• 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.
  • 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.
  • 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.
  • 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.
  • Authors:
    • Ren, T.
    • Zhou, T.
    • Gao, W.
  • Source: SOIL SCIENCE SOCIETY OF AMERICA JOURNAL
  • Volume: 79
  • Issue: 2
  • Year: 2015
  • Summary: The quantity and stability of soil organic matter (SOM) associated with soil aggregates are affected by tillage management, which can be characterized potentially using the technique of thermal analysis. In this study, we evaluated the concentration and thermal stability of SOM occulted with various aggregate classes under no-tillage (NT) and moldboard plow (MP) treatments using thermogravimetry (TG) and differential scanning calorimetry (DSC). Soil samples were collected 10 yr after tillage experiment was started. The results showed that conversion from MP to NT significantly increased SOM concentration and the proportion of large macro-aggregates (>2 mm) in the 0- to 5-cm soil layer. For all aggregate classes the derivatives of thermogravimetry curves (DTG) had three weight loss peaks near 100, 350, and 500°C, and one endothermic peak and three exothermic peaks in the DSC curves. No differences in ignition temperature, peak position, and ending temperature of SOM combustion were observed between tillage treatments and among the soil layers. For both tillage systems, the proportion of thermal labile SOM (weight loss in 200-400°C accounting for that in 200-550°C, Exo1/Exotot) and energy densities (ED) of SOM (energy release per unit SOM) declined with decreasing aggregate size in the 0- to 20-cm soil layer. Moreover, TG-T50 (the temperature resulting in 50% of SOM loss) correlated negatively to aggregate size, but DSC-T50 (the temperature at which 50% of energy resulting from organic matter combustion release) correlated positively to aggregate size. Compared with MP management, NT management improved quantity but decreased thermal stability of SOM in aggregates in the 0- to 5-cm layer, which was indicated by the greater weight loss at combustion, higher Exo1/Exotot ratio, greater energy densities and lower TG-T50. No tillage also led to increased stratification ratios of thermal labile and thermal recalcitrant SOM.
  • Authors:
    • Garcia-Ruiz, R.
    • Hinojosa, M. B.
    • Gomez-Munoz, B.
  • Source: NUTRIENT CYCLING IN AGROECOSYSTEMS
  • Volume: 101
  • Issue: 2
  • Year: 2015
  • Summary: Olive oil orchard occupies a great percentage of the cropland in southern Spain. Thus, changes in nitrogen (N) fertilization might have a great effect on N dynamics at least at regional scale, which should be investigated for a sustainable N fertilization program. In situ net N mineralization (NM) and nitrification (NN) were investigated during a year in comparable organic (OR) and conventional (CV) olive oil orchards of two locations differing their N input. Soil samples were collected in two soil positions (under and between trees canopy) and both buried-bags and soil core techniques were used to quantify both microbial rates. There were differences in NM and NN between sites mainly due to differences in soil total N (TN), and potential mineralisable N (PMN). In all cases NM and NN were higher in soils under tree canopy. NM and NN were higher in OR than in CV managed orchards in the location with high soil TN. Soil TN and PMN explained together a 50 % of the variability in soil N availability, which suggests that these two variables are good predictors of the potential of a soil to provide available N. The highest rates of soil N availability were found in spring, when olive tree demand for N was at its maximum. Annual soil N availability in olive groves was in all cases higher or similar than tree demand suggesting that soil annual supply of N should be taken into account in order to develop sustainable N fertilisation strategies for olive crops.
  • Authors:
    • Al-Kaisi, M.
    • Guzman, J.
    • Parkin, T.
  • Source: SOIL SCIENCE SOCIETY OF AMERICA JOURNAL
  • Volume: 79
  • Issue: 2
  • Year: 2015
  • Summary: The removal of corn residue for bioethanol may require changes in current tillage and fertilization practices to minimize potential alterations to the soil environment that may lead to increase in greenhouse gas (GHG) emission. The objectives of this study were to examine how tillage, N fertilization rates, residue removal, and their interactions affect CO2, and N2O soil surface emissions. Greater CO2 emission coincided with higher soil temperatures typically observed with conventional tillage (CT) compared with no-tillage (NT), resulting in greater annual cumulative CO2 emission in CT (18.1 CO2 Mg ha-1 yr-1) compared with NT (16.2 CO2 Mg ha-1 yr-1) in 2009 and 2010 across sites. However, drier soil conditions during the growing season in 2011 lead to higher soil temperatures compared with 2009 and 2010. Consequently, annual cumulative CO2 emission from NT with 50 and 100% residue removal was (19.5 CO2 Mg ha-1 yr-1) greater than that from CT (17.8 CO2 Mg ha-1 yr-1) across all residue removal rates and from NT (17.5 CO2 Mg ha-1 yr-1) with no residue removal, respectively across all N rates in the Ames central site (AC) in 2011. In the Armstrong southwest site (ASW) site, there were no significant differences between tillage or residue removal rates for annual cumulative CO2 emission (19.9 CO2 Mg ha-1 yr-1) in 2011. Although N2O emission was considerably lower than CO2 emission, differences in N fertilization rates did have a significant impact on global warming potential once these gases were converted on the basis of their radiative forcing of the atmosphere.
  • Authors:
    • Friedel, J. K.
    • Schmid, H.
    • Huelsbergen, K. J.
    • Freyer, B.
    • Kasper, M.
  • Source: JOURNAL OF PLANT NUTRITION AND SOIL SCIENCE
  • Volume: 178
  • Issue: 1
  • Year: 2015
  • Summary: The importance of the soil humus content is indisputable. Soil humus plays an important role in preserving soil fertility and exerts great influence on plant production and yield potential. However, proofing that management-related changes in the stock of soil organic matter (SOM) have taken place against the background of spatial and temporal variation is a difficult task. In most cases, sampling over a long period of time is needed to verify these changes. Alternatively, potential changes in the SOM stock can be estimated using humus balancing models, which help to identify the need for humus reproduction on a farm. In general, a humus balance is the difference between the humus demand of cultivated crops and humus supply through crops and organic fertilizers. In this study, the 'Dynamic Humus Unit Method' within the modelling program REPRO was applied to calculate the humus balance for 29 model-farms that are representative of most of the agricultural production in Austria. Each model-farm represents a specific production type (PT) and farming system in a defined region or main production area (MPA). This approach gives an overview of the humus balances at a large scale and allows a general trend in Austria to be estimated. Besides differing between conventional and organic farming systems, specific site conditions can also be selected in the model. The constructed model-farms belong to different PTs such as "forage production", "cash crops", "refinement", and "permanent crops". The PT "permanent crops" refers to the cultivation of wine. The cropping system of each PT was analyzed in detail, while livestock keeping was considered only when applicable. Positive humus balances were found for all PTs except for permanent crops. The results ranged from -122 to 890 kg C ha(-1) y(-1). Regions and farm structure, e. g., forage production compared to cash crop, were found to have a greater influence than the kind of farming system (i. e., organic vs. conventional farming). Comparing the different PTs, forage production had the highest positive humus balances (219 to 890 kg C ha(-1) y(-1)), followed by cash crop (24 to 239 kg C ha(-1) y(-1)), refinement (-64 to 402 kg C ha(-1) y(-1)) and permanent crops (-122 to -38 kg C ha(-1) y(-1)). Regarding the farming system, organic farming led to more humus accumulation than conventional farming due to a higher share of fodder legumes and catch crops and more diverse crop rotations. The results were within the range of available empirical data on SOM change, and it was therefore concluded that the results are reasonable. In general, humus reproduction can be regarded as sufficient for agricultural production.
  • Authors:
    • Lal, R.
    • Smith, P.
    • Meng, F. Q.
    • Wu, W. L.
    • Liao, Y.
  • Source: BIOGEOSCIENCES
  • Volume: 12
  • Issue: 5
  • Year: 2015
  • Summary: Agricultural intensification has contributed greatly to the sustained food supply of China's population of 1.3 billion over the 30-year period from 1982 to 2011. Intensification has several and widely recognized negative environmental impacts including depletion of water resources, pollution of water bodies, greenhouse gas emissions and soil acidification. However, there have been few studies over this period on the impacts of intensification on soil organic carbon (SOC) at the regional level. The present study was conducted in Huantai County, a typical intensive farming region in northern China, to analyze the temporal dynamics of SOC influenced by climate and farming practices. The results indicate that from 1982 to 2011, SOC content and density in the 0-20 cm layer of the cropland increased from 7.8 ± 1.6 to 11.0 ± 2.3 g kg-1 (41%) and from 21.4 ± 4.3 to 33.0 ± 7.0 Mg ha-1 (54%), respectively. The SOC stock (0-20 cm) of the farmland for the entire county increased from 0.75 to 1.2 Tg (59%). Correlation analysis revealed that incorporation of crop residues significantly increased SOC, while an increase in the mean annual temperature decreased the SOC level. Therefore, agricultural intensification has increased crop productivity and contributed to SOC sequestration in northern China. In the near future, more appropriate technologies and practices must be developed and implemented for a maintenance or enhancement of SOC in this region and elsewhere in northern China, which also reduce non-CO2 greenhouse gas emissions, since the climate benefit from the additional SOC storage is estimated to be smaller than the negative climate impacts of N2O from N fertilizer additions
  • Authors:
    • Wang, J.
    • Mei, X.
    • Zhang, Y.
    • Yan, C.
    • Chen, B.
    • Liu, E.
  • Source: SOIL SCIENCE SOCIETY OF AMERICA JOURNAL
  • Volume: 79
  • Issue: 2
  • Year: 2015
  • Summary: Tillage practices affect soil organic carbon (SOC) pools, which in turn influence soil ecosystem processes. In this study we measured the effects of long-term conventional tillage (CT) and no-till (NT) practices on SOC and its fraction over the winter wheat growing season in surface and subsurface soils. Soil samples were taken during five physiological stages of winter wheat growth to a depth of 60 cm from the long-term (19 yr) experimental station on Loess Plateau in China. While the SOC content increased slowly in the surface soils during winter wheat growth with the NT treatment, it showed less fluctuation with the CT treatment. On average, NT treatment resulted in 82 and 53% higher SOC content in depth of 0 to 5 and 5 to 10 cm than CT treatment (P < 0.05). However, seasonal variations in microbial biomass carbon (MBC) and particulate organic carbon (POC) were similar under NT and CT, and showed maximum values in before-winter anthesis stage. The dissolved organic carbon (DOC) trend was highest before sowing, decreased before the winter and jointed stages, and increased again during the anthesis stage. Particulate organic carbon, MBC, and DOC were all significantly higher with NT than with CT in the upper 10 cm. Soil depth affected SOC and its fraction which decreased from surface to subsurface soil. The POC, MBC, and DOC were highly correlated with the SOC. This study demonstrated that measurements of the effect of tillage practices on SOC based on SOC fractions should include both seasonal changes and profile distribution.