Survival of faecal coliforms in four different types of sludge-amended soils in Botswana

This study aimed at identifying the factors that affected the survival of faecal coliforms as measured by E. coli in four types of soils in Botswana which were amended with sewage sludge. Physico-chemical and biochemical properties and coliform population in the different soils, sludge, and soil/sludge mixtures were determined after sampling, on composing the soil/sludge mixtures, and 90 days after composing. Coliform population in the different soil/sludge mixtures decreased by about 90% after 90 days. The age of the sludge used and the rate at which it was applied to the soils initially determined the population of E. coli in each soil/sludge mixture, but after 90 days, differences inherent in the different soil types were the main determinants of the E. coli population. Percentage reduction of coliforms in Type 1 sludge mixtures were lower (38%) than in Type 2 sludge mixtures (57%). Up to 79.8% of the reduction observed in E. coli population in the Barolong luvisol-sludge mixtures after 90 days was caused by reduction in pH and moisture content, while 72.6%, 84.5% and 55.1% of the reduction in E. coli population in Tuli luvisol-, arenosol- and vertisol-sludge mixtures, respectively, was accounted for by the reduction in moisture content and Olsen P concentration. Coliform survival rates varied with soil types being 12%, 6.4%, 5.3% and 5.8% for the vertisol, arenosol, Barolong luvisol and Tuli luvisol, respectively. A minimum period of 90 days should be allowed between when sludge is applied to similar soils and when seeds are sown. The exact period should, however, be determined by the properties of the soil with fine-textured soils requiring a longer period than coarse-textured soils.     

Effect of biochar,clay substrate and manure application on water availability and tree-seedling performance in a sandy soil

In order to develop a method for extensive pomiculture on marginal soils in semiarid Brazil, a field experiment was conducted to study the impacts of the soil conditioners biochar, clay substrate and goat manure on soil physical parameters of a sandy soil and on seedling performance of Spondias tuberosa Arruda. Manure significantly increased total porosity, soil water content and reduced bulk density of the sandy soil. Water content at field capacity (θ_fc) and at permanent wilting point (θ_pwp) were increased due to manure application. Neither biochar nor clay substrate had a significant impact on the soil physical parameters. Biochar combined with clay substrate led to lower soil water content and significantly reduced the period of retaining atmospheric water. Due to a strong correlation (R² = 0.75) between θ_fc and θ_pwp, the available water capacity within all treatments remained unchanged. Amelioration and initial nutrient supplies had no effect on seedling survival and stem growth of S. tuberosa during the 23-month experiment. This underlines the nondomesticated character of the available plant material of S. tuberosa. The independence of the seedling performance of soil management makes S. tuberosa an interesting species for low-input orchards and for reforestation within the Caatinga.     

Response of Italian ryegrass (Lolium multiflorum Lam.) to coffee waste application on a humid tropical sandy soil

A greenhouse experiment was conducted to study the effect of coffee waste (CW) application on growth and mineral nutrition of Italian ryegrass in a tropical Arenosol. Dry CW was applied at three rates (5, 10, 20 t/ha) and thoroughly mixed with topsoil (0–25 cm), placed in pots and seeded with Italian ryegrass (Lolium multiflorum Lam.) according to a completely randomized design with six replicates. The application of CW greatly stimulated uptake of Ca, Mg, K, N and P, resulting in a significantly increased dry matter (DM) production over three consecutive cropping cycles. DM increases of at least 52, 87 and 81% compared with the unamended controls were obtained for the first, second and third cuts, respectively. Soil analysis after cultivation found that all CW‐amended soils still contained available macronutrients (Ca, Mg, K, N), which could produce residual effects in subsequent crops. Furthermore, CW application increased soil pH owing to its liming effect. This brought about an increase in cation exchange capacity with substantial reduction in phytotoxic Al and a decrease in availability of a number of metals (Cu, Zn, Mn and Fe) and significantly reduced their uptake by ryegrass. The study reveals a high potential of CW to improve the fertility of sandy soils in the humid tropics.     

Entwicklung,Eigenschaften und Klassifikation von Dünenböden der Ostfriesischen Inseln – am Beispiel Spiekeroogs

Pedogenesis, properties, and classification of dune soils of the East Frisian Islands (southern North Sea coast of Germany)—exemplified by the island Spiekeroog The aim of this study was a detailed pedological investigation and exact classification of dune soils of the East Frisian Islands. The following soil‐forming processes were identified on a laboratory‐data basis: humus accumulation and dislocation, carbonate loss, acidification, modification of exchangeable cations, and base‐saturation decrease. A slight iron oxide accumulation was visible in the field, but not confirmed by laboratory data. Applying the qualitatively and quantitatively defined horizons from the German classification, these soils cannot be classified as Regosols, Braunerden, and Podsols but they fit perfectly in the Arenosols as defined in the WRB.     

Shrinkage potential and pore shrinkage capacity of differently developed volcanic ash soils under pastures in southern Chile

The drying process of volcanic ash soils often results in the formation of shrinkage cracks with consequences for their physical properties (i.e., decrease of water retention capacity) and land use management. This study presents the soil water characteristics and shrinkage behaviour (shrinkage phases in terms of void and moisture ratio), the shrinkage potential (COLE index), and the pore shrinkage capacity (PSI) for 5 and 20 cm depth of a Haplic Arenosol (tephric) and two Silandic Andosols under pasture management along a soil gradient from the Andean mountains to the coastal range in southern Chile. The main focus of the presented study is on the effect of soil development in conjunction with the weathering of volcanic ash soils on the shrinkage properties. The water retention and shrinkage curves were continuously determined for undisturbed soil samples (100 cm³) during a drying process under laboratory conditions. In addition, the shrinkage curve data were modelled to distinguish different shrinkage zones. The results suggest that the investigated soil properties vary depending on soil development. The more developed Andosols had higher total porosities (up to 70 cm³ cm^?3) than the less developed Arenosol. The shrinkage behaviour of the Haplic Arenosol showed a wide structural shrinkage phase, whereas the Silandic Andosols revealed a more pronounced proportional shrinkage phase, which is related to the pore size distribution. In addition, wide and narrow coarse pores of the Haplic Arenosol and medium and fine pores of the Silandic Andosols determine the shrinkage potential (COLE) and the pore shrinkage capacity, respectively. The finer‐grained and organic matter‐rich Andosols indicate a higher COLE index (> 0.03–0.09) compared to the Arenosol (≤ 0.03). The pore shrinkage index (PSI) of the total pores (TP) varied significantly (P < 0.05) with values of 0.042–0.149 in 5 cm depth and 0.04–0.091 in 20 cm depth of sites 1–3, respectively.In summary, the shrinkage potential and pore shrinkage capacity are positively correlated to the organic carbon content and decrease with increasing dry bulk density. The study points out a higher risk of soil degradation due to irreversible drying processes for the more clayey and allophane containing Andosols than the Arenosol.