61. Interactions between climate change and sugarcane management systems for improving water quality leaving farms in the Mackay Whitsunday region, Australia

• Authors:
  • Masters, B.
  • Crimp, S.
  • Thorburn, P. J.
  • Biggs, J. S.
  • Attard, S. J.
• Source: Agriculture, Ecosystems & Environment
• Volume: 180
• Year: 2013
• Summary: Nitrogen (N) lost from cropping is one of the major threats to the health of the Great Barrier Reef (GBR) in northern Australia, and there are government initiatives to change farming practices and reduce N losses from farms. Sugarcane is the dominant crop in most catchments draining into the GBR lagoon, especially those of the Mackay Whitsunday region (8400 km(2)) where sugarcane represents >99% of cropping in the catchments, and is grown with large applications of N fertiliser. As farmers and farming systems adapt to a future requiring lower environmental impact, the question arises whether climate change may influence the effectiveness of these changes, an issue rarely considered in past water quality studies. To address this question we used the APSIM farming-systems model to investigate the complex interactions between a factorial of five proposed sugarcane management systems, three soil types, three sub-regional climatic locations and four climate change projections (weak, moderate and strong, with historical climate as a 'control'). These projections, developed from general circulation models and greenhouse gas emission scenarios, estimated that median annual rainfall would be reduced by up to 19%, and maximum and minimum temperatures increased by up to 0.5 degrees C and 0.6 degrees C, respectively. Management practices, such as tillage, fallow management and N inputs, were grouped into five systems according to the perceived benefits to water quality. For example; Management System A grouped together zero tillage, soybean rotation crops, reduced N inputs and controlled traffic practices. While at the other end of the scale, System E included many severe tillage operations, bare fallows, high N inputs and conventional row spacing; practices that are still used in some areas. Importantly, this study parameterised controlled traffic systems, which is considered an important component of 'best' management in the GBR catchment, but for which water quality benefits have yet to be widely quantified. The study predicted that the improvement in farm management needed to meet water quality improvement goals will not be greatly affected by climate change. However, without any interventions, the frequency of years with very high N losses, and hence extreme ecological risk, was predicted to increase by up to 10-15%. Compared with traditional practices, improved management systems were predicted to reduce N losses by up to 66% during these years. The results support continued adoption of improved management systems to achieve proposed water quality targets in both the current and a range of potential future climates. However, there are important uncertainties about the effects of elevated atmospheric CO2 concentration on plant assimilation rates and the characterisation of extreme climate events that deserve further study.

62. Nitrogen fluxes from irrigated common‑bean as affected by mulching and mineral fertilization

• Authors:
  • Heinemann, A. B.
  • Moreira, J. A. A.
  • Silveira, P. M. da
  • Machado, P. L. O. de A.
  • Costa, A. R. da
  • Leal, W. G. de O.
  • Madari, B. E.
  • Carvalho, M. T. de M.
• Source: Pesquisa Agropecuária Brasileira
• Volume: 48
• Issue: 5
• Year: 2013
• Summary: The objective of this work was to measure the fluxes of N2O‑N and NH3‑N throughout the growing season of irrigated common‑bean (Phaseolus vulgaris), as affected by mulching and mineral fertilization. Fluxes of N2O‑N and NH3‑N were evaluated in areas with or without Congo signal grass mulching (Urochloa ruziziensis) or mineral fertilization. Fluxes of N were also measured in a native Cerrado area, which served as reference. Total N2O‑N and NH3‑N emissions were positively related to the increasing concentrations of moisture, ammonium, and nitrate in the crop system, within 0.5 m soil depth. Carbon content in the substrate and microbial biomass within 0.1 m soil depth were favoured by Congo signal grass and related to higher emissions of N2O‑N, regardless of N fertilization. Emission factors (N losses from the applied mineral nitrogen) for N2O‑N (0.01-0.02%) and NH3‑N (0.3-0.6%) were lower than the default value recognized by the Intergovernmental Panel on Climate Change. Mulch of Congo signal grass benefits N2O‑N emission regardless of N fertilization.

63. Greenhouse gas assessment of soybean production: implications of land use change and different cultivation systems

• Authors:
  • Castanheira, E. G.
  • Freire, F.
• Source: Journal of Cleaner Production
• Volume: 54
• Year: 2013
• Summary: The increase in soybean production as a source of protein and oil is being stimulated by the growing demand for livestock feed, food and numerous other applications. Significant greenhouse gas (GHG) emissions can result from land use change due to the expansion and cultivation of soybean. However, this is complex to assess and the results can vary widely. The main goal of this article is to investigate the life-cycle GHG balance for soybean produced in Latin America, assessing the implications of direct land use change emissions and different cultivation systems. A life-cycle model, including inventories for soybean produced in three different climate regions, was developed, addressing land use change, cultivation and transport to Europe. A comprehensive evaluation of alternative land use change scenarios (conversion of tropical forest, forest plantations, perennial crop plantations, savannah and grasslands), cultivation (tillage, reduced tillage and no-tillage) and soybean transportation systems was undertaken. The main results show the importance of land use change in soybean GHG emissions, but significant differences were observed for the alternative scenarios, namely 0.1-17.8 kg CO(2)eq kg(-1) soybean. The original land choice is a critical issue in ensuring the lowest soybean GHG balance and degraded grassland should preferably be used for soybean cultivation. The highest GHG emissions were calculated for tropical moist regions when rainforest is converted into soybean plantations (tillage system). When land use change is not considered, the GHG intensity varies from 0.3 to 0.6 kg CO(2)eq kg(-1) soybean. It was calculated that all tillage systems have higher GHG emissions than the corresponding no-tillage and reduced tillage systems. The results also show that N2O emissions play a major role in the GHG emissions from cultivation, although N2O emission calculations are very sensitive to the parameters and emission factors adopted.

64. Mitigation potential of greenhouse gases under different scenarios of optimal synthetic nitrogen application rate for grain crops in China

• Authors:
  • Zhang, Y.
  • Wu, L.
  • Wang, H.
  • Liu, L.
  • Huang, L.
  • Niu, Y.
  • Chai, R.
• Source: Nutrient Cycling in Agroecosystems
• Volume: 96
• Issue: 1
• Year: 2013
• Summary: Proper management of synthetic nitrogen (N) fertilizer can reduce direct N2O emission from soil and indirect CO2 emission from production and transportation of synthetic N. In the late 1990s, the average application rates of synthetic N were 212, 207 and 207 kg ha(-1), respectively, for rice, wheat, and maize in China's croplands. But research suggests that the optimal synthetic N application rates for the main grain crops in China should be in the range of 110-150 kg ha(-1). Excessive application of synthetic N has undoubtedly resulted in massive emission of greenhouse gases. Therefore, optimizing N application rates for grain crops in China has a great potential for mitigating the emission of greenhouse gases. Nevertheless, this mitigation potential (MP) has not yet been well quantified. This study aimed at estimating the MP of N2O and CO2 emissions associated with synthetic N production and transportation in China based on the provincial level statistical data. Our research indicates that the total consumption of synthetic N on grain crops in China can be reduced by 5.0-8.4 Tg yr(-1) (28-47 % of the total consumption) if the synthetic N application rate is controlled at 110-150 kg ha(-1). The estimated total MP of greenhouse gases, including direct N2O emission from croplands and indirect CO2 emission from production and transportation of synthetic N, ranges from 41.7 to 70.1 Tg CO2_eq. yr(-1). It was concluded that reducing synthetic N application rate for grain crops in China to a reasonable level of 110-150 kg ha(-1) can greatly reduce the emission of greenhouse gases, especially in the major grain-crop production provinces such as Shandong, Henan, Jiangsu, Hebei, Anhui and Liaoning.

65. Nitrogen fluxes from irrigated common-bean as affected by mulching and mineral fertilization

• Authors:
  • Alves Moreira, J. A.
  • da Silveira, P. M.
  • Oliveira de Almeida Machado, P. L.
  • da Costa, A. R.
  • de Oliveira Leal, W. G.
  • Madari, B. E.
  • de Melo Carvalho, M. T.
  • Heinemann, A. B.
• Source: Pesquisa Agropecuária Brasileira
• Volume: 48
• Issue: 5
• Year: 2013
• Summary: The objective of this work was to measure the fluxes of N2O-N and NH3-N throughout the growing season of irrigated common-bean (Phaseolus vulgaris), as affected by mulching and mineral fertilization. Fluxes of N2O-N and NH3-N were evaluated in areas with or without Congo signal grass mulching (Urochloa ruziziensis) or mineral fertilization. Fluxes of N were also measured in a native Cerrado area, which served as reference. Total N2O-N and NH3-N emissions were positively related to the increasing concentrations of moisture, ammonium, and nitrate in the crop system, within 0.5 m soil depth. Carbon content in the substrate and microbial biomass within 0.1 m soil depth were favoured by Congo signal grass and related to higher emissions of N2O-N, regardless of N fertilization. Emission factors (N losses from the applied mineral nitrogen) for N2O-N (0.01-0.02%) and NH3-N (0.3-0.6%) were lower than the default value recognized by the Intergovernmental Panel on Climate Change. Mulch of Congo signal grass benefits N2O-N emission regardless of N fertilization.

66. Stratification ratio of organic matter pools influenced by management systems in a weathered Oxisol from a tropical agro-ecoregion in Brazil

• Authors:
  • Carneiro, M. A. C.
  • Resck, D. V. S.
  • Figueiredo, C. C.
  • Ramos, M. L. G.
  • Sa, J. C. M.
• Source: Soil research
• Volume: 51
• Issue: 2
• Year: 2013
• Summary: Enhancement of organic matter plays an essential role in improving soil quality for supporting sustainable food production. Changes in carbon stocks with impacts on emissions of greenhouse gases may result from the stratification of organic matter as a result of soil use. The objective of this study was to evaluate the impact of soil management systems on soil carbon stocks and stratification ratios (SR) of soil organic matter pools. Total organic carbon (TOC), particulate organic carbon (POC), mineral-associated organic carbon, microbial biomass carbon (MBC) and nitrogen, basal respiration, and particulate organic matter nitrogen (PON) were determined. The field experiment comprised several tillage treatments: conventional tillage, no-till with biannual rotation, no-till with biannual rotation combined with a second crop, no-till with annual rotation, and pasture. The labile fractions indicated a high level of variation among management systems. Pasture proved to be an excellent option for the improvement of soil carbon. While the conventional tillage system reduced total carbon stocks of the soil (0-40 cm), no-tillage presented TOC stocks similar to that of native vegetation. Sensitivity of the TOC SR varied from 0.93 to 1.28, a range of 0.35; the range for POC was 1.76 and for MBC 1.64. The results support the hypothesis that the labile fractions (POC, MBC, and PON) are highly sensitive to the dynamics of organic matter in highly weathered soils of tropical regions influenced by different management systems. Reductions to SRs of labile organic matter pools are related to the impacts of agricultural use of Cerrado soils.

67. Medium-term impact of tillage and residue management on soil aggregate stability, soil carbon and crop productivity.

• Authors:
  • Ndabamenye, T.
  • Lelei, D.
  • Koala, S.
  • Hurisso, T. T.
  • Hoogmoed, M.
  • Gassner, A.
  • Ayuke, F.
  • Vanlauwe, B.
  • Paul, B. K.
  • Six, J.
  • Pulleman, M. M.
• Source: Agriculture Ecosystems and Environment
• Volume: 164
• Year: 2013
• Summary: Conservation agriculture is widely promoted for soil conservation and crop productivity increase, although rigorous empirical evidence from sub-Saharan Africa is still limited. This study aimed to quantify the medium-term impact of tillage (conventional and reduced) and crop residue management (retention and removal) on soil and crop performance in a maize-soybean rotation. A replicated field trial was started in sub-humid Western Kenya in 2003, and measurements were taken from 2005 to 2008. Conventional tillage negatively affected soil aggregate stability when compared to reduced tillage, as indicated by lower mean weight diameter values upon wet sieving at 0-15 cm ( PT<0.001). This suggests increased susceptibility to slaking and soil erosion. Tillage and residue management alone did not affect soil C contents after 11 cropping seasons, but when residue was incorporated by tillage, soil C was higher at 15-30 cm ( PT*R=0.037). Lack of treatment effects on the C content of different aggregate fractions indicated that reduced tillage and/or residue retention did not increase physical C protection. The weak residue effect on aggregate stability and soil C may be attributed to insufficient residue retention. Soybean grain yields tended to be suppressed under reduced tillage without residue retention, especially in wet seasons ( PT*R=0.070). Consequently, future research should establish, for different climatic zones and soil types, the critical minimum residue retention levels for soil conservation and crop productivity.

68. Carbon stocks and cocoa yields in agroforestry systems of Central America.

• Authors:
  • Say, E.
  • Astorga, C.
  • Poveda, V.
  • Alvarado, E.
  • Avila, G.
  • Mavisoy, H.
  • Espin, T.
  • Davila, H.
  • Cifuentes, M.
  • Orozco, L.
  • Cerda, R.
  • Somarriba, E.
  • Deheuvels, O.
• Source: Agriculture Ecosystems and Environment
• Volume: 173
• Year: 2013
• Summary: The cocoa tree ( Theobroma cacao L.) is cultivated typically in agroforestry systems in close association with a rich list of tree species and other useful plants on the same plot. Cocoa based agroforestry systems are credited for stocking significant amounts of carbon and hence have the potential to mitigate climate change. Since cocoa yields decrease non-linearly with increasing shade, a need is to design optimal cocoa agroforestry systems with high yields and high carbon stocks. We estimated the carbon stocked in a network of 229 permanent sample plots in cacao-based agroforestry systems and natural forests in five Central American countries. Carbon stocks were fractioned by both system compartments (aboveground, roots, soil, litter, dead wood - fine and coarse, and total) and tree use/form (cocoa, timber, fruit, bananas, shade and ornamentals, and palms). Cocoa plantations were assigned to a five-class typology and tested for independence with growing region using contingency analysis. Most Central American cocoa plantations had mixed or productive shade canopies. Only 4% of cocoa plantations were full sun or rustic (cocoa under thinned natural forest). Cocoa tree density was low (548192 trees ha -1). Total carbon (soil+biomass+dead biomass) was 11747 Mg ha -1, with 51 Mg ha -1 in the soil and 49 Mg ha -1 (42% of total carbon) in aboveground biomass (cocoa and canopy trees). Cocoa trees accumulated 9 Mg C ha -1 (18% of carbon in aboveground biomass). Timber and fruit trees stored 65% of aboveground carbon. The annual rate of accumulation of carbon in aboveground biomass ranged between 1.3 and 2.6 Mg C ha -1 y -1. Trade-offs between carbon levels and yields were explored qualitatively using functional relationships documented in the scientific and technical literature, and expert knowledge. We argue that it is possible to design cocoa-based AFS with good yields (cocoa and shade canopy) and high carbon stock levels. The botanical composition of the shade canopy provides a large set of morphological and functional traits that can be used to optimize shade canopy design. Our results offer Central American cocoa producers a rigorous estimate of carbon stocks in their cocoa plantations. This knowledge may help them to certify and sell their cocoa, timber, fruits and other goods to niche markets with good prices. Our results will also assist governments and the private sector in (i) designing better legal, institutional and policy frameworks, local and national, promoting an agriculture with trees and (ii) contributing to the development of the national monitoring, reporting and verification systems required by the international community to access funding and payment for ecosystem services.

69. Energy and greenhouse gas emissions reduction potential of sugarcane field residues power generation in Thailand.

• Authors:
  • Sajjakulnukit, B.
  • Jenjariyakosoln, S.
  • Garivait, S.
• Source: International Journal of Environmental Science and Development
• Volume: 4
• Issue: 2
• Year: 2013
• Summary: This paper presents an approach to evaluate the net energy potential of sugarcane field residues in Thailand. It was estimated that around 13,595 ktons of sugarcane field residues was burned in the field annually in the country. Assuming 100% collection efficiency, this amount could be converted to 210.46 PJ through power generation. The quantity of greenhouse gases (GHGs) including CO 2, CH 4, and N 2O emitted from open burning of sugarcane residues was compared to that released from power production using life cycle analysis methodology for the estimation. It was found that the avoided GHG emissions obtained for power generation represent 11,836 ktons CO 2 equivalent, based on the country specific emission factor of electricity production using coal as fuel of 1.09 kg CO 2/kWh. Although this enormous potential for energy production in Thailand, sugarcane field residues availability is subject to seasonal variability, which limits its capacity to serve as fuel for power generation. The total avoided GHG emissions were therefore 11,836 ktons CO 2eq and 8,285 ktons CO 2eq annually for collection efficiency of 100% and 70%, respectively. Comparatively to the national CO 2 emissions from coal power generation of 34,532 ktons CO 2eq in 2011, the avoided GHG emissions would be about 34% and 24% for collection efficiency of 100% and 70%, respectively.

70. Biochar an alternate option for crop residues and solid waste disposal and climate change mitigation.

• Authors:
  • Govindaraj, M.
  • Prabukumar, G.
  • Arunachalam, P.
  • Kannan, P.
• Source: African Journal of Agricultural Research
• Volume: 8
• Issue: 21
• Year: 2013
• Summary: Atmospheric rise of CO 2, N 2O and CH 4 over years, accelerated increase in global temperature, has led to uncertainty in monsoon rainfall and also leading to recurrence of drought, which in turn is severely affecting crop productivity and livelihood security of the farmers in Semi Arid Tropics. Agriculture contributes considerable amount of CO 2, N 2O and CH 4 emission into the atmosphere through different soil and crop management practices. Nevertheless agricultural activities contribute to global warming. The medium of crop production, soil is one of the major sinks of global warming gaseous and it helps to sequester more carbon and cut the N 2O emission by adopting smart soil and crop management techniques. Biochar is one of the viable organic amendments to combat climate change and sustain the soil health with sustainable crop production. It is an anaerobic pyrolysis product derived from organic sources and store carbon on a long term basis in the terrestrial ecosystem and also capable of reducing greenhouse gases (GHG) emission from soil to the atmosphere. Biochar application improved the soil health, increase the carbon capture and storage, reduce the GHG emission and enhance the crop yield with sustained soil health, which enables to meet out the food grain needs of the ever growing population.