• Authors:
    • Ahuja, L. R.
    • Westfall, D. G.
    • Peterson, G. A.
    • Sherrod, L. A.
  • Source: Soil Science Society of America Journal
  • Volume: 67
  • Issue: 5
  • Year: 2003
  • Summary: Soil organic C (SOC) has decreased under cultivated wheat (Triticum aestivum)-fallow (WF) in the central Great Plains.We evaluated the effect of no-till systems of WF, wheat-corn (Zea Mays)-fallow (WCF), wheat-corn-millet (Panicum miliaceum)-fallow, continuous cropping (CC) without monoculture, and perennial grass (G) on SOC and total N (TN) levels after 12 yr at three eastern Colorado locations. Locations have long-term precipitation averages of 420 mm but increase in potential evapotranspiration (PET) going from north to south. Within each PET location, cropping systems were imposed across a topographic sequence of summit, sideslope, and toeslope. Cropping intensity, slope position, and PET gradient (location) independently impacted SOC and TN to a 5-cm soil depth. Continuous cropping had 35 and 17% more SOC and TN, respectively, than the WF system. Cropping intensity still impacted SOC and TN when summed to 10 cm with CC > than WF. Soil organic C and TN 20% in the CC system compared with WF in the 0- to 10-cm depth. The greatest impact was found in the 0- to 2.5-cm layer, and decreased with depth. Soil organic C and TN levels at the high PET site were 50% less than at the low and medium PET sites, and toeslope soils were 30% greater than summit and sideslopes. Annualized stover biomass explained 80% of the variation in SOC and TN in the 0- to 10-cm soil profile. Cropping systems that eliminate summer fallowing are maximizing the amount of SOC and TN sequestered.
  • Authors:
    • Vigil,M. F.
    • Nielsen,D. C.
    • Benjamin,J. G.
  • Source: Geoderma
  • Volume: 116
  • Issue: 1-2
  • Year: 2003
  • Summary: Soil management decisions often are aimed at improving or maintaining the soil in a productive condition. Several indicators have been used to denote changes in the soil by various management practices, but changes in bulk density is the most commonly reported factor. Bulk density, in and of itself, gives little insight on the underlying soil environment that affects plant growth. We investigated using the Least Limiting Water Range (LLWR) to evaluate changes in the soil caused by soil management. The LLWR combines limitations to root growth caused by water holding capacity, soil strength and soil aeration into a single number that can be used to determine soil physical improvement or degradation. The LLWR appeared to be a good indicator of plant productivity when the full potential of water holding capacity on available water can be realized, such as with wheat (Triticum aestivum, L.) grown in a no-till system when the wheat followed a fallow period. A regression of wheat yield to LLWR gave an r(2) of 0.76. The LLWR was a poorer indicator of plant productivity when conditions such as low total water availability limited the expression of the potential soil status on crop production. Dryland corn (Zea mays, L.) yields were more poorly correlated with LLWR (r(2)=0.18), indicating that, under dryland conditions, in-season factors relating to water infiltration may be more important to corn production than water holding capacity. An improved method to evaluate in-season soil environmental dynamics was made by using Water Stress Day (WSD). The WSD was calculated by summing the differences of actual water contents in the field from the limits identified by the LLWR during the growing season. A regression of irrigated corn yield with LLWR as the soil indicator of the soil environment resulted in an r(2) of 0.002. A regression of the same yield data with WSD as the indicator of the soil environment resulted in an r(2) of 0.60. We concluded that the LLWR can be a useful measure of management effects on soil potential productivity. Soil management practices that maximize the LLWR can maximize the potential of a soil for crop production. Knowledge of the LLWR for a soil can help the farm manager optimize growing conditions by helping schedule irrigation and for making tillage decisions. The WSD, calculated from the LLWR and in-season water dynamics, allows us to evaluate changes in the soil caused by differing soil management practices and identify critical periods of stress on the plant that can reduce production.
  • 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:
    • Wang, H.
    • Brandt, S.
    • Lafond, G.
    • Moulin, A.
    • Campbell, C.
    • Curtin, D.
    • Schoenau, J.
    • McConkey, B.
    • Liang, B.
  • Source: Canadian Journal of Soil Science
  • Volume: 83
  • Issue: 1
  • Year: 2003
  • Summary: Light fraction of soil organic C (LFOC) represents a major portion of labile soil organic C (SOC) and is a key attribute of soil quality. Soil respiration (C min) is an important index depicting the potential activity of the labile SOC. Six field experiments, varying in duration (8 to 25 years), in location (brown [aridic Kastanozem], dark brown [typic Kastanozem] and black chernozemic soil zones of Saskatchewan, Canada; all soils were classified as Chernozems) and soil texture, were conducted to evaluate the impact of tillage and crop rotations on crop production and soil quality. We sampled the 0-7.5 cm depth of soil in these experiments to determine the treatment effects on LFOC, the proportion of LFOC in the SOC (LFOC:SOC) and C min. The crops in the rotation were spring wheat, flax, winter wheat, peas and rape. Increasing the frequency of summer fallow in cropping systems decreased the LFOC in all soil zones; it also decreased the proportion of LFOC in SOC and C min. Tillage had little impact on LFOC in the brown and dark brown chernozemic soil zones, although it significantly decreased LFOC in the black chernozemic soil zone. Thus, crop rotation had a greater impact on LFOC than tillage. Tillage did not influence C min in any soil zone. Because adoption of no-till management increased SOC in all soil zones, we concluded that LFOC was not a sensitive indicator of the impact of tillage on this soil quality attribute for these chernozemic soils in Saskatchewan. We also found that LFOC:SOC is directly proportional to sand content. This relationship may assist us in partitioning SOC pools with differing turnover times when modelling SOC dynamics.
  • 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:
    • Clayton, G.
    • Soon, Y.
  • Source: Canadian Journal of Soil Science
  • Volume: 83
  • Issue: 5
  • Year: 2003
  • Summary: The effects of tillage and crop rotations on soil N availability and economy were evaluated over two rotation cycles to address the paucity of such information. From 1993 through 2000, Leith sandy loam soil (Gray Luvisol) of Alberta, Canada was sampled to 120 cm in the autumn from four crop rotations: (i) continuous wheat ( Triticum aestivum); (ii) field pea ( Pisum sativum)-wheat-rape ( Brassica rapa [ B. campestris])-wheat; (iii) red clover ( Trifolium pratense) green manure-wheat-canola-wheat/red clover; (iv) fallow-wheat-rape-wheat, and analysed for KCl-extractable N. The rotations were managed under a conventional tillage (CT) or a no-till (NT) system, and were fertilized based on soil test results. A N budget was constructed for each cropping system comprising N added in seed and fertilizers, and by symbiotic fixation and N exported in the grain. More nitrate accumulated under CT than NT, resulting in lower N fertilizer application rates for CT plots. Soil mineralizable N was higher under NT than CT, and was not influenced by crop rotations. The trend for residual soil nitrate among crop rotations was: fallow rotation > green manure rotation > continuous wheat > field pea rotation, due mostly to residual nitrate following the first phase of the rotations. There was no interaction of tillage with rotation. The continuous wheat and field pea rotation maintained a balanced N budget. The red clover rotation resulted in net N import in each rotation cycle of approximately 25 kg ha -1 under CT and 37 kg ha -1 under NT; net N export from the fallow rotation was 30 kg ha -1 under NT and 46 kg ha -1 under CT.
  • Authors:
    • Black, A. L.
    • Wienhold, B. J.
    • Halvorson, A. D.
  • Source: Soil Science Society of America Journal
  • Volume: 66
  • Issue: 3
  • Year: 2002
  • Summary: Soil C sequestration can improve soil quality and reduce agriculture's contribution to CO2 emissions. The long-term (12 yr) effects of tillage system and N fertilization on crop residue production and soil organic C (SOC) sequestration in two dryland cropping systems in North Dakota on a loam soil were evaluated. An annual cropping (AC) rotation [spring wheat (SW) (Triticum aestivum L.)-winter wheat (WW)-sunflower (SF) (Helianthus annuus L.)] and a spring wheat-fallow (SW-F) rotation were studied. Tillage systems included conventional-till (CT), minimum-till (MT), and no-till (NT). Nitrogen rates were 34, 67, and 101 kg N ha-1 for the AC system and 0, 22, and 45 kg N ha-1 for the SW-F system. Total crop residue returned to the soil was greater with AC than with SW-F. As tillage intensity decreased, SOC sequestration increased (NT > MT > CT) in the AC system but not in the SW-F system. Fertilizer N increased crop residue quantity returned to the soil, but generally did not increase SOC sequestration in either cropping system. Soil bulk density decreased with increasing tillage intensity in both systems. The results suggest that continued use of a crop-fallow farming system, even with NT, may result in loss of SOC. With NT, an estimated 233 kg C ha-1 was sequestered each year in AC system, compared with 25 kg C ha-1 with MT and a loss of 141 kg C ha-1 with CT. Conversion from crop-fallow to more intensive cropping systems utilizing NT will be needed to have a positive impact on reducing CO2 loss from croplands in the northern Great Plains.
  • Authors:
    • Liang, B. C.
    • Zentner, R. P.
    • Sabourin, D.
    • Izaurralde, R. C.
    • Gameda, S.
    • McConkey, B. G.
    • Campbell, C. A.
  • Source: Agriculture Practices and Policies for Carbon Sequestration in Soil
  • Year: 2002
  • Authors:
    • Ulmer, M. G.
    • Cihacek, L. J.
  • Source: Agriculture Practices and Policies for Carbon Sequestration in Soil
  • Year: 2002
  • Summary: from summary: "The significance of soils in sequestering greenhouse gases and reducing global warming may be greater due to C sequestration as inorganic C. Soil IC is a sink for atmospheric CO 2 , which may be more resistant to cropping and tillage effects on sequestered soil C and is likely to persist for decades and perhaps centuries after sequestration."