• Authors:
    • Xu, Z.
    • Wu, H.
    • Rui, Y.
    • Lu, S.
    • Chen, C.
    • Zhou, X.
  • Source: Biology and Fertility of Soils
  • Volume: 48
  • Issue: 2
  • Year: 2012
  • Summary: Little information is available about the effects of cover crops on soil labile organic carbon (C), especially in Australia. In this study, two cover crop species, i.e., wheat and Saia oat, were broadcast-seeded in May 2009 and then crop biomass was crimp-rolled onto the soil surface at anthesis in October 2009 in southeastern Australia. Soil and crop residue samples were taken in December 2009 to investigate the short-term effects of cover crops on soil pH, moisture, NH 4+-N, NO 3--N, soluble organic C and nitrogen (N), total organic C and N, and C mineralization in comparison with a nil-crop control (CK). The soil is a Chromic Luvisol according to the FAO classification with 48.42.2% sand, 19.52.1% silt, and 32.12.1% clay. An exponential model fitting was employed to assess soil potentially labile organic C ( C0) and easily decomposable organic C for all treatments based on 46-day incubations. The results showed that crop residue biomass significantly decreased over the course of 2-month decomposition. The cover crop treatments had significantly higher soil pH, soluble organic C and N, cumulative CO 2-C, C0, and easily decomposable organic C, but significantly lower NO 3--N than the CK. However, no significant differences were found in soil moisture, NH 4+-N, and total organic C and N contents among the treatments. Our results indicated that the short-term cover crops increased soil labile organic C pools, which might have implications for local agricultural ecosystem managements in this region.
  • Authors:
    • Xu, Z.
    • Wu, H.
    • Chen, C.
    • Zhou, X.
  • Source: Journal of Soils and Sediments
  • Volume: 12
  • Issue: 6
  • Year: 2012
  • Summary: Purpose: Cover crop residue is generally applied to improve soil quality and crop productivity. Improved understanding of dynamics of soil extractable organic carbon (EOC) and nitrogen (EON) under cover crops is useful for developing effective agronomic management and nitrogen (N) fertilization strategies. Materials and methods: Dynamics of soil extractable inorganic and organic carbon (C) and N pools were investigated under six cover crop treatments, which included two legume crops (capello woolly pod vetch and field pea), three non-legume crops (wheat, Saia oat and Indian mustard), and a nil-crop control (CK) in southeastern Australia. Cover crops at anthesis were crimp-rolled onto the soil surface in October 2009. Soil and crop residue samples were taken over the periods October-December (2009) and March-May (2010), respectively, to examine remaining crop residue biomass, soil NH 4++N and NO 3--N as well as EOC and EON concentrations using extraction methods of 2 M KCl and hot water. Additionally, soil net N mineralization rates were measured for soil samples collected in May 2010. Results and discussion The CK treatment had the highest soil inorganic N (NH 4+-N+NO 3--N) at the sampling time in December 2009 but decreased greatly with sampling time. The cover crop treatments had greater soil EOC and EON concentrations than the CK treatment. However, no significant differences in soil NH 4+-N, NO 3--N, EOC, EON, and ratios of EOC to EON were found between the legume and non-legume cover crop treatments across the sampling times, which were supported by the similar results of soil net N mineralization rates among the treatments. Stepwise multiple regression analyses indicated that soil EOC in the hot water extracts was mainly affected by soil total C ( R2=0.654, P
  • Authors:
    • Chen, C.
    • Xu, Z.
    • Koetz, E.
    • Wu, H.
    • Zhou, X.
  • Source: Applied Soil Ecology
  • Volume: 53
  • Year: 2012
  • Summary: The conservation farming systems coupled with stubble retention are now widely adopted in southern Australia to improve soil fertility. However, little information is available about the effects of winter crops on soil labile organic carbon (C) and nitrogen (N) pools, especially in an arid agricultural ecosystem. In this study, eight winter cover crop treatments were used to investigate their effects on soil labile organic C and N pools and microbial metabolic profiles and diversity in temperate Australia. These treatments included two legume crops (capello woolly pod vetch and field pea), four non-legume crops (rye, wheat, Saia oat and Indian mustard), and a mixture of rye and capello woolly pod vetch as well as a nil-crop control. At the crop flowering stage, soil and crop samples were collected from the field and we examined aboveground crop biomass, soil NH 4+-N, NO 3--N, extractable organic C (EOC) and N (EON) concentrations using methods of 2 M KCl and hot water, microbial biomass, biologically active organic C (C Bio), and substrate-induced respiration (SIR) using the MicroResp method. Results showed that the crop treatments had lower soil moisture content, NO 3--N and the ratios of EOC to EON, but higher pH, NH 4+-N, EOC, EON, C Bio, microbial metabolic diversity index ( H) and evenness index compared with the control. There were no significant differences in microbial biomass C and N among the treatments. Although no pronounced differences in EOC and EON concentrations were found between the legumes and non-legumes, the legume treatments had lower SIR and higher H than the non-legume treatments. Principal component analysis showed that soil microbial metabolic profiles under the crops were different from those of the control, and the crop treatments had a clear separation along principal component 2. In addition, redundancy analysis showed that soil pH and moisture content were the most important influencing factors, along with EON and crop biomass, determining the patterns of microbial metabolic profiles under the crops.
  • Authors:
    • Evans, N.
    • Agbola, F.
  • Source: Agricultural Systems
  • Volume: 107
  • Year: 2012
  • Summary: Although water markets have been in operation for nearly 30 years, previous empirical studies have ignored farmer's land use response to water trading in the Murray-Darling Basin (MDB), Australia. A Nerlovian partial adjustment model of rice and cotton acreage response in the MDB were specified and estimated using data for the period 1965-2008. The results indicate that acreage response for rice and cotton with respect to the price of water are inelastic in both the short- and long-run. The findings of this study bring into question the effectiveness of water trading scheme as the primary means of ensuring the efficient use of water and highlight the need for other complementary measures in the MDB. The results of this study highlight the complex interdependencies of many factors that influence farmer's land use decisions and draw an important conclusion that although water trading has increased the efficient use of irrigated water, its impact on farmers' land use decisions has been too small to stimulate any significant reduction in irrigated water usage in the MDB. (C) 2011 Elsevier Ltd. All rights reserved.
  • Authors:
    • Sutton, B.
    • Neilsen, J.
    • Mahan, J.
    • Burke, J.
    • Conaty, W.
  • Source: Crop Science
  • Volume: 52
  • Issue: 4
  • Year: 2012
  • Summary: A plant-based thermal optimum approach to irrigation scheduling provides potential benefits in that water applications are scheduled on the basis of plant response to water status. Such irrigation systems require a defined thermal optimum for the crop and while such optimum values have been identified for cotton (Gossypium hirsutum L.) cultivars in the United States, there is no information of this type for cultivars common in Australian production. This paper outlines a threefold approach to determining the optimum temperature (T-opt) of the commercial Australian cotton cultivar Sicot 70BRF in an Australian production system. It combines the use of a laboratory-based fluorescence assay, field-based net C assimilation rate (A) and stomatal conductance to water vapor (g(s)), and canopy temperature (T-c)-yield relations. The fluorescence assay showed a T-opt between 28 and 30 degrees C while leaf gas exchange rates peaked at a leaf temperature (T l) of 29 degrees C. The T-c-yield relations peaked at 26 degrees C, with yield reductions observed when T-c > 28 degrees C. We conclude the T-opt of the Australian upland cotton cultivar Sicot 70BRF to be 28 +/- 2 degrees C. This T-opt will provide valuable information for use in thermal optimum irrigation scheduling systems.
  • Authors:
    • de Figueiredo, M.
    • Figueiredo, M.
    • Detomini, E.
  • Source: Revista de Politica Agricola
  • Volume: 21
  • Issue: 1
  • Year: 2012
  • Summary: The main purpose of this study is to identify the optimum allocation of limited amount of land and irrigation water across a number of alternative farm enterprises, maximising the whole-farm profitability by considering present relative prices, changes in river water availability, irrigation system efficiency and a highly variable climate. It was developed an optimisation model by using linear programming language to maximise the whole-farm profit of farm located in Wee Waa (NSW, Australia), for three different scenarios (dry, average and wet years) over two seasons. The whole-farm profit is highly sensitive to climate variability and also to prices and yields variability, especially in relation to cotton.
  • Authors:
    • Finlay, L. A.
    • Weaver, T. B.
    • Hulugalle, N. R.
    • Lonergan, P.
  • Source: Soil Research
  • Volume: 50
  • Issue: 4
  • Year: 2012
  • Summary: Comparative studies of soil quality and energy use in two- and three-crop rotations in irrigated cotton ( Gossypium hirsutum L.) based cropping systems under varying stubble management practices in Australian Vertosols are sparse. Our primary objective was to quantify selected soil quality indices (salinity, sodicity, exchangeable cations, nitrate-N, pH), crop yields, and greenhouse gas emissions in four irrigated cotton-based cropping systems sown on permanent beds in a Vertosol with subsoil sodicity near Narrabri in north-western New South Wales. A secondary objective was to evaluate the efficacy of sowing vetch in rotation with cotton over a long period on the incidence of black root-rot in cotton seedlings. Results: presented in this report pertain to the period June 2005-May 2011. The experimental treatments were: cotton-cotton; cotton-vetch ( Vicia benghalensis L.); cotton-wheat ( Triticum aestivum L.), where wheat stubble was incorporated; and cotton-wheat-vetch, where wheat stubble was retained as in-situ mulch. Vetch was terminated during or just before flowering by a combination of mowing and contact herbicides, and the residues were retained as in-situ mulch. Soil pH, electrical conductivity (EC 1:5), Cl -, NO 3--N, exchangeable cations, exchangeable sodium percentage (ESP), electrochemical stability index (=EC 1:5/ESP), and EC 1:5/ESC (exchangeable sodium concentration) were evaluated in samples taken from the 0-1.2 m depth before sowing cotton during late September or early October of each year. Incidence of black root-rot was assessed 6 weeks after sowing cotton. Compared with sowing cotton every year, including wheat in cotton-based cropping systems improved cotton yield and reduced soil quality decline, emissions of carbon dioxide equivalents (CO 2-e) per unit area, and CO 2-e emissions per unit of cotton yield. Including vetch in the rotation was of negligible benefit in terms of yield and CO2-e emissions per unit of yield. The rate of soil quality decline was unaffected by including vetch in a cotton-wheat rotation but was accelerated when included in a cotton-cotton sequence. Among all cropping systems, soil quality was best with cotton-wheat and cotton-wheat-vetch but poorest with cotton-vetch. Although CO2-e emissions associated with growing 1ha of cotton could be reduced by 9% by growing vetch because of substituting fixed atmospheric N for N fertiliser derived from fossil fuels, this advantage was partly negated by the emissions from farming operations associated with growing a vetch crop. Relative to a two-crop rotation (one cotton-one rotation crop), negligible benefits in terms of yield, soil quality, greenhouse gas emissions, and black root-rot control accrued from a three-crop rotation (one cotton-two rotation crops). Incidence of black root-rot increased as the number of cotton crops sown increased. In addition to the cropping systems, soil quality indices and yield were significantly influenced by irrigation water quality and climate.
  • Authors:
    • Vervoort, W.
    • Ancev,T.
    • Lee, L. Y.
  • Source: Agricultural Water Management
  • Volume: 109
  • Year: 2012
  • Summary: An integrated biophysical and economic model is used to determine the effects of using more water efficient irrigation systems and trade in water rights on the environmental performance of irrigation enterprises in the Mooki catchment within the Murray-Darling Basin, Australia. We find that improved water use efficiency increased profit in the presence of modern irrigation technologies and water trading. Salinity risk downstream is reduced due to the fall in saline discharge from the catchment, and irrigation water is traded away from ecologically significant regions. It is important that the institutional setup gives confidence in the security of water supplies. When irrigators can be assured about the security of their water entitlements in the context of water reform policies, incentives emerge for them to invest in water efficient irrigation technologies and to participate in the water market. Environmental performance can thereby be improved without the need for financial support from the government. Further, minimal government intervention is required to address salinity; given the conjunctive nature of secondary salinity and water use it can be cost-efficient to address both environmental flow and salinity mitigation with a single policy instrument. (C) 2012 Elsevier BM. All rights reserved.
  • Authors:
    • Grace, P. R.
    • Basso, B.
  • Source: Agricultural Systems
  • Volume: 105
  • Issue: 1
  • Year: 2012
  • Authors:
    • Misra, R. K.
    • Padhi, J.
    • Payero, J. O.
  • Source: Field Crops Research
  • Volume: 126
  • Year: 2012
  • Summary: Plant growth and soil water deficit can vary spatially and temporally in crop fields due to variation in soil properties and/or irrigation and crop management factors. We conducted field experiments with cotton (Gossypium hirsutum L.) over two seasons during 2007-2009 to test if infrared thermography can distinguish systematic variation in deficit irrigation applied to various parts of the field over time. Soil water content was measured with a neutron probe and thermal images of crop plants were taken with a thermal infrared camera. Leaf water potential and stomatal conductance were also measured on selected occasions. All measurements were made at fixed locations within three replicate plots of an irrigation experiment consisting of four soil-water deficit treatments. Canopy temperature related as well with soil water within the root zone of cotton as the stomatal conductance index derived from canopy temperature, but it neglected the effect of local and seasonal variation in environmental conditions. Similarities in the pattern of spatial variation in canopy temperature and soil water over the experimental field indicates that thermography can be used with stomatal conductance index to assess soil water deficit in cotton fields for scheduling of irrigation and to apply water in areas within the field where it is most needed to reduce water deficit stress to the crop. Further confidence with application of infrared thermography can be gained by testing our measurement approach and analysis with irrigation scheduling of other crops. (C) 2011 Elsevier B.V. All rights reserved.