8804) were tested at two levels of lime (0 and 2 t ha−1). Lime application significantly increased the root growth, nodulation, leaf retention, leaf to stem ratio, herbage yield, and crude protein content of alfalfa. Liming had a significant effect on elemental composition of alfalfa shoots. Aluminum (Al) concentration was reduced from 93 mg kg−1 DM in nil lime treatment to 45 mg kg−1 DM in +lime treatment. Similarly, manganese (Mn) and iron (Fe) shoot concentrations w...

Subsoil ridge tillage and lime effects on soil microbial activity, soil pH, erosion, and wheat and pea yield in the Pacific Northwest, USA

Abstract: Soil erosion and the gradual acidification of soils are two major obstacles limiting crop productivity in the Palouse region of eastern Washington and northern Idaho. New tillage practices that replace the traditional moldboard plow are needed to maintain more surface cover to reduce erosion. Two tillage systems and lime were compared at two locations on silt loam soils. Treatment combinations were two levels of tillage (subsoil ridge till (SSRT) and plowing) and two levels of lime (0 and 2.68 Mg ha −1 ). Crop rotations were barley ( Hordeum vulgare L.)–pea ( Pisum sativum L.)–wheat ( Triticum aestivum L.) at both sites in the US that receive 500–560 mm precipitation annually. Tillage and lime options were implemented after barley stubble and studied for 2 years. Microbial biomass, respiration, and dehydrogenase enzyme activity were enhanced at the Washington site under SSRT because of the initially higher residue levels and because residues were maintained at or near the soil surface compared to plowing. Liming increased soil pH and respiration and maintained microbial biomass at about 100 ug C g −1 higher than for the unlimed plots at the end of 2 years. Soil moisture increased under SSRT at some profile depths. Pea seed yield at the Washington site and wheat yield at the Idaho site were significantly higher for SSRT compared to plowing. Lime significantly increased wheat yield only at the Washington site. Significantly higher surface residue was maintained during the study period from SSRT compared to plowing which contributed to lower rates of soil erosion in winter wheat 30 months after plot establishment. At the Washington site, surface residue levels were 20% in spring of 1992 for SSRT compared to less than 1% for plowing. One year later, soil erosion under winter wheat in spring of 1993 was 1.3 Mg ha −1 for SSRT compared to 8.4 Mg ha −1 for plowing. In general, the higher surface residue maintained under SSRT increased microbial activity, maintained higher surface residue, and reduced erosion in winter wheat, the vulnerable phase in the crop rotation for erosion.