• Authors:
    • Nelson, R. G.
  • Source: Biomass and Bioenergy
  • Volume: 22
  • Issue: 5
  • Year: 2002
  • Summary: The focus of this study was to develop a methodology to estimate "hectare-weighted", county-level, corn stover and spring and winter wheat straw removable residue quantities in the USA for 1995-1997 in 37 states (north-south line from North Dakota to Texas and all states east) such that tolerable rainfall and wind soil loss limits were not exceeded.
  • Authors:
    • Westfall, D. G.
    • Peterson, G. A.
    • Ortega, R. A.
  • Source: Agronomy Journal
  • Volume: 94
  • Issue: 4
  • Year: 2002
  • Summary: Crop residue is a valuable resource in Great Plains dryland agroecosystems because it aids in water conservation and soil erosion control. The objectives of our research were to (i) determine the effect of cropping intensity, climate gradient, and soil depth on levels and changes in soil C, soil N, and residue parameters after 8 yr of no-till management in dryland cropping systems and (ii) relate soil and residue parameters to soil C and N levels. Surface soil properties and residue parameters were compared in two cropping systems, wheat (Triticum aestivum L.)-fallow (WF) and wheat-corn (Zea mays L.) or sorghum [Sorghum bicolor (L.) Moench]-proso millet (Panicum miliaceum L.)-fallow (WCMF). The effects were examined on the summit position of a catenary sequence of soils across three environments representing an evapotranspiration (ET) gradient. Soils at the low- and medium-ET sites are classified as Argiustols, and the soil at the high-ET site is an Ustochrept. There was 3.0 Mg ha-1 of residue in the surface 10 cm of soil compared with 2.7 Mg ha-1 of residue on the soil surface averaged over ET gradient and cropping systems. About 90% of the residue in the soil was found within the 2.5-cm soil depth. The highest soil organic C (SOC) and soil organic N (SON) were observed in the surface 0- to 2.5-cm depth. There was a trend (P [<=] 0.16) for the more intense WCMF cropping system to have higher SOC and SON contents than the traditional WF system (C = 6.6 g kg-1 for WF compared with 7.5 g kg-1 for WCMF and N = 0.70 g kg-1 for WF compared with 0.74 g kg-1 for WCMF). From 1985 to 1993, gains in SOC (967 kg ha-1) and SON (74 kg ha-1) occurred in the surface 0- to 2.5- and 2.5- to 5-cm depths while losses were observed in the 5- to 10-cm depth (SOC = -694 kg ha-1; SON = -44 kg ha-1). Climate strongly modified these effects but did not reflect a clear ET gradient effect. The results suggest that higher levels of surface SOC and SON can be attained by increasing cropping intensity under no-till management.
  • Authors:
    • Whitehead, W. F.
    • Singh, B. P.
    • Sainju, U. M.
  • Source: Soil & Tillage Research
  • Volume: 63
  • Issue: 3-4
  • Year: 2002
  • Summary: Maintaining and/or conserving organic carbon (C) and nitrogen (N) concentrations in the soil using management practices can improve its fertility and productivity and help to reduce global warming by sequestration of atmospheric CO2 and N2. We examined the influence of 6 years of tillage (no-till, NT; chisel plowing, CP; and moldboard plowing, MP), cover crop (hairy vetch (Vicia villosa Roth.) vs. winter weeds), and N fertilization (0, 90, and 180 kg N ha-1) on soil organic C and N concentrations in a Norfolk sandy loam (fine-loamy, siliceous, thermic, Typic Kandiudults) under tomato (Lycopersicon esculentum Mill.) and silage corn (Zea mays L.). In a second experiment, we compared the effects of 7 years of non-legume (rye (Secale cereale L.)) and legume (hairy vetch and crimson clover (Trifolium incarnatum L.)) cover crops and N fertilization (HN (90 kg N ha-1 for tomato and 80 kg N ha-1 for eggplant)) and FN (180 kg N ha-1 for tomato and 160 kg N ha-1 for eggplant)) on soil organic C and N in a Greenville fine sandy loam (fine-loamy, kaolinitic, thermic, Rhodic Kandiudults) under tomato and eggplant (Solanum melogena L.). Both experiments were conducted from 1994 to 2000 in Fort Valley, GA. Carbon concentration in cover crops ranged from 704 kg ha-1 in hairy vetch to 3704 kg ha-1 in rye in 1999 and N concentration ranged from 77 kg ha-1 in rye in 1996 to 299 kg ha-1 in crimson clover in 1997. With or without N fertilization, concentrations of soil organic C and N were greater in NT with hairy vetch than in MP with or without hairy vetch (23.5-24.9 vs. 19.9-21.4 Mg ha-1 and 1.92-2.05 vs. 1.58-1.76 Mg ha-1, respectively). Concentrations of organic C and N were also greater with rye, hairy vetch, crimson clover, and FN than with the control without a cover crop or N fertilization (17.5-18.4 vs. 16.5 Mg ha-1 and 1.33-1.43 vs. 1.31 Mg ha-1, respectively). From 1994 to 1999, concentrations of soil organic C and N decreased by 8-16% in NT and 15-25% in CP and MP. From 1994 to 2000, concentrations of organic C and N decreased by 1% with hairy vetch and crimson clover, 2-6% with HN and FN, and 6-18% with the control. With rye, organic C and N increased by 3-4%. Soil organic C and N concentrations can be conserved and/or maintained by reducing their loss through mineralization and erosion, and by sequestering atmospheric CO2 and N2 in the soil using NT with cover crops and N fertilization. These changes in soil management improved soil quality and productivity. Non-legume (rye) was better than legumes (hairy vetch and crimson clover) and N fertilization in increasing concentrations of soil organic C and N.
  • Authors:
    • Albrecht, A.
    • Sa, J. C. D.
    • Ogle, S. M.
    • Denef, K.
    • Feller, C.
    • Six, J.
  • Source: Agronomie
  • Volume: 22
  • Issue: 7
  • Year: 2002
  • Summary: The long-term stabilization of soil organic matter (SOM) in tropical and temperate regions is mediated by soil biota (e. g. fungi, bacteria, roots and earthworms), soil structure (e. g. aggregation) and their interactions. On average, soil C turnover was twice as fast in tropical compared with temperate regions, but no major differences were observed in SOM quality between the two regions. Probably due to the soil mineralogy dominated by 1:1 clay minerals and oxides in tropical regions, we found a higher aggregate stability, but a lower correlation between C contents and aggregate stability in tropical soils. In addition, a smaller amount of C associated with clay and silt particles was observed in tropical versus temperate soils. In both tropical and temperate soils, a general increase in C levels (approximate to 325 +/- 113 kg C.ha(-1).yr(-1)) was observed under no-tillage compared with conventional tillage. On average, in temperate soils under no-tillage, compared with conventional tillage, CH4 uptake (approximate to0.42 +/- 0.10 kg C-CH4.ha(-1) yr(-1)) increased and N2O emissions increased (approximate to 1.95 +/- 0.45 kg N-N2O.ha(-1).yr(-1)). These increased N2O emissions lead to a negative global warming potential when expressed on a CO2 equivalent basis.
  • Authors:
    • Jellum, E. J.
    • Kuo, S.
  • Source: Agronomy Journal
  • Volume: 94
  • Issue: 3
  • Year: 2002
  • Summary: Removing cover crop top growth in the spring for forage or to prevent incorporation problems is one management option. The effects of this residue management on soil quality and productivity need to be determined. This study, conducted from 1994 to 1998 at Puyallup, WA, determined effects of various winter cover crops and residue management on soil N availability, soil C and N, and corn (Zea mays L.) yield. Included in the study were monocultures of rye (Secale cereale L.), ryegrass (Lolium multiflorum Lam), and vetch (Vicia villosa Roth subsp. villosa) and biculture of vetch and rye or ryegrass. Each year, the cover crops were seeded in the fall and incorporated into, or removed from, the soil in the spring. Average top-growth biomass was higher for the bicultures than for the monocultures. Total N accumulation was generally greatest under vetch, followed by the bicultures, and lowest for the monocultured rye or ryegrass. Whereas removing top growth of monocultured vetch or bicultures depressed presidedress soil NO3-N (Ni), the effect was generally not found for monocultured rye or ryegrass. Corn yields were affected by amounts of Ni and N fertilizer applied (r2 > 0.789), irrespective of cover crop species and residue management. Removing top growth of the cover crops limited residue C input and reduced soil organic C and N after 5 yr. Soil organic C and N accumulation, as well as increasing soil C sequestration to reduce CO2 release into atmosphere, should be considered when deciding which residue management option to choose.
  • Authors:
    • McQuaid, J. B.
    • Lewis, A. C.
    • Johnson, C. L.
    • Maw, S. J.
  • Source: Environmental Monitoring and Assessment
  • Volume: 74
  • Issue: 3
  • Year: 2002
  • Summary: The evolution of NOx from grass and maize silages was measured using chemiluminescence in samples kept in airtight containers, in the silos and in a 750 kg mass removed to a mixer waggon. Measurements were made on the grass and maize silos in two consecutive years. The results show that there is continuous evolution of NOx after silos have been opened and that high concentrations persist in the mass which are rapidly released on agitation at the feed-out. The maximum recorded concentrations of NO and NO2 were 1985 and 152 ppbv respectively. These values are orders of magnitude greater than for rural background levels and exceed the maximum hourly exposure of 50 ppbv for NO2 recommended by the UK expert panel for quality standards.
  • Authors:
    • Mosier, A. R.
  • Source: Nutrient Cycling in Agroecosystems
  • Volume: 63
  • Issue: 2
  • Year: 2002
  • Summary: Human-induced input of fixed nitrogen (N) into the earth biosphere, primarily through combustion of fossil fuels, crop biological N-fixation and N-fertilizer use, has provided many human benefits. These benefits have not come, however, without significant cost. According to data compiled by the Food and Agriculture Organization of the United Nations, synthetic N fertilizer input into global agricultural systems increased from by approximately 430% (~19 to ~82 Tg N) from 1965 to 1998. During this period, global grain production, human population and global fossil fuel consumption increased about 250%, 190% and 240%, respectively. Although fuel consumption increased faster than population growth globally, land used to produce grain decreased from 0.2 to 0.12 ha/person over this 30-yr period. Grain production, however, increased 16%/person. Agricultural production increase has come through the use of new crop varieties which respond to increased N-fertilization, pesticide use, irrigation and mechanization. Even though agricultural production has increased dramatically, fertilizer N use efficiency remains relatively low. Globally fertilizer N use efficiency was approximately 50% in 1996. Since fertilizer N is not used efficiently in most parts of the world, N use in excess of crop potential utilization leads to losses to the environment through volatilization and leaching. These N losses result in N fertilization of pristine terrestrial and aquatic systems through NHx and NOydeposition and contribute to global greenhouse gases through N2O production and local elevated ozone concentrations due to NOx emission. Inefficient use of N and energy is exacerbated by the global inequity of use distribution. Some areas don't have enough while others use too much. Additionally, dietary patterns of food consumption which tend to be more inefficient, i.e. cereal-based diets compared to animal-based diets, are changing in global terms. The resulting increasing inefficiencies in N utilization in food production and in energy use lead to large-scale input of N into down wind and down stream terrestrial and aquatic systems. Increasing N-use-efficiency remains a clear goal by which to maintain food production while decreasing excessive N use and unwanted distribution in the environment.
  • Authors:
    • Schimel, D. S.
    • Peterson, G. A.
    • Mosier, A.
    • Parton, W.
    • Ojima, D.
    • Del Grosso, S.
  • Source: Environmental Pollution
  • Volume: 116
  • Issue: Supplement 1
  • Year: 2002
  • Summary: We present evidence to show that DAYCENT can reliably simulate soil C levels, crop yields, and annual trace gas fluxes for various soils. DAYCENT was applied to compare the net greenhouse gas fluxes for soils under different land uses. To calculate net greenhouse gas flux we accounted for changes in soil organic C, the C equivalents of N2O emissions and CH4 uptake, and the CO2 costs of N fertilizer production. Model results and data show that dryland soils that are depleted of C due to conventional till winter wheat/fallow cropping can store C upon conversion to no till, by reducing the fallow period, or by reversion to native vegetation. However, model results suggest that dryland agricultural soils will still be net sources of greenhouse gases although the magnitude of the source can be significantly reduced and yields can be increased upon conversion to no till annual cropping. (C) 2001 Elsevier Science Ltd. All rights reserved.
  • Authors:
    • Reule, C. A.
    • Peterson, G. A.
    • Halvorson, A. D.
  • Source: Agronomy Journal
  • Volume: 94
  • Issue: 6
  • Year: 2002
  • Summary: Winter wheat (Triticum aestivum L.)-fallow (WF) using conventional stubble mulch tillage (CT) is the predominant production practice in the central Great Plains and has resulted in high erosion potential and decreased soil organic C (SOC) contents. This study, conducted from 1990 through 1994 on a Weld silt loam (Aridic Argiustoll) near Akron, CO, evaluated the effect of WF tillage system with varying degrees of soil disturbance [no-till (NT), reduced till (RT), CT, and bare fallow (BF)] and crop rotation [WF, NT wheat-corn (Zea mays L.)-fallow (WCF), and NT continuous corn (CC)] on winter wheat and corn yields, aboveground residue additions to the soil at harvest, surface residue amounts at planting, and SOC. Neither tillage nor crop rotation affected winter wheat yields, which averaged 2930 kg ha-1. Corn grain yields for the CC (NT) and WCF (NT) rotations averaged 1980 and 3520 kg ha-1, respectively. The WCF (NT) rotation returned 8870 kg ha-1 residue to the soil in each 3-yr cycle, which is 2960 kg ha-1 on an annualized basis. Annualized residue return in WF averaged 2520 kg ha-1, which was 15% less than WCF (NT). Annualized corn residue returned to the soil was 3190 kg ha-1 for the CC (NT) rotation. At wheat planting, surface crop residues varied with year, tillage, and rotation, averaging WCF (NT) (5120 kg ha-1) > WF (NT) (3380 kg ha-1) > WF (RT) (2140 kg ha-1) > WF (CT) (1420 kg ha-1) > WF (BF) (50 kg ha-1). Soil erosion potential was lessened with WCF (NT), CC (NT), and WF (NT) systems because of the large amounts of residue cover. Levels of SOC in descending order in 1994 were CC (NT) [>=] WCF (NT) [>=] WF (NT) = WF (RT) = WF (CT) > WF (BF). Although not statistically significant, the CC (NT) treatment appeared to be accumulating more SOC than any of the rotations that included a fallow period, even more rapidly than WCF (NT), which had a similar amount of annualized C addition. Reduced tillage and intensified cropping increased SOC and reduced soil erosion potential.
  • Authors:
    • Grove, J. H.
    • Dí­az-Zorita, M.
  • Source: Soil & Tillage Research
  • Volume: 66
  • Issue: 2
  • Year: 2002
  • Summary: Surface accumulation of soil organic carbon (SOC) under conservation tillage has significant effects on stratification of other nutrients, on crop productivity and in ameliorating the greenhouse effect via atmospheric CO, sequestration. A measure of SOC stratification relative to deeper soil layers has been proposed as a soil quality index. Our objective was to determine the effects of the duration of tillage practices upon the SOC and extractable P distribution with depth in Maury silt loams (Typic Paleudalfs) at similar levels of corn (Zea mays L.) productivity without P fertilization. Soil samples (0-20.0 cm in 2.5 cm increments) were collected under moldboard tillage (MT), chisel tillage (CT) and no-tillage (NT) and in surrounding tall fescue (Festuca arundinacea L.) sods selected from three tillage experiments (1-2-, 8- and 29-year durations) in Kentucky. SOC stratification was greater under conservation tillage (CT and NT) and sods than under MT. SOC and soil-test-extractable P stratification were positively related. Increasing the duration under NT caused the thickness of C stratification to increase. In NT soils, C stratification ratio (CSR) approached CSR in the nearby long-term sods with time. Conservation tillage rapidly promoted the occurrence of CSR greater than 2 while MT always resulted in values lower than 2. The rapid initial change in CSR suggests characterization of thin soil layers (i.e. 2.5 cm depth increments) is desirable under conservation tillage. (C) 2002 Elsevier Science B.V. All rights reserved.