The results obtained by other investigators which have a bearing on the variability of the sulphur content of wool are reviewed briefly. The variability of the sulphur content is discussed on the basis of the various factors that might affect it.The effect of light is appreciable and is a very important one. Any sulphuric acid formed by the action of light, or present owing to some other cause, is difficult to remove by ordinary washing. The effect of boiling water is small. Kempy fibres contain less sulphur than non-kempy fibres of the same wool. The root portions of fibres have a higher sulphur content than the tip portions, while middle portions have intermediate values.The writers' results and those of other investigators which are reproduced do not allow of any definite relation being drawn between sulphur content and fineness.
A modification of Pregl's micromethod for the determination of sulphur in organic compounds has been found to be satisfactory and convenient when applied on a macro scale to wool.The investigation of various methods of cleaning the samples shows that the best results are obtained when the wool wax is extracted with a solvent before washing with water. It is shown that a treatment with dilute hydrochloric acid is not necessary in preparing the sample.Three different procedures have been followed in determining the dry weight of the sample and the differences in the results are discussed. Results obtained by the new method are compared with those obtained by other recognized methods, and the agreement with the results of the Benedict-Denis-Barritt method is shown to be very good.
Yield increases by use of phosphorus (P) fertiliser has been a defining aspect of last century's agriculture, but in many countries P inputs are now being regulated to avoid ecological damage and improve agricultural sustainability. We tested the hypothesis that P forms and functions in agricultural soils have changed over a period of 50–70 years of agricultural change using topsoils from 35 agricultural sites in North East Scotland compared at ‘original’ and ‘resampled’ timepoints. The original dried and archived samples were collected between 1951 and 1981, and resampling took place in the autumn of 2017 with all samples reanalysed at the same time and by same methods. A range of soil extractants, from labile (water soluble) P, carbon (C) and nitrogen (N) forms, to surface exchangeable P (acid ammonium oxalate extraction), to complexed P (NaOH‐EDTA extraction), were compared with agronomic soil test P (modified Morgan; MM‐P), soil pH, and, on a subset of five time pairs (n = 10), specific P compounds using 31P NMR spectroscopy. Whilst MM‐P had declined significantly in time, all soils were originally and remained at high soil P status. In contrast, no change in labile P pools, nor in the more refractory P pools that replenish labile P, were observed. In the subset analysed by NMR, orthophosphate P consistently increased in concentration. This suggests that soil P shows a slow (multidecadal) response to the documented reductions in fertiliser P for the study region. Significantly greater soil pH (by 0.4 units) over time and reduced water‐soluble C and N forms suggests that labile P in contemporary soils exists in a biogeochemical environment of enhanced solubility and in excess to other available macronutrients that control its microbial cycling. This study represents a long and important period of changing drivers acting on soil P change with potential to improve understanding future soil P trajectories. The value of archived historical soils samples is shown, if care in interpretation of storage implications is made. Highlights Phosphorus fractions in agricultural soil were compared at two timepoints 50–70 years apart. Whilst soil test P declined with time, other labile and refractory P pools did not change. The readjustment of P pools is slow even to substantial change in fertiliser inputs. The investigation of long‐term land use to inform future policy is enabled by soil archives.
The methods described were employed in the laboratories of the National Research Council for the examination of wool samples sent from the University of Alberta. The samples (as mentioned in Part I) were from sheep used to investigate the effect of various environmental factors on wool growth and quality.The determination of crimp, staple length, fibre length, tensile strength, elongation, fibre diameter, moisture content, wool wax, suint, dirt, and yield of clean wool is described. The methods for the measurement of fibre diameter and for the determination of wool wax, suint, dirt, and clean wool involved new technique and some novel features; they are, therefore, described more fully than the others.
<p>Understanding how the solubility of forms of inorganic and organically-complexed phosphorus (P) in agricultural soil is affected by inputs of organic matter (OM) could inform decisions on sustainable future farming practices. Different forms of OM provide organic P, carbon (C) and other nutrients to the system at different rates, depending upon their recalcitrance to decomposition, and the stoichiometric balance of elements between soil, OM amendment and microbial requirements.</p><p>&#160;</p><p>We describe an 18-month pot experiment that tested the hypothesis that additions of organic matter will affect the solubility of P forms in soil. Mesocosms (~30 kg soil) of two agricultural top-soils, of moderate and low P availability, were amended with a commercial humic soil amendment (lignite) or crop residue (barley straw) at two addition levels. Treatments with/without chemical P fertilizer were superimposed on OM treatments. The system was planted with Lolium perenne (perennial rye grass) and exposed to a natural rain and temperature regime. Leachate was collected and analyzed for soluble P, nitrogen and dissolved organic C (DOC) at 6 weekly intervals in order to investigate solubility over time. Destructive sampling at the end of the experiment yielded plant and soil samples for comparison of C, N and P stoichiometry between the treatments.</p><p>&#160;</p><p>Initial results showed increases in leachate DOC relating to crop residue OM treatments and a positive effect of P fertilizer on plant biomass in the low P soil. Concentrations of dissolved P in leachate were higher in the moderately P-sorbing soil compared to the highly P-sorbing soil. Ongoing analysis includes measures of biological activity including soil microbial biomass C, N and P by fumigation-extraction and soil phosphatase activity. Chemical measures include total C, N and P, soil carbon forms using Fourier-transform infrared spectroscopy (FTIR), total organic P and water and acid ammonium oxalate extractions. Interpretation of the final results will consider how the release of C and nutrients from OM and their subsequent impact on the system, are controlled by microbial activity and macronutrient stoichiometry. These results should help to inform future research into improving P utilization in agriculture through balancing nutrient ratios to regulate nutrient cycling. Such research seeks to improve agronomic P efficiencies alongside wider benefits associated with the drive to increase soil C.</p>
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