• Authors:
    • Liska, A. J.
    • Archer, D.
    • Karlen, D. L.
    • Meyer, S.
  • Source: Council for Agricultural Science and Technology
  • Issue: 48
  • Year: 2012
  • Summary: Quantifying energy issues associated with agricultural systems, even for a two-crop corn ( Zea mays L.) and soybean ( Glycine max [L.] Merr.) rotation, is not a simple task. It becomes even more complicated if the goal is to include all aspects of sustainability (i.e., economic, environmental, and social). This Issue Paper examines energy issues associated with and affecting corn/soybean rotations by first defining the size of the system from both a U.S. and global perspective and then establishing boundaries based on the Farm Bill definition of sustainability. This structured approach is essential to help quantify energy issues within corn/soybean systems that are themselves best described as "systems of systems" or even "systems within ecosystems" because of their complex linkages to global food, feed, and fuel production. Two key economic challenges at the field and farm scale for decreasing energy use are (1) overcoming adoption barriers that currently limit implementation of energy-conserving production practices and (2) demonstrating the viability of sustainable bioenergy feedstock, production as part of a landscape management plan focused not only on corn/soybean production but on all aspects of soil, water, and air resource management. It is also important to look beyond direct energy consumption to address the complex economics affecting energy issues associated with corn/soybean systems. To help address the complex energy issue, life cycle assessment is used as a tool to evaluate the impact of what many characterize as a simple production system. This approach demonstrates the importance of having accurate greenhouse gas and soil organic carbon information for these analyses to be meaningful. Traditional and emerging market and policy forces affecting energy issues within corn/soybean systems are examined to project the effects of increasing bioenergy demand associated with the Energy Independence and Security Act of 2007. Uncertainty with regard to biofuel policy is a major factor affecting energy issues in all aspects of agriculture. This uncertainty affects investments in biofuel production and energy demand, which together influence commodity prices, price volatility for food and feed, and agricultural energy decisions. The authors conclude by offering an approach, including decreased or more efficient energy use, that can enhance all aspects of sustainability. Their strategy, defined as a "landscape vision," is suggested as an agricultural system approach that could meet increasing global demand for food, feed, fiber, and fuel in a truly sustainable manner.
  • Authors:
    • Schwarz, G.
    • Noleppa, S.
    • Kern, M.
  • Source: Pest Management Science
  • Volume: 68
  • Issue: 11
  • Year: 2012
  • Summary: BACKGROUND: A major global challenge is to provide agricultural production systems that are able to sustain growing demands for food, feed, fibre and renewable raw materials without exacerbating climate change. Detailed and reliable data on the CO2 balance of different agricultural management activities and inputs as a basis to quantify carbon footprints of agriculture are still lacking. This study aims to fill this gap further by quantifying the net balance of emitted and assimilated CO2 due to the application of crop protection treatments on the farm, and by assessing their partial contribution to GHG emissions and mitigation in agriculture. The study focuses on key agricultural crops including wheat, corn, oilseeds and sugar crops. RESULTS: The final CO2 balance, considering GHG emissions due to on-farm CPP treatment in comparison with CO2 storage in additional biomass, CO2 protected with respect to agrotechnical inputs and land inputs and CO2 saved with respect to associated global land use changes, is positive and may reach multiples of up to nearly 2000. CONCLUSION: The results highlight the importance of the positive yield effects of the CPP programme applications on the farm, resulting in additional assimilated biomass at the farm level and less land use changes at the global level, and thus lower pressure on environmentally important indicators of overall agricultural sustainability.
  • Authors:
    • Kim, D.
  • Source: Agroforestry Systems
  • Volume: 86
  • Issue: 2
  • Year: 2012
  • Summary: Nitrogen (N)-fixing tree and crop intercropping systems can be a sustainable agricultural practice in sub-Saharan Africa and can also contribute to resolving climate change through enhancing soil carbon (C) sequestration. A study conducted by Makumba et al. (Agric Ecosyst Environ 118:237-243, 2007) on the N-fixing tree gliricidia and maize intercropping system in southern Malawi provides a rare dataset of both sequestered soil C and C loss as soil carbon dioxide (CO2) emissions. However, no soil C gain and loss estimates were made so the study failed to show the net gain of soil C. Also absent from this study was potential benefit or negative impact related to the other greenhouse gas, nitrous oxide (N2O) and methane (CH4) emissions from the intercropping system. Using the data provided in Makumba et al. (Agric Ecosyst Environ 118:237-243, 2007) a C loss as soil CO2 emissions (51.2 +/- A 0.4 Mg C ha(-1)) was estimated, amounting to 67.4% of the sequestered soil C (76 +/- A 8.6 Mg C ha(-1) in 0-2 m soil depth) for the first 7 years in the intercropping system. An annual net gain of soil C of 3.5 Mg C ha(-1) year(-1) was estimated from soil C sequestered and lost. Inclusion of the potential for N2O mitigation [0.12-1.97 kg N2O-N ha(-1) year(-1), 0.036-0.59 Mg CO2 equivalents (eq.) ha(-1) year(-1)] within this intercropping system mitigation as CO2 eq. basis was estimated to be 3.5-4.1 Mg CO2 eq. ha(-1) year(-1). These results suggest that reducing N2O emission can significantly increase the overall mitigation benefit from the intercropping system. However, significant uncertainties are associated with estimating the effect of intercropping on soil N2O and CH4 emissions. These results stress the importance of including consideration of quantifying soil CO2, N2O and CH4 emissions when quantifying the C sequestration potential in intercropping system.
  • Authors:
    • De Figueiredo, E. B.
    • La Scala Junior, N.
    • Panosso, A. R.
  • Source: Brazilian Journal of Biology
  • Volume: 72
  • Issue: 3
  • Year: 2012
  • Summary: Agricultural areas deal with enormous CO2 intake fluxes offering an opportunity for greenhouse effect mitigation. In this work we studied the potential of soil carbon sequestration due to the management conversion in major agricultural activities in Brazil. Data from several studies indicate that in soybean/maize, and related rotation systems, a significant soil carbon sequestration was observed over the year of conversion from conventional to no-till practices, with a mean rate of 0.41 Mg C ha(-1) year(-1). The same effect was observed in sugarcane fields, but with a much higher accumulation of carbon in soil stocks, when sugarcane fields are converted from burned to mechanised based harvest, where large amounts of sugarcane residues remain on the soil surface (1.8 Mg C ha(-1) year(-1)). The higher sequestration potential of sugarcane crops, when compared to the others, has a direct relation to the primary production of this crop. Nevertheless, much of this mitigation potential of soil carbon accumulation in sugarcane fields is lost once areas are reformed, or intensive tillage is applied. Pasture lands have shown soil carbon depletion once natural areas are converted to livestock use, while integration of those areas with agriculture use has shown an improvement in soil carbon stocks. Those works have shown that the main crop systems of Brazil have a huge mitigation potential, especially in soil carbon form, being an opportunity for future mitigation strategies.
  • Authors:
    • van Kessel, C.
    • Pittelkow, C.
    • Adviento-Borbe, M. A.
    • van Groenigen,K. J.
    • Linquist, B.
  • Source: Global Change Biology
  • Volume: 18
  • Issue: 1
  • Year: 2012
  • Summary: Agricultural greenhouse gas (GHG) emissions contribute approximately 12% to total global anthropogenic GHG emissions. Cereals (rice, wheat, and maize) are the largest source of human calories, and it is estimated that world cereal production must increase by 1.3% annually to 2025 to meet growing demand. Sustainable intensification of cereal production systems will require maintaining high yields while reducing environmental costs. We conducted a meta-analysis (57 published studies consisting of 62 study sites and 328 observations) to test the hypothesis that the global warming potential (GWP) of CH4 and N2O emissions from rice, wheat, and maize, when expressed per ton of grain (yield-scaled GWP), is similar, and that the lowest value for each cereal is achieved at near optimal yields. Results show that the GWP of CH4 and N2O emissions from rice (3757 kg CO2 eq ha-1 season-1) was higher than wheat (662 kg CO2 eq ha-1 season-1) and maize (1399 kg CO2 eq ha-1 season-1). The yield-scaled GWP of rice was about four times higher (657 kg CO2 eq Mg-1) than wheat (166 kg CO2 eq Mg-1) and maize (185 kg CO2 eq Mg-1). Across cereals, the lowest yield-scaled GWP values were achieved at 92% of maximal yield and were about twice as high for rice (279 kg CO2 eq Mg-1) than wheat (102 kg CO2 eq Mg-1) or maize (140 kg CO2 eq Mg-1), suggesting greater mitigation opportunities for rice systems. In rice, wheat and maize, 0.68%, 1.21%, and 1.06% of N applied was emitted as N2O, respectively. In rice systems, there was no correlation between CH4 emissions and N rate. In addition, when evaluating issues related to food security and environmental sustainability, other factors including cultural significance, the provisioning of ecosystem services, and human health and well-being must also be considered.
  • Authors:
    • Williams, S.
    • Easter, M.
    • Paustian, K.
    • Lokupitiya, E.
    • Andren, O.
    • Katterer, T.
  • Source: Biogeochemistry
  • Volume: 107
  • Issue: 1-3
  • Year: 2012
  • Summary: Carbon (C) added to soil as organic matter in crop residues and carbon emitted to the atmosphere as CO(2) in soil respiration are key determinants of the C balance in cropland ecosystems. We used complete and comprehensive county-level yields and area data to estimate and analyze the spatial and temporal variability of regional and national scale residue C inputs, net primary productivity (NPP), and C stocks in US croplands from 1982 to 1997. Annual residue C inputs were highest in the North Central and Central and Northern Plains regions that comprise similar to 70% of US cropland. Average residue C inputs ranged from 1.8 (Delta States) to 3.0 (North Central region) Mg C ha(-1) year(-1), and average NPP ranged from 3.1 (Delta States) to 5.4 (Far West region) Mg C ha(-1) year(-1). Residue C inputs tended to be inversely proportional to the mean growing season temperature. A quadratic relationship incorporating the growing season mean temperature and total precipitation closely predicted the variation in residue C inputs in the North Central region and Central and Northern Plains. We analyzed the soil C balance using the crop residue database and the Introductory Carbon Balance regional Model (ICBMr). Soil C stocks (0-20 cm) on permanent cropland ranged between 3.07 and 3.1 Pg during the study period, with an average increase of similar to 4 Tg C year(-1), during the 1990s. Interannual variability in soil C stocks ranged from 0 to 20 Tg C (across a mean C stock of 3.08 +/- A 0.01 Pg) during the study period; interannual variability in residue C inputs varied between 1 and 43 Tg C (across a mean input of 220 +/- A 19 Tg). Such interannual variation has implications for national estimates of CO(2) emissions from cropland soils needed for implementation of greenhouse gas (GHG) mitigation strategies involving agriculture.
  • Authors:
    • Morrison, M. J.
    • Biswas, D. K.
    • Liang, B. C.
    • Ma, B. L.
    • McLaughlin, N. B.
  • Source: Nutrient Cycling in Agroecosystems
  • Volume: 94
  • Issue: 1
  • Year: 2012
  • Summary: Studies on the sustainability of crop production systems should consider both the carbon (C) footprint and the crop yield. Knowledge is urgently needed to estimate the C cost of maize (Zea mays L.) production in a continuous monoculture or in rotation with a leguminous crop, the popular rotation system in North America. In this study, we used a 19-year field experiment with maize under different levels of synthetic N treatments in a continuous culture or rotation with forage legume (Alfalfa or red clover; Medicago sativa L./Trifolium pratense L.) or soybean (Glycine max L. Merr) to assess the sustainability of maize production systems by estimating total greenhouse gas (GHG) emissions (kg CO2 eq ha(-1)) and the equivalent C cost of yield or C footprint (kg CO2 eq kg(-1) grain). High N application increased both total GHG emissions and the C footprint across all the rotation systems. Compared to continuous maize monoculture (MM), maize following forage (alfalfa or red clover; FM) or grain (soybean; SM) legumes was estimated to generate greater total GHG emissions, however both FM and SM had a lower C footprint across all N levels due to increased productivity. When compared to MM treated with 100 kg N ha(-1), maize treated with 100 kg N ha(-1), following a forage legume resulted in a 5 % increase in total GHG emissions while reducing the C footprint by 17 %. Similarly, in 18 out of the 19-year period, maize treated with 100 kg N ha(-1), following soybean (SM) had a minimal effect on total GHG emissions (1 %), but reduced the C footprint by 8 %. Compared to the conventional MM with the 200 kg N ha(-1) treatment, FM with the 100 kg N ha(-1) treatment had 40 % lower total GHG emissions and 46 % lower C footprint. Maize with 100 kg N ha(-1) following soybean had a 42 % lower total GHG emissions and 41 % lower C footprint than MM treated with 200 kg N ha(-1). Clearly, there was a trade-off among total GHG emissions, C footprint and yield, and yield and GHG emissions or C footprint not linearly related. Our data indicate that maize production with 100 kg N ha(-1) in rotation with forage or grain legumes can maintain high productivity while reducing GHG emissions and the C footprint when compared to a continuous maize cropping system with 200 kg N ha(-1).
  • Authors:
    • Villar Sanchez, B.
    • Gonzalez Estrada, A.
    • Livera Munoz, M.
    • Cortes Flores, J. I.
    • Turrent Fernandez, A.
    • Camas Gomez, R.
    • Lopez Martinez, J.
    • Espinoza Paz, N.
    • Cadena Iniguez, P.
  • Source: Revista Mexicana de Ciencias Agricolas
  • Volume: 3
  • Issue: 2
  • Year: 2012
  • Summary: In Chiapas, Mexico, soil erosion is the main problem affecting the sustainability of hillside lands. As a result, yields and incomes are low, and soil quality continues to decrease. With the aim of finding sustainable technological alternatives, an evaluation was performed on the following systems: maize in conservation tillage (MLC); maize in plant barriers (MBMV) and maize alternated with fruit trees (MIAF), in terms of surface runoff, production of sediments and loss of nitrogen and phosphorous from June to November, 2009. The systems were setup in adjacent microbasins, belonging to the basin of river Catarina, Jiquipilas, Chiapas. The soil is a Typic haplustepts, with a slope that varies between 30 and 40%. Out of the total rainfalls, 54% caused soil erosion, 15% of these with rains of over 40 mm 62% of the total erosion. The runoff coefficient and the specific soil degradation were similar and lower in the micro basins; MIAF (12,5.8 t ha -1) and MBMV (13,6.3 t ha -1) than in the microbasin with MLC (19,16.8 t ha -1), respectively. In MIAF, the runoff filter and total cover provided by maize and bean plants during most of the growth season played an important part in obtaining these results, despite this microbasin presenting a greater slope steepness and length. In regards to the nutrients, there was a greater loss of nitrates in the microbasin with the system MBMV, possibly due to the nitrogen contribution by the leftovers of the pruning of Gliricidia sepium. In regard to phosphorous, the system MIAF displayed a greater loss, caused by the yearly phosphoric fertilization performed on the guava trees for three years.
  • Authors:
    • Chase, C.
    • Cwach, D.
    • Delate, K.
  • Source: Renewable Agriculture and Food Systems
  • Volume: 27
  • Issue: 1
  • Year: 2012
  • Summary: Novel technologies to reduce tillage in organic systems include a no-tillage roller/crimper for terminating cover crops prior to commercial crop planting. The objective of this experiment was to compare: (1) weed management and yield effects of organic tilled and no-tillage systems for corn ( Zea mays L.), soybean [ Glycine max (L.) Merr.] and irrigated tomato ( Lycopersicon esculentum Mill.), using a roller/crimper and two cover crop combinations [hairy vetch/rye ( Vicia villosa Roth/ Secale cereale L.) and winter wheat/Austrian winter pea ( Triticum vulgare L./ Pisum sativum L. ssp. arvense (L.) Poir.)]; and (2) the economic performance of each system. Weed management ranged from fair to excellent in the organic no-tillage system for soybean and tomato crops, with the rye/hairy vetch mulch generally providing the most weed suppression. Corn suffered from low rainfall, competition from weeds and hairy vetch re-growth and, potentially, low soil nitrogen (N) from lack of supplemental fertilization and N immobilization during cover crop decomposition. No-tillage corn yields averaged 5618 and 634 kg ha -1 in 2006 and 2007, respectively, which was 42-92% lower than tilled corn. No-tillage soybeans in 2007 averaged 2793 kg ha -1 compared to 3170 kg ha -1 for tilled soybeans, although no-tillage yields were 48% of tilled yields in the dry year of 2006. Irrigated tomato yields averaged 40 t ha -1 in 2006 and 63 t ha -1 in 2007, with no statistical differences among tillage treatments. Economic analysis for the three crops revealed additional cover crop seed and management costs in the no-tillage system. Average organic corn returns to management were US$1028 and US$2466 ha -1 greater in the tilled system compared to the no-tillage system in 2006 and 2007, respectively, which resulted mainly from the dramatically lower no-tillage yields. No-tillage soybean returns to management were negative in 2006, averaging US$ -14 ha -1, compared to US$742 ha -1 for tilled soybeans. However, in 2007, no-tillage soybean returns averaged US$1096 ha -1. The 2007 no-tillage irrigated tomato returns to management averaged US$53,515 compared to US$55,515 in the tilled system. Overall, the organic no-tillage soybean and irrigated tomato system demonstrated some promise for reducing tillage in organic systems, but until economic benefits from soil carbon enhancement can be included for no-tillage systems, soil improvements probably cannot offset the economic losses in no-tillage systems. Irrigation could improve the performance of the no-tillage system in dry years, especially if grain crops are rotated with a high-value irrigated tomato crop.
  • Authors:
    • Davison, D. R.
    • Petersen, J. L.
    • Shaver, T. M.
    • Donk, S. J. van
  • Source: Transactions of the ASABE
  • Volume: 55
  • Issue: 1
  • Year: 2012
  • Summary: Reduced tillage, with more crop residue remaining on the soil surface, is believed to conserve water, especially in arid and semi-arid climates. However, the magnitude of water conservation is not clear. An experiment was conducted to study the effect of crop residue removal on soil water content, soil quality, and crop yield at North Platte, Nebraska. The same field plots were planted to soybean ( Glycine max) in 2009 and 2010. There were two treatments: residue-covered soil and bare soil. Residue (mostly corn residue in 2009 and mostly soybean residue in 2010) was removed every spring from the same plots using a flail chopper and subsequent hand-raking. The experiment consisted of eight, 12.2 m * 12.2 m, plots (two treatments with four replications each). Soybeans were sprinkler-irrigated, but purposely water-stressed, so that any water conservation in the residue-covered plots might translate into higher yields. After four years of residue removal, soil organic matter content and soil residual nitrate nitrogen were significantly smaller, and soil pH was significantly greater, in the bare-soil plots compared to the residue-covered plots. The residue-covered soil held approximately 90 mm more water in the top 1.83 m compared to the bare soil near the end of the 2009 growing season. In addition, mean soybean yield was 4.5 Mg ha -1 in the residue-covered plots, compared to 3.9 Mg ha -1 in the bare-soil plots. Using two crop production functions, it is estimated that between 74 and 91 mm of irrigation water would have been required to produce this extra 0.6 Mg ha -1. In 2010, mean soybean yield was 3.8 Mg ha -1 in the residue-covered plots, compared to 3.3 Mg ha -1 in the bare-soil plots. Between 64 and 79 mm of irrigation water would have been required to produce this extra 0.5 Mg ha -1. In both years, several processes may have contributed to the differences observed: (1) greater evaporation of water from the soil in the bare-soil treatment, and (2) greater transpiration by plants in the bare-soil treatment in the beginning of the growing season as a result of more vegetative growth due to higher soil temperatures in the bare-soil treatment.