Fall 1970

How Water Moves in the Soil by Walter H. Gardner (page 3) Editorial (9) Turf Bulletin\u27s Photo Quiz by Fred Cheney (9) Public Relations by Marlin Ball (10) Turf Bulletin\u27s Photo Quiz Answer (11) Climate in the \u2770\u27s by James E. Newman (12) Know Your Seed--Ideas about Seed Quality by A.S. Carter (15)Seed Prices and Handling by Dwight M. Brown (16) Factors influencing Effectiveness of Two Surfactants on Water Repellent Soils by M.A. Mustafa and J. Letey (21

Effect of Particle Size on Droplet Infiltration into Hydrophobic Porous Media As a Model of Water Repellent Soil

The wettability of soil is of great importance for plants and soil biota, and in determining the risk for preferential flow, surface runoff, flooding,and soil erosion. The molarity of ethanol droplet (MED) test is widely used for quantifying the severity of water repellency in soils that show reduced wettability and is assumed to be independent of soil particle size. The minimum ethanol concentration at which droplet penetration occurs within a short time (≤10 s) provides an estimate of the initial advancing contact angle at which spontaneous wetting is expected. In this study, we test the assumption of particle size independence using a simple model of soil, represented by layers of small (0.2–2 mm) diameter beads that predict the effect of changing bead radius in the top layer on capillary driven imbibition. Experimental results using a three-layer bead system show broad agreement with the model and demonstrate a dependence of the MED test on particle size. The results show that the critical initial advancing contact angle for penetration can be considerably less than 90° and varies with particle size, demonstrating that a key assumption currently used in the MED testing of soil is not necessarily valid

Deficiencies in the soil quality concept and its application

Soil quality is a concept that has deeply divided the soil science community. It has been institutionalized and advocated without full consideration of concept weaknesses and contradictions. Our paper highlights its disfunctional definition, flawed approach to quantification, and failure to integrate simultaneous functions, which often require contradictory soil properties and/or management. While the concept arose from a call to protect the environment and sustain the soil resource, soil quality indexing as implemented may actually impair some soil functions, environmental quality, or other societal priorities. We offer the alternative view that emphasis on known principles of soil management is a better expenditure of limited resources for soil stewardship than developing and deploying subjective indices which fail to integrate across the necessary spectrum of management outcomes. If the soil quality concept is retained, we suggest precisely specifying soil use, not function or capacity, as the criteria for attribute evaluation. Emphasis should be directed toward using available technical information to motivate and educate farmers on management practices that optimize the combined goals of high crop production, low environmental degradation, and a sustained resource

Wettability decay in an oil-contaminated waste-mineral mixture with dry-wet cycles

The dependency of soil particle wettability on soil water content implies that soils subjected to drying-wetting cycles become wettable with wetting and water repellent with drying. While this has been demonstrated widely, the results are contradictory when water repellent soils are subjected to a sequence of cycles. Added to this, past wettability measurements were seldom done in batches of samples collected from the field at natural or dry water contents, with little appreciation that slight particle size variations, different drying-wetting histories and fabric (as required by different wettability measurement methods) may alter the results. This note presents soil particle wettability—soil water content relations by means of an index test following staged drying and wetting paths over a period of 8 months for an untreated, oil-contaminated anthropogenic soil (a mixture of slag, coal particles, fly ash and mineral particles) from Barry Docks (UK), a site formally used for oil storage, which is to be remediated and redeveloped for housing. The results revealed a decrease in the water repellency and increasing mineralization and bacterial activity with the wetting and drying cycles.postprin

The elusive role of soil quality in nutrient cycling: a review

peer-reviewedCycling of nutrients, including nitrogen and phosphorus, is one of the ecosystem services we expect agricultural soils to deliver. Nutrient cycling incorporates the reuse of agricultural, industrial and municipal organic residues that, misleadingly, are often referred to as ‘wastes’. The present review disentangles the processes underlying the cycling of nutrients to better understand which soil properties determine the performance of that function. Four processes are identified (i) the capacity to receive nutrients, (ii) the capacity to make and keep nutrients available to crops, (iii) the capacity to support the uptake of nutrients by crops and (iv) the capacity to support their successful removal in harvested crop. Soil properties matter but it is imperative that, as constituents of ‘soil quality’, they should be evaluated in the context of management options and climate and not as ends in their own right. The effect of a soil property may vary depending on the prevailing climatic and hydrologic conditions and on other soil properties. We recognize that individual soil properties may be enhancing one of the processes underlying the cycling of nutrients but simultaneously weakening others. Competing demands on soil properties are even more obvious when considering other soil functions such as primary production, purification and flow regulation of water, climate modification and habitat provision, as shown by examples. Consequently, evaluations of soil properties and management actions need to be site-specific, taking account of local aspects of their suitability and potential challenges.Horizon 202