• Authors:
    • Samarah, N. H.
    • Harb, A. M.
  • Source: Journal of Crop Improvement
  • Volume: 29
  • Issue: 1
  • Year: 2015
  • Summary: Drought is a major abiotic stress that restricts growth and productivity of many crops. The objectives of this study were to assess the morphological and physiological responses of barley plants at the vegetative stage to controlled severe drought, and to test the expression of drought-responsive genes (HvHsdr4, HvNCED2, HvDHN1, HvDHN9, and HvCBF3) in a time course of drought treatment. Barley plants of two genotypes (Rum and Yarmouk) were exposed to controlled severe drought (25% field capacity) in a greenhouse experiment. The two genotypes showed a similar and significant reduction in net photosynthetic rate and plant height. At the molecular level, a differential gene expression of drought-responsive genes was shown between the two genotypes. The results indicate that drought-responsive genes can be useful marker genes to study the differential response of barley genotypes to drought stress conditions.
  • Authors:
    • Tett, S. F. B.
    • Mineter, M. J.
    • Rivington, M.
    • Harding, A. E.
  • Source: CLIMATIC CHANGE
  • Volume: 128
  • Issue: 1-2
  • Year: 2015
  • Summary: Five stakeholder-relevant indices of agro-meteorological change were analysed for the UK, over past (1961-1990) and future (2061-2090) periods. Accumulated Frosts, Dry Days, Growing Season Length, Plant Heat Stress and Start of Field Operations were calculated from the E-Obs (European Observational) and HadRM3 (Hadley Regional Climate Model) PPE (perturbed physics ensemble) data sets. Indices were compared directly and examined for current and future uncertainty. Biases are quantified in terms of ensemble member climate sensitivity and regional aggregation. Maps of spatial change then provide an appropriate metric for end-users both in terms of their requirements and statistical robustness. A future UK is described with fewer frosts, fewer years with a large number of frosts, an earlier start to field operations (e.g., tillage), fewer occurrences of sporadic rainfall, more instances of high temperatures (in both the mean and upper range), and a much longer growing season.
  • Authors:
    • Leinweber, P.
    • Baum, C.
    • Acksel, A.
    • Jandl, G.
  • Source: Soil and Tillage Research
  • Volume: 148
  • Year: 2015
  • Summary: Assessing the organic C (Corg) sequestration in no-till soils under perennial crops requires molecular-level quality indicators. Therefore, we investigated the quality of soil organic matter (SOM) in the topsoil under Salix viminalis L. and Lolium perenne L. at two test sites in Central Sweden. The willow S. viminalis (clone 78021) was grown in short rotation coppice, and the grass L. perenne in an adjacent meadow for 17 (site Ultuna) and 15 years (site Enköping), respectively. The concentrations of aliphatic lipids, determined by gas chromatography/mass spectrometry (GC/MS), as well as the molecular composition and thermal stability of the bulk SOM, determined by pyrolysis-field ionization mass spectrometry (Py-FIMS), were tested as indicators for the crop-specific SOM quality. Larger Corg concentrations (factor 1.4) in the topsoil (site Ultuna) under S. viminalis than under L. perenne corresponded to higher concentrations of summed aliphatic lipids (factor 1.6), mainly saturated n-alkanoic acids (factor 2.1) and n-alkanols (factor 1.5) in the GC/MS-analyses. Moreover, in the willow stand (site Ultuna) at soil depth of 0-10cm disproportionally higher concentrations of saturated n-alkanoic acids (C17-C36) (factor 2.4) and n-alkanes (C21-C36) (factor 2.6) indicated a preferential sequestration of aliphatic C because the bulk Corg concentrations were only larger by factor 1.4. This crop-specific impact on SOM at soil depth of 0-10cm was proven for both test sites. Furthermore, the Py-FIMS showed larger abundances of thermally stabile alkylaromatics (factor 1.4), and non-peptidic N-containing compounds (factor 1.3) in the S. viminalis plot (site Enköping), which supported a crop-specific Corg-sequestration of these compounds. Thus, in summary, accumulations in extracted long C-chain aliphatic lipids and the thermal stability of some substance classes indicated that the Corg sequestration by no-till may be more distinct in soils under S. viminalis than under L. perenne.
  • Authors:
    • Bish, D. L.
    • Xu, R.
    • Yuan, M.
    • Jiang, J.
  • Source: SOIL & TILLAGE RESEARCH
  • Volume: 146
  • Issue: Pt. B
  • Year: 2015
  • Summary: The content of available phosphorus in variable-charge soils is often low due to the strong adsorption of phosphate by the soils. The application of crop straw-derived biochars can change surface chemical properties of variable-charge soils, and thus, should affect phosphate adsorption and phosphorus availability in the soils. However, little information is available on the effect of biochars on the mobility and bioavailability of phosphate in variable-charge soils. The objectives of this study were to investigate the effect of crop straw-derived biochars incorporated on phosphate adsorption by variable-charge soils, and then gain insight into the mechanisms for the effect of biochars on phosphate adsorption. Results showed that crop straw-derived biochars are characterized by large specific surface area, highly negative charged surface, ample of anionic functional groups, and moderate concentrations of divalent Ca2+ and Mg2+. The incorporation of the biochars increased soil CEC (cation-exchange capacity), thus, increased the repulsion of soil surfaces to phosphate, and subsequently decreased the phosphate adsorption by the soils. The ample anionic functional groups on added biochars competed for the adsorption sites on the variable-charge soils with phosphate, and thus, inhibited phosphate adsorption by the soils. The Ca2+ and Mg2+ from the biochars formed precipitates with phosphate in the soils and have the potential to increase apparent phosphate adsorption. Rice straw biochar with the higher CEC and the lowest contents of Ca2+ and Mg2+ showed the greatest inhibition on the phosphate adsorption, and thus, could likely be the best choice as amendment to mobilize phosphate in the variable-charge soils. The phosphate adsorption by both control soil and biochars-amended soils decreased with rising pH. Incorporation of the biochars increased the pH of the amended soils, thereby, further mobilizing phosphate in the soils.
  • Authors:
    • Wichmann, S.
    • Tanneberger, F.
    • Krawczynski, R.
    • Gaudig, G.
    • Joosten, H.
    • Wichtmann, W.
  • Source: Soil carbon: science, management and policy for multiple benefits
  • Year: 2015
  • Summary: Conventional peatland agriculture and forestry is based on drainage, which enhances peat oxidation, causes massive greenhouse gas emissions and eventually destroys the peatland subsistence base. In contrast, paludicultures use biomass from wet and rewetted peatlands under conditions that maintain the peat body, facilitate peat accumulation and provide the associated natural peatland ecosystem services. In the temperate, subtropical and tropical zones, i.e. those zones of the world where plant productivity is high, peat is generally formed by roots and rhizomes, and peatlands by nature hold vegetation of which aboveground parts can be harvested without substantially harming peat conservation and formation. Besides traditional yields of food, feed, fibre and fuel, the biomass can be used as a raw material for industrial biochemistry, for producing high-quality liquid or gaseous biofuels and for further purposes like extracting and synthesizing pharmaceuticals and cosmetics. Some outstanding examples are introduced, including low-intensity grazing with water buffalos, biofuels from fens, common reed as industrial raw material and sphagnum farming for horticultural growing media. Paludicultures may support substantial co-benefits, including the preservation and sequestration of carbon, regulation of water dynamics (flood control) and quality, and conservation and restoration of typical peatland flora and fauna. They can provide sustainable income from sites that have been abandoned or degraded. In many cases, paludicultures can compete effectively with drainage-based peatland agriculture and forestry, certainly when external costs are adequately considered. Various technical and political constraints, however, still hamper large-scale implementation of this promising type of land use.
  • Authors:
    • Gicheru, P. T.
    • Kamoni, P. T.
  • Source: Soil carbon: science, management and policy for multiple benefits
  • Year: 2015
  • Summary: Organic matter is of great importance in soil, because it impacts on the physical, chemical and biological properties of soils. Physically, it promotes aggregate stability and therefore water infiltration, percolation and retention. Biologically, it stimulates the activity and diversity of organisms in soil. Decomposing organic matter releases nutrients, such as nitrogen (N), phosphorus (P), sulfur (S) and potassium (K), essential for plant and microbial growth. Sustainable land management practices enhance carbon sequestration and sustain agricultural productivity, thus mitigating against climate change. In Western Africa, there is a rapid decline of soil organic carbon (SOC) levels with continuous cultivation. For the sandy soils, average annual losses may be as high as 4.7%, whereas with sandy loam soils, losses are lower, with an average of 2%. In the equatorial forest zone with higher rainfall, abundant moisture favours high biomass production, which in turn brings about higher SOC (~24.5 g kg -1 organic C) and nitrogen contents. In the Sudan savannah, organic carbon (~3.3-6.8 g kg -1) and total nitrogen are very low, because of low biomass production and high rates of decomposition. Estimates of SOC stocks and changes made for Kenya using the Global Environmental Facility Soil Organic Carbon (GEFSOC) Modelling System indicated soil C stocks of 1.4-2.0 Pg (0-20 cm), which compared well with a soil and terrain (SOTER)-based approach that estimated ~1.8-2.0 Pg (0-30 cm) of soil C between 2000 and 2030 in Kenya. Direct field sampling and laboratory measurements of soil carbon in Kenya has been going on for over half a century, and the data exist in the form of numerous technical and research reports, theses, journal papers and workshop proceedings, Kenya Agricultural Research Institute annual reports and geographic information system (GIS) databases. A combination of biomass measurements and empirical equations has also been employed in Kenya to measure organic carbon stocks. Stratified random sampling of herbaceous standing crop has been carried out at Nairobi National Park to estimate primary production of the grassland savannah. The Carbon Benefits Project, developed between 2009 and 2012 by Colorado State University (USA) in collaboration with Kenya, Nigeria, Niger and China, is able to estimate carbon stocks and greenhouse gas (GHG) emissions. Increasing soil organic matter content can both improve soil fertility and reduce the impact of drought, improving adaptive capacity, making agriculture less vulnerable to climate change, while also sequestering carbon. Agronomic practices in western Kenya include using improved crop varieties, extending crop rotations, notably those with perennial crops that allocate more C below ground, and avoiding or reducing the use of bare unplanted fallow among others. Increasing the soil carbon in farms improves soil fertility, hence improves food security, increases economic returns from carbon revenues and creates business development opportunities for farmers to diversify income-generating activities.
  • Authors:
    • Stott, D. E.
    • Smith, J. L.
    • Maul, J. E.
    • Manter, D. K.
    • Lundgren, J. G.
    • Kremer, R. J.
    • Johnson, J. M. F.
    • Jin, V. L.
    • Halvorson, J. J.
    • Ducey, T. F.
    • Collins, H. P.
    • Cambardella, C. A.
    • Buyer, J. S.
    • Acosta-Martinez, V.
    • Lehman, R. M.
  • Source: JOURNAL OF SOIL AND WATER CONSERVATION
  • Volume: 70
  • Issue: 1
  • Year: 2015
  • Authors:
    • Chen, Y.
    • Zhang, H.
    • Jiang, Q.
    • Guo, L.
    • Liu, Y.
  • Source: Soil and Tillage Research
  • Volume: 148
  • Year: 2015
  • Summary: Soil organic carbon density (SOCD) has strong spatial variability and dependency, and its impact factors vary with changes in scale and geographic location. With 272 topsoil samples (0-30cm) collected from Chahe Town in the Jianghan Plain, China, we (i) investigated the impacts of environmental variables and land cover types on the spatial distribution of SOCD; (ii) estimated the spatial distribution of SOCD by using global and local spatial interpolation models, including geographically weighted regression kriging (GWRK), regression kriging, geographically weighted regression (GWR), multiple linear regression (MLR), and ordinary kriging; and (iii) used mean absolute estimation error (MAEE), mean relative error (MRE), root mean square error (RMSE) and Pearson's correlation coefficients (r) to evaluate the performance of these models. SOCD was significantly correlated with elevation, normalized difference moisture index (NDMI), and the nearest distance to road (TRD) and residential area (p<0.05). The SOCD ranged from 0.33kgha-1 to 10.14kgha-1 for the topsoil in the study area. Most of the study area, especially the middle region, exhibited SOCD ranging from 4.3kgha-1 to 7.2kgha-1. The highest SOCD value was in wetland (5.45kgha-1) and the lowest was in unused land (4.18kgha-1). The effects of different environmental variables on SOCD can be revealed by the coefficients of GWR and MLR. The spatial distribution map of dominant variables can help us distinguish the essential environmental influence variables for SOCD in different geographical locations. GWRK outperformed the other models in terms of the lowest MAEE (0.984kgha-1), RMSE (1.665kgha-1), MRE (0.190), and high r (0.559) values. Thus, GWRK is a promising approach for mapping SOCD at a local scale.
  • Authors:
    • Jiang, Y. J.
    • Long, G. Q.
    • Sun, B.
  • Source: SOIL & TILLAGE RESEARCH
  • Volume: 146
  • Issue: Pt. B
  • Year: 2015
  • Summary: Dissolved organic matter (DOM) plays an important role in soil biological activity and transport of pollutants and nutrients in soils, but very little information is available with regard to the long-term impact of agricultural management practices on the dynamics and fate of DOM in acidic soils. The seasonal and inter-annual variation of dissolved organic carbon (DOC) and nitrogen (DON) contents and leaching were investigated in an acidic clay soil (Ferric Acrisol) by a long-term field lysimeter experiment in subtropical China. The experiment was conducted from 2002 to 2010 with 4 fertilization treatments under maize monoculture: no manure (CK), low-rate manure with 150kgNha-1y-1 (LM), high-rate manure with 600kgNha-1y-1 (HM), and high-rate manure with 600kgNha-1y-1 and lime at 3000kg Ca(OH)2ha-13y-1 (HML). Manure application resulted in a seasonal variation of soil DOC and DON, and significant effects were observed by manure DOC, microbial biomass and soil water content. Soil DOC, which was mainly determined by soil organic matter and soil water content, increased yearly until the seventh year when it was stabilized. Manure application on acidic clay soil did not alter DOC leaching, whereas DON leaching clearly increased after three years of high manure application of 600kgNha-1y-1. The average annual DON leaching losses under long-term manure application had a range of 3.8-5.4kgha-1, accounting for 6-11% of total nitrogen leached. The addition of lime, combined with manure application, produced no impact on soil dynamics and leaching of DOC and DON, with the exception of increasing emission of CO2.
  • Authors:
    • Brunetti, P.
    • Mancinelli, R.
    • Marinari, S.
    • Campiglia, E.
  • Source: SOIL & TILLAGE RESEARCH
  • Volume: 145
  • Year: 2015
  • Summary: An experiment concerning the biological and chemical responses of soil to cover crop mulching was carried out in two adjacent experimental fields (2012 and 2013) under different climatic conditions in the Mediterranean environment (Central Italy). The Monthly Aridity Index was calculated in order to verify the relationship between soil properties and climatic factors under three different cover crop mulches: Vicia villosa Roth (HV), Phacelia tanacetifolia Benth. (LP), and Sinapis alba L. (WM). A conventional management was also included in the experimental fields as control (C). Soil samples were collected at 0-20cm depth after the transplanting and the harvesting of tomato (May and August, respectively), in order to assess the initial and residual effects of mulching on soil quality. In the two experimental years, the amount of precipitation from May to August was 110mm in 2012 and 172mm in 2013. The average values of AI were 18 and 49 in 2012 and 2013, respectively. LP mulching was sensitive to low precipitation levels in terms of aboveground decomposition rate (the variation of dry matter from May to August 2012 was -53% in LP, 64% in HV and 69% in WM) and a lower tomato yield compared to the control in 2012 (4.2kgm-2 in LP and 5.2kgm-2 in C). WM mulching was sensitive to low precipitation in terms of soil nutrient storage (from May to August 2012 the variation of soil C was 19% in WM., 6% in C, -5 % in LP and 10% in HV; the variation of soil N was 44% in WM, 2% in C, -2% in LP and 13% in HV). Soil microbial activity and functional diversity were strongly affected by the climatic conditions in all mulching treatments. In particular, precipitation influenced soil C availability, which enhanced microbial functional diversity. In short, the effects of lacy phacelia, white mustard and hairy vetch mulching on soil quality, microbial functions and tomato yield were influenced by summer precipitation and temperature in the Mediterranean environment. © 2014 Elsevier B.V.