Browsing by Author "Christensen, CL"

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    DISTRIBUTION OF CARBON IN SIZE-FRACTIONS OF A PASTURE SOIL 26 MONTHS AFTER ADDING BIOCHAR
    (Farmed Landscapes Research Centre (FLRC), Massey University, 2018) Calvelo Pereira, R; Camps-Arbestain, M; Saiz Rubio, R; Kong, Y; Shen, Q; Currie, LD; Christensen, CL
    Fractionating soils according to size and/or density of particles improves our understanding of the importance of interactions between organic and inorganic soil components on the turnover of soil organic carbon (SOC). Conventional soil physical fractionation methodologies misrepresent the contribution of pyrogenic C (e.g., biochar-derived C) to the total SOC because of the relative long turnover time of this fraction, regardless the physical SOC physical fraction in which this is found. In this study, a combination of particle size fractionation and wet sieving, as well as chemical analysis (dichromate oxidation) was tested to isolate meaningful SOC fractions in a set of 34 soils with C content ranging from 19.1–43.0 g SOC/kg soil. Topsoil and subsoil samples were obtained after 26 months of simulating cultivation at pasture renewal including pine biochar (10 t/ha) as amendment (below 10 cm depth) and growth of contrasted plant species (ryegrass vs a mixture of red clover and cocksfoot) in a lysimeter experiment using a silt loam soil (Tokomaru soil, a Pallic soil with limited drainage at depth). Across all the soils considered, the allocation of SOC in size-fractions (i.e., 2000-200, 250-53 and <53 m) was obtained by conventional wet sieving. Additionally, the total content of resistant forms of SOC (i.e.both alkyl C forms and pyrogenic C from biochar) was calculated as the sum of the dichromate-resistant C obtained in the different size-fractions. This sum of all dichromate-resistant C pools can be used as a proxy to estimate contribution of pyrogenic C to the total SOC in the soils studied. The different C fractions isolated by the appropriate combination of methodologies (particle size fractionation, wet chemistry) is proposed as an alternative to obtain the particulate, humus and resistant organic carbon fractions (POC, HOC and ROC, respectively) used in models (e.g. RothC). The developed methodology will help to improve the prediction of SOC dynamics and any impact of climate change on SOC stocks when these contain pyrogenic C.
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    FEASIBILITY STUDY, EXTENDING THE SWATH WIDTH OF TOPDRESSING AIRCRAFT TO REDUCE STRIPING OF FERTILISER MIXES
    (Massey University, ) Brown HA; Grafton MCE; Davies CE; Currie, LD; Christensen, CL
    Fertiliser mixes of magnesium oxide coated urea and super phosphate require high application rates 250kg/ha - 500kg/ha. These rates are inclined to clog spreaders reducing their efficiency and compromising operational safety. As a result, the current spreader design is, not fitted for these rates. The swath width from a Cresco 08-600 without a spreader is only 12m wide, meaning many passes are required to cover a field. The mixture also tends to segregate which leads to striping. A new method of spreading fertilizer, which provides a wider swath width and an even distribution, is required. This method must be able to meet the CAA requirements for topdressing safety, minimise segregation in fertiliser mixtures and preferably should be applicable to most bulk fertilizers in common use; the method must not add any significant weight to the aircraft that would decrease its operating capacity. The feasibility of developing a means of initiating spreading of bulk fertilisers from topdressing aircraft hoppers from regions outside of the influence of the prop wash are investigated. If feasible, the system should be able to apply fertiliser across a 40m swath width at the target application rate, in a single pass. This would reduce flight time and improve the distribution pattern leading to reduced operating costs and higher crop yield. This preliminary report suggests that it is mathematically possible to widen the swath width of the Cresco 08-600 to 40m at an application rate of 350kg/ha by means of a screw conveyor transporting and evenly releasing fertiliser along the length of the wing up until the dihedral is reached. The next stage in this project will be to design the screw conveyor system and test it on the ground to see its limitations and potential safety concerns.
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    The ballistics of separation of fertiliser blends at wide bout widths
    (28/02/2014) Grafton MCE; Yule IJ; Currie, LD; Christensen, CL
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    The potential of plantain based pastures to reduced nitrogen losses from dairy systems
    Navarrete Quijada S; Rodriguez MJ; Kemp PD; Hedley MJ; Horne DJ; Hanly JA; Currie, LD; Christensen, CL
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    Three years of duration-controlled grazing: What have we found?
    (2012-02) Christensen, CL; Hedley, MJ; Hanly, JA; Horne, DJ; Currie, LD; Christensen, CL