Zero-tillage Systems Research Articles

Effects zero tillage on cassava ( Manihot esculentsa crantz ) in Southwestern Nigeria.

A field study was conducted on a sandy clay loamy soil (Alfisol) at Owo, Southwest Nigeria to evaluate the effects of four tillage methods on soil physical and chemical properties and cassava performance. Tillage treatments were: zero tillage, Conventional tillage, manual mounding and manual ridging. Zero tillage had significantly higher soil bulk density and low total porosity than other tillage treatments at the 0-10cm soil layer. Soil moisture contents given by zero-tillage/manual mounding ridging were significantly higher (p=0.05) than that of conventional- tillage. Soil fertility status as indicated by organic C, total N, available P, and Exchangeable K, Ca and Mg contents, declined in the tilled plots compared with zero tillage. The conventional tillage gave least values of soil chemical properties. Tillage produced on significant effect on the biomass and tuber yields of cassava in the first and second years. It was apparent that no tillage did not reduce the total biomass yields of cassava. Zero tillage system is suitable for cassava production. Nigerian Journal of Soil Science Vol. 17 2007: pp. 81-86

A decade of herbicide-resistant crops in Canada

This review examines some agronomic, economic, and environmental impacts of herbicide-resistant (HR) canola, soybean, corn, and wheat in Canada after 10 yr of growing HR cultivars. The rapid adoption of HR canola and soybean suggests a net economic benefit to farmers. HR crops often have improved weed management, greater yields or economic returns, and similar or reduced environmental impact compared with their non-HR crop counterparts. There are no marked changes in volunteer weed problems associated with these crops, except in zero-tillage systems when glyphosate is used alone to control canola volunteers. Although gene flow from glyphosate-HR canola to wild populations of bird’s rape (Brassica rapa L.) in eastern Canada has been measured, enrichment of hybrid plants in such populations should only occur when and where herbicide selection pressure is applied. Weed shifts as a consequence of HR canola have been documented, but a reduction in weed species diversity has not been demonstrated. However, reliance on HR crops in rotations using the same mode-of-action herbicide and/or multiple in-crop herbicide applications over time can result in intense selection pressure for weed resistance and consequently, greater herbicide use in the future to control HR weed biotypes. History has repeatedly shown that cropping system diversity is the pillar of sustainable agriculture; stewardship of HR crops must adhere to this fundamental principle. Key words: Canola, Brassica napus, corn, Zea mays, soybean, Glycine max, wheat, Triticum aestivum, gene flow, herbicide resistance, transgenic crop, volunteer crop

Agronomic and economic responses to integrated weed management systems and fungicide in a wheat-canola-barley-pea rotation

Changes in tillage intensity and herbicide use can influence the incidence of weeds, insects and diseases, crop yields and economic returns. We examined the effects of six integrated weed management systems (with varying combinations of tillage methods, seeding rate, seeding date, time when weed control was applied, and annual fungicide applications on pest incidence, grain yield and quality, and economic returns for a spring wheat (Triticum aestivum L.)-canola (Brassica napus L.)-barley (Hordeum vulgare L.)-pea (Pisum sativum L.) rotation in the Dark Brown soils of the Moist Mixed Grassland Ecoregion of Saskatchewan. Herbicide use intensity was reduced without a significant increase in weed biomass in five of the six systems in most crops and years. The complete elimination of herbicides in one system resulted in significant crop yield losses. Certain insects were more prevalent in the cropping systems with early planting dates. Zero tillage systems produced higher yields, and yields generally declined as tillage intensity increased. For all crops, the high herbicide-zero tillage system produced the highest yields, whereas the lowest yields were obtained in the no herbicide-high tillage system. Management method had minimal impact on seed quality. Application of fungicide generally increased yields of barley, wheat and pea, but the increases were not sufficient to recover fungicide cost. High herbicide-zero tillage, medium herbicide-zero tillage, and low herbicide-zero tillage systems produced the highest net return and no herbicide-high tillage system the lowest net return, under all grain price scenarios. Key words: Agronomic, economic, tillage, herbicide, fungicide, weed management systems, weed, insect, disease

Symposium A multistudy approach to understanding weed population shifts in medium- to long-term tillage systems

Abstract Production systems based on reduced-tillage practices account for over 60% of the cropped land on the Canadian Prairies. Concerns have been expressed regarding potential shifts in weed communities as a result of changing tillage practices. Study objectives were to (1) determine the feasibility of combining and analyzing weed abundance data from 10 medium- to long-term studies on the Canadian Prairies that compared conventional-, reduced-, and zero-tillage systems, (2) identify species that are associated with specific tillage systems, and (3) place species into plant response groups according to the similarity of their tillage system response. Conventional-tillage systems were defined as including both a fall and spring sweep-plow operation before seeding spring crops, whereas reduced tillage consisted of only one sweep-plow operation shortly before seeding. Crops within zero-tillage systems were planted directly into the previous crop's stubble. The association between weed species and tillage s...

Evaluation of Fibre Flax (Linum usitatissimum L.) Performance under Minimal and Zero Tillage in Eastern Canada

AbstractThe feasibility of producing fibre flax in minimum tillage or zero tillage (ZT) systems was investigated. The results were variable between the sites, which differed in soil type and previous cropping history. Tillage regime had no impact on fibre flax phenological development including number of days to emergence, days to flowering and days to harvest at either site. However, tillage regime had a significant effect on mean stem diameter, dry matter content and plant height at all three sampling dates at the sandy loam site, and a significant effect on mid‐season plant height at the clay site. At the sandy loam site, ZT plots had the highest populations of plants with the finest stem diameters, the lowest branching ratios, but the shortest plants by the end of the season. Overall, plant densities were greater, stem diameters thinner, and biomass production higher in the heavier soil of the clay site. These results indicate that under the growing conditions present in 1998, fibre flax can successfully be grown in minimum or ZT systems on different soil types in Eastern Canada. Moreover, the growth of fibre flax in these systems does not compromise the proportion of tall plants having thin stems and minimal branching, a critical quality parameter for fibre flax production.

Glyphosate Timing and Tillage System Effects on Glyphosate-Resistant Canola (Brassica napus)1

Glyphosate-resistant canola has been widely adopted in western Canada. This has prompted producer interest in the timing of glyphosate application, particularly under zero tillage, where glyphosate is often applied preseeding. Field experiments were conducted at Lacombe, Edmonton, and Beaverlodge in Alberta in 1997, 1998, and 1999 to determine the importance of preseeding glyphosate and the most effective growth stage to apply glyphosate to canola to optimize yield and weed management. Treatments consisted of zero-tillage systems, with and without preseeding glyphosate, and a conventional-tillage system involving preseeding tillage operations. Glyphosate was applied at the one- to two-, three- to four-, or five- to six-leaf stages of canola in each tillage system. Canola yield and weed dry weight were largely unaffected by the tillage system. In most instances, the highest canola yields occurred when glyphosate was applied early to the crop. The opposite occurred at Lacombe and Edmonton in 1999, however, ...

Traffic and residue cover effects on infiltration

Wheel traffic can lead to compaction and degradation of soil physical properties. This study, as part of a study of controlled traffic farming, assessed the impact of compaction from wheel traffic on soil that had not been trafficked for 5 years. A tractor of 40 kN rear axle weight was used to apply traffic at varying wheelslip on a clay soil with varying residue cover to simulate effects of traffic typical of grain production operations in the northern Australian grain belt. A rainfall simulator was used to determine infiltration characteristics. Wheel traffic significantly reduced time to ponding, steady infiltration rate, and total infiltration compared with non-wheeled soil, with or without residue cover. Non-wheeled soil had 4—5 times greater steady infiltration rate than wheeled soil, irrespective of residue cover. Wheelslip greater than 10% further reduced steady infiltration rate and total infiltration compared with that measured for self-propulsion wheeling (3% wheelslip) under residue-protected conditions. Where there was no compaction from wheel traffic, residue cover had a greater effect on infiltration capacity, with steady infiltration rate increasing proportionally with residue cover (R 2 = 0.98). Residue cover, however, had much less effect on inf iltration when wheeling was imposed. These results demonstrated that the infiltration rate for the non-wheeled soil under a controlled traffic zero-till system was similar to that of virgin soil. However, when the soil was wheeled by a medium tractor wheel, infiltration rate was reduced to that of long-term cropped soil. These results suggest that wheel traffic, rather than tillage and cropping, might be the major factor governing infiltration. The exclusion of wheel traffic under a controlled traffic farming system, combined with conservation tillage, provides a way to enhance the sustainability of cropping this soil for improved infiltration, increased plant-available water, and reduced runoff-driven soil erosion.

Effect of Tillage on Weed Populations in Continuous Barley (Hordeum vulgare)1

The influence of four tillage systems, varying from intensive to zero tillage, on weed populations and the vertical distribution of weed seeds in the soil was determined at Alliance, Hairy Hill, and Wainwright in northeastern Alberta. The soil was sampled at two depths (0 to 5 and 5 to 10 cm) in fall. Weed seedling emergence in the greenhouse over the winter was assumed to represent the type and amount of weed seeds present in the soil seedbank. Emerged weed seedlings were also identified and counted in the field in spring. In the zero-tillage system, most of the weed seeds were close to the soil surface (0 to 5 cm) at Alliance and Wainwright but were deeper (5 to 10 cm) at Hairy Hill. The winter annuals, field pennycress, shepherd's-purse, and flixweed, and the summer annuals, wild buckwheat and common lambsquarters, increased in the soil seedbank as tillage was reduced, but the higher populations in the soil seedbank did not always result in higher spring seedling populations under zero tillage. In contrast to the seedbank, spring seedling populations of common lambsquarters at Alliance and field pennycress and ball mustard at Hairy Hill were lowest in the zero-tillage system, suggesting that the requirement for herbicides for controlling these weeds in the crop may be least under zero tillage. Both soil seedbank and spring seedling populations of shepherd's-purse at Wainwright and Alliance and of flixweed at Alliance were highest in the zero-tillage system. At Alliance, wild buckwheat seedling emergence in the spring tended to be highest in the minimum-tillage system (one tillage operation prior to seeding). Both soil seedbank and spring seedling populations of green foxtail decreased as tillage was reduced, indicating that green foxtail should become less of a problem under reduced tillage.Nomenclature: Ball mustard, Neslia paniculata (L.) Desv. #3 NEAPA; common lambsquarters, Chenopodium album L. CHEAL; field pennycress, Thlaspi arvense L. THLAR; flixweed, Descurainia sophia (L.) Webb. ex Prantl. DESSO; green foxtail, Setaria viridis (L.) Beauv. SETVI; shepherd's-purse, Capsella bursa-pastoris (L.) Medik. CAPBP; wild buckwheat, Polygonum convolvulus L. POLCO.Additional index words: Intensive tillage, moderate tillage, minimum tillage, zero tillage.

TILLAGE SYSTEMS AND STUBBLE MANAGEMENT IN A MEDITERRANEAN-TYPE ENVIRONMENT IN RELATION TO CROP YIELD AND SOIL MOISTURE

The effect of tillage and crop rotations can only be seen over many crop years. Crop yield and soil results are evaluated from two long-term trials, established in 1978–79 and 1985–86 to investigate various forms of tillage and the timing of such operations in various wheat (Triticum aestivum)-based rotations on a Calcixerollic Xerochrept in northern Syria. In a tillage systems trial involving two wheat–legume–watermelon (Citrullus lanatus) rotations, deep tillage showed no advantage over a shallow sweep-tillage system, either for soil moisture storage or yield increase of any crop. The zero-till system suited legume crops but gave lower productivity in wheat due to a build up of grassy weeds, and was not suitable for watermelon. Minimum tillage, with its higher energy-use efficiency and yield levels equal to or even slightly above those of deep-tillage systems, appears promising for the lowland areas of West Asia and North Africa. In a tillage timing trial, wheat in a wheat–lentil (Lens culinaris) rotation yielded best after conventional deep disc-plough tillage, but lentil yields were higher in a zero-till system.

Distribution and forms of P under cultivator- and zero-tillage for continuous- and fallow-wheat cropping systems in the semi-arid Canadian prairies

Conservation tillage may affect the dynamics of nutrient transformations in the soil. We assessed the effect of fallow-wheat, and continuous wheat under zero-tillage and cultivator-tillage management on phosphorus concentration in the grain (GPC), phosphorus uptake in the grain, NaHCO 3 extractable-P (Olsen-P) and on forms and distribution of P in the surface 10 cm of the soil for a 12-year tillage field experiment established on an Orthic Brown Chernozemic soil (Aridic Haploboroll) in southwestern Saskatchewan, Canada. Grain yield was the main factor affecting GPC, with the lower-yielding continuous-wheat system having the highest GPC, most likely resulting from luxury uptake of P. Phosphorus taken in the grain, however, was directly proportional to grain yield. Olsen-P in the soil was highly variable from year to year, and was not affected by tillage or rotation. From 1982 to 1989, when P removed in the grain was less than P applied as fertilizer, Olsen-P in spring samples increased, on average, by 0.9 mg kg −1 year −1 in the fallow-wheat and by 1.4 mg kg −1 year −1 in the continuous-wheat cropping systems. From 1990 to 1994, when grain yields increased due to more favourable moisture conditions, crop removal of P exceeded P fertilization, and Olsen-P concentration remained relatively stable. Converting the original cultivator tilled fallow-wheat system to zero-tilled continuous wheat produced a significant increase in total soil P as a result of increased accumulation of labile and moderately labile forms of P in the surface 6 cm of the soil, especially in organic forms. When either zero-tillage or continuous-wheat were adopted by themselves, there were no changes in the amounts of P in the different pools. The proportion of organic P in the labile and moderately labile pools in the surface 6 cm of soil, however, increased significantly with respect to the cultivator tilled fallow-wheat control. This reflected increased levels of crop residues returned to the soil in the continuous-wheat cropping system and reduced rates of residue decomposition in the zero-tillage system. The increase in labile forms of P near the surface in zero-tilled soils may have substantial impact on soil sampling for prediction of P fertilizer requirements, and on surface water quality in reduced tillage systems.

Conservation Tillage Systems for Dryland Farming: On-Farm Research and Extension Experiences

Conservation tillage covers a wide spectrum of production systems, ranging from zero-tillage systems to reduced tillage systems, using various forms of traction; manual, animal or tractor. Each con...

Soil microbial biomass and carbon dioxide flux under wheat as influenced by tillage and crop rotation

Soil organic matter is important both from an agronomic and an environmental perspective because it affects the capacity of the soil to sustain crop growth, and it is a source and sink of atmospheric CO2-C. Soil microbial biomass comprises a small proportion of total soil organic matter, but it is more dynamic than total soil organic matter. Therefore, measurements of soil microbial biomass may show the effects of soil management on potential changes in soil organic matter before such effects can be detected by measuring total soil organic matter. The effects of tillage and crop rotation on soil microbial biomass and activity were studied in 1995–1997 in the wheat phase of different cropping rotations that had been established in 1992 under zero tillage or conventional tillage in northern Alberta. Soil microbial biomass was often significantly (P < 0.05) higher, but never significantly lower, under zero tillage than under conventional tillage. However, CO2 evolution (basal respiration) was usually higher under conventional tillage than under zero tillage, resulting in higher specific respiration (qCO2) under conventional tillage than under zero tillage. The higher additions but lower losses of labile C under zero tillage mean that more C is sequestered in the soil in the zero-tillage system. Thus, this system contributes less to atmospheric CO2 than conventional tillage, and that soil organic matter accumulates more under zero tillage. Plots preceded by summerfallow, especially under conventional tillage, usually had the lowest microbial biomass and CO2 evolution, and plots preceded by legume crops had higher microbial biomass and lower qCO2 than other treatments. Tillage and rotation had little effect on total soil organic matter 5 yr after the treatments had been imposed, probably because of the cold climate of northern Alberta, but the results confirm that the labile forms of soil C are more sensitive indicators of soil organic C trends than total soil organic C. These effects of tillage and rotation on soil microbial biomass were similar to those on microbial diversity reported previously. These results confirm that zero tillage and legume-based crop rotations are more sustainable crop management systems than conventional tillage and fallowing in the Gray Luvisolic soils of northern Alberta. Key words: Carbon sequestration, carbon mineralization, microbial activity, soil organic matter

Effects of tillage method and fallow frequency on leaf spotting diseases of spring wheat in the semiarid Canadian prairies

Leaf spotting diseases of wheat ( Triticum spp.) are widespread in western Canada. Because these diseases are residue-borne, they are expected to be affected by changes in the quality and quantity of crop residues. A field study was conducted to determine the effects of summerfallow and tillage practices on leaf spotting diseases of spring wheat ( T. aestivum L.) in the semiarid area of the western Canadian prairies. Leaf spot severity was greater in wheat grown after fallow than in continuous wheat when these systems were managed using either cultivator- or zero-tillage methods. Disease severity in wheat after fallow was similar in all three tillage methods: cultivator-, reduced-, and zero-tillage. Pyrenophora tritici-repentis (Died.) Drechs. (tan spot) was the pathogen most commonly isolated from lesioned leaf tissue. Crop residues collected in the spring of 1995 and 1996 from cultivator- and zero-tillage treatments were examined for the presence and density of fungal infective structures. The density of mature and immature structures, especially of P. tritici-repentis, was greater in residues from two years previous than in those from the previous growing season. Most of the residues in the continuous wheat system were from the previous crop. The apparent lower amount of initial inoculum available in a continuous wheat system than in wheat grown after fallow would explain the higher leaf spotting severity in the latter system. In addition, lower levels of infective structures on residues were found in wheat after fallow in zero- rather than in cultivator-tillage. However, similar disease levels in cultivator- and zero-tillage treatments suggest that the more favourable microclimate for disease development in a zero-tillage system might have compensated for the lower amounts of residue-borne inoculum.

Tillage and N source influence soil-emitted nitrous oxide in the Alberta Parkland region

Zero tillage systems are receiving attention as possible strategies for sequestering atmospheric carbon. This benefit may be offset by increased N2O emissions, which have been reported for soils under zero tillage (ZT) compared to those under more intensive tillage (IT). Comparisons of N2O emissions from the two systems have been restricted to the growing season, but substantial losses of N2O have been reported during spring thaw events in many regions. Inorganic and organic additions of nitrogen and fallowing have also been shown to increase levels of soil-emitted N2O. The objectives for this study were: (i) to confirm that losses of N2O are higher under ZT than under IT in Alberta Parkland agroecosystems; (ii) to compare the relative influence of urea fertilizer (56 or 100 kg N ha−1), field pea residue (dry matter at 5 Mg ha−1), sheep manure (dry matter at 40 Mg ha−1) additions, and fallow on total N2O losses; and (iii) to investigate possible interactions between fertility and tillage treatments. Gas samples were collected using vented soil covers at three sites near Edmonton, Alberta during 1993, 1994, and 1995. Gas samples were analyzed using a gas chromatograph equipped with a 63Ni electron capture detector. Estimated annual N2O loss ranged from 0.1 to 4.0 kg N ha−1. Emissions during summer were slightly higher, similar, or lower on ZT compared to those under IT, but were consistently lower on ZT plots during spring thaw. Combined estimates (spring plus summer) of N2O loss under ZT were equal to or lower than those under IT. Highest overall losses were observed on fallow plots, followed by fertilizer, pea residue, and then either manure or control plots. We conclude that ZT management systems have potential for reducing agricultural greenhouse gas emissions in the Alberta Parkland region. Key words: Nitrous oxide, thawing soil, tillage, nitrogen fertilizer, manure, fallow

Cattle manure as a nutrient source for barley and oilseed crops in zero and conventional tillage systems

Manure application should be equally effective in meeting crop nutrient requirements in zero and conventional tillage systems in order to be sustainable in a semi-arid region. A study was conducted from 1993 to 1996 at Scott and Melfort, Saskatchewan, to determine if feedlot cattle manure and inorganic N fertilizer were equally effective as nutrient sources for barley (Hordeum vulgare L.), canola (Brassica rapa L.) and flax (Linum usitatissumum L.) production, and soil N dynamics, in zero and conventional tillage systems. Inorganic fertilizer was compared with a factorial combination of two manure treatments: manure composition (fresh versus stockpiled), and application rate and frequency (annual versus once every four years). Barley and oilseed yields at Scott did not differ between fertilizer and manure treatments, whether manure was applied annually or once every 4 yr. At Melfort, the site with the highest yield potential, grain yields were 24% lower with manure. This yield reduction could be related to soil N availability; net N mineralization was 37 kg ha−1 lower in plots that received manure rather than inorganic fertilizer. Yield responses to the different types of manure and inorganic fertilizer were similar under zero-till and conventional tillage management. Low levels of N volatilization from the manure, and similar levels of net N mineralization, explained why crop responses to nutrient source did not differ with tillage system. Feedlot cattle manure can be applied as a nutrient source when surface applied in a zero-till system without significant yield reductions compared with soil incorporation in a conventional tillage system. Key words: Cattle manure, tillage, zero-till, barley, canola, flax

Distribution of phosphorus fractions in a Brazilian Oxisol under different tillage systems

Changes in residue management resulting from adoption of conservation tillage systems have the potential to alter the concentration and distribution of phosphorus (P) in the soil surface. The objective of this study was to determine the effect of methods of tillage management on the distribution and concentration of organic and inorganic forms of soil P near the soil surface (0–10 cm depth) for an Oxisol in southern Brazil. The tillage systems included zero tillage (ZT) (seeding directly onto the standing stubble of the previous crop), minimum tillage (MT) (seeding the crop after chisel plowing to 15-cm depth and disk harrowing to 7.5 cm), or conventional tillage (CT) (seeding after disk plowing to 20-cm depth with nearly total soil inversion plus two disk harrowings to 10-cm depth). After a period of five years, reducing tillage through adoption of MT or ZT practices increased total P in the surface 10 cm by 15% when compared to CT. Although there were no differences in amounts of total P between MT and ZT systems, under ZT management larger amounts of labile organic and inorganic forms of P accumulated close to the soil surface, followed by a reduction below the 6-cm depth. Under MT, the labile organic and inorganic forms of P were uniformly distributed within the surface 10 cm of soil. The accumulation of high levels of labile P near the soil surface under ZT followed a distribution pattern similar to the accumulation of organic residues in the soil. This would help explain why other workers have found increased P uptake by crops grown under ZT, and why more available P can be extracted by common soil testing methods from the surface 7 to 10 cm of soils under ZT than under CT management.

Tillage and Nitrogen Influence Weed Population Dynamics in Barley (Hordeum vulgare)

Field experiments were initiated at Alliance and Hairy Hill, Alberta, in 1989 to investigate the effects of conventional tillage, zero tillage, and four levels of nitrogen fertilizer on continuous barley production. In both tillage systems, the nitrogen was banded 6 to 8 cm deep between alternate barley rows. Herbicides were used for weed control each year. The influence of tillage and nitrogen on weed seed population dynamics was determined in 1991 and 1992. In the zero-tillage system, a large proportion of the weed seeds were present either at the soil surface or at the 5- to 10-cm depth. Green foxtail, the dominant species at Alliance, was also present at Hairy Hill where field pennycress was dominant. Green foxtail was consistently associated with low (residual) nitrogen and, in most cases, with conventional tillage. At both locations, green foxtail populations tended to decrease to very low levels as nitrogen rate increased, especially in zero tillage. At Hairy Hill, field pennycress populations in the soil seedbank were higher in zero tillage compared with conventional tillage, but plants that emerged from the soil seedbank in the field in spring were lower in zero tillage. Field pennycress populations were highest under low nitrogen. The results indicate that banding nitrogen has the potential to be an effective tool for green foxtail and field pennycress management in conventional- and zero-tillage systems, resulting in less dependence on herbicides for their control.

Economic factors contributing to the adoption of reduced tillage technologies in central Saskatchewan

The zero-tillage and minimum-tillage technologies, which are now being rapidly adopted in many areas of western Canada, have made a significant contribution to the sustainability of the soil resource. As a measure of economic viability of these practices this study uses the Top Management Model to simulate the 5-yr ending equity given stochastic prices and yields for a consensus farm in central Saskatchewan. Simulations are used to compare a minimum disturbance, zero-tillage system to a more conventional direct-seeding system. At 1994 crop and input prices, and a 10% yield advantage, zero-tillage systems compared favourably with conventional direct-seeding system. The relative crop yield and glyphosate price are key determinants to the short-run profitability of adopting zero-tillage technologies with fuel price having a smaller influence. When the switch to zero tillage allows a net reduction in machinery stock, this simultaneously increases the profitability, and reduces the financial risk for the producer. We conclude that in areas of Saskatchewan where zero-tillage systems provide a yield advantage, producers will continue to adopt these systems as an economically viable means of sustaining their soil resource. Key words: Adoption, zero tillage, economic determinants, herbicide prices, risk

Sustainability and economic issues for cereal crop residue export

Soil conservation and sustainability concerns, and a lack of markets for crop residues, have left producers with few alternatives for cereal residue export beyond cattle feed or livestock bedding. With the increasing producer use of minimum and zero-tillage systems, the management of crop residues has become an important issue. Opportunities for residue removal may exist provided markets are developed for the material and long-term soil sustainability concerns are addressed.Recent research on the effect of residue removal in Saskatchewan has shown that there is little or no impact on soil organic matter provided adequate fertilization is practised and tillage is reduced. Assuming that 750 kg ha−1 of retained residue is adequate for erosion protection in reduced tillage systems, significant quantities of residues may be available for export from the Black Soil zone. The economic returns to producers are such that residue export is an attractive diversification option. Key words: Crop residues, economics, residue export, soil erosion, soil nutrients, soil carbon

Row spacing and seeding rate effects in wheat and barley under a conventional fallow management system

Varying seed row spacing had no effect on the yield of spring wheat (Triticum aestivum L.) or barley (Hordeum vulgare L.) when grown under a conventional-tillage fallow-management system. Grain yields were improved with increased seeding rates by 14% in wheat and 32% in barley. The absence of a row-spacing-by-seeding-rate interaction suggests that adjustments in seeding rates are not required with changes in row spacing. The presence of surface residues and standing stubble cannot explain the lack of a row-spacing effect when using a zero-tillage stubble-cropping system, since similar results were obtained with a conventional-tillage fallow management system in this study. Key words: Yield, yield components, plant density