• Authors:
    • Rodriguez, L. C.
    • May, B.
    • Herr, A.
    • Farine, D.
    • O'Connell, D.
  • Source: Energy Policy
  • Volume: 39
  • Issue: 4
  • Year: 2011
  • Authors:
    • Bird, M. I.
    • Beeton, R. J. S.
    • Menzies, N. W.
    • Witt, G. B.
    • Noel, M. V.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 141
  • Issue: 1-2
  • Year: 2011
  • Authors:
    • Blanco-Canqui, H.
  • Source: Soil Use and Management
  • Volume: 27
  • Issue: 1
  • Year: 2011
  • Summary: Soil water repellency (SWR) is an intrinsic and dynamic soil property that can influence soil hydrology and crop production. Although several land use systems have been shown to induce water repellency in soil, the specific effects of no-till cropping on SWR are poorly understood. This article reviews the impacts of no-till on SWR and identifies research needs. No-till cropping generally induces 1.5 to 40 times more SWR than conventional tillage, depending on soil type. This may result from near-surface accumulation of hydrophobic organic C compounds derived from crop residues, microbial activity and reduced soil disturbance. While large SWR may have adverse impacts on soil hydrology and crop production, the level of SWR under no-till relative to conventional tillage may contribute to aggregate stabilization and intra-aggregate C sequestration. More research is needed to discern the extent and relevance of no-till induced SWR. This includes: (1) further assessment of SWR under different tillage systems across a wide range of soil textures and climates, (2) comparison of the various methods for measuring SWR over a range of water contents, (3) inclusion of SWR in routine soil analysis and its use as a parameter to evaluate management impacts, (4) assessment of the temporal and spatial changes in SWR under field conditions, (5) further assessment of the impacts of the small differences in SWR between no-till and conventionally tilled soils on crop production, soil hydrology and soil C sequestration, and (6) development of models to predict SWR for different tillage systems and soils.
  • Authors:
    • Dalal, R. C.
    • Allen, D. E.
    • Wang, W. J.
    • Reeves, S.
    • Gibson, I.
  • Source: Soil & Tillage Research
  • Volume: 112
  • Issue: 2
  • Year: 2011
  • Summary: Conservation agricultural practices such as no-till (NT) and crop residue retention (CRR), and nutrient application, increases soil organic C (SOC) and are considered effective measures of C sequestration in soil. However, long-term effects of individual components of conservation agriculture and their interactions on SOC are rarely evaluated; as a result, conflicting findings of these practices on SOC are reported in the literature. We measured SOC and soil total N in a balanced factorial experiment, conducted on a Vertisol, consisting of tillage practices (conventional mechanical tillage, CT; and no-tillage, NT), crop residue management (crop residue burned, CRB; and crop residue retained, CRR) and N fertiliser application (no N, 30 kg N ha -1 year -1; and 90 kg N ha -1 year -1). The site, in a semiarid subtropical region, was cropped with wheat ( Triticum aestivum L.) except for 3 years of barley ( Hordeum vulgare L.), for 40 years using conservation practices. In general, tillage effects on SOC and soil total N were small. Crop residue and N fertiliser interactively increased SOC and total N stocks at 0-0.1 m depth and cumulative stocks at 0-0.2 m and 0-0.3 m depths; that is, CRR increased SOC and soil total N only when N fertiliser was applied, and fertilisation increased SOC and soil total N only under CRR treatment. Depletion of delta 13C values in CRR treatments and delta 15N values in N treatments strongly indicated the contribution of crop residue (and root biomass) and N fertiliser to soil organic matter in this Vertisol. From this study and previous findings from this site, it appears, however, the effects of crop residue retention and N fertiliser occurred in early years, and did not continually increase SOC and total soil N with increasing period of conservation practices.
  • Authors:
    • Allen, D. E.
    • Reeves, S.
    • Menzies, N. W.
    • Dalal, R. C.
    • Wang, W.
  • Source: Soil Science Society of America Journal
  • Volume: 75
  • Issue: 6
  • Year: 2011
  • Summary: Land-use change from perennial grasslands to cultivated croplands leads to reduced soil organic C (SOC) and total N. Among other factors, introduction of annual crops and soil disturbance by tillage may account for reduced amounts of SOC and total N. However, agricultural practices of no-till and N fertilizer application may maintain soil N in cropped soils. We measured soil N changes and N-use efficiency in a field experiment initiated in 1968, consisting of completely randomized tillage practices (conventional mechanical till [CT], and no-till [NT]), crop residue management (residue burned [RB], and residue retained [RR]), and N fertilization (0, 30, and 90 kg N ha -1) on a Vertisol (Ustic Pellusert) over 40 yr. Crops grown were mainly wheat ( Triticum aestivum L.) except for five barley ( Hordeum vulgare L.) crops early in the experiment. Significant effects of treatments on soil total N were primarily confined to the top 0.1-m depth. Soil total N exponentially declined in all treatments even though apparent fertilizer N recoveries during this period (1969-2008) were only 46 and 59% of N applied at 90 and 30 kg N ha -1, respectively. Mineral N in the soil profile (0-1.2 m) ranged from 68 to 496 kg N ha -1. Nitrogen-use efficiency was similar ( P=0.13) under CT and NT in this Vertisol. However, crop residue retention and a low rate of N application had greater N-use efficiency (35-40%) than RB and a high rate of N application (21-25%) under the annual cereal grain cropping system. If perennial grasslands are considered ecological benchmarks for agricultural sustainability, primarily through large root biomass that utilizes water and nutrients efficiently, then the challenge remains to develop cropping systems that successfully mimic grassland ecosystems.
  • Authors:
    • Flower, K. C.
    • Crabtree, W. L.
  • Source: Field Crops Research
  • Volume: 121
  • Issue: 1
  • Year: 2011
  • Summary: On acid soils, no-tillage farmers are often advised to apply lime to the soil surface without incorporation by tillage. As such, it can take a number of years before the subsoil acidity is decreased. However, no-tillage seeders vary in the level of soil disturbance caused during seed placement. The consequence of such variations in soil disturbance for the effectiveness of lime in no-tillage cropping has not been explored. Our objectives were (i) to determine if the liming effect could be accelerated by increasing the rate of lime and level of soil disturbance during no-tillage seeding, and (ii) evaluate the effect of no-tillage seeding method, rate of lime and soil pH on yield of wheat, barley, canola and lupins. Three trials, each with a factorial design consisting of four seeding methods and four lime rates, were established in 1999 and continued until 2005. The soil had a texture contrast with about 15-20 cm of sand over yellow sandy clay loam and the initial pH (CaCl 2) at both 0-10 and 10-20 cm was between 4.5 and 4.7. The four seeding treatments were: low disturbance zero-till disc openers (ZT), higher disturbance no-tillage tines with narrow knife-points (NT), higher disturbance full cut seeding with sweeps (FC) for the first three years followed by ZT from then on, and FC for the first year followed by NT thereafter. The four lime rates were 0, 1, 2 and 4 t ha -1. The liming effect was more rapid with the higher disturbance seeding of NT, FCZT and FCNT, compared with ZT; the seeding effect on soil pH diminished with time and was not detected in the subsoil after four years. Higher rates of lime increased this effect and there was no interaction between seeding method and lime rate. This indicated that soil pH under the different seeding methods responded in a similar manner to increased lime. Nonetheless, significant positive linear regressions were found between yield and soil pH for wheat and barley and a negative relationship for lupins. Canola showed no response to soil pH, possibly because establishment was affected by seeding method, and soil pH was not low enough to elicit a response. The ZT seeding method gave lower yields than the other methods for canola and lupins in some years, but had no effect on wheat and barley yields. Higher disturbance at the time of no-till seeding can, therefore, accelerate the liming effect, making earlier economic gains possible.
  • Authors:
    • Pan, G.
    • Ogle, S.
    • Siebner, C.
    • McConkey, B.
    • Katterer, T.
    • Grace, P. R.
    • Goidts, E.
    • Etchevers, J.
    • Dodd, M.
    • Cerri, C. E. P.
    • Andren, O.
    • Paustian, K.
    • vanWesemael, B.
  • Source: Plant and Soil
  • Volume: 338
  • Issue: 1-2
  • Year: 2011
  • Summary: As regional and continental carbon balances of terrestrial ecosystems become available, it becomes clear that the soils are the largest source of uncertainty. Repeated inventories of soil organic carbon (SOC) organized in soil monitoring networks (SMN) are being implemented in a number of countries. This paper reviews the concepts and design of SMNs in ten countries, and discusses the contribution of such networks to reducing the uncertainty of soil carbon balances. Some SMNs are designed to estimate country-specific land use or management effects on SOC stocks, while others collect soil carbon and ancillary data to provide a nationally consistent assessment of soil carbon condition across the major land-use/soil type combinations. The former use a single sampling campaign of paired sites, while for the latter both systematic (usually grid based) and stratified repeated sampling campaigns (5-10 years interval) are used with densities of one site per 10-1,040 km2. For paired sites, multiple samples at each site are taken in order to allow statistical analysis, while for the single sites, composite samples are taken. In both cases, fixed depth increments together with samples for bulk density and stone content are recommended. Samples should be archived to allow for re-measurement purposes using updated techniques. Information on land management, and where possible, land use history should be systematically recorded for each site. A case study of the agricultural frontier in Brazil is presented in which land use effect factors are calculated in order to quantify the CO2 fluxes from national land use/management conversion matrices. Process-based SOC models can be run for the individual points of the SMN, provided detailed land management records are available. These studies are still rare, as most SMNs have been implemented recently or are in progress. Examples from the USA and Belgium show that uncertainties in SOC change range from 1.6-6.5 Mg C ha-1 for the prediction of SOC stock changes on individual sites to 11.72 Mg C ha-1 or 34% of the median SOC change for soil/land use/climate units. For national SOC monitoring, stratified sampling sites appears to be the most straightforward attribution of SOC values to units with similar soil/land use/climate conditions (i. e. a spatially implicit upscaling approach).
  • Authors:
    • Ortega-Farias, S.
    • Selles, G.
  • Source: ISHS Acta Horticulturae
  • Issue: 889
  • Year: 2011
  • Summary: These proceedings contain 79 papers on irrigation systems for horticultural crops. Specific topics covered include the following: improvement of water use for agriculture at catchment level under drought conditions; impact of climatic change on irrigated fruit tree production; effects of the irrigation regime and partial root zone drying on grape cv. Vermentino in Sardinia, Italy; effects of canopy exposure changes on plant water status in grape cv. Syrah; water use by drip-irrigated early-season peach trees; soil water content variations as water stress indicator in peach trees; reduction in the number of fruits in peach (T204) due to postharvest deficit irrigation; effects of irrigation management and N fertilizer on the yield and quality of apple cv. Gala; canopy temperature as an indicator of water status in citrus trees; effects of root anatomy on sap flow rate in avocado trees; influence of rootstock on the response of avocado cv. Hass to flooding stress; methods of selection for drought tolerance in potato; and drip irrigation for the establishment of strawberry transplants in southern California.
  • Authors:
    • Ward, J.
    • King, D.
    • Bryan, B.
  • Source: Ecological Indicators
  • Volume: 11
  • Issue: 1
  • Year: 2011
  • Summary: On-farm actions to better manage natural resources often involve an opportunity cost associated with foregone agricultural production. Spatial information on agricultural opportunity costs is a key indicator that has been demonstrated to increase the cost-effectiveness of environmental investment through spatial targeting. In this paper we develop a method for calculating expected profit as a more robust spatial measure of economic rent accruing from agricultural land and indicator of opportunity cost for use in landscape and planning for natural resource management. We apply this method to the Lower Murray region in southern Australia. Agricultural profit is calculated for three farming system phases (cereals, legumes, and grazing) by census zones based on agricultural statistics and cost of production information within a GIS environment. Zonal profit layers are smoothed using pycnophylactic (mass preserving) interpolation. Farming system rotations are quantified as a set of continuous spatial probability layers for each phase using a moving window kernel density technique based on existing land use data and these probability layers are used in a weighted allocation of expected profit across the landscape. The expected profit layer provides a high spatial resolution description of opportunity costs associated with natural resource management over the Lower Murray region suitable for input into systematic landscape planning analyses. Validation of the opportunity cost layer by field survey identified both random and systematic error. Interpretation of systematic error highlighted the need to augment pycnophylactic interpolation techniques with consideration of covariates of profit such as rainfall for better estimation in areas with high profit gradients.
  • Authors:
    • Luck, J.
    • Finlay, K.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 144
  • Issue: 1
  • Year: 2011
  • Summary: Global climate change threatens world food production via direct effects on plant growth and alterations to pest and pathogen prevalence and distribution. Complex relationships between host plant, pest, pathogen and environment create uncertainty particularly involving vector-borne diseases. We attempt to improve the understanding of the effects of climate change via a detailed review of one crop-vector-pathogen system. The bird cherry-oat aphid, Rhopalosiphum padi, is a global pest of cereals and vector of yellow dwarf viruses that cause significant crop losses in cereals. R. padi exhibits both sexual and parthenogenetic reproduction, alternating between crops and other host plants. In Australia, only parthenogenesis occurs due to the absence of the primary host, thus the aphid continuously cycles from grasses to cereals, allowing for continuous virus acquisition and transmission. We have reviewed the potential impact of future climate projections on R. padi population dynamics, persistence, abundance, dispersal and migration events as well as the interactions between vector, virus, crop and environment, all of which are critical to the behaviour and development of the vector and its ability to transmit the virus. We identify a number of knowledge gaps that currently limit efforts to determine how this pathosystem will function in a future climate.