Effects of conservation agriculture on soil quality and productivity in contrasting agro‐ecological environments of Zimbabwe

Experimentation by farmers with conservation agriculture (CA) is increasing in southern Africa, but local longer term data on these new production systems are scarce. This study focuses on CA research at two contrasting on‐farm sites and one on‐station long‐term trial in Zimbabwe. The on‐farm trials were conducted at Chikato village on a sandy soil at Zimuto Communal Area with low rainfall and at Hereford farm near Bindura on a clay‐rich soil in a high rainfall area. The on‐station trial was at Henderson Research Station near Mazowe where more in‐depth soil studies were possible. Results of CA systems from the on‐station site show on average 38 and 65% greater water infiltration on ripline‐seeded (RS) and direct‐seeded CA treatments compared with conventionally ploughed control treatments. Results from on‐farm sites show a 123 and 168% greater aggregate stability at Hereford and 11 and 24% lower dispersion ratio at Chikato on the two CA compared with the conventionally ploughed control treatments. Soil carbon increased by 46% in the first 20 cm on the sandy soils at Chikato in RS and by 104% in direct‐seeded CA treatments in four cropping seasons from 2004 to 2008, while it stayed at low levels on the conventionally tilled control treatment. Yields on CA plots were higher on the sandy soils in dry seasons, but lower in very wet seasons because of waterlogging. Yields on clay soils were less affected by the rainfall season. Crop productivity from CA systems increased at all sites over time owing to better management although significant differences between CA and conventional treatments on the three sites were apparent only after several cropping seasons. Conservation agriculture offers practical solutions to small‐scale farmers threatened by future soil degradation and fertility loss, but its successful use will depend on weed control and adequate application of fertilizers. The results indicate that there is no immediate increase in maize (Zea mays L.) yield when changing from a tilled to a CA system, but there is gradual improvement in some soil quality indicators over time.     

Hydraulic characteristics of conventionally and zero-tilled field plots

A silage corn crop was grown on field plots entering their 2nd-year cycle of zero tillage, and on control plots representing traditional tillage practices. Concurrent measurements of soil matric suction and water content were made under transient conditions of a draining profile without evaporation. The results indicated some similarity in the soil moisture characteristics of the untilled soils which produced high crop yields. The time rate of change of soil water content, the root extraction rate and the unsaturated hydraulic conductivity were always smaller in the zero-tilled plots than in the conventionally tilled plots.     

Soil erosion under simulated rainfall in relation to phenological stages of soybeans and tillage methods in Lages, SC, Brazil

Soil tillage may increase vulnerability to water erosion, whereas no tillage and other conservation cultivation techniques are viewed as strategies to control soil erosion. The objective of this research was to quantify runoff and soil losses by water erosion under different soil tillage systems at the Santa Catarina Highlands, southern Brazil. A field study was carried out using a rotating-boom rainfall simulator with 64 mm h⁻¹ rainfall intensity on a Typic Hapludox, between April 2003 and May 2004. Five rainfall tests were applied along successive cropstages. Surface cover was none (fallow) or soybean (Glycine max, L.). Five treatments were investigated, replicated twice. These treatments were conventional tillage on bare soil (BS) as a control treatment and the following treatments under soybean: conventional tillage (CT), no tillage over burnt crop residues on never before cultivated land (NT-B), no tillage over desiccated crop residues, also on never before cultivated land (NT-D) and traditional no tillage over desiccated crop residues on a soil tilled 4 years before this experiment (NT-PT). Water losses by surface runoff seemed to be more influenced by vegetative crop stadium than by tillage system and consequently a wide range of variation in surface runoff was found, following successive cropstages. The most efficient tillage system in reducing surface runoff and soil losses was no tillage, particularly the NT-PT treatment. Sediment losses were more influenced by tillage system than water losses. In the NT-B, NT-D and NT-PT treatments the rate of sediment losses along the crop vegetative cycle showed a tendency to increase from the first to the second cropstages and later to decrease from the third cropstage onwards. In the conventionally tilled treatment (CT) soil losses were greater than in any of the no tillage treatments (NT-D, NT-B and NT-PT) during the initial growth periods, but at the end of the vegetative period differences in sediment rates between tilled and non-tilled treatments tended to be smaller. In the BS control treatment, soil losses progressively increased following the vegetative growth season of soybean.     

Infiltration and random roughness of a tilled and untilled claypan soil

No-tillage is generally assumed to increase infiltration and reduce runoff, but runoff from a claypan soil in Central Missouri, however, was greater from no-tillage plots than from moldboard plowed plots. The effect of simulated rainfall on infiltration and random roughness of tilled and untilled soil was measured. Four different tillage systems, each with and without surface cover were studied. An exponential decay function describes the change in random roughness for tilled soil exposed to rainfall kinetic energy. Although the differences were not statistically significant, among the uncovered tilled plots those with the highest random roughness had the highest infiltration. The bare no-tillage treatment had the lowest infiltration. Plots protected with shredded foam rubber infiltrated 88–248% more rainfall than similar bare plots.     

Effect of Tillage Systems and Axle Load on Undisturbed Soil Hydraulic Properties

The effects of tillage treatment and axle load resulting from wheeled traffic on tilled soil (0 to 20 cm) were evaluated by measuring the changes in soil physical properties (bulk density and infiltration rate) and by measuring the impact on water retention in comparison with controlled plots. Data obtained from the experimental plots showed that infiltration rate was strongly affected by tillage treatments in 0‐ to 20‐cm depths. Dry bulk density was affected in 0‐ to 20‐cm depths by tillage treatments and axle load. Tillage system changed the ability of the soils to hold moisture and decreased the plant‐available water capacity.     

Impact of tillage and crop establishment methods on crop yields,profitability and soil physical properties in rice–wheat system of Indo‐Gangetic Plains of India

Conservation agriculture (CA) based on best‐bet crop management practices may increase crop and water productivity, as well as conserve and sustain soil health and natural resources. In a 2‐year study, we assessed the effects of tillage and crop establishment (TCE) methods on productivity, profitability and soil physical properties in a rice–wheat (RW) system. The six TCE treatments were used to study the impact, which are puddled transplanted rice followed by conventionally tilled wheat (CTPR–CTW), direct‐seeded rice on the flat followed by zero‐till wheat (CTDSR–ZTW), zero‐till direct‐seeded rice with residue followed by zero‐till wheat with residue (ZTDSR+R–ZTW+R), transplanted rice after rotavator puddling followed by zero‐till wheat (RTTPR–ZTW), transplanted rice after rotavator puddling followed by rotary till wheat (RTTPR–RTW) and farmer practice rice–wheat (FP–RW). Result of the study revealed that mean rice yield was not significantly affected by different TCE methods. Wheat planted with ZTDSR+R–ZTW+R gave 30% larger grain yield than FP‐RW. Overall, among all the TCE treatments, the RW system yields and net returns were maximum under ZTDSR+R–ZTW+R. The fastest mean infiltration rate (0.10 cm hr^–1) was registered in ZTDSR+R–ZTW+R plots, whereas the slowest was in FP‐RW plots (0.05 cm hr^–1). Bulk density at 15–20 cm soil depth was least in ZTDSR+R–ZTW+R (1.70 Mg m^–3) and greatest in FP‐RW (1.73 Mg m^–3). Results from this study revealed that conventionally tilled (CT) and transplanting of rice could be successfully replaced by adoption of the profitable double ZT–RW system.     

Properties of soil aggregates as influenced by tillage practices

Abstract. Changes in aggregate stability, density, and porosity as well as the water retention and nutrient contents of different aggregate size fractions due to intensive tillage were investigated. Three soils from Vicarello, Fagna and Gambassi in North Central Italy which had been under permanent vegetation, minimum or conventional tillage for more than seven years were studied. The aggregates on conventionally tilled plots were slightly denser and less porous than those on the untilled or minimum-tilled plots. The aggregates were less stable under conventional tillage on all soils. Conventional tillage reduced the proportion or macro-aggregates by 22% at Vicarello and 35% at Gambassi. There were no differences in macro-aggregate proportions between minimum- and conventionally tilled plots at Fagna. The potential of the dry aggregates to distintegrate upon contact with water was greatest in the conventionally tilled and least in the untilled treatments. The proportions of dry macro-aggregates (> 0.25 mm) in the untilled and tilled plots were 90 and 71%, respectively. The soil of the tilled plots contained less carbon and nitrogen than that of the untilled plots in all aggregate size fractions. The silt-plus-clay contents of the aggregates accounted for between 65 and 93% of variability in the water they retained at small potentials while organic carbon contents accounted for between 71 and 90% of variability in the stability of the aggregates irrespective of the tillage treatments.     

Effect of Mulching with Vegetative Residues on Soil Water Erosion and Water Balance in an Oxisol Cropped by Cassava in East Cameroon

Soil water erosion is a major agricultural concern in tropical Africa with high precipitation and low soil fertility where Oxisols are generally distributed. A field experiment was conducted in east Cameroon during the rainy season in 2013 to investigate the effects of surface mulching with the residues of Imperata cylindrica on soil losses and surface runoff water generation in a cassava cropland on an Oxisol. Three treatments were established using two small plots for each treatment: bare plot (BA), cassava plot (CA) and cassava with mulch plot (CM). Soil loss and surface runoff water were measured, and water budgets of rainfall, surface runoff and soil moisture within rainfall events were measured in all treatment plots. Runoff coefficients in all treatment plots were suppressed below 8·0% because the large volume of large pores of surface soil of Oxisols contributed to the high drainage capacity over a rainy season even under wet soil moisture conditions. Total soil loss in CM was decreased by 49% compared with that in BA and CA, despite there not being a large difference in runoff water among treatments. These results suggest that surface mulching with the residues of I. cylindrica can substantially suppress soil losses caused by particle detachment by raindrops, while it maintain soil surface with originally high permeability in cassava croplands on Oxisols. Copyright © 2016 John Wiley & Sons, Ltd.     

Infiltration patterns into two soils under conventional and conservation tillage: influence of the spatial distribution of plant root structures and soil animal activity

The characteristics and properties of the soil macropore system may cause different infiltration behavior under different tillage practices. To evaluate the effect of a specific tillage system on infiltration and percolation with particular regard to the influence of crop structure and soil animal activity dye tracer irrigation experiments were conducted in a silty (Luvisol) as well as in a sandy loam soil (Podzolluvisol). The spatial distribution of water flow paths was experimentally examined at four square areas of 0.49 m², under conservation and conventional tillage. Natural rainstorms were simulated by irrigating the plots with 2.8×10⁻³ M methylene blue solutions. For both soils the root crowns of the agricultural crop, wormcasts and stained soil sections as well as macroscopic conduits were traced on plastic sheets. The investigated soil depths were 0, 5, 10 and 20 cm for the both soils. For the Luvisol, the 30, 40, 50, 80 and 120 cm depths were also studied.For the Luvisol, the conservation tillage plot revealed pronounced vertical connectivity and continuity of the macropore network (maximum depth of stained pores=120 cm), while at the conventional tillage plot, continuous macropores were observed to soil depths of 50 cm, but mainly restricted to the ploughed topsoil (0–30 cm soil depth).For the Podzolluvisol, at the conservation tillage site extensive mulch residues prevented water transport beneath 5 cm soil depth. In contrast, at the conventionally tilled site stained water reached a depth of 20 cm. For all investigated plots on both soil types, the location of the root crowns of agricultural crop and of wormcasts was not related to percolation patterns.The results suggest that conservation tillage on silty soils under agricultural landuse could induce an increased water retention capacity reducing the significance of fast runoff components.     

Interactions between soil properties and moisture content in crust formation, runoff and interrill erosion from tilled loess soils

Soil-surface seals and crusts resulting from aggregate breakdown reduce the soil infiltration rate and may induce erosion by increasing runoff. The cultivated loess areas of northwestern Europe are particularly prone to these processes.Surface samples of ten tilled silty loamy loess soils, ranging in clay content from 120 to 350 g kg⁻¹ and in organic carbon from 10 to 20 g kg⁻¹, were packed into 0.5 m² plots with 5% slopes and subjected to simulated rainfall applied at 30 mm h⁻¹. The 120 minutes rainfall events were applied to initially field-moist soil, air-dried soil and rewetted soil to investigate the effect of soil moisture content prior to rainfall. Runoff and eroded sediments were collected at 5 minutes intervals. Aggregate stability of the soils was assessed by measuring particle-size distribution after different treatments.All soils formed seals. Runoff rates were between 70 and 90% by the end of the rainfall event for field-moist plots. There were large differences between soil runoff rates for the air-dried and rewetted plots. Interrill erosion was associated with runoff, and sediment concentration in runoff readily reached a steady-state value. Measurements of aggregate stability for various treatments were in good agreement with sealing, runoff and erosion responses to rainfall. Runoff and erosion were lower for air-dried plots than for field-moist plots, and were either intermediate or lowest for rewetted plots, depending on soil characteristics. Soils with a high clay content had the lowest erosion rate when they were rewetted, whereas the soil with a high organic-carbon content had the lowest erosion rate in air-dry conditions. The results indicate the complexity of the effect of initial moisture content, and the interactions between soil properties and climate.     

耕作方式与地表覆盖量对苜蓿及小麦地水蚀过程的影响

通过模拟降雨对定西苜蓿-春小麦轮作土壤的水蚀过程进行了研究，试验结果表明：苜蓿翻耕（T1）处理的地面积水产生时间最长，苜蓿不翻耕处理（T2）径流产生时间最长，显著高于其它3个处理。在整个模拟降雨过程中，不翻耕处理的径流产生速率总是低于翻耕处理的径流产生速率，其中以苜蓿不翻耕处理（T2）的径流速率最小，而两个翻耕处理的径流速率之间无显著性差异。T2处理的入渗速率始终高于其他3个处理；秸秆覆盖可有效地降低累积径流量和总侵蚀量，增加累积入渗量；在不同处理中，以苜蓿不翻耕处理加100％秸秆覆盖抗水蚀的效果比较明显。     

Soil erosion on Alfisols in Western Nigeria: V. The changes in physical properties and the response of crops

Erosion-induced changes in the physical characteristics of the surface soil under different soil and crop management treatments were monitored over a period of two years. These studies were conducted on field runoff plots established on natural slopes of 1, 5, 10 and 15%. The soil and crop management treatments consisted of bare-fallow, maize-maize (plowed and mulched), maize-maize (plowed), maize-cowpeas (no-till) and cowpeas-maize (plowed).Soil erosion increased the gravel content and decreased the silt and clay contents of the surface horizon. The moisture retention capacity of the surface soil decreased significantly. The infiltration rate decreased from 3.5 cm/min on all plots in February 1972 to 0.2 cm/min under bare-fallow, to 0.6 cm/min under maize-maize (mulch), to 1.5 cm/min under maize-cowpeas (no-till) and to 0.1 cm/min under maize-maize (plowed) in February 1974. Maize yields on the mulch and no-till treatments were maintained while those on plowed plots declined. Artificial soil removal resulted in significant reductions of maize and cowpea yields.     

A comparison between seasonal changes in soil water storage and penetration resistance under conventional and conservation tillage systems in Aragón

Low and extremely variable precipitations limit dryland crop production in the semi-arid areas of Aragón (NE Spain). These areas are also affected by high annual rates of topsoil losses by both wind and water erosion. A long-term experiment to determine the feasibility of conservation tillage in the main winter barley production areas of Aragón was initiated in 1989 at four locations, three on loam to silt loam soils (Xerollic Calciorthid) and one on a silty clay loam (Fluventic Ustochrept), receiving between 300 and 600 mm of average annual rainfall. In this study, we compared, under both continuous cropping and cereal-fallow rotation, the effects of conventional tillage (mouldboard plough) and two conservation tillage systems, reduced tillage (chisel plough) and no-tillage, on soil water content and penetration resistance during the first two growing seasons. Whereas reduced and conventionally tilled treatments generally had similar soil water content during the experimental period, the effects of no-tillage were inconsistent. No-tilled plots had from 26% less to 17% more stored soil water (0–80 cm) than conventional tilled plots at the beginning of the growing season. In contrast to the conventional and reduced tillage treatments, penetration resistances were between 2 and 4 MPa after sowing in most of the plough layer (0–40 cm) under no-tillage at all sites. Fallow efficiencies in moisture storage in the cereal-fallow rotation, when compared with the continuous cropping system, ranged from −8.7 to 12%. The highest efficiencies were recorded when the rainfall in the months close to primary tillage exceeded 100 mm. Since this event is very unlikely, long fallowing (9–10 months) appears to be an inefficient practice for water conservation under both conventional and conservation management. Our results suggest that, up to now, only reduced tillage could replace conventional tillage without adverse effects on soil water content and penetration resistance in the dryland cereal-growing areas of Aragón.     

Soil erosion on alfisols in Western Nigeria: I. Effects of slope,crop rotation and residue management

The effect of slope, crop rotation and residue management on runoff and soil loss was investigated using field runoff plots of 25 m × 4 m on natural slopes of 1, 5, 10 and 15% on an Alfisol on the International Institute of Tropical Agriculture (IITA) research site near Ibadan, Nigeria. The soil and crop management treatments consisted of conventionnally plowed bare fallow, maize-maize (conventionally plowed and mulched), maize-maize (conventionally plowed), maize-cowpeas (zero-tillage), and cowpeas-maize (conventionally plowed). The effect of two contour lengths of 12.5 and 37.5 m was also investigated for the maize-cowpeas rotation.Soil erosion under slopes of 5, 10 and 15% is severe for these soils and if not controlled can limit crop growth.Mulching and no-till treatments had negligible runoff and soil loss. During 1973 the annual runoff losses from the 15% slope were 36, 2 and 2% of the total annual rainfall for the bare-fallow, mulched and no-till treatments, respectively. Annual soil losses during 1973 from the 15% slope were 230 t/ha from bare-fallow, 0.0 t/ha from maize-maize (mulched), 41 t/ha from maize-maize (conventional plowing), 0.1 t/ha from maize-cowpeas (no-till) and 43 t/ha from cowpeas-maize (plowed). Significant soil erosion was associated with only a few extremely intense storms. The soil loss during a single rainstorm increased exponentially with an increase in slope gradient. There was no definite relationship between contour length and runoff or soil loss.     

Influence of basin‐based conservation agriculture on selected soil quality parameters under smallholder farming in Zimbabwe

The research was carried out to determine the effect of basin‐based conservation agriculture (CA) on selected soil quality parameters. Paired plots (0.01 ha) of CA and conventional tillage based on the animal‐drawn mouldboard plough (CONV) were established between 2004 and 2007 on farm fields on soils with either low (12–18% – sandy loams and sandy clay loams) or high clay levels (>18–46% – sandy clays and clays) as part of an ongoing project promoting CA in six districts in the smallholder farming areas of Zimbabwe. We hypothesized that CA would improve soil organic carbon (SOC), bulk density, aggregate stability, soil moisture retention and infiltration rate. Soil samples for SOC and aggregate stability were taken from 0 to 15 cm depth and for bulk density and soil moisture retention from 0 to 5, 5 to 10 and 10 to 15 cm depths in 2011 from maize plots. Larger SOC contents, SOC stocks and improved aggregate stability, decreased bulk density, increased pore volume and moisture retention were observed in CA treatments. Results were consistent with the hypothesis, and we conclude that CA improves soil quality under smallholder farming. Benefits were, however, greater in high clay soils, which is relevant to the targeting of practices on smallholder farming areas of sub‐Saharan Africa.     

Effects of tillage on soil microrelief, surface depression storage and soil water storage

Conservation of soil water is an important management objective for crop production in the semi-arid tropics where droughts are persistent. Identification of the best tillage methods to achieve this objective is thus imperative. The integrated effects of conservation tillage on soil micro topography and soil moisture on a sandy loam soil were evaluated. The field experiment consisted of five tillage treatments, namely tied ridging (TR), no till (NT), disc plough (DP), strip catchment tillage (SCT) and hand hoe (HH). Data measured in the field included soil moisture content, surface roughness, infiltration and sorghum grain yield. A depth storage model was used to estimate depression storage TR treatment and the higher the surface roughness, the greater the depression storage volume. Regression analysis showed that random roughness decreased exponentially with increase in cumulative rainfall. Higher moisture contents were associated with treatments having higher depressional storage. Infiltration rate was significantly higher in the tilled soils than the untilled soils. The DP treatment had the highest cumulative infiltration while NT had the lowest. The Infiltration model which was fitted to the infiltration data gave good fit. Grain yield was highest in TR and least in NT, whereas DP and HH had similar yields.     

基于蒸渗仪测量的水文要素影响因素分析

降水入渗、地表径流、潜水蒸发等水文要素是研究流域水文及生态环境的重要因素。采用五道沟水文试验站蒸渗仪测量资料,统计分析前期土壤含水量、降水强度、地下水埋深及作物对降水入渗补给、地表径流及潜水蒸发的影响。结果表明:不考虑超渗产流,且在其它条件一致时,前期土壤含水量越大,降水强度越小,入渗补给和地表径流系数越大。无论地表有无作物覆盖,入渗补给、地表径流及潜水蒸发系数均随地下水埋深的增加而减少。降水量小于100mm时,无作物比有作物时的入渗补给系数大;降水量大于100mm时,无作物时的入渗补给系数较小。无作物比有作物时地表径流系数大、潜水蒸发系数小,而潜水蒸发系数的差异在作物生长旺季更为明显。研究成果对淮北地区水土流失治理和生态环境保护具有重要的理论和实际意义。     

Runoff and soil erosion under rainfall simulation of Andisols from the Ecuadorian Páramo: effect of tillage and burning

In northern Ecuador, soils of high altitude grasslands (páramos) are mainly non-allophanic Andisols developed on Holocenic volcanic ash. These soils have a high water retention capacity and are the “water tank” of central Ecuador. To assess the effect of land use (burning and tillage) on soil hydrodynamic properties, rainfall simulation was conducted at two different sites. At Pichincha near Quito, the simulation was conducted on a recent volcanic ash soil comparing natural, tilled and burned plots. At El Angel, the simulation was conducted on a mature non-allophanic Andisol comparing natural, recently tilled and formerly cultivated plots.On natural plots, the infiltration rate was very high and sediment loss very low. Results for infiltration rate and runoff indicated that land use change on páramos increased runoff flow and reduced saturated hydraulic conductivity. Superficial reorganisation of the soil surfaces occurred on tilled plots at both sites. This crusting process was fast and resulted in surfaces with very low conductivity at Pichincha. The same processes seemed to be slower at El Angel. The soil surface of recent Andisols at Pichincha was prone to crusting whereas the mature Andisol, at El Angel, with a lower bulk density, was compacted when the kinetic energy of raindrops was high. Water repellency occurred after burning at Pichincha and following long natural air drying after tillage in the non-allophanic A horizon at El Angel. Water repellency combined with the low bulk density of soil aggregates explain the intensity of sediment losses in the abandoned soils after cultivation (Bare fallow plots). Erosion occurred in these areas through floating hydrophobic and stable aggregates.     

Interflow in a tilled,cracking clay soil under simulated rain

On the uplands of the Darling Downs, runoff and erosion during summer fallows are a major problem. Interflow has been reported in tilled catchments in this area and might be controlled to reduce surface runoff and soil erosion. In view of the lack of data on interflow in tilled soils, this paper reports rates of interflow in a tilled soil for a range of stubble mulch rates, and describes the mechanisms of flow observed.Plots 22.5 × 4 m carrying surface mulches of 3,2,1 and 0.1 t ha⁻¹ wheat stubble were prepared on a shallow black, cracking clay on 6% slope. The plots were pre-wet, and then simulated rain at 95 mm h⁻¹ was applied (using a rainulator) for a 50-min test period. Perched water tables developed in the tilled layer and interflow was clearly visible flowing out beneath the collection gutter at the downslope end of the plot. Interflow rates were calculated from

• 1.(a) measurements of surface runoff on the rainulator plots at the end of the 50-min test periods;
• 2.(b) measurements of steady, deep infiltration rate for the site made using a rotating disc rainfall simulator.

The interflow rates calculated for the rainulator plots were significantly related to stubble rates. Stubble appeared to increase interflow by reducing sediment loads in runoff water, thereby reducing the clogging of large voids in the tilled layer by sediment. Large, interconnected voids in the tilled layer must have been the major pathway for interflow.     

Effects of tillage and traffic on crop production in dryland farming systems: II. Long-term simulation of crop production using the PERFECT model

Soil water conservation is critical to long-term crop production in dryland cropping areas in Northeast Australia. Many field studies have shown the benefits of controlled traffic and zero tillage in terms of runoff and soil erosion reduction, soil moisture retention and crop yield improvement. However, there is lack of understanding of the long-term effect of the combination of controlled traffic and zero tillage practices, as compared with other tillage and traffic management practices.In this study, a modeling approach was used to estimate the long-term effect of tillage, traffic, crop rotation and type, and soil management practices in a heavy clay soil. The PERFECT soil–crop simulation model was calibrated with data from a 5-year field experiment in Northeast Australia in terms of runoff, available soil water and crop yield; the procedure and outcomes of this calibration were given in a previous contribution. Three cropping systems with different tillage and traffic treatments were simulated with the model over a 44-year-period using archived weather data.Results showed higher runoff, and lower soil moisture and crop production with conventional tillage and accompanying field traffic than with controlled traffic and zero tillage. The effect of traffic is greater than the effect of tillage over the long-term. The best traffic, tillage and crop management system was controlled traffic zero tillage in a high crop intensity rotation, and the worst was conventional traffic and stubble mulch with continuous wheat. Increased water infiltration and reduced runoff under controlled traffic resulted in more available soil water and higher crop yield under opportunity cropping systems.