51. An analysis of the socio-economic factors influencing the adoption of conservation agriculture as a climate change mitigation activity in Australian dryland grain production

• Authors:
  • Dargusch, P.
  • Rochecouste, J. -F
  • Cameron, D.
  • Smith, C.
• Source: Agricultural Systems
• Volume: 135
• Year: 2015
• Summary: The cropping sector in Australia contributes 2.5% of national greenhouse gas emissions, not accounting for the historical loss of soil carbon. The Australian Government is developing policy initiatives targeted at farmers to encourage changes in management practices that aim to reduce emissions from the agricultural sector. The main policy proposal being developed is a market-based mechanism to pay farmers from an Emissions Reduction Fund using methodologies specified under the Australian Carbon Farming Initiative. The adoption of conservation agriculture practices in the dryland grain sector in Australia shows the potential to achieve emissions reductions in the order of three million tCO2e annually. This paper presents a series of systems models that describe the process of how Australian dryland grain farmers decide to change and adopt conservation agriculture practices. Results indicate that a number of economic and social factors drive the rate of practice change, and change seems to be motivated mostly by the pursuit of productivity benefits rather than environmental benefits. We postulate that it may be more effective for climate policy to directly target the adoption of conservation agriculture practices amongst Australian dryland grain farmers by promoting the crop productivity benefits likely to be achieved by such practices, rather than attempting to develop a market-based mechanism for carbon payments. Under this approach, emissions reduction outcomes and carbon payments would not be the primary driver for changing farming practices, but rather a concurrent benefit.

52. Carbon balance, partitioning and photosynthetic acclimation in fruit-bearing grapevine (Vitis vinifera L. cv. Tempranillo) grown under simulated climate change (elevated CO2, elevated temperature and moderate drought) scenarios in temperature gradient greenhouses

• Authors:
  • Sánchez-Díaz, M.
  • Aguirreolea, J.
  • Sanz-Sáez, T.
  • Erice, G.
  • Pascual, I.
  • Aranjuelo, I.
  • Salazar-Parra, C.
  • Irigoyen, J. J.
  • Araus, J. L.
  • Morales, F.
• Source: Journal of plant physiology
• Volume: 174
• Year: 2015
• Summary: Although plant performance under elevated CO2 has been extensively studied in the past little is known about photosynthetic performance changing simultaneously CO2, water availability and temperature conditions. Moreover, despite of its relevancy in crop responsiveness to elevated CO2 conditions, plant level C balance is a topic that, comparatively, has received little attention. In order to test responsiveness of grapevine photosynthetic apparatus to predicted climate change conditions, grapevine (Vitis vinifera L. cv. Tempranillo) fruit-bearing cuttings were exposed to different CO2 (elevated, 700ppm vs. ambient, ca. 400ppm), temperature (ambient vs. elevated, ambient +4°C) and irrigation levels (partial vs. full irrigation). Carbon balance was followed monitoring net photosynthesis (AN, C gain), respiration (RD) and photorespiration (RL) (C losses). Modification of environment 13C isotopic composition (d13C) under elevated CO2 (from -10.30 to -24.93‰) enabled the further characterization of C partitioning into roots, cuttings, shoots, petioles, leaves, rachides and berries. Irrespective of irrigation level and temperature, exposure to elevated CO2 induced photosynthetic acclimation of plants. C/N imbalance reflected the inability of plants grown at 700ppm CO2 to develop strong C sinks. Partitioning of labeled C to storage organs (main stem and roots) did not avoid accumulation of labeled photoassimilates in leaves, affecting negatively Rubisco carboxylation activity. The study also revealed that, after 20 days of treatment, no oxidative damage to chlorophylls or carotenoids was observed, suggesting a protective role of CO2 either at current or elevated temperatures against the adverse effect of water stress.

53. The economic and environmental impacts of precision agriculture and interactions with agro-environmental policy

• Authors:
  • Schieffer, J.
  • Dillon, C.
• Source: PRECISION AGRICULTURE
• Volume: 16
• Issue: 1
• Year: 2015
• Summary: A whole-farm model was used to investigate the interacting effects of precision agriculture technology and agro-environmental policy on the production choices of a representative grain farm. Although some precision agriculture technologies did increase efficiency of resource use, they also decreased the effectiveness of policy, especially policies that rely on economic incentives (e.g., emission taxes). Precision agriculture can lead to higher marginal abatement costs in the form of forgone profits, decreasing producers' responsiveness to those policies. Policy-makers targeting pollution reductions from agriculture should take into account the increasing use of precision agriculture techniques and their varying effects on agro-environmental policy.

54. Impact of no-till and reduced tillage on aggregation and aggregate-associated carbon in Northern European agroecosystems

• Authors:
  • Alakukku, L.
  • Regina, K.
  • Sheehy, J.
  • Six, J.
• Source: Soil and Tillage Research
• Volume: 150
• Year: 2015
• Summary: Minimum tillage practices have been shown to enhance soil aggregation and soil organic carbon (SOC) stabilization. Carbon turnover rate slows down when soil aggregation increases and SOC is protected within stable microaggregates (53-250. µm). However, this has not been investigated in boreal soils. Therefore, the objective of this study was to quantify the long-term effects of no-till (NT) and reduced tillage (RT) on SOC stabilization in four soils typical for the boreal region. Distribution of SOC in different soil fractions in a 0-20. cm soil layer was analyzed by wet sieving and further isolation of microaggregates (mM) from large (>2000. µm, LM) and small (250-2000. µm, sM) macroaggregates. Aggregate size decreased in the order of NT. >. RT. >. CT at all study sites. In addition to increased mean weight diameter (MWD) under NT, a general trend of redistribution of SOC into these formed macroaggregates was found at all study sites, i.e., the LM fraction gained SOC. However SOC was lost in other fractions under NT compared to CT at some sites and none of the sites showed any significant changes in bulk soil SOC content under NT or RT. Also our hypothesis that there would be more SOC incorporated in mM fraction in NT and RT compared to CT was corroborated only at site 4 under NT. Thus, although the potential to accumulate SOC under NT or RT compared to CT seems to be limited in boreal agroecosystems, the redistribution of SOC to the more stable conditions within the aggregates indicates positive impacts of no-till practice.

55. Agronomic and economic response of tillage and water conservation management in maize, central rift valley in Ethiopia

• Authors:
  • Mohammed, H.
  • Aune, J. B.
  • Sime, G.
• Source: Soil and Tillage Research
• Volume: 148
• Year: 2015
• Summary: In response to the intensive tillage in maize, operating under high seasonal rainfall variability, this study examined the agronomic and economic responses of tillage and water conservation management in the central rift valley (CRV) of Ethiopia. An experiment was laid out as a split plot design with conventional tillage (CT), minimum tillage (MT) and zero tillage (ZT) as main plots and mulch, no mulch and planting basin as subplots. The MT and ZT were considered as conservation agriculture (CA) plots. Results showed that CT had 13-20% higher grain yield than MT and 40-55% higher than ZT; and MT had 27-37% higher yields than ZT. Mulching had 23-33% and 14-19% higher grain yield than no mulch and planting basin respectively. The CT had 28 and 89% higher labor productivity and 6 and 60% higher gross margin than MT and ZT respectively. The MT had 37% higher gross margin than ZT. The highest yield response in CT resulted in its highest gross margin and labor productivity. This shows that regardless of water conservation management, CT yielded better agronomic and economic responses over CA. However, the practice of CT is highly constrained by the availability of draft power and the short window period for planting. Likewise, regardless of tillage management, mulching tended to be more attractive and promising in suppressing weed density and hence reducing labor demand for weeding, despite improving volumetric soil moisture content and maize yield. Yet the viability of practicing mulching is highly constrained by the widely practiced open grazing on stubble after harvest. Therefore, future studies are needed to further identify appropriate tillage and water conservation management which make maize more resilient to the high rainfall variability, and sustainably improve food security, and farmers' livelihoods in the CRV of Ethiopia.

56. Nitrogen fertilization and tillage reversal affected water-extractable organic carbon and nitrogen differentially in a Black Chernozem and a Gray Luvisol

• Authors:
  • Dyck, M. F.
  • Feng, Y. S.
  • Chang, S. X.
  • Sun, L.
  • Puurveen, D.
• Source: SOIL & TILLAGE RESEARCH
• Volume: 146
• Issue: Pt. B
• Year: 2015
• Summary: Reversing land management from no tillage to conventional tillage (tillage reversal) to deal with weed infestation and accumulation of crop residue in long-term no tillage systems may dramatically alter soil carbon (C) dynamics. We studied the impact of nitrogen (N) fertilization and tillage reversal on the quantity and quality of water-extractable organic C (WEOC) and N (WEON) in the 0-10cm soil layer in two contrasting soil types located at Ellerslie (high organic matter content) and Breton (low organic matter content) in central Alberta, Canada. We used a split-plot design with N assigned to the main plot and tillage to the subplot. Each treatment had two levels which included addition of 0 (N0) vs. 100kgNha-1yr-1 (N100) N fertilizer and long-term no tillage (NT) vs. tillage reversal (TR); straw was retained on site in all treatments as part of the management regime. Our results showed that soil organic C and N storage were not affected by long-term N fertilization or tillage reversal at Ellerslie but were increased at Breton. Soil WEOC was significantly higher under N100 than under N0 at both sites. Soil WEOC was TR<NT at Breton but was not affected by tillage at Ellerslie. Soil WEON was influenced by the interaction effects of N fertilization and tillage reversal at both sites. The highest WEON concentration was in the N100-TR treatment combination (17.8±1.5 and 10.5±0.7µgg-1 at Ellerslie and Breton, respectively). Nitrogen fertilization decreased the aromaticity of WEOC at both sites but had different effects on WEOC condensation between Ellerslie and Breton. Nitrogen fertilization increased non-aromatic compounds in WEOC and the stability of WEOC at Breton but not at Ellerslie. Neither tillage nor tillage×fertilizer interaction affected the quality of WEOC in either soil. Therefore, N fertilization was the main factor controlling the quality and quantity of WEOC in the studied soils.

57. Yield response of maize (Zea mays L.) to conservation agriculture cropping system in Southern Africa

• Authors:
  • Rusinamhodzi, L.
  • Matemba-Mutasa, R.
  • Thierfelder, C.
• Source: SOIL & TILLAGE RESEARCH
• Volume: 146
• Issue: Pt. B
• Year: 2015
• Summary: The effect of different conservation agriculture (CA) systems on maize grain yield was studied across four countries in southern Africa. Maize yield data was obtained from plots under no-tillage as well as from conventionally tilled plots. Crop residues were retained in no-till plots, whereas they were removed from conventional tillage plots in line with current farmer practices. Rotations or intercropping systems with grain legumes were introduced at all sites. Fertiliser treatments were uniform across tillage treatments at each trial location but varied across countries, based on local fertilizer recommendations. Focus group discussions were conducted with farmers in the study sites to understand the constraints related to the successful integration of CA into the farming systems and to document farmers' perceptions about CA. In the majority of cases (80%), yield responses from a range of CA systems were greater than those of the conventional control plot at the respective site. In 20% of the cases there was a negative response to CA, due to lack of experience by farmers in the initial year, slow increase in soil fertility at the respective site and waterlogging in some years with too much rainfall. Yield advantages on two manual CA systems, planted with a dibble stick with sole maize and maize-legume intercropping in Malawi were 1152kgha-1 and 1172kgha-1, respectively. Animal traction CA systems had slightly smaller yield benefits (458kgha-1 on a ripline seeded system and 761kgha-1 on an animal traction direct seeding systems) as compared to a ploughed control treatment. Yield benefits increased with increasing years of practicing CA, highlighting the need to gain experience to master critical management steps such as timely planting, weeding, fertiliser application and crop harvest residue management. Yields from CA system responded better to increasing clay and silt content in the top soil and were more resilient to seasonal rainfall variability than conventional control treatments. Results suggest that the niche for CA in southern Africa is larger than expected although rainfalls regimes below 600mm are challenging to sustain large maize biomass production to provide effective soil cover in CA systems. The success of CA implementation will largely depend on addressing critical challenges observed in the field, which will need adaptation of CA system to the site and farmer circumstances.

58. Greenhouse gas intensity of three main crops and implications for low-carbon agriculture in China

• Authors:
  • Lin, E. D.
  • Ju, X. T.
  • de Perthuis, C.
  • Lin, Y. B.
  • Su, M.
  • Li, Y. C.
  • Guo, L. P.
  • Wang, W.
  • Moran, D.
• Source: CLIMATIC CHANGE
• Volume: 128
• Issue: 1-2
• Year: 2015
• Summary: China faces significant challenges in reconciling food security goals with the objective of becoming a low-carbon economy. Agriculture accounts for approximately 11 % of China's national greenhouse gas (GHG) emissions with cereal production representing a large proportion (about 32 %) of agricultural emissions. Minimizing emissions per unit of product is a policy objective and we estimated the GHG intensities (GHGI) of rice, wheat and maize production in China from 1985 to 2010. Results show significant variations of GHGIs among Chinese provinces and regions. Relative to wheat and maize, GHGI of rice production is much higher owing to CH4 emissions, and is more closely related to yield levels. In general, the south and central has been the most carbon intensive region in rice production while the GHGI of wheat production is highest in north and northwest provinces. The southwest has been characterized by the highest maize GHGI but the lowest rice GHGI. Compared to the baseline scenario, a 2 % annual reduction in N inputs, combined with improved water management in rice paddies, would mitigate 17 % of total GHG emissions from cereal production in 2020 while sustaining the required yield increase to ensure food security. Better management practices will entail additional gains in soil organic carbon further decreasing GHGI. To realize the full mitigation potential while maximizing agriculture development, the design of appropriate policies should accommodate local conditions.

59. Methane and nitrous oxide emissions from rice and maize production in diversified rice cropping systems

• Authors:
  • Butterbach-Bahl, K.
  • Alberto, M. C. R.
  • Wassmann, R.
  • Ayag, K. R. P.
  • Kraus, D.
  • Weller, S.
  • Kiese, R.
• Source: NUTRIENT CYCLING IN AGROECOSYSTEMS
• Volume: 101
• Issue: 1
• Year: 2015
• Summary: Traditional irrigated double-rice cropping systems have to cope with reduced water availability due to changes of climate and economic conditions. To quantify the shift in CH4 and N2O emissions when changing from traditional to diversified double cropping-systems, an experiment including flooded rice, non-flooded "aerobic" rice and maize was conducted during the dry season (February-June 2012) in the Philippines. Two automated static chamber-GC systems were used to continuously measure CH4 and N2O emissions in the three cropping systems of which each included three different nitrogen fertilization regimes. Turning away from flooded cropping systems leads to shifts in greenhouse gas emissions from CH4 under wet soil to N2O emissions under drier soil conditions. The global warming potential (GWP) of the non-flooded crops was lower compared to flooded rice, whereas high CH4 emissions under flooded conditions still override enhanced N2O emissions in the upland systems. The yield-scaled GWP favored maize over aerobic rice, due to lower yields of aerobic rice. However, the lower GHG emissions of upland systems are only beneficial if they are not overwhelmed by enhanced losses of soil organic carbon.

60. Land use effects on organic carbon storage in soils of Bavaria: The importance of soil types

• Authors:
  • Schilling, B.
  • Reischl, A.
  • Hangen, E.
  • Geuß, U.
  • Spörlein, P.
  • Lützow, M. V.
  • Wiesmeier, M.
  • Kögel-Knabner, I.
• Source: SOIL & TILLAGE RESEARCH
• Volume: 146
• Issue: Pt. B
• Year: 2015
• Summary: Numerous studies have reported substantial changes of soil organic carbon (SOC) stocks after converting forests into agricultural land and vice versa. However, some studies suggested that agricultural soils might contain similar amounts of SOC as forest soils. Losses of SOC induced by cultivation might be overestimated due to shallow soil sampling and application of inaccurate pedotransfer functions. We investigated the impact of different land uses on total SOC storage down to the subsoil on the basis of 270 soil profiles in southeast Germany under similar climatic and pedogenic conditions using an equivalent soil mass (ESM) approach. Land use effects on SOC storage were strongly affected by soil class, which comprised soil types with similar pedogenesis. Both slightly lower (<20%) and even higher SOC stocks were found under cropland compared with forest land for different soil classes. A comparison of different soil classes under grassland and forest land also showed no considerable differences of SOC stocks. Soil cultivation may not generally be associated with a strong decline of SOC, as tillage probably promotes the formation of organo-mineral associations and a relocation of SOC with depth may decrease its decomposition. This finding should be taken into consideration when estimating and managing the emission and sequestration of C in soils. We assume that many studies based on topsoils alone may have underestimated agricultural SOC stocks, particularly when an ESM approach is used. Our results highlight the need for soil type-specific evaluations in terms of interpreting the effects of land use management on SOC stocks.