Soil particle-size analysis: A comparison of two methods

Knowing the proportion of particle sizes in soil is important to soil scientists and agronomists. The mixture of sand, silt, and clay influences water movement, solute transport, nutrient retention, and many other properties and processes in soil. The standard method for particle size determination is a somewhat time-consuming process. An equally accurate but shorter method would be appealing for many reasons. The objective of this study was to compare a standard method of particle-size analysis using a hydrometer to an abbreviated hydrometer method, which, instead of 12 h for the standard method, requires about 3 h to complete. Twenty-four soil samples of varying textural classes determined by the standard method were reprocessed for particle-size and textural-class determination using an abbreviated hydrometer method. Results of the methods comparison showed that the textural class from the abbreviated method matched that of the standard method in only 10 of 24 samples and that the abbreviated method over-estimated the amount of total sand in the soil sample. The abbreviated method was reasonably accurate in comparison to the standard method with respect to percentages of clay and silt. Based on this comparison, the time savings gained with the abbreviated method do not outweigh the lack of accuracy of particle-size determination with coarsetextured soils, but may be justifiable for fine-textured soils without a large fraction of sand-sized material

Conceptual designs for in situ analysis of Mars soil

A goal of this research is to develop conceptual designs for instrumentation to perform in situ measurements of the Martian soil in order to determine the existence and nature of any reactive chemicals. Our approach involves assessment and critical review of the Viking biology results which indicated the presence of a soil oxidant, an investigation of the possible application of standard soil science techniques to the analysis of Martian soil, and a preliminary consideration of non-standard methods that may be necessary for use in the highly oxidizing Martian soil. Based on our preliminary analysis, we have developed strawman concepts for standard soil analysis on Mars, including pH, suitable for use on a Mars rover mission. In addition, we have devised a method for the determination of the possible strong oxidants on Mars

Assessment of leaf cover and crop soil cover in weed harrowing research using digital images

Objective assessment of crop soil cover, defined as the percentage of leaf cover that has been buried in soil due to weed harrowing, is crucial to further progress in post-emergence weed harrowing research. Up to now, crop soil cover has been assessed by visual scores, which are biased and context dependent. The aim of this study was to investigate whether digital image analysis is a feasible method to estimate crop soil cover in the early growth stages of cereals. Two main questions were examined: (1) how to capture suitable digital images under field conditions with a standard high-resolution digital camera and (2) how to analyse the images with an automated digital image analysis procedure. The importance of light conditions, camera angle, size of recorded area, growth stage and direction of harrowing were investigated in order to establish a standard for image capture and an automated image analysis procedure based on the excess green colour index was developed. The study shows that the automated digital image analysis procedure provided reliable estimations of leaf cover, defined as the as the proportion of pixels in digital images determined to be green, which were used to estimate crop soil cover. A standard for image capture is suggested and it is recommended to use digital image analysis to estimated crop soil cover in future research. The prospects of using digital image analysis in future weed harrowing research are discussed

Environmental aspects of soil phosphorus testing

peer-reviewedSoil phosphorus testing in Ireland uses Morgan’s reagent from samples taken to 10 cm depth for agronomic recommendations. However, its suitability as an environmental indicator has been questioned in terms of sample depth and extraction solution. Seven grassland sites were sampled to depths of 2, 5 and 10 cm and extracted for Morgan’s P, the standard agronomic test, as well as iron-oxide impregnated paper strip P (FeOP), calcium chloride extractable P (CaCl2-P) and water soluble P (WSP), all proposed as environmental soil tests. Extractable soil P decreased with increasing sample depth, as did variances in each test, such that, 2 cm samples had highest concentrations and variances. The current standard sample depth (10 cm) was linearly related to corresponding data from samples taken to 2 and 5 cm, indicating that surface soil P can be consistently estimated from the current standard depth. When soil tests were compared with dissolved reactive P (DRP) in overland flow collected from two field sites, certain soil tests were better indicators of P loss than others. The relative difference in Morgan’s P values at the standard sample depth (10 cm) was reflected in the relative difference in P loss between the two sites. Average values of DRP collected from two sites ranged from 0.032 to 0.067 mg/l at the low P site and 0.261 to 0.620 at the high P site. Average DRP values from the high P site and maximum DRP values from the low P site were simulated using water-soluble P extraction at water to soil ratios 5 to 250 l/kg. In this study, Morgan’s P to 10 cm gave a good indication of the relative difference in DRP loss between the two sites

Microflora in soils of desert regions

Desert soil samples, collected using aseptic techniques, are low in organic matter and cation exchange capacity. Aerobic and microaerophilic bacteria are most abundant, next are algae and molds. Chemical and physical properties are determined by standard procedures, including the Kjeldahl method and the use of Munsell soil color charts

Prediction of soil available phosphorus based on soil organic carbon

There are many cases in which it is desirable to determine relationships among some soil physical and chemical properties. In soil studies, soil available phosphorous (AP) are often determined using laboratory tests, but it may be more suitable and economical to develop a pedotransfer function which uses some easily available soil properties. In this study, a pedotransfer function for predicting soil AP from soil organic carbon(OC) was suggested and soil AP was estimated as a function of soil OC. The soil AP predicted from the soil AP pedotransfer function was compared to the soil AP determined by laboratory test using the paired samples test and the Bland-Altman approach. The soil AP predicted by the soil AP pedotransfer function was not significantly different from the soil AP determined by laboratory test (P>0.05). The mean difference between the soil AP pedotransfer function and laboratory test was 1.57 ppm (95% confidence interval: -2.88 and 6.03 ppm; P = 0.453). The standard deviation of the soil AP differences was 7.01 ppm. The statistical results of the study indicated that the soil AP pedotransfer function provides an easy, economic and brief methodology to estimate soil AP and in order to predict soil AP based on soil OC the pedotransfer function AP = 0.7927 e 4.9922 OC with R2 = 0.92 can be recommended

Sounds of Soil: A New World of Interactions under Our Feet?

Soils are biodiversity-dense and constantly carry chemical flows of information, with our mental image of soil being dark and quiet. But what if soil biota tap sound, or more generally, vibrations as a source of information? Vibrations are produced by soil biota, and there is accumulating evidence that such vibrations, including sound, may also be perceived. We here argue for potential advantages of sound/vibration detection, which likely revolve around detection of potential danger, e.g., predators. Substantial methodological retooling will be necessary to capture this form of information, since sound-related equipment is not standard in soils labs, and in fact this topic is very much at the fringes of the classical soil research at present. Sound, if firmly established as a mode of information exchange in soil, could be useful in an ‘acoustics-based’ precision agriculture as a means of assessing aspects of soil biodiversity, and the topic of sound pollution could move into focus for soil biota and processes

Improving fertiliser management: redefining the relationship between soil tests and crop responses for wheat in WA

Most soils in Western Australia (WA) are highly weathered with very low levels of phosphorus. WA soils initially contained adequate indigenous soil potassium for cropping but removal of potassium over time in harvested grain has gradually resulted in the some soils becoming potassium-deficient for grain production. Fertiliser costs represent a significant part of the variable costs of growing crops in WA. Chen et al. (2009) identified the need for updated soil test interpretations due to substantial changes in farming systems, fertiliser practices and crop yield potential. The aims of this study were (1) to compile experimental data containing the standard soil test measurements and observed wheat crop yield responses for both nil and fertilised treatments across different soil types and seasons from published or unpublished sources, and (2) to critically analyse soil test-crop response relationships to derive better critical soil test values in soils and environments suitable for wheat grain production in WA