Topsoil Organic Matter Research Articles

A soil wetness class map for Scotland: New assessments of soil and climate data for land evaluation

In many humid, temperate countries the soil water regime is one of the major factors determining land use. In Scotland prolonged saturation of the soils severely limits land use options across extensive areas. The assessment of these limitations within a standardized framework provides one of the essential datasets for use in the formulation of regional agricultural and land use policy. This work combines observed soil properties and soil map information with new climate maps. The spatial distribution of soils is derived from the digital 1:250,000 scale Soil Survey maps for Scotland with the soil assessments being made using information held in the Scottish soils database. These datasets are manipulated within geographic information system and relational database environments to produce an assessment of the soil water regimes for the dominant soil in each one kilometre square under prevailing climatic conditions. The synthesis revealed a number of deficiencies in both the original soil map and the soil assessment model. The soil map failed to sufficiently distinguish different categories of organic soils, whilst the model had to be adapted to differentiate soils on the basis of the topsoil organic matter contents and to accommodate soils with thin topsoils overlying slowly permeable drifts. The work serves to identify those areas which can be refined in the future by taking a more stochastic approach to the synthesis of these types of data.

Mineralisation of organic matter in topsoils subjected to stockpiling and restoration at opencast coal sites

Topsoil stockpiled for 4 years resulted in an accumulation of NH4-N at depths of 1m or more in mound, as measured by an ammonia gas-sensing electrode. When leached with water these soils were also found to contain high concentrations of dissolved organic C below 1m. Both NH4-N and DOC were products of microbial mineralisation of soil organic matter that accumulated under anaerobic conditions. When these soils were restored a flush of decomposition took place, fuelled by labile organic matter and soluble nitrogen.

Transformations of Nitrogen‐15‐Labeled Fertilizer Nitrogen and Carbon Mineralization in Incubated Coal Mine Spoils and Disturbed Soil

AbstractLimited information is available concerning N transformations in exposed geologic materials of disturbed lands in the western USA. A laboratory incubation study was therefore conducted using 15N to trace the dynamics of fertilizer 15NH+4 added to samples of one topsoil and five coal mine spoils from Colorado and Wyoming. Carbon dioxide evolution, N mineralization, nitrification, microbial immobilization, and NH+4 fixation within clay minerals were monitored over time. The organic matter in three of the spoils was considerably less susceptible to microbial decomposition than the topsoil organic matter, whereas the organic matter in the fourth spoil was slightly less susceptible than, and in the fifth spoil comparable to, topsoil organic matter in susceptibility to microbial decomposition. However, the amount of plant‐available N mineralized was at least five times higher in the topsoil than in any of the spoil materials. The data suggest that, under field conditions, none of the spoil materials evaluated in this study will likely be able to adequately supply the N requirements of a reseeded plant community. The significantly more active microbial population of the topsoil immobilized more of the added 15NH+4 than in any of the spoils except the shale, whereas more of the added 15NH+4 was nitrified and remained as NO−3 in the spoils than in the topsoil. The data indicate that under field conditions, a larger proportion of added fertilizer NH+4 will be susceptible to loss via NO−3 leaching or volatilization in the spoils than in the topsoil.

Soil Properties and Pine Growth Affected by Site Preparation after Clearcutting

Abstract A pine-hardwood sawtimber stand in southeast Texas was clearcut in September 1972. Random plots were burned, chopped, KG-bladed, or left untreated. In the spring of 1974, 1-0 loblolly pine seedlings (Pinus taeda L.) were handplanted at 8 by 10 foot spacing. Data from soil samples, taken from the 0-5 inch depth before clearcutting and 1, 3, and 5 years after site preparation showed that burning appeared to have changed soil nutrient levels the least. Of the two mechanical treatments, KG-blading altered the chemical composition of the soil most, probably because topsoil organic matter was removed. Planted pines survived and grew best on mechanically prepared areas, producing 1.5 to 3.3 times more cubic-foot volume per acre than either of the other treatments by the end of the eighth year.