181. Irrigation system and tillage effects on soil carbon and nitrogen fractions

• Authors:
  • Evans, R. G.
  • Stevens, W. B.
  • Sainju, U. M.
  • Iversen, W. M.
• Source: SOIL SCIENCE SOCIETY OF AMERICA JOURNAL
• Volume: 77
• Issue: 4
• Year: 2013
• Summary: Irrigation and tillage systems may affect surface residue and soil C and N fractions by influencing crop biomass yield, residue placement, and movement of water soluble C and N in the soil. We studied the effects of irrigation (mid-elevation spray application [MESA] and low energy precision application [LEPA ]) and tillage (conventional [CT] and strip-tillage [ST]) systems on crop biomass (stems and leaves) yield, surface residue, and soil C and N fractions at the 0- to 20-cm depth from 2004 to 2007 in a Savage clay loam (fine, smectitic, frigid Vertic Argiustolls) in Sidney, MT. Soil C and N fractions were soil organic carbon (SOC) and total nitrogen (STN), particulate organic carbon and nitrogen (POC and PON), microbial biomass carbon and nitrogen (MBC and MBN), potential carbon and nitrogen mineralization (PCM and PNM), NH4-N, and NO3-N. While crop biomass across treatments increased from 2004 to 2007, surface residue was greater with ST than with CT from 2005 to 2007. The NH4-N and NO3-N contents at 5 to 10 and 10 to 20 cm in 2005 and STN at 0 to 5 cm in 2007 were greater with ST than with CT, but SOC at 5 to 10 and 10 to 20 cm, POC and MBN at 5 to 10 cm, and PNM at 0 to 5 cm in 2007 were greater with CT than with ST. The MBC at 0 to 5 cm and MBN at 10 to 20 cm were greater in LEPA than in MESA. The PCM at 10 to 20 cm was greater with CT than with ST in LEPA . While ST increased surface soil residue and N storage, residue incorporation to a greater depth in CT increased soil C storage, microbial activity, and N mineralization. Slow rate of water application near the soil surface increased microbial biomass in LEPA.

182. Two-chamber, two-gas and one-chamber, one-gas methods for measuring the soil-gas diffusion coefficient: Validation and inter-calibration

• Authors:
  • De Jonge, L. W.
  • Moldrup, P.
  • Eden, M.
  • Schjønning, P.
• Source: SOIL SCIENCE SOCIETY OF AMERICA JOURNAL
• Volume: 77
• Issue: 3
• Year: 2013
• Summary: We constructed a new two-chamber device for gas diffusion measurements in the laboratory, where the diffusion process is followed by two counter-diffusing gases. One of the two chambers of the new apparatus is flushed with Ar, and the diffusion process is started by removing a metal slide separating the chamber from the soil sample. The partial pressure of Ar as well as O2 is timelapse monitored in the flush chamber as well as in a passive chamber coupled to the other end of the soil sample. We measured the gas diffusion coefficient for undisturbed and remolded soil when the samples were drained to a matric potential of -300 hPa. Cores of autoclaved, aerated concrete (AAC) were prepared in the sizes fitting the new device as well as an existing onechamber apparatus. Gas diffusion was measured through the AAC cores and through simple tubes for both methods. The relative gas diffusivity of Ar and O2 for soil samples in the two-chamber device closely followed a 1:1 relation, indicating no significant O2 consumption during measurements. The relative diffusivities for the cylindrical tubes were identical to their cross-sectional area, providing a quantitative assessment of the absolute accuracy. The intercalibration of the two methods based on the AAC cores showed no significant difference, and also indicates that the error from not taking the storage aspect into account for the one-chamber system is negligible for moist soil samples. We consider the new two-chamber, two-gas methodology as promising for detailed studies of gas diffusion in soil.

183. Soil organic carbon and nitrogen after application of nine organic amendments

• Authors:
  • Gollany, H. T.
  • Wuest, S. B.
• Source: SOIL SCIENCE SOCIETY OF AMERICA JOURNAL
• Volume: 77
• Issue: 1
• Year: 2013
• Summary: The amount and type of C-containing amendments applied to soil can have an influence on soil organic carbon (SOC) levels. To test the hypothesis that amendment type is more important than amount, we applied 250 g C m-2 as manure, legume foliage, wheat (Triticum aestivum L.) residue, municipal biosolid, wood sawdust, brassica (Brassica napus L.) residue, composted wheat residue, sucrose, and cotton linters to both fallow soil and an annual winter wheat crop for five consecutive years. After an additional 3.5 yr with no inputs and all plots being fallow, the SOC of biosolid, manure, and wood amended plots were significantly (P < 0.0001) greater than the unamended check. The application of biosolid increased SOC 492 g m-2, and manure increased SOC 316 g m-2, over the fallow check plots in the top 300 kg m -2 of soil (approximately 0-25 cm). The increase in SOC relative to the check ranged from 0 to 39% of the amendment C applied. The SOC content was 482 g m-2 greater under continuous winter wheat than under fallow. The amendment and wheat crop effects on soil C and N changed little during the 3.5 yr after treatments ended, indicating that decomposition occurred soon after application. Wood sawdust was unique in that it increased SOC even though it was low in N content, and it changed the soil C/N ratio from 12.3 to 13.4. This field research demonstrated that amendments applied at the same C rate can have variable effects on SOC accretion.

184. Why do farmers adopt conservation tillage? An experimental investigation of framing effects

• Authors:
  • Gramig, B. M.
  • Clawson, R. A.
  • Andrews, A. C.
  • Raymond, L.
• Source: JOURNAL OF SOIL AND WATER CONSERVATION
• Volume: 68
• Issue: 6
• Year: 2013
• Summary: In this paper, framing effects are investigated in a new context: farmer decision making about conservation tillage practices. Primary hypotheses include the following: (1) frames (i.e., different arguments about or conceptions of an issue) portraying conservation tillage as "profitable" will generate more interest in the tillage technique among farmers than a control frame presenting only basic information; (2) frames discussing potential payments for "environmental benefits" will generate more positive attitudes than frames discussing payment for "storing carbon (C)" to limit climate change; and (3) framing effects will vary based on subjects' prior beliefs and experiences. These hypotheses were tested using a survey-based experiment administered to a national sample of row-crop farmers. Contrary to expectations, the profit frame and both payment frames had no effect on farmers' interest in conservation tillage across our entire sample. Consistent with the third hypothesis, however, a negative framing effect was found for the profit frame on nonadopters who reported no use of no-till in the past two years. These results support the argument regarding the importance of prior beliefs in reactions to frames. They also suggest the possibility of modest financial payments "crowding out" intrinsic motivations for contributions to public goods such as soil conservation. From a policy perspective, these findings also suggest the relative inefficacy of offers of modest conservation payments or profitability frames in promoting no-till farming, especially among nonadopters, and the need to find alternative frames that avoid reinforcing an argument that nonadopters appear to have already considered and rejected.

185. Impacts of conservation agriculture on soil aggregation and aggregate-associated N under an irrigated agroecosystem of the Indo-Gangetic Plains

• Authors:
  • Ganeshan, V.
  • Pramanik, P.
  • Das, T. K.
  • Bhattacharyya, R.
  • Saad, A. A.
  • Sharma, A. R.
• Source: Web Of Knowledge
• Volume: 96
• Issue: 2-3
• Year: 2013
• Summary: We evaluated impacts of conservation agriculture (zero tillage, bed planting and residue retention) on changes in total soil N (TSN) and aggregate-associated N storage in a sandy loam soil of the Indo-Gangetic Plains. Cotton (Gossypium hirsutum) and wheat (Triticum aestivum) crops were grown during the first 3 years (2008-2011) and in the last year, maize (Zea mays) and wheat were cultivated. Results indicate that after 4 years the plots under zero tillage with bed planting (ZT-B) and zero tillage with flat planting (ZT-F) had 15 % higher TSN concentrations than conventional tillage and bed planting plots (CT-B) (0.63 g kg(-1) soil) in the 0-5 cm soil layer. CT-B plots had lower soil bulk density that ZT plots in that layer. Plots under ZT-B (0.57 Mg ha(-1)) contained 20 % higher TSN stock in the 0-5 cm soil layer than CT-B plots (0.48 Mg ha(-1)). However, tillage had no impact on TSN concentration or stock in the sub-surface (5-15 and 15-30 cm) soil layers. Thus, in the 0-30 cm soil layer, ZT-B plots contained 6 and 5 % higher (P > 0.05) TSN stock compared with CT-B (2.15 Mg N ha(-1)) and CT-F (2.19 Mg N ha(-1)) plots respectively after 4 years. Plots that received cotton/maize + wheat residue (C/M + W RES) contained 16 % higher TSN concentration than plots with residues removed (N RES; 0.62 g kg(-1) soil) in the surface (0-5 cm) layer. Plots with only cotton/maize residue (C/M RES) or only wheat residue (W RES) retention/incorporation had similar TSN concentrations and stocks in the subsurface layer. Plots under ZT-B also had more macroaggregates (0.25-8 mm) and greater mean weight diameter with lower silt + clay sized particles than CT-B plots in that layer. A greater proportion of large macroaggregates (2-8 mm) in the plots under C/M + W RES compared with N RES were observed. In the 5-15 cm soil layer ZT-B and C/M + W RES treated plots had more macroaggregates and greater mean weight diameter than CT-B and N RES treated plots, respectively. Because of the greater amount of large aggregates, plots under ZT-B and C/M + W RES had 49 and 35 % higher large macroaggregate-associated N stocks than CT-B (38 kg TSN ha(-1)) and N RES (40 kg TSN ha(-1)) plots, respectively, in the 0-5 cm soil layer, although aggregates had similar TSN concentrations in all plots. Both tillage and residue retention had greater effects on aggregate-associated N stocks in the 5-15 cm layers. In addition to N content within large macroaggregates, small macroaggregate-associated N contents were also positively affected by ZT-B and C/M + W RES. Tillage and residue retention interaction effects were not significant for all parameters. Thus, the adoption of ZT in permanent beds with crop residue addition is a better management option for improvement of soil N (and thus possibly a reduced dose of fertilizer N can be adopted in the long run), as the management practice has the potential to improve soil aggregation with greater accumulation of TSN within macroaggregates, and this trend would likely have additive effects with advancing years of the same management practices in this region.

186. Changes in soil carbon and nitrogen following tillage conversion in a long-term experiment in Northern France.

• Authors:
  • Labreuche, J.
  • Cohan, J. P.
  • Dimassi, B.
  • Mary, B.
• Source: Agriculture Ecosystems and Envirtoment
• Volume: 169
• Year: 2013
• Summary: Although continuous no-till (NT) is recommended for erosion control and carbon sequestration, it often has a limited duration since farmers alternate between NT and full inversion tillage (FIT) to control weed infestation and avoid soil compaction. In this paper, we evaluate the effect of continuous tillage and tillage conversion of NT to FIT and vice versa on SOC and SON stocks, in a long-term experiment at Boigneville in Northern France. Continuous NT (CNT) and FIT (CFIT) treatments were established in 1991 and maintained until 2011 while half of the plots were converted in 2005: from CNT to new FIT (NFIT) and CFIT to new NT (NNT). Bulk densities and organic C and N contents were determined in 2001 and 2011 down to the old ploughing depth ( opd) which was also measured. SOC and SON stocks were calculated at equivalent soil mass by correcting either bulk densities or the opd. Both methods produced very close results and similar conclusions. A typical gradient of SOC and SON concentrations vs depth was observed in CNT as opposed to a rather uniform distribution in CFIT. CNT resulted in SOC concentration in the top soil (0-5 cm) higher by 38% in 2001 and 53% in 2011 compared to CFIT. Conversely, it led to a SOC reduction in the deeper layer ( ca. 10-28 cm) by 14% in 2001 and 18% in 2011. The global effect was no significant change in SOC and SON stocks between treatments over the old ploughed layer (4060 t soil ha -1) in both years: 43.2 and 45.0 t C ha -1 in 2001 and 44.7 and 45.8 t C ha -1 in 2011, in CNT and CFIT, respectively. In 2011, six years after tillage conversion, the stratification of SOC and SON had disappeared in NFIT whereas a new one had appeared in NNT with a smaller gradient than in CNT. SOC or SON stocks over the old ploughed layer did not differ significantly between treatments after 6 years of conversion: SOC stocks were 45.8, 43.2, 44.7 and 43.1 t C ha -1 in the CFIT, NFIT, CNT and NNT treatments, respectively. Furthermore, SOC stocks below the old ploughed layer ( ca. 28-40 cm) were slightly greater in FIT than in NT treatment (10.9 vs 8.7 t C ha -1). In this experiment, continuous or conversion tillage did not result in any C sequestration benefit.

187. Conservation tillage systems: a review of its consequences for greenhouse gas emissions

• Authors:
  • Smith, P.
  • Williams, M.
  • Forristal, D.
  • Lanigan, G.
  • Osborne, B.
  • Abdalla, M.
  • Jones, M. B.
• Source: Soil Use and Management
• Volume: 29
• Issue: 2
• Year: 2013
• Summary: Conservation tillage (CT) is an umbrella term encompassing many types of tillage and residue management systems that aim to achieve sustainable and profitable agriculture. Through a global review of CT research, the objective of this paper was to investigate the impacts of CT on greenhouse gas (GHG) emissions. Based on the analysis presented, CT should be developed within the context of specific climates and soils. A number of potential disadvantages in adopting CT practices were identified, relating mainly to enhanced nitrous oxide emissions, together with a number of advantages that would justify its wider adoption. Almost all studies examined showed that the adoption of CT practices reduced carbon dioxide emissions, while also contributing to increases in soil organic carbon and improvements in soil structure.

188. Managing soil carbon for climate change mitigation and adaptation in Mediterranean cropping systems: A meta-analysis

• Authors:
  • Gimeno, B. S.
  • Gattinger, A.
  • Lassaletta, L.
  • Aguilera, E.
• Source: Agriculture, Ecosystems & Environment
• Volume: 168
• Year: 2013
• Summary: Mediterranean croplands are seasonally dry agroecosystems with low soil organic carbon (SOC) content and high risk of land degradation and desertification. The increase in SOC is of special interest in these systems, as it can help to build resilience for climate change adaptation while contributing to mitigate global warming through the sequestration of atmospheric carbon (C). We compared SOC change and C sequestration under a number of recommended management practices (RMPs) with neighboring conventional plots under Mediterranean climate (174 data sets from 79 references). The highest response in C sequestration was achieved by those practices applying largest amounts of C inputs (land treatment and organic amendments). Conservation tillage practices (no-tillage and reduced tillage) induced lower effect sizes but significantly promoted C sequestration, whereas no effect and negative net sequestration rates were observed for slurry applications and unfertilized treatments, respectively. Practices combining external organic amendments with cover crops or conservation tillage (combined management practices and organic management) showed very good performance in C sequestration. We studied separately the changes in SOC under organic management, with 80 data sets from 30 references. The results also suggest that the degree of intensification in C input rate is the main driver behind the relative C accumulation in organic treatments. Thus, highest net C sequestration rates were observed in most eco-intensive groups, such as "irrigated", "horticulture" and controlled experiments ("plot scale"). (C) 2013 Elsevier B.V. All rights reserved.

189. 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.

190. Greenhouse gas mitigation potential from green harvested sugarcane scenarios in Sao Paulo State, Brazil

• Authors:
  • Adami, M.
  • Aguiar, D. A.
  • de Figueiredo, E. B.
  • Bordonal, R. de O.
  • Rudorff, B. F. T.
  • La Scala, N.
• Source: Biomass and Bioenergy
• Volume: 59
• Year: 2013
• Summary: Brazil is a major sugarcane producer and Sao Paulo State cultivates 5.5 million hectares, close to 50% of Brazil's sugarcane area. The rapid increase in production has brought into question the sustainability of biofuels, especially considering the greenhouse gas (GHG) emissions associated to the agricultural sector. Despite the significant progress towards the green harvest practices, 1.67 million hectares were still burned in Sao Paulo State during the 2011 harvest season. Here an emissions inventory for the life cycle of sugarcane agricultural production is estimated using IPCC methodologies, according to the agriculture survey data and remote sensing database. Our hypothesis is that 1.67 million hectares shall be converted from burned to green harvest scenarios up to years 2021 (rate 1), 2014 (rate 2) or 2029 (rate 3). Those conversions would represent a significant GHG mitigation, ranging from 50.5 to 70.9 megatons of carbon dioxide equivalent (Mt CO(2)eq) up to 2050, depending on the conversion rate and the green harvest systems adopted: conventional (scenario 51) or conservationist management (scenario S2). We show that a green harvest scenario where crop rotation and reduced soil tillage are practiced has a higher mitigation potential (70.9 Mt CO(2)eq), which is already practiced in some of the sugarcane areas. Here we support the decision to not just stop burning prior to harvest, but also to consider other better practices in sugarcane areas to have a more sustainable sugarcane based ethanol production in the most dense cultivated sugarcane region in Brazil. (C) 2013 Elsevier Ltd. All rights reserved.