• Authors:
    • Bouma, J.
    • Marinissen, J.
    • Jongmans, A.
    • Pulleman, M.
  • Source: Soil Use and Management
  • Volume: 19
  • Issue: 2
  • Year: 2003
  • Summary: We compared the effects of conventional and organic arable farming on soil organic matter (SOM) content, soil structure, aggregate stability and C and N mineralization, which are considered important factors in defining sustainable land management. Within one soil series, three different farming systems were selected, including a conventional and an organic arable system and permanent pasture without tillage. The old pasture represents optimal conditions in terms of soil structure and organic matter inputs and is characterized by high earthworm activity. More than 70 years of different management has caused significant differences in soil properties. SOM content, mineralization, earthworm activity and water-stable aggregation decreased as a result of tillage and arable cropping when compared with pasture, but were significantly greater under organic farming than under conventional farming. Total SOM contents between 0 and 20 cm depth amounted to 15, 24 and 46 g kg-1 for the conventional arable, organic arable and permanent pasture fields, respectively. Although less sensitive to slaking than the conventionally managed field, the soil under organic farming was susceptible to compaction when high pressures were exerted on the soil under wet conditions. The beneficial effects of organic farming are generally associated with soil biochemical properties, but soil physical aspects should also be considered. Depending on soil type and climate, organic farmers need to be careful not to destroy the soil structure, so that they can enjoy maximum advantage from their organic farming systems.
  • Authors:
    • Angers, D. A.
    • Gregorich, E. G.
    • VandenBygaart, A. J.
  • Source: Canadian Journal of Soil Science
  • Volume: 83
  • Issue: 4
  • Year: 2003
  • Summary: To fulfill commitments under the Kyoto Protocol, Canada is required to provide verifiable estimates and uncertainties for soil organic carbon (SOC) stocks, and for changes in those stocks over time. Estimates and uncertainties for agricultural soils can be derived from long-term studies that have measured differences in SOC between different management practices. We compiled published data from long-term studies in Canada to assess the effect of agricultural management on SOC. A total of 62 studies were compiled, in which the difference in SOC was determined for conversion from native land to cropland, and for different tillage, crop rotation and fertilizer management practices. There was a loss of 24 ± 6% of the SOC after native land was converted to agricultural land. No-till (NT) increased the storage of SOC in western Canada by 2.9 ± 1.3 Mg ha–1; however, in eastern Canada conversion to NT did not increase SOC. In general, the potential to store SOC when NT was adopted decreased with increasing background levels of SOC. Using no-tillage, reducing summer fallow, including hay in rotation with wheat (Triticum aestivum L.), plowing green manures into the soil, and applying N and organic fertilizers were the practices that tended to show the most consistent increases in SOC storage. By relating treatment SOC levels to those in the control treatments, SOC stock change factors and their levels of uncertainty were derived for use in empirical models, such as the United Nations Intergovernmental Panel on Climate Change (IPCC) Guidelines model for C stock changes. However, we must be careful when attempting to extrapolate research plot data to farmers fields since the history of soil and crop management has a significant influence on existing and future SOC stocks.
  • Authors:
    • Liu, A.
    • Hamel, C.
    • Madramootoo, C.
    • Elmi, A.
  • Source: Biology and Fertility of Soils
  • Volume: 38
  • Issue: 6
  • Year: 2003
  • Summary: There is a growing interest in the adoption of conservation tillage systems [no-till (NT) and reduced tillage (RT)] as alternatives to conventional tillage (CT) systems. A 2-year study was conducted to investigate possible environmental consequences of three tillage systems on a 2.4-ha field located at Macdonald Research Farm, McGill University, Montreal. The soil was a sandy loam (0.5 m depth) underlain by a clay layer. Treatments consisted of a factorial combination of CT, RT, and NT with the presence or absence of crop residue. Soil NO 3 --N concentrations tended to be lower in RT than NT and CT tillage treatments. Denitrification and N 2O emissions were similar among tillage systems. Contrary to the popular assumption that denitrification is limited to the uppermost soil layer (0–0.15 m), large rates of N 2O production were measured in the subsurface (0.15–0.45 m) soil, suggesting that a significant portion of produced N 2O may be missed if only soil surface gas flux measurements are made. The N 2O mole fraction (N 2O:N 2O+N 2) was higher in the drier season of 1999 under CT than in 2000, with the ratio occasionally exceeding 1.0 in some soil layers. Dissolved organic C concentrations remained high in all soil depths sampled, but were not affected by tillage system .
  • Authors:
    • Cadisch, G.
    • Cook, H.
    • Regar, A.
    • Pihlatie, M.
    • Stevenson, M.
    • Baggs, E. M.
  • Source: Plant and Soil
  • Volume: 254
  • Issue: 2
  • Year: 2003
  • Summary: Emissions of N2O were measured following combined applications of inorganic N fertiliser and crop residues to a silt loam soil in S. E. England, UK. Effects of cultivation technique and residue application on N2O emissions were examined over 2 years. N2O emissions were increased in the presence of residues and were further increased where NH4NO3 fertiliser (200 kg N ha(-1)) was applied. Large fluxes of N2O were measured from the zero till treatments after residue and fertiliser application, with 2.5 kg N2O- N ha(-1) measured over the first 23 days after application of fertiliser in combination with rye ( Secale cereale) residues under zero tillage. CO2 emissions were larger in the zero till than in the conventional till treatments. A significant tillage/residue interaction was found. Highest emissions were measured from the conventionally tilled bean ( Vicia faba) (1.0 kg N2O- N ha(-1) emitted over 65 days) and zero tilled rye (3.5 kg N2O-N ha(-1) over 65 days) treatments. This was attributed to rapid release of N following incorporation of bean residues in the conventionally tilled treatments, and availability of readily degradable C from the rye in the presence of anaerobic conditions under the mulch in the zero tilled treatments. Measurement of N-15-N2O emission following application of N-15-labelled fertiliser to microplots indicated that surface mulching of residues in zero till treatments resulted in a greater proportion of fertiliser N being lost as N2O than with incorporation of residues. Combined applications of N-15 fertiliser and bean residues resulted in higher or lower emissions, depending on cultivation technique, when compared with the sum of N2O from single applications. Such interactions have important implications for mitigation of N2O from agricultural soils.
  • Authors:
    • Merrill, S.
    • Tanaka, D.
    • Anderson, R.
  • Source: Agricultural Water Management
  • Volume: 58
  • Issue: 3
  • Year: 2003
  • Summary: The predominate crops grown in the northern Great Plains of the United States are cereal grains, which are well adapted to the region's semiarid climate and short growing season. However, rotations are changing because minimum- and no-till production systems improve precipitation-use-efficiency. Therefore, producers are seeking diversity in crop choices to improve the design of their rotations. Our objective with this study was to examine water relations and agronomic performance of seven broadleaf crops that may be suitable for a semiarid climate. Dry pea ( Pisum sativum L.), dry bean ( Phaseolus vulgaris L.), and sunflower ( Helianthus annuus L.) were the most favorable for this region considering crop yield and water-use-efficiency (WUE). Soybean ( Glycine max L.), crambe ( Crambe abyssinica Hochst), canola ( Brassica rapa L.), and safflower ( Carthamus tinctorius L.) were less successful. Water use for grain production ranged from 23 to 37 cm among crops whereas water-use-efficiency varied three-fold. Soil water extraction patterns differed between sunflower and dry pea, with sunflower extracting more water as well as accessing water deeper in the soil profile. Integrating oilseed and legume crops with cereal grains in a cycle-of-four rotation will aid producers in managing diseases and weeds, as well as improve grain yield due to the rotation effect.
  • Authors:
    • McDonald, C.
    • Stevenson, F.
    • Zentner, R.
    • McConkey, B.
    • Miller, P.
    • Gan, Y.
  • Source: Agronomy Journal
  • Volume: 95
  • Issue: 2
  • Year: 2003
  • Summary: Crops grown in previous years impact the amounts of residual soil water and nutrients available for subsequent plant growth. Appropriate sequences allow efficient use of the available soil resources by the crop to increase yields at a system's level. This study was conducted to determine whether the grain yield and grain crude protein concentration (GCPC) of durum wheat ( Triticum turgidum L.) were related to crops grown in the previous 2 yr. Durum was grown following pulses [chickpea ( Cicer arietinum L.), lentil ( Lens culinaris Medik.), and dry pea ( Pisum sativum L.)], oilseed [mustard ( Brassica juncea L.) or canola ( B. napus L.)], and spring wheat ( Triticum aestivum L.) in southwest Saskatchewan from 1996 to 2000. Durum increased grain yields by 7% and GCPC by 11% when grown after pulse crops rather than after spring wheat. Durum after oilseeds increased grain yield by 5% and GCPC by 6%. Pulse and oilseed crops grown for the previous 2 yr increased durum grain yield 15% and GCPC 18% compared with continuous wheat systems. Fall residual soil NO 3-N and available soil water accounted for 3 to 28% of the increased durum yield in two of five site-years, whereas those two factors accounted for 12 to 24% of the increased GCPC in three of five site-years. Durum grain yield was negatively related to GCPC. The relationship was stronger when durum was preceded by oilseeds compared with pulses. Broadleaf crops in no-till cropping systems provide significant rotational benefits to durum wheat in the semiarid northern Great Plains.
  • Authors:
    • Diffey, S.
    • Good, A.
    • Mead, J.
    • Hocking, P.
  • Source: Australian Journal of Experimental Agriculture
  • Volume: 43
  • Issue: 11
  • Year: 2003
  • Summary: Land preparation for canola (oilseed rape; Brassica napus L.) by conventional cultivation can involve a number of workings, resulting in soil degradation and reduced crop growth. Minimum-tillage systems may help overcome these problems, but the placement of fertiliser at sowing must avoid chemical injury to germinating seed. The responses of canola cultivars to tillage and fertiliser placement were studied for 2 seasons at high (Breakfast Creek, 1997; Harden, 1998) and low (Ardlethan, 1997-98) rainfall sites. The tillage treatments were conventional cultivation, one-pass, and no-till (direct drill). The fertiliser treatments were 200 kg/ha 'starter' fertiliser (a compound fertiliser supplying 30 kg N, 26 kg P and 22 kg S/ha) either placed with the seed, or broadcast, or banded to the side and 3 cm below the seed. In 1997 the canola was sown after wheat, and in 1998 after pasture. Plant establishment of all cultivars was reduced by 40-65% when fertiliser was placed with the seed; tillage treatment did not alter this response. Placing fertiliser with the seed reduced dry matter/m 2 by up to 40% in plants at flowering, but by physiological maturity, there were no differences in dry matter/m 2 due to fertiliser placement. Analysis of the combined seed yields for both years showed that although plants in the with-seed placement compensated by producing more seed/plant, this compensation was sufficient only at Breakfast Creek for yields to be comparable to those of the other fertiliser placements. Tillage had little effect on seed yields. In 1997, no-till yielded more than one-pass at Ardlethan, but in 1998 at Ardlethan no-till yielded less than the other tillage systems. Fertiliser placement and tillage had no effect on seed oil concentration and meal protein content. Cone penetrometer measurements (1998) showed no differences in soil strength between tillage treatments at Ardlethan; while at Harden, one-pass had less soil strength than the other tillage treatments. Crop water extraction was not affected by tillage at any site. It is concluded that a conservation-farming system involving no-till or one-pass tillage, and separation of seed and fertiliser has the potential for producing high yielding canola crops, reducing the risk of soil degradation, as well as saving time and land-preparation costs.
  • Authors:
    • Brandt, S.
    • Moulin, A.
    • Curtin, D.
    • Campbell, C.
    • Liang, B.
    • McConkey, B.
    • Lafond, G.
  • Source: Soil & Tillage Research
  • Volume: 74
  • Issue: 1
  • Year: 2003
  • Summary: Carbon sequestration was determined for different tillage systems in semiarid to sub-humid climates and coarse to fine-soil texture in Saskatchewan, Canada. Annually cropped rotations sequestered 27-430 kg C ha -1 per year more than crop rotations containing bare fallow. The potential for sequestering soil organic C (SOC) with crop rotations without bare fallow was greater in the sub-humid than in the drier climates. No-tillage (NT) sequestered 67-512 kg C ha -1 per year more than tilled systems. With elimination of both tillage and bare fallow, the SOC increase was approximately 300 kg C ha -1 per year in the semiarid climate regardless of soil texture, and approximately 800 kg C ha -1 per year in the sub-humid climate. Relative annual increase in SOC under no-till was approximately a linear function of clay content across locations. Fine-textured soils have a greater potential for gains in SOC under no-till in Canadian prairie region.
  • Authors:
    • Simpfendorfer, S.
    • Backhouse, D.
    • Moore, K.
    • Verrell, A.
  • Source: Update of research in progress at the Tamworth Agricultural Institute 2002
  • Year: 2003
  • Summary: A replicated, fully phased, field trial was conducted in Tamworth, New South Wales, Australia, to determine the effects of the most common winter and summer break crops on crown rot (caused by Fusarium pseudograminearum) in wheat. The experiment was established in 2000 by sowing F. pseudograminearum-colonized ryegrass seed with wheat cv. Janz into plots. In 2001, rape, chickpea, faba bean, sorghum or wheat cv. Janz were grown under a no-till system. In 2002, wheat cv. Sunstate was planted across the winter break crop plots. All four rotation crops proved effective breaks for crown rot. They encouraged breakdown of the 2000 Janz residue. Stubble ground cover in May 2002 was 15% for sorghum, 28% for faba beans, 30% for rape, and 41% for chickpea compared with 88% for continuous no-till wheat (and 60% long fallow). The rotation crops also reduced survival of the pathogen with recovery of F. pseudograminearum ranging from 7-13% in crowns to 10-15% in stubble following break crops compared with 33% in crowns and 49% in stubble for continuous no-till wheat. These effects carried through to the 2002 wheat crop where infection of Sunstate plants at tillering ranged from 25% for wheat after rape to 39% for continuous wheat.
  • Authors:
    • Gracia, R.
    • Moret, D.
    • Arrúe, J. L.
    • López, M. V.
  • Source: Soil & Tillage Research
  • Volume: 72
  • Issue: 1
  • Year: 2003
  • Summary: Maintenance of crop residues on the soil surface is considered the most effective method to control wind erosion. In semiarid Aragon (NE Spain), where the risk of wind erosion can be high, the adoption of conservation tillage systems has been encouraged as a fallow management alternative. However, little information concerning the dynamics of residue cover during fallow is available for this area. We report here results on the evolution of barley residues during two fallow periods under conventional tillage (CT), reduced tillage (RT) and no-tillage (NT). The three tillage treatments were compared under both continuous cropping (CC) and cereal-fallow (CF) rotation. The CC system involves a summer fallow period of 5-6 months and the CF rotation a long-fallow of 17-18 months. Effects of specific tillage operations on soil cover are also presented and discussed in relation to wind erosion control during the long-fallow period. Average dry mass of barley residues at harvest was 1395 and 729 kg ha(-1) in the first and second year of the study, respectively. In general, crop residues at harvest were not significantly affected by tillage or cropping system. Primary tillage operations had the major influence on residue incorporation with reduction percentages of residue cover of 90-100% in CT (mouldboard ploughing) and 50-70% in RT (chiselling). During the two long-fallow periods, large clods (4-10 cm diameter) produced by mouldboard ploughing did not fully compensate for the complete burial of residues and the soil surface was insufficiently protected against wind erosion (soil covers