An investigation into the fertilizer particle dynamics off-the-disc

The particle size range specifications for two biosolids-derived organomineral fertilizers (OMF) known as OMF10 (10:4:4) and OMF15 (15:4:4) were established. Such specifications will enable field application of OMF with spinning disc systems using conventional tramlines spacing. A theoretical model was developed, which predicts the trajectory of individual fertilizer particles off-the-disc. The drag coefficient (Cd) was estimated for small time steps (10-6 s) in the trajectory of the particle as a function of the Reynolds number. For the range of initial velocities (20 to 40 m s-1), release angles (0° to 10°) and particle densities (1000 to 2000 kg m-3) investigated, the analysis showed that OMF10 and OMF15 need to have particle diameters between 1.10 and 5.80 mm, and between 1.05 and 5.50 mm, respectively, to provide similar spreading performance to urea with particle size range of 1.00 to 5.25 mm in diameter. OMF10 and OMF15 should have 80% (by weight) of particles between 2.65 and 4.30 mm, and between 2.55 and 4.10 mm, respectively. Due to the physical properties of the material, disc designs and settings that enable working at a specified bout width by providing a small upward particle trajectory angle (e.g., 10°) are preferred to high rotational velocities. However, field application of OMF with spinning discs applicators may be restricted to tramlines spaced at a maximum of 24 m; particularly, when some degree of overlapping is required between two adjacent bouts. The performance of granular fertilizers can be predicted based on properties of the material, such as particle density and size range, using the contour plots developed in this study

Field-scale evaluation of furrow fertigation using liquid nitrogen

On average about one third of applied nitrogen is lost which costs the cotton industry $32 million each year. Fertiliser use efficiency can be improved through site-specific application of liquid nitrogen (N) in surface irrigation systems. A field-scale fertigation trial was conducted to assess: (1) the uniformity of distribution of the fertiliser applied; and (2) the agronomic performance of furrow fertigated crop based on fertiliser N recovery. The results reported in this study will aid the development of a set of practical recommendations concerning furrow fertigation in cotton to improve use efficiency of fertiliser N

Quantifying the impacts of coal seam gas (CSG) activities on the soil resource of agricultural lands in Queensland, Australia

Coal seam gas (CSG) activities in the Surat and Bowen Basin areas of Queensland, Australia, cover approximately 300,000 km2 including regions of good quality agricultural lands. Without adequate knowledge of soil properties, hydrologic processes and control measures, the disturbed soil structure and landform in these regions are highly susceptible to soil degradation. The construction and installation of CSG infrastructures (e.g. roads, pipelines, hardstand and plant areas) cause various degrees of disturbance to the soil physical, chemical and biological characteristics. This disturbance may result in soil degradation through various forms including compaction, erosion processes, changes to organic carbon and soil nutrient store, exposure of potentially reactive/poor quality soils (e.g. acid sulphate soils, hyper-saline soils) or introduction of outside contaminants (poor quality water, weeds). Not only are soils directly disturbed by the footprint of the CSG operation but the surrounding soil landscape may be disturbed by secondary processes such as erosion and sedimentation. Soil compaction changes caused by CSG operations, including vehicle impacts and trench line installation, have been assessed by soil bulk density measurements. This measurement has been identified as a common impact by CSG operation and a key element of soil degradation of agricultural areas contributing poor vegetation establishment, tunnel and surface erosion processes and an ongoing decline for soil productivity. Quantifying the impacts of CSG activities on soils will inform the development of industry guidelines for impact minimisation and management of the soil resource on joint CSG-agricultural lands

Proton-proton scattering above 3 GeV/c

A large set of data on proton-proton differential cross sections, analyzing powers and the double polarization parameter A_NN is analyzed employing the Regge formalism. We find that the data available at proton beam momenta from 3 GeV/c to 50 GeV/c exhibit features that are very well in line with the general characteristics of Regge phenomenology and can be described with a model that includes the rho, omega, f_2, and a_2 trajectories and single Pomeron exchange. Additional data, specifically for spin-dependent observables at forward angles, would be very helpful for testing and refining our Regge model.Comment: 16 pages, 19 figures; revised version accepted for publication in EPJ

Field evaluation of controlled traffic farming in central Europe using commercially available machinery

The progressive increase in the size and weight of farm machinery causes concerns due to the increased risk of soil compaction that arises from non-organized vehicle traffic. Controlled traffic farming (CTF) offers an effective means to manage compaction by confining all load-bearing wheels to the least possible area of permanent traffic lanes. Although CTF is relatively well-established in Australia and in some countries in Northern Europe, its benefits and suitability for Central European conditions have not been demonstrated. A long-term experimental site was established in 2010 in Nitra, Slovakia, using a 6 m 'OutTrac-CTF' system with shallow non-inversion tillage practices. The 16 ha experimental field of loam soil is representative of land used for arable cropping in Central Europe. Four traffic intensities (non-trafficked, one traffic event per year with a single pass, multiple passes with permanent traffic lanes, and random traffic) were evaluated using two traffic systems: controlled (CTF) and non-controlled traffic farming (referred to as random traffic farming or RTF). This article reports the findings derived from the first four years of the project and focuses on the effects of traffic systems on yields observed in cereal crops (winter wheat, spring barley, and maize) grown at the site in a rotation cycle. Significant differences (p < 0.1) in yield are reported due to the heterogeneity of the field and the seasonal effect of weather. The results of this investigation suggest that CTF systems have potential to increase production sustainably in arable farming systems in Central Europe. Well-designed CTF systems using commercially available machinery allow for reductions in the area affected by traffic of up to 50% compared with random, non-organized traffic systems. Results also show that in years when soil moisture was not limiting, the yield penalty from a single (annual) machine pass was relatively small (~5%). However, in dry years, compaction caused by multiple machinery passes may lead to yield losses of up to 33%. When considering the ratio of non-trafficked to trafficked area within the different CTF systems evaluated in this study, yield improvements of up to 0.5 t ha-1 for cereals are possible when converting from RTF to CTF. Given the assumptions made in the analyses, such yield increases translate into increased revenues of up to 117 USD ha-1 (1 Euro= 1.1 USD). For Central European farming systems, the main benefit of CTF appears to be improved efficiency and enhanced agronomic stability, especially in dry seasons, where the significant yield penalty from machinery passes is likely

Measurement of the Collins and Sivers asymmetries on transversely polarised protons

The Collins and Sivers asymmetries for charged hadrons produced in deeply inelastic scattering on transversely polarised protons have been extracted from the data collected in 2007 with the CERN SPS muon beam tuned at 160 GeV/c. At large values of the Bjorken x variable non-zero Collins asymmetries are observed both for positive and negative hadrons while the Sivers asymmetry for positive hadrons is slightly positive over almost all the measured x range. These results nicely support the present theoretical interpretation of these asymmetries, in terms of leading-twist quark distribution and fragmentation functions.Comment: 9 Pages, 5 figure

A new measurement of the Collins and Sivers asymmetries on a transversely polarised deuteron target

New high precision measurements of the Collins and Sivers asymmetries of charged hadrons produced in deep-inelastic scattering of muons on a transversely polarised 6LiD target are presented. The data were taken in 2003 and 2004 with the COMPASS spectrometer using the muon beam of the CERN SPS at 160 GeV/c. Both the Collins and Sivers asymmetries turn out to be compatible with zero, within the present statistical errors, which are more than a factor of 2 smaller than those of the published COMPASS results from the 2002 data. The final results from the 2002, 2003 and 2004 runs are compared with naive expectations and with existing model calculations.Comment: 40 pages, 28 figure

The Spin Structure of the Nucleon

We present an overview of recent experimental and theoretical advances in our understanding of the spin structure of protons and neutrons.Comment: 84 pages, 29 figure