• 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.
  • Authors:
    • Chen, N.
    • Ti, C.
    • Gao, J.
  • Source: Science Journal
  • Volume: 10
  • Issue: 1
  • Year: 2015
  • Summary: Straw is considered to be a renewable resource for bioenergy and biomaterial. However, about 70% of straw is burned in fields, which causes serious air pollution in China. In this study, a life cycle assessment (LCA) model, together with emergy evaluation, was built to compare four straw applications after harvest vs. direct burning, including bioethanol (BE), combined heat and power plant (CHP), corrugated base paper (CP), and medium-density fiberboard (MDF). The results showed that BE and MDF would avoid greenhouse gas (GHG) emissions by 82% and 36%, respectively, while CHP and CP would emit 57% and 152% more GHG, respectively, compared with direct straw burning. Bioethanol had the highest renewability indicator (RI) of 47.7%, and MDF obtained the greatest profit of 657 Yuan.bale(-1). The applications CHP and CP had low RI (< 10.3%) and profit (< 180 Yuan.bale(-1)). Due to water recycling and electrical power as a coproduct, BE had the lowest value (3 x 10(11) sej.Yuan(-1)) of EmPM (emergy per unit money profit); the EmPM value of CP was 18.6 times higher than that of BE. The four straw applications would also greatly reduce particles emission (57 to 98%) to air. BE was judged to be the most environmentally friendly application among the four straw applications. Imposing a carbon tax would encourage investment in BE, but discourage the applications CHP and CP.
  • Authors:
    • Fransen, S.
    • Okwany, R. O.
    • Girma, K.
  • Source: Agronomy Journal
  • Volume: 107
  • Issue: 1
  • Year: 2015
  • Summary: Managing the soil profile NO 3-N through crop selection and irrigation is an important consideration for the sustainable production of cellulosic biofuel feedstock crops. Data from two seasons were collected and analyzed from a 4-yr study conducted in Prosser, WA, to assess the effect of biofuel feedstock grasses and irrigation levels on soil profile NO 3-N. The experimental design was a split plot with three replications. The main plots had three irrigation levels (60, 80, and 100% evapotranspiration, ET), and the subplots contained three cultivars of switchgrass ( Panicum virgatum L.) and gamagrass ( Tripsacum dactyloides L.) cultivars. Soil and root samples were collected in fall 2011 (Season1) and winter of 2012 (Season2). Soil profile NO 3-N concentrations were highest at the lowest irrigation levels. In Season1, the soil profile NO 3-N concentration averaged over depths was 1.7 mg kg -1 for the switchgrass cultivars and 5.6 mg kg -1 for gamagrass. In Season2, the concentrations were 1.4 and 2.2 mg kg -1 for the switchgrass cultivars and gamagrass, respectively. We found a significant correlation between switchgrass root mass and soil profile NO 3-N; r=0.63-Kanlow; r=0.58-Blackwell; and r=0.46-Shawnee. Our results suggest that soil profile NO 3-N was lower under the switchgrass cultivars than gamagrass. More root mass and NO 3-N were accumulated at lower irrigation levels. The results reported here can help in developing practical decision tools for managing fertilizer N in biomass biofuel crops.
  • Authors:
    • Bu, Q.
    • Sun, Z.
    • Li, Z.
    • Lu X.
  • Source: Agronomy Journal
  • Volume: 107
  • Issue: 1
  • Year: 2015
  • Summary: Straw mulching is used widely to improve soil fertility in the black soil region of northeastern China, but there have been few evaluations of its effects on soil water content, N use by crops, and crop growth. Field experiments were conducted during two growing seasons in Jilin Province, to study the effects of straw mulching on maize yield, evapotranspiration (ET), water use efficiency (WUE), and nitrogen use efficiency (NUE) under rainfed conditions. Measurements were conducted in a treatment with maize straw mulch on the soil surface (SM) and a control treatment with no mulch (NM). The SM treatment caused a significant decline of soil temperature and increase of soil moisture in the early growing season, compared to the NM treatment. However, the use of mulching reduced maize yields by 18% in 2011 and 26% in 2012. It also decreased WUE by 16% in 2011 and 21% in 2012, and decreased NUE by 27% in 2012, though it had no effect on total ET. Therefore, the use of mulch is not recommended as an approach for improving water and N use and maize yields, in the semi-humid black soil region of northeastern China, when the water content of soil is sufficient for maize growth.
  • Authors:
    • Southard, R. J.
    • Horwath, W. R.
    • Shrestha, A.
    • Mitchell, J. P.
    • Madden, N.
    • Veenstra, J.
    • Munk, D. S.
  • Source: Article
  • Volume: 107
  • Issue: 2
  • Year: 2015
  • Summary: Rising costs and air quality regulations have created interest in California's San Joaquin Valley (SJV) in production systems that reduce tillage operations and soil disturbance. From 1999 to 2009, we evaluated conventional (CT) and reduced tillage (RT) systems for a cotton ( Gossypium hirsutum L.)/tomato ( Solanum lycopersicon Mill.) rotation with (CC) and without (NO) cover crops in a Panoche clay loam soil (fine-loamy, mixed, superactive, thermic Typic Haplocambid) in Five Points, CA, in terms of yield, soil C, and the NRCS soil conditioning index (SCI). The RT reduced tractor operations by 50% for tomato and 40% for cotton. Cover cropping produced 38.7 t ha -1 of biomass. Tomato yields were 9.5% higher in RT vs. CT systems and 5.7% higher in NO vs. CC systems. The CT cotton yields were 10.0% higher than RT yields and 4.8% higher in NO systems, but yield patterns were not consistent from 2005 to 2009. Soil C content was uniform (0-30-cm depth) in 1999 (19.72 t ha -1) and increased in all systems in 2007 (t ha -1): RTCC 29.11, CTCC 26.36, RTNO, 24.09, and CTNO 22.65. Soil C content of RT and CT systems did not differ, but was greater in CC than in NO systems. In the 0- to 15-cm depth, RT increased soil C, indicating stratification, and also increased C in the occluded light and mineral fractions. The SCI was positive for RT treatments, predicting a soil C increase, and negative for CT systems, predicting a soil C decline, but measured soil C content increased in all systems. Results show that RT maintains or increases yields relative to CT, and CC stores more soil C than NO.
  • Authors:
    • Dufour, J.
    • I., Diego
    • Peters, J. F.
  • Source: Science Article
  • Volume: 49
  • Issue: 8
  • Year: 2015
  • Summary: The application of biochar as a soil amendment is a potential strategy for carbon sequestration. In this paper, a slow pyrolysis system for generating heat and biochar from lignocellulosic energy crops is simulated and its life-cycle performance compared with that of direct biomass combustion. The use of the char as biochar is also contrasted with alternative use option's: cofiring in coal power plants, use as charcoal, and use as a fuel for heat generation. Additionally, the influence on the results of the longterm stability of the biochar in the soil, as well as of biochar effects on biomass yield, is evaluated. Negative greenhouse gas emissions are obtained for the biochar system, indicating a significant carbon abatement potential. However, this is achieved at the expense of lower energy efficiency and higher impacts in the other assessed categories when compared to direct biomass combustion. When comparing the different use options of the pyrolysis char, the most favorable result is obtained for char cofiring substituting fossil coal, even assuming high long-term stability of the char. Nevertheless, a high sensitivity to biomass yield increase is found for biochar systems, In this sense, biochar application to low-quality soils where high yield increases are expected would show a more favorable performance in terms of global warming.
  • Authors:
    • Rubenstein, D.
    • Notenbaert, A.
    • Beringer, T.
    • Thornton, P. K.
    • Estes, L.
    • Searchinger, T. D.
    • Heimlich, R.
    • Licker, R.
    • Herrero, M.
  • Source: Article
  • Volume: 5
  • Issue: 5
  • Year: 2015
  • Summary: Do the wet savannahs and shrublands of Africa provide a large reserve of potential croplands to produce food staples or bioenergy with low carbon and biodiversity costs? We find that only small percentages of these lands have meaningful potential to be low-carbon sources of maize (1/42%) or soybeans (9.5-11.5%), meaning that their conversion would release at least one-third less carbon per ton of crop than released on average for the production of those crops on existing croplands. Factoring in land-use change, less than 1% is likely to produce cellulosic ethanol that would meet European standards for greenhouse gas reductions. Biodiversity effects of converting these lands are also likely to be significant as bird and mammal richness is comparable to that of the world's tropical forest regions. Our findings contrast with influential studies that assume these lands provide a large, low-environmental-cost cropland reserve. © 2015 Macmillan Publishers Limited. All rights reserved.
  • Authors:
    • Margenot,A. J.
    • Calderón,F. J.
    • Bowles,T. M.
    • Parikh,S. J.
    • Jackson,L. E.
  • Source: Soil Science Society of America Journal
  • Volume: 79
  • Issue: 3
  • Year: 2015
  • Summary: The objectives of this study were to examine soil organic matter (SOM) functional group composition and its relationship to labile SOM fractions with diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). We analyzed soils from 13 organically managed tomato (Solatium lycopersicum) fields in northern California for labile organic C, N, and P fractions and by DRIFTS for bands representing organic functional groups, including aliphatic C-H (2924, 2850, 1470, 1405, 1390 cm-1), aromatic C=C (1650 cm-1) and C-H (920, 840 cm-1), polysaccharide and phenol C-O (1270, 1110, 1080 cm-1), and amine and amide N-H (3400, 1575 cm-1). Significant differences in relative band intensities occurred among the 13 organic tomato fields, in particular a relative increase in absorbance of bands representing aliphatic C-H positively associated with soil organic carbon (SOC), as well as permanganate-oxidizable carbon (POXC), extractable organic carbon (EOC) and nitrogen (EON), and potentially mineralizable N (PMN). In comparison, organic P fractions like sodium bicarbonate extractable (NaHCO3-P0) and sodium hydroxide extractable organic P (NaOH-P0) were poorly associated with SOC and functional groups represented by bands, including aliphatic C-H. This could reflect limitations of DRIFTS, but is consistent with hypotheses of greater decoupling of C and P vs. C and N in soils. This study implicates relative differences in organic functional groups with differences in SOC and labile SOM fractions, and in agreement with previous studies, identifies absorbance of infrared bands representing aliphatic C-H functional groups in these systems as a potential indicator of SOM transformations related to changes in its labile fractions. © Soil Science Society of America, 5585 Guilford Rd., Madison Wl 53711 USA.
  • Authors:
    • Montemurro,Francesco
    • Tittarelli,Fabio
    • Lopedota,Ornella
    • Verrastro,Vincenzo
    • Diacono,Mariangela
  • Source: Nutrient Cycling in Agroecosystems
  • Volume: 102
  • Issue: 2
  • Year: 2015
  • Summary: In organic farming, soil application of processed agro-industrial by-products could sustain soil fertility for vegetables, which have short cropping cycles. Therefore, the objectives of this 2-year research on organic spinach crop were to assess the productive performance of different experimental fertilizers, the effects on soil fertility, and investigate the dynamics of some soil properties and the N balance. Two types of olive pomace mixtures, with a different initial C/N ratio, were composted and both stopped at the active phase (A1 and B1) and processed until maturation (A2 and B2). Also an anaerobic digestate (DA), and the B2 applied as amendment (B2A) were studied. The four composts, DA, and B2A were compared with a commercial organic fertilizer (Org), and a control (N0). The Org resulted as not sustainable in maintaining soil fertility in the long-term, mainly due to reduction in the soil of total organic carbon by 32 %, compared to the average of the other treatments. Conversely, choosing stage of maturity and adequate C/N of starting mixtures was among the best practices for compost use in spinach crop. The great content of nutrients (N and K higher by 102 and 86 % than Org, respectively), and N surplus (1431 kg ha(-1)) in the B2A plots would suggest that they could accumulate after subsequent soil applications, with the risk of losses in the environment. The DA appeared to be the most suitable fertilizer to get a favorable trade-off among yield, quality and N-use efficiency, when applied according to best agronomic practices.
  • Authors:
    • Pathak,H.
    • Jain,N.
    • Bhatia,A.
  • Source: Web Of Knowledge
  • Volume: 11
  • Issue: 4
  • Year: 2015
  • Summary: Indian agriculture is highly prone to the risks due to climate change caused by increase in the concentration of atmospheric greenhouse gases (GHGs) i.e., carbon dioxide (CO 2), methane (CH 4) and nitrous oxide (N 2O). The recent Assessment Report of the Inter-Governmental Panel on Climate Change (IPCC) reiterated that the warming of the climate system is unequivocal and may intensify in coming decades. Climate change can affect agriculture through direct and indirect effects on the crops, soils, livestock and pests. Development of technologies for adaptation and mitigation and their uptake at speedy rate by the farmers are essential for climate change management. Potential adaptation strategies include developing cultivars tolerant to heat and salinity stress and resistant to flood and drought, modifying crop management practices, improving water management, adopting new farm techniques such as resource conserving technologies (RCTs), crop diversification, improving pest management, better weather forecasts and crop insurance and harnessing the indigenous technical knowledge of farmers. There is a need to develop policy framework for implementing the adaptation and mitigation strategies so that the farmers are saved from the adverse impacts of climate change and the food and nutritional security of the country is ensured.