• Authors:
    • Marland, G.
    • West, T. O.
  • Source: Biogeochemistry
  • Volume: 63
  • Issue: 1
  • Year: 2003
  • Summary: There is a potential to sequester carbon in soil by changing agricultural management practices. These changes in agricultural management can also result in changes in fossil-fuel use, agricultural inputs, and the carbon emissions associated with fossil fuels and other inputs. Management practices that alter crop yields and land productivity can affect the amount of land used for crop production with further significant implications for both emissions and sequestration potential. Data from a 20-year agricultural experiment were used to analyze carbon sequestration, carbon emissions, crop yield, and land-use change and to estimate the impact that carbon sequestration strategies might have on the net flux of carbon to the atmosphere. Results indicate that if changes in management result in decreased crop yields, the net carbon flux can be greater under the new system, assuming that crop demand remains the same and additional lands are brought into production. Conversely, if increasing crop yields lead to land abandonment, the overall carbon savings from changes in management will be greater than when soil carbon sequestration alone is considered.
  • Authors:
    • Wiemken, A.
    • Boller, T.
    • Mader, P.
    • Ineichen, K.
    • Sieverding, E.
    • Oehl, F.
  • Source: Applied and Environmental Microbiology
  • Volume: 69
  • Issue: 5
  • Year: 2003
  • Summary: The impact of land use intensity on the diversity of arbuscular mycorrhizal fungi (AMF) was investigated at eight sites in the "three-country corner" of France, Germany, and Switzerland. Three sites were low-input, species-rich grasslands. Two sites represented low- to moderate-input farming with a 7-year crop rotation, and three sites represented high-input continuous maize monocropping. Representative soil samples were taken, and the AMF spores present were morphologically identified and counted. The same soil samples also served as inocula for "AMF trap cultures" with Plantago lanceolata, Trifolium pratense, and Lolium perenne. These trap cultures were established in pots in a greenhouse, and AMF root colonization and spore formation were monitored over 8 months. For the field samples, the numbers of AMF spores and species were highest in the grasslands, lower in the low- and moderate-input arable lands, and lowest in the lands with intensive continuous maize monocropping. Some AMF species occurred at all sites ("generalists"); most of them were prevalent in the intensively managed arable lands. Many other species, particularly those forming sporocarps, appeared to be specialists for grasslands. Only a few species were specialized on the arable lands with crop rotation, and only one species was restricted to the high-input maize sites. In the trap culture experiment, the rate of root colonization by AMF was highest with inocula from the permanent grasslands and lowest with those from the high-input monocropping sites. In contrast, AMF spore formation was slowest with the former inocula and fastest with the latter inocula. In conclusion, the increased land use intensity was correlated with a decrease in AMF species richness and with a preferential selection of species that colonized roots slowly but formed spores rapidly.
  • Authors:
    • Searchinger,Timothy D.
    • Sehy,Ulrike
    • Ruser,Reiner
    • Munch,Jean Charles
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 99
  • Issue: 1
  • Year: 2003
  • Summary: Nitrous oxide emissions and selected soil properties in a high and a low yielding area of a maize field were monitored weekly over a 1-year period. In both the high and the low yielding area, N2O emissions from a treatment subject to site-specific N-fertilization were compared to a conventionally fertilized control. Emission peaks were measured following N fertilization, rainfall, harvest, tillage and freeze-thaw cycles from all treatments in conditions favorable for denitrification. Between 80 and 90% of annual emissions were released between April and September. A value of 60% WFPS was identified as a threshold for the induction of elevated N2O emissions (>50 mug N2O-N m(-2) h(-1)). A significant relationship (r(2) = 0.41) between N2O flux rates and WFPS was found when neither soil nitrate contents nor temperature were limiting for microbial denitrification. Mean cumulative N2O emissions from the control treatments in the high yielding area, located in a footslope position and thus receiving lateral water and nutrient supply, more than doubled those from the control treatments in the low yielding area in a shoulder position (8.7 and 3.9 kg N2O-N ha(-1), respectively). Higher average WFPS in the high yielding area was identified as responsible for this difference. The site-specific fertilized treatments in the low yielding area were supplied with 125 kg N fertilizer ha-1 as compared to 150 kg N fertilizer ha(-1) (control treatments). This reduction resulted in 34% less N2O released in roughly 10 months following differentiated fertilization while crop yield remained the same. In the high yielding area, N fertilizer supply in the site-specific fertilized treatment was 175 kg N ha(-1) as compared to 150 kg N ha(-1) in the control. Neither crop yield nor N2O emissions were significantly affected by the different fertilizer rates. (C) 2003 Elsevier Science B.V. All rights reserved.
  • 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:
    • Cotrufo, M. F.
    • Peressotti, A.
    • Six, J.
    • Del Galdo, I.
  • Source: Global Change Biology
  • Volume: 9
  • Issue: 8
  • Year: 2003
  • Summary: Within the framework of the Kyoto Protocol, the potential mitigation of greenhouse gas emissions by terrestrial ecosystems has placed focus on carbon sequestration following afforestation of former arable land. Central to this soil C sequestration are the dynamics of soil organic matter (SOM). In North Eastern Italy, a mixed deciduous forest was planted on continuous maize field soil with a strong C-4 isotopic C signature 20 years ago. In addition, a continuous maize field and a relic of the original permanent grassland were maintained at the site, thus offering the opportunity to compare the impacts on soil C dynamics by conventional agriculture, afforestation and permanent grassland. Soil samples from the afforested, grassland and agricultured systems were separated in three aggregate size classes, and inter- vs. intra-aggregate particulate organic matter was isolated. All fractions were analyzed for their C content and isotopic signature. The distinct (13) C signature of the C derived from maize vegetation allowed the calculation of proportions of old vs. forest-derived C of the physically defined fractions of the afforested soil. Long-term agricultural use significantly decreased soil C content (-48%), in the top 10 cm, but not SOM aggregation, as compared to permanent grassland. After 20 years, afforestation increased the total amount of soil C by 23% and 6% in the 0-10 and in the 10-30 cm depth layer, respectively. Forest-derived carbon contributed 43% and 31% to the total soil C storage in the afforested systems in the 0-10 and 10-30 cm depths, respectively. Furthermore, afforestation resulted in significant sequestration of new C and stabilization of old C in physically protected SOM fractions, associated with microaggregates (53-250 mum) and siltclay (<53 mum).
  • Authors:
    • Hibbard, B. E.
    • McMullen, M. D.
    • Darrah, L. L.
    • Flint-Garcia, S. A.
  • Source: Theoretical and Applied Genetics
  • Volume: 107
  • Issue: 7
  • Year: 2003
  • Summary: Maize (Zea mays L.) stalk lodging is breakage of the stalk at or below the ear, which may result in loss of the ear at harvest. Stalk lodging is often intensified by the stalk tunneling action of the second-generation of the European corn borer (2-ECB) [Ostrinia nubilalis (Hübner)]. Rind penetrometer resistance (RPR) has been used to measure stalk strength and improve stalk lodging resistance, and quantitative trait loci (QTL) have been identified for both RPR and 2-ECB damage. Phenotypic recurrent selection (PS) increases the frequency of favorable alleles over cycles of selection. Several studies have indicated that marker-assisted selection (MAS) is also a potentially valuable selection tool. The objective of this study was to compare the efficiency of PS versus MAS for RPR and 2-ECB. Marker-assisted selection for high and low RPR was effective in the three populations studied. Phenotypic selection for both high and low RPR was more effective than MAS in two of the populations. However, in a third population, MAS for high RPR using QTL effects from the same population was more effective than PS, and using QTL effects from a separate population was just as effective as PS. Marker-assisted selection for resistance and susceptibility to 2-ECB using QTL effects from the same population was effective in increasing susceptibility, but not in increasing resistance. Marker-assisted selection using QTL effects from a separate population was effective in both directions of selection. Thus, MAS was effective in selecting for both resistance and susceptibility to 2-ECB. These results demonstrated that MAS can be an effective selection tool for both RPR and 2-ECB resistance. These results also validate the locations and effects of QTL for RPR and 2-ECB resistance identified in earlier studies.
  • Authors:
    • Shapouri, H.
    • Gauthier, W.
    • Wailes, E.
    • Fritz, J.
    • Dikeman, M.
    • Gallagher, P. W.
  • Source: Environmental and Resource Economics
  • Volume: 24
  • Issue: 4
  • Year: 2003
  • Summary: The components of social costs included in the supply analysis are cash outlays and opportunity costs associated with harvest and alternative residue uses, potential environmental damage that is avoided by excluding unsuitable land, and costs in moving residues from farms to processing plants. Regional estimates account for the growing conditions and crops of the main agricultural areas of the United States. Estimates include the main U. S. field crops with potential for residue harvest: corn, wheat, sorghum, oats, barley, rice and cane sugar. The potential contribution of residues to U. S. energy needs is discussed.
  • 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:
    • Yang, H.
    • Walters, D. T.
    • Dobermann, A.
    • Cassman, K. G.
  • Source: Annual Review of Environment and Resources
  • Volume: 28
  • Issue: 1
  • Year: 2003
  • Summary: Agriculture is a resource-intensive enterprise. The manner in which food production systems utilize resources has a large influence on environmental quality. To evaluate prospects for conserving natural resources while meeting increased demand for cereals, we interpret recent trends and future trajectories in crop yields, land and nitrogen fertilizer use, carbon sequestration, and greenhouse gas emissions to identify key issues and challenges. Based on this assessment, we conclude that avoiding expansion of cultivation into natural ecosystems, increased nitrogen use efficiency, and improved soil quality are pivotal components of a sustainable agriculture that meets human needs and protects natural resources. To achieve this outcome will depend on raising the yield potential and closing existing yield gaps of the major cereal crops to avoid yield stagnation in some of the world's most productive systems. Recent trends suggest, however, that increasing crop yield potential is a formidable scientific challenge that has proven to be an elusive goal.
  • Authors:
    • Shanahan, J. F.
    • Wienhold, B. J.
    • Mortensen, D. A.
    • Johnson, C. K.
    • Doran, J. W.
  • Source: Agronomy Journal
  • Volume: 95
  • Issue: 2
  • Year: 2003
  • Summary: Site-specific management (SSM) can potentially improve both economic and ecological outcomes in agriculture. Effective SSM requires strong and temporally consistent relationships among identified management zones; underlying soil physical, chemical, and biological parameters; and crop yields. In the central Great Plains, a 250-ha dryland experiment was mapped for apparent electrical conductivity (EC a). Eight fields were individually partitioned into four management zones based on equal ranges of deep (EC DP) and shallow (EC SH) EC a (approximately 0-30 and 0-90 cm depths, respectively). Previous experiments documented negative correlations between ECSH and soil properties indicative of productivity. The objectives of this study were to examine EC SH and EC DP relationships with 2 yr of winter wheat ( Triticum aestivum L.) and corn ( Zea mays L.) yields and to consider the potential applications of EC a-based management zones for SSM in a semiarid cropping system. Within-zone wheat yield means were negatively correlated with EC SH ( r=-0.97 to -0.99) and positively correlated with EC DP ( r=0.79-0.97). Within-zone corn yield means showed no consistent relationship with EC SH but positive correlation with EC DP ( r=0.81-0.97). Equal-range and unsupervised classification methods were compared for EC SH; within-zone yield variances declined slightly (0-5%) with the unsupervised approach. Yield response curves relating maximum wheat yields and EC SH revealed a boundary line of maximum yield that decreased with increasing EC SH. In this semiarid system, EC SH-based management zones can be used in SSM of wheat for: (i) soil sampling to assess residual nutrients and soil attributes affecting herbicide efficacy, (ii) yield goal determination, and (iii) prescription maps for metering inputs.