• Authors:
    • Liu, R.
    • Phillips, D. L.
    • Lee, J. J.
  • Source: Water, Air, & Soil Pollution
  • Volume: 70
  • Issue: 1
  • Year: 1993
  • Summary: The EPIC model was used to simulate soil erosion and soil C content at 100 randomly selected sites in the US corn belt. Four management scenarios were run for 100 years: (1) current mix of tillage practices maintained; (2) current trend of conversion to mulch-till and no-till maintained; (3) trend to increased no-till; (4) trend to increased no-till with addition of winter wheat cover crop. As expected, the three alternative scenarios resulted in substantial decreases in soil erosion compared to the current mix of tillage practices. C content of the top 15 cm of soil increased for the alternative scenarios, while remaining approximately constant for the current tillage mix. However, total soil C to a depth of 1 m from the original surface decreased for all scenarios except for the no-till plus winter wheat cover crop scenario. Extrapolated to the entire US corn belt, the model results suggest that, under the current mix of tillage practices, soils used for corn and/or soybean production will lose 3.2 x 10^6 tons of C per year for the next 100 years. About 21% of this loss will be C transported off-site by soil erosion; an unknown fraction of this C will be released to the atmosphere. For the base trend and increased no-till trend, these soils are projected to lose 2.2 x 10^6 t-C yr-1 and 1.0 x 10^6 t-C yr-1, respectively. Under the increased no-till plus cover crop scenario, these soils become a small sink of 0.1 x 10^6 t-C yr-1. Thus, a shift from current tillage practices to widespread use of no-till plus winter cover could conserve and sequester a total of 3.3 x 10^6 t-C yr-1 in the soil for the next 100 years.
  • Authors:
    • Zentner, R. P.
    • Campbell, C. A.
  • Source: Soil Science Society of America Journal
  • Volume: 57
  • Issue: 4
  • Year: 1993
  • Summary: Few studies conducted in western Canada have assessed how crop rotations and fertilization influence soil organic matter content on land that has been cropped for many years. We monitored soil organic matter in the 0- to 0.15- and 0.15- to 0.3-m depths of a 24-yr crop rotation experiment conducted on a medium-textured Aridic Haploboroll in southwestern Saskatchewan. Prior to the study, the land had been in a hard red spring wheat (Triticum aestivum L.)-fallow rotation for {approx}50 yr. Only the 0- to 0.15-m segment showed significant treatment effects. Due to good weather and crop yields in the first 15 yr, soil organic matter had increased under well-fertilized annually cropped rotations, and it remained constant under fallow-containing rotations and under continuous wheat receiving inadequate N fertilizer. Because of several dry years in the final 9 yr of the study, all rotations except a well-fertilized, fallow-winter cereal-wheat system lost organic matter. Changes in organic matter were directly related to the amount of crop residues produced by these systems and their ease of eroding. Soil organic matter was inversely related to apparent N deficit (i.e., N exported in grain minus N applied as fertilizer). The fallow-flax (Linum usitatissimum L.)-wheat rotation receiving N and P fertilizer had the lowest soil organic matter, partly due to low production of crop residues by flax, partly to greater leaching of NO3, and partly due to some loss of flax residues blown from the plots. Soil organic matter in the well-fertilized fallow-winter cereal-wheat rotation remained constant because its shorter fallow period reduced soil erosion, and due to its more efficient use of N, as evidenced by minimal leached NO3-N.
  • Authors:
    • Douglas, C. L.,Jr.
    • Rasmussen, P. E.
    • Collins, H. P.
  • Source: Soil Science Society of America Journal
  • Volume: 56
  • Issue: 3
  • Year: 1992
  • Summary: Understanding microbial dynamics is important in the development of new management strategies to reverse declining organic-matter content and fertility of agricultural soils. To determine the effects of crop rotation, crop residue management, and N fertilization, we measured changes in microbial biomass C and N and populations of several soil microbial groups in long-term (58-yr) plots under different winter wheat (Triticum aestivum L.) crop rotations. Wheat-fallow treatments included: wheat straw incorporated (5 Mg ha-1), no N fertilization; wheat straw incorporated, 90 kg N ha-1; wheat straw fall burned, no N fertilization; and wheat straw incorporated, 11 Mg barnyard manure ha-1. Annual-crop treatments were: continuous wheat, straw incorporated, 90 kg N ha-1; wheat-pea (Pisum sativum L.) rotation (25 yr), wheat and pea straw incorporated, 90 kg N ha-1 applied to wheat; and continuous grass pasture. Total soil and microbial biomass C and N contents were significantly greater in annual-crop than wheat-fallow rotations, except when manure was applied. Microbial biomass C in annual-crop and wheat-fallow rotations averaged 50 and 25%, respectively, of that in grass pasture. Residue management significantly influenced the level of microbial biomass C; for example, burning residues reduced microbial biomass to 57% of that in plots receiving barnyard manure. Microbial C represented 4.3, 2.8, and 2.2% and microbial N 5.3, 4.9, and 3.3% of total soil C and N under grass pasture, annual cropping, and wheat-fallow, respectively. Both microbial counts and microbial biomass were higher in early spring than other seasons. Annual cropping significantly reduced declines in soil organic matter and soil microbial biomass.
  • Authors:
    • Cole, C.
    • Westfall, D.
    • Peterson, G.
    • Wood, C.
    • Willis, W.
  • Source: Agronomy Journal
  • Volume: 83
  • Issue: 3
  • Year: 1991
  • Summary: Soil-crop management affects the soil-N balance and, thus, has a direct bearing on soil productivity. This study determined the effects of cropping intensity (crops/time) under no-till and grassland establishment on aboveground biomass production and the system-N balance after 4 yr (1985-1989). The effects were examined across toposequences in the West Central Great Plains that had been tilled and frequently fallowed for > 50 yr. Production systems included wheat (Triticum aestivum L.)-fallow (WF), wheat-corn (Zea mays L.) or sorghum (Sorghum vulgare L.)-millet (Panicum miliaceum L.)-fallow (WCMF), and perennial grass (CG). Intense agronomic systems (WCMF) had greater aboveground production, greater N uptake, and greater percent plant residue retention than WF. Continuous grass systems had less aboveground production and N uptake but greater percent plant residue retention than agronomic systems. Soil-profile NO3-N was lower under WCMF systems than WF systems, but organic N showed the opposite trend implying that more intense systems are at less risk for NO3-N leaching, and have greater potential for replenishment of soil-organic N via enhanced immobilization. Aboveground biomass production and plant residue production increased downslope, but slope position had little effect on plant-N uptake, plant residue retention, or soil-N dynamics. Imposing no-till and perennial grassland systems created a N-balance disequilibrium, but more time will be required to ascertain the trajectory of N loss or gain due to establishment of no-till or grassland management on these soils.
  • Authors:
    • Lafond, G. P.
    • Zentner, R. P.
    • Biederbeck, V. O.
    • Campbell, C. A.
  • Source: Canadian Journal of Soil Science
  • Volume: 71
  • Issue: 3
  • Year: 1991
  • Summary: The effects of crop rotations and various cultural practices on soil organic matter quantity and quality in a Rego, Black Chernozem with a thin A horizon were determined in a long-term study at Indian Head, Saskatchewan. Variables examined included: fertilization, cropping frequency, green manuring, and inclusion of grass Jegume hay crop in predominantly spring wheat (Triticum aestiyum L.) production systems. Generally, fertilizer increased soil organic C and microbial biomass in continuous wheat cropping but not in fallow-wheat or fallow-wheat-wheat rotations. Soil organic C, C mineralization (respiration) and microbial biomass C and N increased (especially in the 7.5- to l5-cm depth) with increasing frequency of cropping and with the inclusion of legumes as green manure or hay crop in the rotation. The influence of treatments on soil microbial biomass C (BC) was less pronounced than on microbial biomass N. Carbon mineralization was a good index for delineating treatment effects. Analysis of the microbial biomass C/N ratio indicated that the microbial suite may have been modified by the treatments that increased soil organic matter significantly. The treatments had no effect on specific respiratory activity (CO2-C/BC). However, it appeared that the microbial activity, in terms of respiration, was greater for systems with smaller microbial biomass. Changes in amount and quality of the soil organic matter were associated with estimated amount and C and N content of plant residues returned to the soil.
  • Authors:
    • Kitchen, N. R.
  • Source: Dissertation Abstracts International. B, Sciences and Engineering
  • Volume: 51
  • Issue: 8
  • Year: 1990
  • Summary: A long-term study was conducted at 2 sites in E. Colorado to study the influence of N fertilizer rate and source/placement/timing (NSP), and crop rotation wheat/fallow (WF), and wheat, maize or sorghum/fallow (MSF) on no-tillage dryland cropping systems. Grain yield and vegetative biomass increased linearly with fertilizer N rate up to 84 kg/ha for wheat and 101 kg/ha for maize indicating that current N recommendations at Colorado State University may be insufficient for meeting N needs of no-tillage crops. N fertilizer recovery efficiency (NFRE) decreased with N fertilizer rate. Production increased more with N fertilizer additions in the MSF than in the WF rotation system. If differences occurred with NSP treatments, banding gave greater production and NFRE than broadcast application. In 1989 at one location, wheat production from the MSF rotation was greater than from the WF rotation. The av. annual grain and vegetative production from MSF was approx. double that produced in the WF cropping system. Water conservation with no-tillage systems allowed more intense cropping than a WF rotation. N loss from the MSF rotation was significant, increased with N rate and was attributed to N loss in both inorganic- and organic-N pools. Nitrate leaching in the no-tillage MSF rotation was unlikely since NO 3 decreased with soil depth.
  • Authors:
    • Rohde, C. R.
    • Rasmussen, P. E.
  • Source: Soil Science Society of America Journal
  • Volume: 52
  • Issue: 4
  • Year: 1988
  • Summary: Maintaining or improving soil organic matter has high priority in agriculture because of its beneficial effect on soil physical, chemical, and biological properties. Soil organic N and C were measured 44 yr after establishment of a long-term experiment to evaluate tillage and fertilizer effects in a winter wheat (Triticum aestivum L.)-fallow rotation on a coarse-silty mixed mesic Typic Haploxeroll. Main treatments consisted of three primary tillage systems, one conventional (moldboard plow) and two stubble mulch (offset disc, subsurface sweeps). Subplots consisted of six N treatments, 493, 728, 986, 1221, 1714, and 2207 kg N ha−1 applied over 44 yr. Organic N and C in the top 75 mm of soil were 26 and 32% higher, respectively, in the two stubble mulch systems than in conventional tillage, and equal below 75 mm. Stubble mulch plots contained 245 kg more N ha−1 than conventionally tilled plots, representing the conservation of 5.7 kg N ha−1 yr−1. Nitrogen fertilization increased soil N linearly in all tillage treatments, with 18% of the applied N incorporated into the soil organic fraction. Applied N also increased soil C linearly on plots with previous S application. Soil C was higher on plots with no previous S than on comparable plots with previous S, however, which suggests an S deficiency that altered S, but not N, transformations in soil. Identical N fertilization effects on soil organic N and C in both stubble mulch and conventional tillage suggests that N transformations were the same in both systems.
  • Authors:
    • Harman, W.
    • Jones, O.
    • Smith, S.
  • Source: Optimum erosion control at least cost. Proceedings of the National Symposium on Conservation Systems, December 14-15, 1987, Chicago, IL, USA
  • Year: 1987
  • Summary: Graded-terraced field-size watersheds have been cropped in a dryland wheat - fallow - sorghum - fallow (2 crops in 3 years) sequence with no-till and conventional (stubble-mulch) tillage systems at Bushland, Texas since 1982. No-till had little effect on wheat yields but increased sorghum yields 14% due to reduced evaporation, as a result of surface residue. No-till reduced erosion by 66%; however, soil loss with conventional tillage was also low due to terracing and contouring. NPK loss was very low. Economically, no-till performed very well, due mainly to reduced equipment inventories and lower operating costs. No-till gave increased storm runoff due to soil crusting, and there were problems with grass weeds. A system consisting of successive no-tillage and stubble-mulch tillage is proposed.
  • Authors:
    • Elharis, M. K.
    • Cochran, V. L.
    • Elliott, L. F.
    • Bezdicek, D. F.
  • Source: Soil Science Society of America Journal
  • Volume: 47
  • Issue: 6
  • Year: 1983
  • Authors:
    • Woody, W. M.
    • Papendick, R. I.
    • Cochran, V. L.
  • Source: Agronomy Journal
  • Volume: 65
  • Issue: 4
  • Year: 1973
  • Summary: Potassium azide (KN3) and 2-chloro-6-(trichloromethyl) pyridine (N-Serve) were evaluated as nitrification inhibitors for anhydrous NH3 field applied on irrigated and nonirrigated Ritzville silt loam and on nonirrigated Naff silt loam in eastern Washington. Formulations of KN3, N-Serve in liquid NH3, or NH3 alone were applied to fallow soil in midsummer at a rate of 90 kg N/ha. Irrigations were 15 cm of water sprinkler applied 1 day or 2 weeks after fertilizer application, and 10 to 15 cm of water each time at 4, 8, and 13 weeks after NH3 application. The NH3 retention zone was sampled for NH+4 and NO-3 periodically through December for the Naff soil and through February for the Ritzville soil. Both KN3 and N-Serve effectively inhibited nitrification of the applied NH3 on nonirrigated Ritzville soil when temperature and soil moisture were favorable for rapid nitrification. However, KN3 was completely ineffective following irrigation or, for the Naff soil, after rainwater penetrated below the retention zone 2 weeks after N application. Where irrigated 1 day or 2 weeks after fertilization application, all of the applied N had disappeared from the initial NH3 retention zone in the Ritzville soil in 8 to 13 weeks for both NH3 alone and NH3 + KN3. Results with the Naff soil for these applications were similar to results with the irrigated Ritzville soil. By contrast, N-Serve effectively suppressed nitrification under leaching and nonleaching conditions. For the Ritzville soil, total N uptake by the wheat (Triticum aestivum L.) crop for different rates of fertilizer application followed the order of NH3 + KN3 > NH3 + N-Serve > NH3 alone, but grain yields with NH3 + inhibitor were not different from yields with NH3 alone. For the Naff soil there was no N-uptake or grain-yield response to N rates, and thus no response to the inhibitors.