• Authors:
    • Wilkinson, S. R.
    • Stuedemann, J. A.
    • Franzluebbers, A. J.
  • Source: Soil Science Society of America Journal
  • Volume: 65
  • Issue: 3
  • Year: 2001
  • Summary: Improved forage management impacts on soil organic C and S depth distribution and surface residue accumulation could be large, but detailed temporal data are not available. We evaluated the factorial combination of three levels of N fertilization [inorganic, crimson clover (Trifolium incarnatum L.) cover crop plus inorganic, and broiler litter] and four levels of harvest strategy (unharvested, low grazing pressure, high grazing pressure, and hayed monthly) on soil bulk density, soil organic C, and total S, and surface residue C and S during the first 5 yr of 'Coastal' bermudagrass [Cynodon dactylon (L.) Pers.] management. Soil bulk density of the 0- to 6-cm depth responded very little to management, but across treatments it decreased 0.06 Mg m-3 yr-1 due to increasing soil organic matter with time. Soil organic C did not respond significantly to fertilization strategy during the 5 yr, but total S of the 0- to 6-cm depth was greater under broiler litter than under other fertilization strategies at the end of 3, 4, and 5 yr. Low and high grazing pressure were similar in their effect on soil organic C accumulation, averaging 140 g m-2 yr-1. Most of the net change in soil organic C occurred in the 0- to 2-cm depth. Soil under unharvested and hayed management accumulated organic C at rates less than one-half of those observed under cattle grazing. Cattle grazing shunted C more directly from forage to the soil, which contributed to greater sequestration of soil organic C than with haying or unharvested management.
  • Authors:
    • Kascak, C. A.
    • Fuglie, K. O.
  • Source: Applied Economic Perspectives and Policy
  • Volume: 23
  • Issue: 2
  • Year: 2001
  • Summary: A national sample of U.S. farms is used to estimate the long-term trends in adoption and diffusion of conservation tillage, IPM, and soil fertilizer testing, technologies designed to reduce environmental exteralities from agriculture. Results from a duration model show that diffusion of these technologies has been relatively slow, with long lags in adoption due to differences in land quality, farm size, farmer education, and regional factors.
  • Authors:
    • Wagoner, P.
    • Drinkwater, L. E.
    • Douds, D. D.
    • Galvez, L.
  • Source: Plant and Soil
  • Volume: 228
  • Issue: 2
  • Year: 2001
  • Summary: Low-input agricultural systems that do not rely on fertilizers may be more dependent on vesicular-arbuscular mycorrhizal [VAM] fungi than conventionally managed systems. We studied populations of spores of VAM fungi, mycorrhiza formation and nutrient utilization of maize (Zea mays L.) grown in moldboard plowed, chisel-disked or no-tilled soil under conventional and low-input agricultural systems. Maize shoots and roots were collected at four growth stages. Soils under low-input management had higher VAM fungus spore populations than soils under conventional management. Spore populations and colonization of maize roots by VAM fungi were higher in no-tilled than in moldboard plowed or chisel-disked soil. The inoculum potential of soil collected in the autumn was greater for no-till and chisel-disked soils than for moldboard plowed soils and greater for low-input than conventionally farmed soil. The effects of tillage and farming system on N uptake and utilization varied with growth stage of the maize plants. The effect of farming system on P use efficiency was significant at the vegetative stages only, with higher efficiencies in plants under low-input management. The effect of tillage was consistent through all growth stages, with higher P use efficiencies in plants under moldboard plow and chisel-disk than under no-till. Plants grown in no-tilled soils had the highest shoot P concentrations throughout the experiment. This benefit of enhanced VAM fungus colonization, particularly in the low-input system in the absence of effective weed control and with likely lower soil temperatures, did not translate into enhanced growth and yield.
  • Authors:
    • Letson, D.
    • Lander, C.
    • Kellogg, R.
    • Ribaudo, M.
    • Caswell, M.
    • Gollehon, N.
  • Source: Agriculture Information Bulletin No. (AIB771)
  • Year: 2001
  • Summary: Census of agriculture data were used to estimate manure nutrient production and the capacity of cropland and pastureland to assimilate nutrients. Most farms (78 percent for nitrogen and 69 percent for phosphorus) have adequate land on which it is physically feasible to apply the manure produced onfarm at agronomic rates. (The costs of applying manure at these rates have not been assessed). Even so, manure that is produced on operations that cannot fully apply it to their own land at agronomic rates accounts for 60 percent of the Nation's manure nitrogen and 70 percent of the manure phosphorus. In these cases, most counties with farms that produce "excess" nutrients have adequate crop acres not associated with animal operations, but within the county, on which it is feasible to spread the manure at agronomic rates. However, barriers to moving manure to other farms need to be studied. About 20 percent of the Nation's onfarm excess manure nitrogen is produced in counties that have insufficient cropland for its application at agronomic rates (23 percent for phosphorus). For areas without adequate land, alternatives to local land application--such as energy production--will need to be developed.
  • Authors:
    • Travis, G. R.
    • Larney, F. J.
    • Chang, C.
    • Hao, X.
  • Source: Journal of Environmental Quality
  • Volume: 30
  • Issue: 2
  • Year: 2001
  • Summary: The emission of greenhouse gases (GHG) during feedlot manure composting reduces the agronomic value of the final compost and increases the greenhouse effect A study was conducted to determine whether GHG emissions are affected by composting method. Feedlot cattle manure was composted with two aeration methods-passive (no turning) and active (turned six times). Carbon lost in the forms of CO2 and CH4 was 73.8 and 6.3 kg C Mg-1 manure for the passive aeration treatment and 168.0 and 8.1 kg C Mg-1 manure for the active treatment. The N loss in the form of N2O was 0.11 and 0.19 kg N Mg-1 manure for the passive and active treatments. Fuel consumption to turn and maintain the windrow added a further 4.4 kg C Mg-1 manure for the active aeration treatment. Since CH4 and N2O are 21 and 310 times more harmful than CO2 in their global warming effect, the total GHG emission expressed as CO2-C equivalent was 240.2 and 401.4 kg C Mg-1 manure for passive and active aeration. The lower emission associated with the passive treatment was mainly due to the incomplete decomposition of manure and a lower gas diffusion rate. In addition, turning affected N transformation and transport in the windrow profile, which contributed to higher N2O emissions for the active aeration treatment. Gas diffusion is an important factor controlling GHG emissions. Higher GHG concentrations in compost windrows do not necessarily mean higher production or emission rates.
  • Authors:
    • Williams, S.
    • Schuler, J.
    • Killian, K.
    • Kautza, T.
    • Elliott, T.
    • Easter, M.
    • Cipra, J.
    • Bluhm, G.
    • Paustian, K.
    • Brenner, J.
  • Year: 2001
  • Summary: Land managers have long known the importance of soil organic matter in maintaining the productivity and sustainability of agricultural land. More recently, interest has developed in the potential for using agricultural soils to sequester C and mitigate increasing atmospheric carbon- dioxide by adopting practices that increase standing stocks of carbon in soil organic matter and vegetation. Practices that increase the amount of CO2 taken up by plants (through photosynthesis), which then enter the soil as plant residues, tend to increase soil C stocks. Likewise, management practices that reduce the rate of decay or turnover of organic matter in soils will also tend to increase carbon stocks.
  • Authors:
    • Elliott, E. T.
    • Paustian, K.
    • Conant, R. T.
  • Source: Ecological Applications
  • Volume: 11
  • Issue: 2
  • Year: 2001
  • Summary: Grasslands are heavily relied upon for food and forage production. A key component for sustaining production in grassland ecosystems is the maintenance of soil organic matter (SOM), which can be strongly influenced by management. Many management techniques intended to increase forage production may potentially increase SOM, thus sequestering atmospheric carbon (C). Further, conversion from either cultivation or native vegetation into grassland could also sequester atmospheric carbon. We reviewed studies examining the influence of improved grassland management practices and conversion into grasslands on soil C worldwide to assess the potential for C sequestration. Results from 115 studies containing over 300 data points were analyzed. Management improvements included fertilization (39%), improved grazing management (24%), conversion from cultivation (15%) and native vegetation (15%), sowing of legumes (4%) and grasses (2%), earthworm introduction (1%), and irrigation (1%). Soil C content and concentration increased with improved management in 74% of the studies, and mean soil C increased with all types of improvement. Carbon sequestration rates were highest during the first 40 yr after treatments began and tended to be greatest in the top 10 cm of soil. Impacts were greater in woodland and grassland biomes than in forest, desert, rain forest, or shrubland biomes. Conversion from cultivation, the introduction of earthworms, and irrigation resulted in the largest increases. Rates of C sequestration by type of improvement ranged from 0.11 to 3.04 Mg C·ha-1 yr-1, with a mean of 0.54 Mg C·ha-1·yr-1, and were highly influenced by biome type and climate. We conclude that grasslands can act as a significant carbon sink with the implementation of improved management.
  • Authors:
    • Dabney,S. M.
    • Delgado,J. A.
    • Reeves,D. W.
  • Source: Communications in Soil Science and Plant Analysis
  • Volume: 32
  • Issue: 7-8
  • Year: 2001
  • Summary: This article reviews literature about the impacts of cover crops in cropping systems that affect soil and water quality and presents limited new information to help fill knowledge gaps. Cover crops grow during periods when the soil might otherwise be fallow. While actively growing, cover crops increase solar energy harvest and carbon flux into the soil, providing food for soil macro and microrganisms, while simultaneously increasing evapotranspiration from the soil. Cover crops reduce sediment production from cropland by intercepting the kinetic energy of rainfall and by reducing the amount and velocity of runoff. Cover crops increase soil quality by improving biological, chemical and physical properties including: organic carbon content, cation exchange capacity, aggregate stability, and water infiltrability. Legume cover crops contribute nitrogen (N) to subsequent crops. Other cover crops, especially grasses and brassicas, are better at scavenging residual N before it can leach. Because growth of these scavenging cover crops is usually N limited, growing grass/legume mixtures often increases total carbon inputs without sacrificing N scavenging efficiency. Cover crops are best adapted to warm areas with abundant precipitation. Water use by cover crops can adversely impact yields of subsequent dryland crops in semiarid areas. Similarly, cooler soil temperatures under cover crop residues can retard early growth of subsequent crops grown near the cold end of their range of adaptation. Development of systems that reduce the costs of cover crop establishment and overcome subsequent crop establishment problems will increase cover crop utilization and improve soil and water quality.
  • Authors:
    • Paustian, K. H.
    • Elliott, E. T.
    • Mooney, S.
    • Capalbo, S. M.
    • Antle, J. M.
  • Source: Journal of Agricultural and Resource Economics
  • Volume: 26
  • Issue: 2
  • Year: 2001
  • Summary: This study develops an integrated assessment approach for analysis of the economic potential for carbon sequestration in agricultural soils. By linking a site-specific economic simulation model of agricultural production to a crop ecosystem model, the approach shows the economic efficiency of soil carbon (C) sequestration depends on site-specific opportunity costs of changing production practices and rates of soil C sequestration. An application is made to the dryland grain production systems of the U.S. Northern Plains which illustrates the sensitivity of the sequestration costs to policy design. The marginal cost of soil C ranges from $12 to $500 per metric ton depending upon the type of contract or payment mechanism used, the amount of carbon sequestered, and the site-specific characteristics of the areas.
  • Authors:
    • Ries, R.
    • Merrill, S.
    • Krupinsky, J.
    • Tanaka, D.
  • Source: Proceedings of the 5th International Safflower Conference, Williston, North Dakota and Sidney, Montana, USA, 23-27 July, 2001. Safflower: a multipurpose species with unexploited potential and world adaptability
  • Year: 2001
  • Summary: Safflower is a good crop to include in cereal based cropping systems in the Northern Great Plains of the USA and Canada because it is adapted to semi-arid regions of the world. No-till field research was conducted 11 km southwest of Mandan, ND to determine the influences of previous crop and crop residue on safflower ( Carthamus tintorius) production. Four replicates of safflower were seeded over ten crop residues [canola ( Brassica napus), crambe ( Crambe abysinnica), dry pea ( Pisum sativum L.), dry bean ( Phaseolus vulgaris L.), flax ( Linum usitatissimum L.), safflower, soybean (Glycine max (L.) Merr.), sunflower ( Helianthus annuus L.), wheat ( Triticum aestivum L.), and barley ( Hordeum vulgare L.)] in 1999 and 2000. Averaged over the two years, surface residue cover after seeding safflower was the highest for wheat, barley, and flax (95 to 86%) and the lowest for dry pea, dry bean, and sunflower (82 to 31%). Safflower production after flax, barley, wheat, and dry pea was 220 to 150% greater than safflower production after safflower. The sustainability of diversified cropping systems that include safflower will be determined by the previous crop and crop residues and the crop sequence in which safflower is grown.