• Authors:
    • Jarvis, S. C.
    • Yamulki, S.
  • Source: Biology and Fertility of Soils
  • Volume: 36
  • Issue: 3
  • Year: 2002
  • Summary: N2O, NO, NO2, CO2 and CH4 fluxes were measured simultaneously from tilled and compacted soil in a factorial design to investigate the effect of management on trace gas emissions. Six treatments in combinations of with and without N application, tillage and compaction were investigated for a period of 3 weeks using the closed-chamber technique (for N2O, CO2 and CH4) and the open-chamber technique (for NO and NO2). Total NO emissions from the tilled plots were 2.4 times greater than from the non-tilled plots, whereas CO2 emissions were 1.8 times greater from the non-tilled plots. Compaction increased the emissions of N2O and CH4 3.5- and 4.4-fold, respectively, compared with emissions from uncompacted plots. The effects of tillage and compaction on the gaseous emissions are discussed in relation to their production, transport and lifetime within the soil. The results showed that the best option for reducing gaseous emission from fertilised soil, with regards to tillage or compaction, would be the least compacted system, regardless of the tillage status as reflected, at least in the short term, by minimal emissions of N2O and CH4 and to some extent those of NO, NO2 and CO2.
  • 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:
    • Leary, M.
    • Roberti, D. A.
    • Medina, J.
    • Eaton, D.
    • Paparian, M.
    • Jones, S. R.
    • Moulton-Patterson, L.
  • Year: 2002
  • Summary: from exec summary: "This project sought to quantify the effect of compost feedstocks (green waste and poultry manure), compost maturity, and soil texture on vegetable crops. All of the field work was conducted in cooperation with commercial vegetable growers in Santa Cruz, Santa Clara, and San Benito Counties. Initially, the intent was to work equally with conventionally and organically farmed crops. However, in the end, the majority of the field trials occurred on conventional farms. Efforts to match similar crops to trials performed on different soil textures (conventional and organic) were largely unsuccessful due to the inevitable complications inherent in on-farm studies."
  • Authors:
    • Sakamoto, K.
    • Inubushi, K.
    • Li, X.
  • Source: Biology and Fertility of Soils
  • Volume: 35
  • Issue: 2
  • Year: 2002
  • Summary: A field experiment was conducted to determine N2O concentrations in the soil profile and emissions as influenced by the application of N fertilizers and manure in a typical Japanese Andisol, which had been under a rotation of oat and carrot for the previous 3 years. The treatments include ammonium sulphate (AS). controlled-re lease fertilizer (CRF) and cattle manure (CM) in addition to a control; all the fertilizers were applied either at 150 kg N ha(-1) or 300 kg N ha(-1) at the time of sowing carrot. NO emissions from the soil surface were measured with closed-chamber techniques. while N2O concentrations in the soil profile were measured using stainless steel sampling probes inserted into the soil at depths of 10, 20. 40, 60, 80 and 100 cm. Moreover. soil water potential, soil temperature and rainfall data were also recorded. The results indicated that N2O concentrations in the soil profile were always greater than in the atmosphere, ranging from 0.36 mul N2O-N 1(-1) to 5.3 mul N2O-N l(-1). The relatively large accumulation of N2O in the lower profiles may be a significant source for N2O flux. Taking the changes of soil mineral N into consideration, most emissions of NO were probably produced from nitrification. The accumulation of NO in the soil profile and emissions to the atmosphere were differently influenced by the amendments of N fertilizers and manure. being consistently higher in CRF than in CM and AS treatments at the corresponding application rates, but no significant difference existed with respect to the various N sources.
  • 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:
    • 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:
    • Follett, R. F.
    • Paustian, K.
    • Sperow, M.
    • Eve, M. D.
  • Source: Environmental Pollution
  • Volume: 116
  • Issue: 3
  • Year: 2002
  • Summary: Average annual net change in soil carbon stocks under past and current management is needed as part of national reporting of greenhouse gas emissions and to evaluate the potential for soils as sinks to mitigate increasing atmospheric CO2. We estimated net soil C stock changes for US agricultural soils during the period from 1982 to 1997 using the IPCC (Intergovernmental Panel on Climate Change) method for greenhouse gas inventories. Land use data from the NRI (National Resources Inventory; USDA-NRCS) were used as input along with ancillary data sets on climate, soils, and agricultural management. Our results show that, overall, changes in land use and agricultural management have resulted in a net gain of 21.2 MMT C year-1 in US agricultural soils during this period. Cropped lands account for 15.1 MMT C year-1, while grazing land soil C increased 6.1 MMT C year-1. The land use and management changes that have contributed the most to increasing soil C during this period are (1) adoption of conservation tillage practices on cropland, (2) enrollment of cropland in the Conservation Reserve Program, and (3) cropping intensification that has resulted in reduced use of bare fallow.
  • Authors:
    • Franzluebbers, A. J.
  • Source: Soil & Tillage Research
  • Volume: 66
  • Issue: 2
  • Year: 2002
  • Summary: Soil quality is a concept based on the premise that management can deteriorate, stabilize, or improve soil ecosystem functions. It is hypothesized that the degree of stratification of soil organic C and N pools with soil depth, expressed as a ratio, could indicate soil quality or soil ecosystem functioning, because surface organic matter is essential to erosion control, water infiltration, and conservation of nutrients. Stratification ratios allow a wide diversity of soils to be compared on the same assessment scale because of an internal normalization procedure that accounts for inherent soil differences. Stratification ratios of soil organic C were 1.1, 1.2 and 1.9 under conventional tillage (CT) and 3.4, 2.0 and 2.1 under no tillage (NT) in Georgia, Texas, and Alberta/British Columbia, respectively. The difference in stratification ratio between conventional and NT within an environment was inversely proportional to the standing stock of soil organic C to a depth of 15-20 cm across environments. Greater stratification of soil C and N pools with the adoption of conservation tillage under inherently low soil organic matter conditions (i.e., warmer climatic regime or coarse-textured soil) suggests that standing stock of soil organic matter alone is a poor indication of soil quality. Stratification of biologically active soil C and N pools (i.e., soil microbial biomass and potential activity) were equally or more sensitive to tillage, cropping intensity, and soil textural variables than stratification of total C and N. High stratification ratios of soil C and N pools could be good indicators of dynamic soil quality, independent of soil type and climatic regime, because ratios >2 would be uncommon under degraded conditions. Published by Elsevier Science B.V.
  • Authors:
    • Jackson, R. B.
    • Maherali, H.
    • Anderson, L. J.
    • Johnson, H. B.
    • Polley, H. W.
    • Gill, R. A.
  • Source: Nature
  • Volume: 417
  • Issue: 6886
  • Year: 2002
  • Summary: Carbon sequestration in soil organic matter may moderate increases in atmospheric CO2 concentrations (C-a) as C-a increases to more than 500 mumol mol(-1) this century from interglacial levels of less than 200 mumol mol(-1) (refs 1- 6). However, such carbon storage depends on feedbacks between plant responses to Ca and nutrient availability(7,8). Here we present evidence that soil carbon storage and nitrogen cycling in a grassland ecosystem are much more responsive to increases in past Ca than to those forecast for the coming century. Along a continuous gradient of 200 to 550 mumol mol(-1) (refs 9, 10), increased C-a promoted higher photosynthetic rates and altered plant tissue chemistry. Soil carbon was lost at subambient C-a, but was unchanged at elevated C-a where losses of old soil carbon offset increases in new carbon. Along the experimental gradient in C-a there was a nonlinear, threefold decrease in nitrogen availability. The differences in sensitivity of carbon storage to historical and future C-a and increased nutrient limitation suggest that the passive sequestration of carbon in soils may have been important historically, but the ability of soils to continue as sinks is limited.