• Authors:
    • Hrstkova, P.
    • Chloupek, O.
    • Schweigert, P.
  • Source: Field Crops Research
  • Volume: 85
  • Issue: 2-3
  • Year: 2004
  • Summary: Officially published data for the Czech Republic (CR) from 1920 to 2000 and for selected European countries (mostly from 1960 to 2000) were analysed. In the last 40 years, the yield of the five main crops was comparable with European Union (EU) for wheat, barley and rape, but lower for potato and sugar beet. The fastest yield growth was found for flax (2.15% per year), maize and wheat (1.61 and 1.53%), while growth was slower for hops and root crops and slowest for grassland hay (0.22%). The highest yield variation caused by individual years was for wine grapes (32.5%), poppy, edible legumes and flax (18.5-18.3%), while the lowest level of variation was for cereals, i.e. oats, barley, wheat, rye and hay from arable land (9.7-12.0%). For many crops, yield variation decreased over time. The most adaptable crops, whose yield increased most in fertile years, were flax, wheat, edible legumes, maize, rape and barley (regression coefficient of 1.76-1.24), while the lowest level of adaptability was shown by hops, sugar beet, hay from grassland and poppy (0.68-0.14). The higher the level of adaptability the higher the yield growth over the 75 years analysed. The differences in yield of the most commonly grown crops between the EU and the CR can be explained by the different levels of adaptability of the crops in the two regions. Of the five most commonly grown CR crops, wheat was the most adapted crop in 7 of the 10 European countries studied (without regard to other countries), and sugar beet was the least adapted in 6 countries, Within the 10 countries analysed (without regard for the adaptability of the crop in particular countries) wheat, rape and sugar beet were most adaptable in Spain; barley was most adaptable in Italy; and potato was most adaptable in Hungary. The crops in other countries showed more stability across years. Yields of these five crops in the 10 countries were correlated to each other, with only the yield of potato and sugar beet in the former Soviet Union and that of rape in United Kingdom not being influenced by general factors affecting other countries. The higher the yield of sugar beet in a country of the 10 evaluated, the higher was its adaptability in that country (r = 0.717*). Crop diversity in the CR decreased significantly over the period. Each year the percentage of the three most commonly grown crops increased by 0.41% (percentage of the five most commonly grown crops by 0.14%). The percentage of particular cereals on arable land (wheat 23.0%, barley 17.1%, rye 5.1%, oat 5.2%) and their yields were related to their response to fertilisation over the last 40 years. The average temperature increased significantly during the last 50 years, on average by 0.021 degreesC each year, but in the last 10 years by 0.087 degreesC each year. These climate changes were favourable for the most of the commonly grown crops (wheat, barley, rape, sugar beet, rye, maize and legumes), since the crops gave higher yields in warmer years that were accompanied by more hours of sunshine. The other crops were indifferent to climate changes. Fertilisers have been used in the CR to a greater extent since 1946/1947 (22 kg of nutrients per hectare) with maximum usage in 1985/1986 (273 kg ha(-1), including 105 kg N, 86 kg P and 82 kg K). The consumption rate of nutrients increased by 2.91 kg ha(-1) annually from 1918 to 2000, as found by the regression coefficient. One kilogram of nutrients (N + P + K) increased yields of cereals by 6.7-10.1 kg ha(-1) of grain, rape by 5.2, root crops by 26.1-37.8, hops and wine grapes by 2.0-2.6 kg ha(-1). Yield growth due to fertilisation varied from 9.1% (hay from arable land) up to 84.1% (hops) of the entire growth (=100%). The percentage in grain crops (cereals, grain legumes and rape) was 54.3 (maize)-69.8% (barley), and 63.3% on average in the eight crops. It was also similar in root crops, but only 13.4% for wine grape yields. The highest yield growth per 1 kg of nutrients from fertilisers was found in wheat, rape, sugar beet and potato at the level of application of 70-120 kg ha(-1) nutrients. The efficiency of applied nutrients was higher in years with average precipitation than in years with over-average precipitation, and much higher than in dry years. The yield growth for 1 kg nutrients in all grain crops was lowest in years with average temperature, and highest in most of the crops in years with low mean annual temperature. The estimated balance of nitrogen (applied nitrogen in fertilisers minus nitrogen utilised in harvested crops) was negative during 1947-1960, positive during 1970-1990, and slightly negative again from 1995 to 2000. The surplus of applied mineral nitrogen reached in the years of positive balance was 18.5-36.8 kg ha(-1). The impact of the weather was less than the influence of fertilisation. The dynamics of yield in Germany was studied by multiple regression analysis from 1946 to 1999. The annual increase of wheat yield was 50 kg ha(-1), and per kilogram of N-fertiliser by 10 kg ha(-1). The increase per year in the multiple regression was only 73% of the increase in the simple regression. Therefore, 27% of the increase was related to N-fertilisation (and also to other inputs). The corresponding figures were 25% for rye, 30% for rape, 36% for oats, 47% for potato and 66% for flax. No significant influence of N-fertiliser could be found for other crops. It is concluded that those crops exhibiting the highest increase in yield in the CR over the 75 years investigated were also the most adaptable to inter-annual variability in weather, cultivars grown and to cultivation technologies used. The least adapted crop across 10 European countries was sugar beet, for which adaptability was correlated to yield in the particular country. Among the factors studied, the high response to fertilisation was an important factor in the adaptability of particular crops over the 75 years studied. The adaptability of crops to inter-annual variation is therefore a very important trait for consideration by plant breeders. (C) 2003 Elsevier B.V. All rights reserved.
  • Authors:
    • Porter, G. A.
    • Griffin, T. S.
  • Source: Biology and Fertility of Soils
  • Volume: 39
  • Issue: 5
  • Year: 2004
  • Summary: Information is needed on the ability of different crop management factors to maintain or increase soil C and N pools, especially in intensively tilled short crop rotations. Soil samples from field experiments in Maine were used to assess the effect of cover crop, green manure (GM) crop, and intermittent or annual amendment on soil C and N pools. These field experiments, of 6-13 years' duration, were all characterized by a 2-year rotation with either sweet corn (Zea mays L.) or potato (Solanum tuberosum L.), and primary tillage each year. Total, particulate organic matter (POM), and soil microbial biomass (SMB)-C and -N pools were assessed for each experiment. Total C and N stocks were not affected by red clover (Trifolium pratense L.) cover crop or legume GM, but were increased by 25-53% via a single application of papermill sludge or an annual manure and/or compost amendment. With the exception of continuous potato production which dramatically reduced the SMB-C and SMB-N concentration, SMB-C and -N were minimally affected by changes in cropping sequence, but were quite sensitive to amendments, even those that were primarily C. POM-C and -N, associated with the coarse mineral fraction (53-2,000 mum), were more responsive to management factors compared to total C and N in soil. The change in soil C fractions was a linear function of increasing C supply, across all experiments and treatments. Within these intensively tilled, 2-year crop rotations, substantial C and N inputs from amendments are needed to significantly alter soil C and N pools, although cropping sequence changes can influence more labile pools responsible for nutrient cycling.
  • Authors:
    • Laslo, J. J.
    • Meers, S.
    • Hall, L. M.
    • Beckie, H. J.
    • Stevenson, F. C.
  • Source: Weed Technology
  • Volume: 18
  • Issue: 3
  • Year: 2004
  • Summary: A 3-yr study was conducted in Wheatland County, Alberta to determine if agronomic practices of growers influenced the occurrence of herbicide resistance in wild oat. Wild oat seeds were collected in 33 fields in 1997 and in 31 fields in each of 1998 and 1999 (one field per grower). Seedlings were screened for resistance to two acetyl-CoA carboxylase (ACCase) inhibitors, imazamethabenz, an acetolactate synthase (ALS) inhibitor, and triallate, a thiocarbamate herbicide. A questionnaire on herbicide resistance awareness and management practices was completed by each grower. Both ACCase and ALS inhibitor resistance in wild oat were linked to a lack of crop rotation diversity. In addition, ALS inhibitor-resistant wild oat was associated with conservation-tillage systems and recent use of herbicides with that mode of action. Results of this study suggest that timely tillage and inclusion of fall-seeded and perennial forage crops in rotations will effectively slow the selection of resistance in this grass species.
  • 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:
    • Wu, J. J.
    • Plantinga, A. J.
  • Source: Land Economics
  • Volume: 79
  • Issue: 1
  • Year: 2003
  • Summary: Besides climate change mitigation, policies encouraging the conversion of agricultural land to forest may generate additional environmental benefits. We estimate the reductions in agricultural externalities (soil erosion, nitrogen, and atrazine pollution) from an afforestation program in Wisconsin. Existing benefits estimates are used to quantify the value of reduced soil erosion and some benefits from enhanced wildlife habitat. These values are the same order of magnitude as the costs of the carbon sequestration policy, indicating that the co-benefits of forest carbon sinks are an important factor for countries to consider in designing a portfolio of climate mitigation strategies.
  • 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:
    • Paustian, K.
    • Eve, M.
    • Sperow, M.
  • Source: Climatic Change
  • Volume: 57
  • Issue: 3
  • Year: 2003
  • Summary: Soil carbon sequestration has been suggested as a means to help mitigate atmospheric CO2 increases, however there is limited knowledge aboutthe magnitude of the mitigation potential. Field studies across the U.S. provide information on soil C stock changes that result from changes in agricultural management. However, data from such studies are not readily extrapolated to changes at a national scale because soils, climate, and management regimes vary locally and regionally. We used a modified version of the Intergovernmental Panel on Climate Change (IPCC) soil organic C inventory method, together with the National Resources Inventory (NRI) and other data, to estimate agricultural soil C sequestration potential in the conterminous U.S. The IPCC method estimates soil C stock changes associated with changes in land use and/or land management practices. In the U.S., the NRI provides a detailed record of land use and management activities on agricultural land that can be used to implement the IPCC method. We analyzed potential soil C storage from increased adoption of no-till, decreased fallow operations, conversion of highly erodible land to grassland, and increased use of cover crops in annual cropping systems. The results represent potentials that do not explicitly consider the economic feasibility of proposed agricultural production changes, but provide an indication of the biophysical potential of soil C sequestration as a guide to policy makers. Our analysis suggests that U.S. cropland soils have the potential to increase sequestered soil C by an additional 60–70 Tg (1012g) C yr-1, over present rates of 17 Tg C yr-1 (estimated using the IPCC method), with widespread adoption of soil C sequestering management practices. Adoption of no-till on all currently annually cropped area (129 Mha) would increase soil C sequestration by 47 Tg C yr-1. Alternatively, use of no-till on 50% of annual cropland, with reduced tillage practices on the other 50%, would sequester less – about 37 Tg C yr-1. Elimination of summer fallow practices and conversion of highly erodible cropland to perennial grass cover could sequester around 20 and 28 Tg C yr-1, respectively. The soil C sequestration potential from including a winter cover crop on annual cropping systems was estimated at 40 Tg C yr-1. All rates were estimated for a fifteen-year projection period, and annual rates of soil C accumulations would be expected to decrease substantially over longer time periods. The total sequestration potential we have estimated for the projection period (83 Tg C yr-1) represents about 5% of 1999 total U.S. CO2 emissions or nearly double estimated CO2 emissions from agricultural production (43 Tg C yr-1). For purposes of stabilizing or reducing CO2 emissions, e.g., by 7% of 1990 levels asoriginally called for in the Kyoto Protocol, total potential soil C sequestration would represent 15% of that reduction level from projected 2008 emissions (2008 total greenhouse gas emissions less 93% of 1990 greenhouse gasemissions). Thus, our analysis suggests that agricultural soil C sequestration could play a meaningful, but not predominant, role in helping mitigate greenhouse gas increases.
  • Authors:
    • Beauchamp, E. G.
    • Tenuta, M.
  • Source: Canadian Journal of Soil Science
  • Volume: 83
  • Issue: 5
  • Year: 2003
  • Summary: One field and two laboratory experiments were conducted to determine the relative magnitude and pattern of N2O production from several granular N fertilizers including urea, ammonium nitrate, calcium nitrate, ammonium sulfate and, in a laboratory experiment, monoammonium and diammonium phosphates. Several parameters, in particular soil water content, were studied for their roles in N2O production with these fertilizers. The field experiment was conducted at the Elora Research Station (20 km north of Guelph) on Conestoga silt loam during July on a site previously cropped to barley. Three methods were employed to assess N2O production following N fertilizer treatments in the field experiment, viz., soil cover, soil core and profile distribution. The data with each method revealed that incorporated urea produced the greatest quantity of N2O especially in the first few days following application. Shortly after urea application and incorporation (10 cm), N2O was detected at a depth of 50 cm indicating gas produced in the tilled layer was transported to lower depths. Data obtained with the intact core method showed that nitrification preceeded denitrification as the source of N2O produced during a wetting event as air-filled porosity decreased from 65% to less than 50%, respectively. The laboratory experiments showed that under aerobic conditions N2O production was generally greater with urea than the other N fertilizers. The greater production of N2O with urea was associated with NO2-accumulation. In the second laboratory experiment, saturating the soil following 14 d of aerobic incubation showed enhanced N2O production with ammonium phosphate fertilizers. Our findings indicate refinement of methods to predict N2O emissions based on N fertilizer source use and moisture can reduce uncertainties in national estimates of N2O emissions from agricultural soils.
  • Authors:
    • Angers, D. A.
    • Gregorich, E. G.
    • VandenBygaart, A. J.
  • Source: Canadian Journal of Soil Science
  • Volume: 83
  • Issue: 4
  • Year: 2003
  • Summary: To fulfill commitments under the Kyoto Protocol, Canada is required to provide verifiable estimates and uncertainties for soil organic carbon (SOC) stocks, and for changes in those stocks over time. Estimates and uncertainties for agricultural soils can be derived from long-term studies that have measured differences in SOC between different management practices. We compiled published data from long-term studies in Canada to assess the effect of agricultural management on SOC. A total of 62 studies were compiled, in which the difference in SOC was determined for conversion from native land to cropland, and for different tillage, crop rotation and fertilizer management practices. There was a loss of 24 ± 6% of the SOC after native land was converted to agricultural land. No-till (NT) increased the storage of SOC in western Canada by 2.9 ± 1.3 Mg ha–1; however, in eastern Canada conversion to NT did not increase SOC. In general, the potential to store SOC when NT was adopted decreased with increasing background levels of SOC. Using no-tillage, reducing summer fallow, including hay in rotation with wheat (Triticum aestivum L.), plowing green manures into the soil, and applying N and organic fertilizers were the practices that tended to show the most consistent increases in SOC storage. By relating treatment SOC levels to those in the control treatments, SOC stock change factors and their levels of uncertainty were derived for use in empirical models, such as the United Nations Intergovernmental Panel on Climate Change (IPCC) Guidelines model for C stock changes. However, we must be careful when attempting to extrapolate research plot data to farmers fields since the history of soil and crop management has a significant influence on existing and future SOC stocks.
  • Authors:
    • Lal, R.
  • Source: Critical Reviews in Plant Sciences
  • Volume: 22
  • Issue: 2
  • Year: 2003
  • Summary: An increase in atmospheric concentration of CO2 from 280 ppmv in 1750 to 367 ppmv in 1999 is attributed to emissions from fossil fuel combustion estimated at 270 +/- 30 Pg C and land use change at 136 +/- 55 Pg. Of the emissions from land use change, 78 +/- 12 Pg is estimated from depletion of soil organic carbon (SOC) pool. Most agricultural soils have lost 50 to 70% of their original SOC pool, and the depletion is exacerbated by further soil degradation and desertification. The restoration of degraded soils, conversion of agriculturally marginal lands to appropriate land use, and the adoption of recommended management practices on agricultural soils can reverse degradative trends and lead to SOC sequestration. Technological options for SOC sequestration on agricultural soils include adoption of conservation tillage, use of manures, and compost as per integrated nutrient management and precision fanning strategies, conversion of monoculture to complex diverse cropping systems, meadow-based rotations and winter cover crops, and establishing perennial vegetation on contours and steep slopes. The global potential of SOC sequestration and restoration of degraded/desertified soils is estimated at 0.6 to 1.2 Pg C/y for about 50 years with a cumulative sink capacity of 30 to 60 Pg. The SOC sequestration is a cost-effective strategy of mitigating the climate change during the first 2 to 3 decades of the 21(st) century. While improving soil quality, biomass productivity and enhanced environment quality, the strategy of SOC sequestration also buys us time during which the non-carbon fuel alternatives can take effect.