- Authors:
- Climate, Community and Biodiversity Alliance
- Volume: 2009
- Year: 2009
- Authors:
- O'Leary, G.
- Fisher, P.
- Abuzar, M.
- Rab, M.
- Fitzpatrick, J.
- Armstrong, R.
- Source: Crop & Pasture Science
- Volume: 60
- Issue: 9
- Year: 2009
- Summary: A major barrier to the adoption of precision agriculture in dryland cropping systems is our current inability to reliably predict spatial patterns of grain yield for future crops for a specific paddock. An experiment was undertaken to develop a better understanding of how edaphic and climatic factors interact to influence the spatial variation in the growth, water use, and grain yield of different crops in a single paddock so as to improve predictions of the likely spatial pattern of grain yields in future crops. Changes in a range of crop and soil properties were monitored over 3 consecutive seasons (barley in 2005 and 2007 and lentils in 2006) in the southern section of a 167-ha paddock in the Mallee region of Victoria, which had been classified into 3 different yield (low, moderate, and high) and seasonal variability (stable and variable) zones using normalised difference vegetation index (NDVI) and historic yield maps. The different management zones reflected marked differences in a range of soil properties including both texture in the topsoil and potential chemical-physical constraints in the subsoil (SSCs) to root growth and water use. Dry matter production, grain yield, and quality differed significantly between the yield zones but the relative difference between zones was reduced when supplementary irrigation was applied to barley in 2005, suggesting that some other factor, e.g. nitrogen (N), may have become limiting in that year. There was a strong relationship between crop growth and the use of soil water and nitrate across the management zones, with most water use by the crop occurring in the pre-anthesis/flowering period, but the nature of this relationship appeared to vary with year and/or crop type. In 2006, lentil yield was strongly related to crop establishment, which varied with soil texture and differences in plant-available water. In 2007 the presence of soil water following a good break to the season permitted root growth into the subsoil where there was evidence that SSCs may have adversely affected crop growth. Because of potential residual effects of one crop on another, e.g. through differential N supply and use, we conclude that the utility of the NDVI methodology for developing zone management maps could be improved by using historical records and data for a range of crop types rather than pooling data from a range of seasons.
- Authors:
- Source: Soil & Tillage Research
- Volume: 104
- Issue: 1
- Year: 2009
- Summary: This proceedings contains 9 papers providing information on the potential of conservation tillage in a wide-range of geographical, climatological and socioeconomical situations. Results from studies in China, Australia, Iran and Ethiopia are presented. Topics covered include: sustainable tillage methods for irrigated wheat production in different regions of Iran; conservation tillage models for small-scale farming; functional relationships between soil water infiltration and wheeling and rainfall energy; controlled traffic farming in restoring soil structure; short-term effects of tillage and manure on some soil physical properties and maize root growth in a sandy loam soil in western Iran; the impact of 14 years of conventional and no-till cultivation on the physical properties and crop yields of a loam soil at Grafton NSW, Australia; conservation tillage implements and systems for smallholder farmers in semi-arid Ethiopia; controlled traffic farming with no tillage for improved fallow water storage and crop yield on the Chinese Loess Plateau; the effect of alternative tillage and residue cover on yield and water use efficiency in annual double cropping system in North China Plain.
- Authors:
- Ciesiolka, C. A. A.
- Ghadiri, H.
- Yu, B.
- Sanjari, G.
- Rose, C. W.
- Source: Soil Research
- Volume: 47
- Issue: 8
- Year: 2009
- Summary: The time-controlled rotational grazing (TC grazing) has become popular in Australia and elsewhere in the world to provide graziers and ranchers with improved productivity over traditional practices. However, this grazing system, which involves short periods of intensive grazing, has raised concerns about sustainability and environmental impacts on water and soil resources, and ecosystem health generally. A runoff experiment at the catchment scale was established on the grazing property 'Currajong' in the south-east region of Queensland, Australia, to investigate the effects of continuous and TC grazing on runoff and sediment generation from 2001 to 2006. Sediment loss was reduced significantly under TC grazing compared with continuous grazing irrespective of the size of runoff events. This effect was more pronounced in the catchments with soils of gentler slopes and greater depths. The reduction in soil erosion was achieved despite the fact that the increase in ground cover under TC grazing had little effect on runoff coefficient or runoff depth. Decrease in runoff in relation to the increase in surface cover only occurred for small events, whereas for large rainfall events, runoff generated irrespective of the level of ground cover. This study showed that ground cover is a key driver in reducing sediment concentration, resulting in a significantly lower sediment loss under TC grazing. In the study area a minimum of 70% of surface cover as a threshold appeared to be needed to efficiently protect the soil surface from erosive forces of rain and runoff and to control soil erosion. The results also indicate that TC grazing has a superior capability to produce and maintain a higher level of ground cover (up to 90%) than continuous grazing (up to 65%). The long rest periods in TC grazing are seen as the major contributor to soil and pasture recovery after intensive defoliations by grazing animals, leading to an increase in above-ground organic material and thus surface cover over time.
- Authors:
- Bhattarai, S. P.
- Midmore, D. J.
- Source: Journal of Integrative Plant Biology
- Volume: 51
- Issue: 7
- Year: 2009
- Summary: Impacts of salinity become severe when the soil is deficient in oxygen. Oxygation (using aerated water for subsurface drip irrigation of crop) could minimize the impact of salinity on plants under oxygen-limiting soil environments. Pot experiments were conducted to evaluate the effects of oxygation (12% air volume/volume of water) on vegetable soybean (moderately salt tolerant) and cotton (salt tolerant) in a salinized vertisol at 2, 8, 14, 20 dS/m EC e. In vegetable soybean, oxygation increased above ground biomass yield and water use efficiency (WUE) by 13% and 22%, respectively, compared with the control. Higher yield with oxygation was accompanied by greater plant height and stem diameter and reduced specific leaf area and leaf Na + and Cl - concentrations. In cotton, oxygation increased lint yield and WUE by 18% and 16%, respectively, compared with the control, and was accompanied by greater canopy light interception, plant height and stem diameter. Oxygation also led to a greater rate of photosynthesis, higher relative water content in the leaf, reduced crop water stress index and lower leaf water potential. It did not, however, affect leaf Na + or Cl - concentration. Oxygation invariably increased, whereas salinity reduced the K +:Na + ratio in the leaves of both species. Oxygation improved yield and WUE performance of salt tolerant and moderately tolerant crops under saline soil environments, and this may have a significant impact for irrigated agriculture where saline soils pose constraints to crop production.
- Authors:
- Buck, R.
- Hinz, C.
- Murphy, D. V.
- Butterbach-Bahl, K.
- Gatter, D.
- Kiese, R.
- Barton, L.
- Source: Global Change Biology
- Volume: 14
- Issue: 1
- Year: 2008
- Summary: Understanding nitrous oxide (N2O) emissions from agricultural soils in semi-arid regions is required to better understand global terrestrial N2O losses. Nitrous oxide emissions were measured from a rain-fed, cropped soil in a semi-arid region of south-western Australia for one year on a sub-daily basis. The site included N-fertilized (100 kg N ha-1 yr-1) and nonfertilized plots. Emissions were measured using soil chambers connected to a fully automated system that measured N2O using gas chromatography. Daily N2O emissions were low (-1.8 to 7.3 g N2O-N ha-1 day-1) and culminated in an annual loss of 0.11 kg N2O-N ha-1 from N-fertilized soil and 0.09 kg N2O-N ha-1 from nonfertilized soil. Over half (55%) the annual N2O emission occurred from both N treatments when the soil was fallow, following a series of summer rainfall events. At this time of the year, conditions were conducive for soil microbial N2O production: elevated soil water content, available N, soil temperatures generally >25 °C and no active plant growth. The proportion of N fertilizer emitted as N2O in 1 year, after correction for the "background" emission (no N fertilizer applied), was 0.02%. The emission factor reported in this study was 60 times lower than the IPCC default value for the application of synthetic fertilizers to land (1.25%), suggesting that the default may not be suitable for cropped soils in semi-arid regions. Applying N fertilizer did not significantly increase the annual N2O emission, demonstrating that a proportion of N2O emitted from agricultural soils may not be directly derived from the application of N fertilizer. "Background" emissions, resulting from other agricultural practices, need to be accounted for if we are to fully assess the impact of agriculture in semi-arid regions on global terrestrial N2O emissions.
- Authors:
- Carter,D.
- L.,Barton
- Biswas,W. K.
- Source: Water and Environment Journal
- Volume: 22
- Issue: 3
- Year: 2008
- Authors:
- de Klein, C. A. M.
- Eckard, R. J.
- Source: Australian Journal of Experimental Agriculture
- Volume: 48
- Year: 2008
- Authors:
- Chen, D.
- Suter, H.
- Islam, A.
- Edis, R.
- Freney, J.
- Walker, C.
- Source: Soil Research
- Volume: 46
- Issue: 4
- Year: 2008
- Authors:
- Source: Eddy covariance flux measurements of CH4 and N2O exchange
- Year: 2008
