• Authors:
    • He, X.
    • Qin, S.
    • Hu, C.
    • Zhang, Y.
    • Dong, W.
  • Source: European Journal of Soil Biology
  • Volume: 46
  • Issue: 3-4
  • Year: 2010
  • Summary: This study compared the responses of soil chemical and microbial indicators to the conservational tillage (CT) versus traditional tillage (TT) in a Haplic Cambisol in the North China Plain (NCP). These indicators included soil organic C (SOC), soil total N (STN), soil available P (SAP), cation exchange capacity (CEC), exchangeable Ca 2+ and Mg 2+, microbial biomass C (MBC), microbial biomass N (MBN), alkaline phosphomonoesterase (AP), beta-glucosidase, N-acetyl-beta-glucosaminidase (NAG), nitrate reductase (NR), protease, urease and the geometric mean of the assayed enzymes (GMea). Our results showed that almost all investigated parameters, except the contents of CEC, Ca 2+, Mg 2+ and the ratios of GMea/MBN and C/N, were significantly higher under the CT (no-till, NT and reduced-till, RT) than those under the TT, whilst the crop yield was not significantly affected by tillage treatments. Principle component analysis (PCA) showed that the first and second component explained 67.2% and 16.6% of the total variation, respectively. The first component was significantly correlated with GMea, MBC, MBN and beta-glucosidase, and effectively discriminated soils under the NT or RT from those under the TT. Our results indicated that the 6-year CT improved the quality of the Haplic Cambisol by enhancing its chemical and microbial properties, whilst GMea, MBC, MBN and beta-glucosidase were among the most effective indicators for monitoring these improvements.
  • Authors:
    • Zhang, J.
    • Zhang, X.
    • Sun, J.
    • Kang, S.
    • Du, T.
  • Source: Agricultural Water Management
  • Volume: 97
  • Issue: 1
  • Year: 2010
  • Summary: Water shortage is the major bottleneck that limits sustainable development of agriculture in north China. Crop physiological water-saving irrigation methods such as temporal (regulated deficit irrigation) and spatial (partial root zone irrigation) deficit irrigation have been tested with much improved crop water use efficiency (WUE) without significant yield reduction. Field experiments were conducted to investigate the effect of (1) spatial deficit irrigation on spring maize in arid Inland River Basin of northwest China during 1997-2000; (2) temporal deficit irrigation on winter wheat in semi-arid Haihe River Basin during 2003-2007 and (3) temporal deficit irrigation on winter wheat and summer maize in Yellow River Basin during 2006-2007. Results showed that alternate furrow irrigation (AFI) maintained similar photosynthetic rate ( Pn) but reduced transpiration rate ( Tr), and thus increased leaf WUE of maize. It also showed that the improved WUE might only be gained for AFI under less water amount per irrigation. The feasible irrigation cycle is 7d in the extremely arid condition in Inner River Basin of northwest China and less water amount with more irrigation frequency is better for both grain yield and WUE in semi-arid Haihe River Basin of north China. Field experiment in Yellow River Basin of north China also suggests that mild water deficit at early seedling stage is beneficial for grain yield and WUE of summer maize, and the deficit timing and severity should be modulated according to the drought tolerance of different crop varieties. The economical evapotranspiration for winter wheat in Haihe River Basin, summer maize in Yellow River Basin of north China and spring maize in Inland River Basin of northwest China are 420.0 mm, 432.5 mm and 450.0 mm respectively. Our study in the three regions in recent decade also showed that AFI should be a useful water-saving irrigation method for wide-spaced cereals in arid region, but mild water deficit in earlier stage might be a practical irrigation strategy for close-planting cereals. Application of such temporal and spatial deficit irrigation in field-grown crops has greater potential in saving water, maintaining economic yield and improving WUE.
  • Authors:
    • Slafer, G. A.
    • Mariano Cossani, C.
    • Savin, R.
  • Source: Crop and Pasture Science
  • Volume: 61
  • Issue: 10
  • Year: 2010
  • Summary: In semiarid Mediterranean environments, low nitrogen (N) and water availabilities are key constraints to cereal productivity. Theoretically, for a given level of N or water stress, crops perform better when co-limitation occurs. Empirical evidence of this theoretical concept with field crops is rather scarce. Using data from field experiments we evaluated whether N-use efficiency (NUE) and water-use efficiency (WUE) in small grain cereals increases with the degree of co-limitation. Four field experiments were carried out during three growing seasons including factorial combinations of bread wheat, durum wheat and barley, grown under different N fertiliser rates and water regimes. Yield gap was calculated as the difference between maximum attainable yield and actual yield while stress indices for N (NSI) or water (WSI) were calculated as the ratios between actual N uptake or water use and those required to achieve maximum yields, respectively. Water and N co-limitation was calculated as CWN=1-|NSI-WSI|. The relationships of yield gap, NUE and WUE with the different co-limitation indices were evaluated. Yield gap (range from -3.8 to -8.1 Mg ha -1) enlarged (was more negative) with the highest levels of stress and, as expected from theory, it was reduced with the degree of co-limitation. WUE ranged from 6.3 to 21.8 kg ha -1 mm -1 with the maximum values observed under conditions in which co-limitation increased. Reduction in yield gap with increased degree of co-limitation was mainly due to a positive effect of this variable on WUE.
  • Authors:
    • Barton, L.
    • Murphy, D. V.
    • Kiese, R.
    • Butterbach-Bahl, K.
  • Source: GCB Bioenergy
  • Volume: 2
  • Issue: 1
  • Year: 2010
  • Summary: Understanding nitrous oxide (N2O) and methane (CH4) fluxes from agricultural soils in semi-arid climates is necessary to fully assess greenhouse gas emissions from bioenergy cropping systems, and to improve our knowledge of global terrestrial gaseous exchange. Canola is grown globally as a feedstock for biodiesel production, however, resulting soil greenhouse gas fluxes are rarely reported for semi-arid climates. We measured soil N2O and CH4 fluxes from a rain-fed canola crop in a semi-arid region of south-western Australia for 1 year on a subdaily basis. The site included N fertilized (75 kg N ha−1 yr−1) and nonfertilized plots. Daily N2O fluxes were low (−1.5 to 4.7 g N2O-N ha−1 day−1) and culminated in an annual loss of 128 g N2O-N ha−1 (standard error, 12 g N2O-N ha−1) from N fertilized soil and 80 g N2O-N ha−1 (standard error, 11 g N2O-N ha−1) from nonfertilized soil. Daily CH4 fluxes were also low (−10.3 to 11.9 g CH4-C ha−1 day−1), and did not differ with treatments, with an average annual net emission of 6.7 g CH4–C ha−1 (standard error, 20 g CH4–C ha−1). Greatest daily N2O fluxes occurred when the soil was fallow, and following a series of summer rainfall events. Summer rainfall increased soil water contents and available N, and occurred when soil temperatures were >25 °C, and when there was no active plant growth to compete with soil microorganisms for mineralized N; conditions known to promote N2O production. The proportion of N fertilizer emitted as N2O, after correction for emissions from the no N fertilizer treatment, was 0.06%; 17 times lower than IPCC default value for the application of synthetic N fertilizers to land (1.0%). Soil greenhouse gas fluxes from bioenergy crop production in semi-arid regions are likely to have less influence on the net global warming potential of biofuel production than in temperate climates.
  • Authors:
    • Horwath, W. R.
    • Rolston, D. E.
    • Kallenbach, C. M.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 137
  • Issue: 3
  • Year: 2010
  • Summary: Agricultural management practices such as subsurface drip irrigation (SDI) and winter legume cover cropping (WLCC) influence soil water dynamics as well as carbon and nitrogen cycling, potentially changing emission rates of soil CO2 and N2), principal greenhouse gases. A split plot tomato field trial in California's Central Valley was used to evaluate the use of SDI and WLCC on event-based CO2 and N2O emissions. SDI and WLCC were compared to the region's more conventional practices: furrow irrigation (FI) and no cover crop (NCC). Our results indicate that SDI offers the potential to manage cover crops without the significant increases in greenhouse gas production during the growing season as seen under FI cover-cropped systems. The highest N2O emissions occurred during the beginning of the rainy season in November in the FI-WLCC treatment(5 mg m-2 h-1) and the lowest in August in the SDI-NCC treatments (4.87 [micro]g m-2 h-1). CO2 emissions under WLCC were 40% and 15% greater compared to NCC under FI and SDI, respectively. The treatment with the greatest effect on CO2 and N2O emissions was WLCC, which increased average growing season N2O and CO2 emissions under FI by 60 [micro]g N2O m-2 h-1 and 425 mg CO2 m-2 h-1 compared to NCC. In SDI there was no effect of a cover crop on growing season CO2 and N2O emissions. In the rainy season, however, SDI N2O and CO2 emissions were not different from FI. In the rainy season, the cover crop increased N2O emissions in SDI only and increased CO2 emissions only under FI. Subsurface drip shows promise in reducing overall N2O emissions in crop rotations with legume cover crops.
  • Authors:
    • Fine, P.
    • Clapp, C. E.
    • Zhang, Y.
    • Chen, D.
    • Venterea, R. T.
    • Bloom, P.
    • Tamir, G.
    • Bar-Tal, A.
    • Heller, H.
  • Source: Journal of Environmental Quality
  • Volume: 39
  • Issue: 2
  • Year: 2010
  • Summary: The use of organic residues as soil additives is increasing, but, depending on their composition and application methods, these organic amendments can stimulate the emissions of CO2 and N2O. The objective of this Study was to quantify the effects of management practices in irrigated sweet corn (Zea mays L.) on CO2 and N2O emissions and to relate emissions to environmental factors. In a 3-yr study, corn residues (CR) and pasteurized chicken manure (PCM) Were used as soil amendments compared with no residue (NR) under three management practices: shallow tillage (ST) and no tillage (NT) under consecutive corn crops and ST Without crop. Tillage significantly increased (P < 0.05) CO2 and N2O fluxes in residue-amended plots and in NR plots. Carbon dioxide and N2O fluxes were correlated with soil NH4 concentrations and with days since tillage and days since seeding, Fluxes of CO2 were correlated with soil water content, whereas N2O flux had higher correlation with air temperature. Annual CO2 emissions were higher with PCM than with CR and NR (9.7, 2.9, and 2.3 Mg C ha(-1), respectively). Fluxes of N2O were 34.4, 0.94, and 0.77 kg N ha(-1) yr(-1) with PCM, CR, and NR, respectively. Annual amounts of CO2-C and N2O-N emissions from the PCM treatments were 64 and 3% of the applied C and N, respectively. Regardless of cultivation practices, elevated N2O emissions were recorded in the PCM treatment. These emissions could negate some of the beneficial effects of PCM on soil properties.
  • Authors:
    • Dalal, R. C.
    • Page, K. L.
    • Pringle, M. J.
    • Allen, D. E.
  • Source: The Rangeland Journal
  • Volume: 32
  • Issue: 2
  • Year: 2010
  • Summary: The accurate measurement of the soil organic carbon (SOC) stock in Australian grazing lands is important due to the major role that SOC plays in soil productivity and the potential influence of soil C cycling on Australia's greenhouse gas emissions. However, the current sampling methodologies for SOC stock are varied and potentially conflicting. It was the objective of this paper to review the nature of, and reasons for, SOC variability; the sampling methodologies commonly used; and to identify knowledge gaps for SOC measurement in grazing lands. Soil C consists of a range of biological materials, in various SOC pools such as dissolved organic C, micro- and meso-fauna (microbial biomass), fungal hyphae and fresh plant residues in or on the soil (particulate organic C, light-fraction C), the products of decomposition (humus, slow pool C) and complexed organic C, and char and phytoliths (inert, passive or resistant C); and soil inorganic C (carbonates and bicarbonates). Microbial biomass and particulate or light-fraction organic C are most sensitive to management or land-use change; resistant organic C and soil carbonates are least sensitive. The SOC present at any location is influenced by a series of complex interactions between plant growth, climate, soil type or parent material, topography and site management. Because of this, SOC stock and SOC pools are highly variable on both spatial and temporal scales. This creates a challenge for efficient sampling. Sampling methods are predominantly based on design-based (classical) statistical techniques, crucial to which is a randomised sampling pattern that negates bias. Alternatively a model-based (geostatistical) analysis can be used, which does not require randomisation. Each approach is equally valid to characterise SOC in the rangelands. However, given that SOC reporting in the rangelands will almost certainly rely on average values for some aggregated scale (such as a paddock or property), we contend that the design-based approach might be preferred. We also challenge soil surveyors and their sponsors to realise that: (i) paired sites are the most efficient way of detecting a temporal change in SOC stock, but destructive sampling and cumulative measurement errors decrease our ability to detect change; (ii) due to (i), an efficient sampling scheme to estimate baseline status is not likely to be an efficient sampling scheme to estimate temporal change; (iii) samples should be collected as widely as possible within the area of interest; (iv) replicate of laboratory analyses is a critical step in being able to characterise temporal change. Sampling requirements for SOC stock in Australian grazing lands are yet to be explicitly quantified and an examination of a range of these ecosystems is required in order to assess the sampling densities and techniques necessary to detect specified changes in SOC stock and SOC pools. An examination of techniques that can help reduce sampling requirements (such as measurement of the SOC fractions that are most sensitive to management changes and/or measurement at specific times of the year, preferably before rapid plant growth, to decrease temporal variability), and new technologies for in situ SOC measurement is also required.
  • Authors:
    • Reid, R.
  • Source: Plant Science
  • Volume: 178
  • Issue: 1
  • Year: 2010
  • Summary: High boron concentrations in soil and in irrigation water reduce crop productivity in many areas of the world. Plant tolerance to boron toxicity has been identified in a range of genotypes and recent research has revealed a physiological mechanism behind this tolerance in cereals. Cultivars with high levels of expression of a gene encoding a boron-efflux transporter in roots and shoots have been reported to show tolerance to high boron in soils and in solution culture experiments conducted under controlled conditions in glasshouses and growth rooms. However, field trials of tolerant cultivars in rain-fed semi-arid environments have been disappointing with few showing even modest improvements in yield, and others showing either no effect or a decrease in yields.
  • Authors:
    • Sommer, R.
    • Ryan, J.
  • Source: Proceedings of the 19th World Congress of Soil Science: Soil solutions for a changing world, Brisbane, Australia, 1-6 August 2010. Division Symposium 3.2 Nutrient best management practices
  • Year: 2010
  • Summary: While globally fertilizers have had a major impact on food production for the past half-century, the general use of chemical fertilizers in the semi-arid areas of the world is a more recent development. This is particularly true of the Mediterranean region, especially in North Africa and West Asia. Traditionally, the cropping system involved growing cereals (barley and wheat) in rotation with fallow to conserve moisture; sheep and goats were an integral part of the low-input system. Drought was a constant constraint on crop yields. In the past few decades, significant developments have occurred to increase agricultural output; new high-yielding disease resistant varieties; mechanization; irrigation; pest control; and particularly the use of chemical fertilizers as a supplement to the limited animal manures available. Research at the International Center for Agricultural Research in the Dry Areas (ICARDA) in collaboration with the national agricultural systems in the mandate countries of the region has made significant strides in fertilizer research. While much has been achieved in terms of best fertilizer management practices, much remains to be done. This presentation examines the use of fertilizers under the headings of the best management practice concept; right source, right application rate, right time of application, and right place. As fertilizer use will expand in the Mediterranean region, efficiency of use will be an underlying consideration. As agricultural land is on a global level is finite, with limited possibilities to expand cultivation, the increasing population of the world has correspondingly increased the needs for food and fibre. An inevitable development has been intensification of land use, particularly in developing countries of the world, leading to poverty and increased concerns about food security (Borlaug 2007). Pressure on land has been particularly acute in the arid and semi-arid regions, which are characterized by drought and land degradation. The lands surrounding the Mediterranean have been cultivated for millennia and are the site of settled agriculture and the center of origin of some of the world's major crops, especially cereals and pulses. Much development efforts have centered on the West Asia- North Africa (WANA) area, which is characterized by a Mediterranean climate and where drought is the main production constraint (Smith and Harris 1981).
  • Authors:
    • Weeks, C.
    • Robertson, M.
    • Oliver, Y.
  • Source: Agricultural Water Management
  • Volume: 98
  • Issue: 2
  • Year: 2010
  • Summary: The practice of long fallowing, by omitting a year of cropping, is gaining renewed focus in the low rainfall zone of the northern agriculture region of Western Australia. The impetus behind this practice change has been a reduced use of pasture breaks in cereal crop rotations, and the belief that a fallow can improve soil water accumulation and thus buffer the negative effects of dry seasons on crop yields. We evaluated the benefits of long fallowing (full stubble retention, no weed growth allowed) in a continuous wheat sequence via simulation modelling with APSIM at two rainfall locations and five soil types. The simulated benefits to long fallowing were attributable to soil water accumulation only, as the effects on soil nitrogen, diseases or weeds were not evaluated. The long-term (100 years) mean wheat yield benefit to fallowing was 0.36-0.43 t/ha in clay, 0.20-0.23 t/ha in sand and loam, and 0-0.03 t/ha in shallow sand and shallow loams. Over the range of seasons simulated the response varied from -0.20 to 3.87 t/ha in the clay and -0.48 to 2.0 t/ha for the other soils. The accumulation of soil water and associated yield benefits occurred in 30-40% of years on better soils and only 10-20% on poorer soils. For the loam soil, the majority of the yield increases occurred when the growing-season (May-September) rainfall following the fallow was low (30 mm), although yield increase did occur with other combinations of growing-season rainfall and soil water. Over several years of a crop sequence involving fallow and wheat, the benefits from long fallowing due to greater soil water accumulation did not offset yield lost from omitting years from crop production, although the coefficient of variation for inter-annual farm grain production was reduced, particularly on clay soils during the 1998-2007 decade of below-average rainfall. We conclude that under future drying climates in Western Australia, fallowing may have a role to play in buffering the effects of enhanced inter-annual variability in rainfall. Investigations are required on the management of fallows, and management of subsequent crops (i.e. sowing earlier and crop density) so as to maximise yield benefits to subsequent crops while maintaining groundcover to prevent soil erosion.