Sulfur in Ghanaian soils

Studies were carried out to examine factors which might influence the distribution of S in Ghanaian soils. Nine soil profiles developed over granitic rocks, three each representing the upper slope (US), middle slope (MS) and lower slope (LS) of catena in the evergreen high rain forest (ERF), semi-deciduous rain forest (SDF) and the interior savanna (ISAV) zone of Ghana were selected. The total S contents varied from 9 to 347 ppm; the average for all the surface and subsurface horizons was 141 ppm and for subsoils 105 ppm. The contents also varied according to: (1) the ecological zone as follows: ERF 0) SDF>ISAV and (2) the topographic position: US>MS>LS. The total S was closely correlated with organic C and total N in the surface and subsurface horizons (r=0.931^*** and 0.941^*** respectively). Inorganic sulfate was generally higher in the subsoils than in the surface and subsurface horizons of the ERF and SDF profiles whereas the opposite was the case in the ISAV profiles. Based on the critical value of 6 ppm in surface soils, all the savanna soils would be considered S deficient.The total organic S, which constituted from 56 to over 95% of the total S in the profiles, was significantly correlated with total N both in the surface and subsurface horizons (N:S ratio=9.1:1) and in the subsoils (N:S ratio=7.6:1). Fractionation of the organic S showed that HI-reducible S ranged from 14 to 117 ppm in the surface and subsurface horizons (average 55 ppm, equivalent to 47% of the total organic S) and from 2 to 169 ppm (average 55 ppm, equivalent to 60% of the total organic S) in the subsoils. The C-bonded S ranged from 6 to 223 ppm (average 73 ppm, equivalent to 57% of the total organic S) in the surface and subsurface horizons and from 1 to 83 ppm (average 29 ppm, equivalent to 32% of the total organic S) in the subsoils. HI-reducible S was significantly correlated with organic C (r=0.805^***) and total N (r=0.845^***) in the surface and subsurface horizons only whereas C-bonded S was significantly correlated with organic C and total N in both the surface and subsurface horizons and subsoils (r=0.870^*** and 0.624^*** respectively).The N:S ratios varied from 6.0 to 12.7 in the surface and subsurface horizons and from 0.5 to 27.3 in the subsoils. However the N:S ratio was less variable within the profile than the C:S ratio. The C:N:S ratios varied considerably within the profile and among the different soils but they fall within the range of values reported world-wide.     

Yeasts in Antarctic soils

The yeast flora of 126 soil samples from the Ross Dependency of Antarctica was examined and compared with that of eight samples from East Greenland. Fifty-two Antarctic samples contained yeasts, in numbers ranging from 5 to over 100,000/g; species isolated belonged to the generaDebaryomyces, Cryptococcus, Candida, Trichosporon andRhodotorula. Nearly all isolates ofCandida were obligate psychrophils; they belonged toCandida scottii, C. nivalis, C. gelida andC. frigida. Duplicate samples, taken at the same site within a few yards of one another, contained the same size and kind of yeast populations. Although not all samples which contained plants (algae, lichens or mosses) contained yeasts, almost all samples which contained yeasts contained plants. There was no correlation between yeast population and the pH of the sample, nor between yeast populations and the presence of vertebrate animals. The samples from East Greenland, which were from an area sufficiently warm and moist to support growth of higher plants, all contained yeasts, in numbers from 200 to 56,000/g. Species isolated were similar to those from Antarctic material.     

Cyanobacteria in rice soils

Cyanobacteria were recovered from each of 38 soil samples collected from local rice fields. Of the 84 species belonging to 31 genera that were isolated, 42 were heterocystous diazotrophic species belonging to 14 genera and the remaining were non-heterocystous. Fischerella, Nostoc and Calothrix were widespread.Z.U.M. Khan is with the Department of Botany, Jahangirnagar University, Savar, Dhaka, Bangladesh. Z.N. Tahmida Begum and M.Z. Hossain are with the Department of Botany and R. Mandal is with the Department of Soil Science, bot at the University of Dhaka, Dhaka-1000, Bangladesh;     

Functional domains in soils

Soil processes are significantly regulated by biological activities. Soil ecosystem engineers (predominantly termites, earthworms and ants) and roots produce biogenic structures, aggregates or pores that determine the structure and architecture of soil. The sum of structures produced by a population or community of invertebrate engineers creates a specific environment defined here as a functional domain. Functional domains are characterized by (i) the nature and spatial array of the biogenic structures, solid aggregates, mounds or constructs and pores of different shapes or sizes; (ii) the specific communities of smaller organisms from the meso- and microfauna and micro-organisms that they host; and (iii) the spatial and temporal scales at which soil processes operate. The regulation of processes caused by the physical organization of the soil environment and the redistribution of organic resources have been described and quantified in several studies. In soil, the relative importance of regulation imposed by ecosystem engineering is likely to be greater than regulation by trophic relationships because of the specific ecological constraints observed in this environment when compared to above-ground conditions.     

Sulfur in Ghanain soils

Sulfur availability in twenty selected surface soils (0–22 cm), which varied in both physical and chemical properties and sampled under cultivated and uncultivated management in the various ecological zones of Ghana, was studied. Texture varied from coarse sand to clay, with 16–85% sand and 10–51% clay. Organic C varied from 0.45 to 2.24% and total N from 0.034 to 0.215%; soil pH (0.01M CaCl₂) from 3.69 to 7.43 and total S from 44 to 273 ppm. Inorganic sulfate formed 2.3 to 14.8% of the total S, HI-reducible S 4.4 to 28.2, C-bonded S 4.4 to 28.2 and unidentified organic S 12.7 to 63.2%. Sulfur availability was assessed by chemical extraction methods and electroultrafiltration technique as follows: (i) extraction with Ca(H₂PO₄)₂·H₂O solution containing 500 ppm P, (ii) extraction with 0.1M LiCl and (iii) electroultrafiltration (EUF) at 80°C, 400 V for 10 min and also on seven of the soils the standard EUF fractionation procedure of Neméth. Ca(H₂PO₄)₂-extractable S was not significantly correlated with LiCl-extractable S nor with any of the EUF values. LiCl-extractable S was not significantly correlated with sulfate extractable by and EUF?1+2+3 fractions (r=0.911^**). Dry matter yield of oat seedlings and EUF?1+2+3 fractions (r=0.911^**). Dry matter yield of oat seedlings was not correlated with any of the availability indexes. Total S uptake was significantly correlated with LiCl-extractable S (r=0.629^** without S and 0.729^** with S applied) and with EUF-80°C, 400 V/10 min (r=0.561^**), EUF-1 (r=0.953^***) and EUF-2 (r=0.912^**). On all the soils, more S was taken up by oat plants than could be accounted for by the inorganic S and S mineralized from organic S during an incubation period of 4 weeks.     

Denitrification in field soils

Summary Recent denitrification research is reviewed to answer questions a) how much N is lost from the soil as N₂ and N₂O and b) how do agronomic practices affect this loss? The methods used to quantify denitrification are also discussed. Gaseous losses of inorganic N range between the equivalent of 0 to 20 per cent of the fertilizer N applied to arable soils and 0–7 per cent on grassland soils. Losses are greater on undrained land and also after using direct drilling to establish arable crops.Appendix 1 summarizes reported measurements of gaseous N losses.Introductory lecture     

Urease activity in soils

Summary The availability of Ca from different levels of gypsum and calcium carbonate in a non-saline sodic soil has been investigated. Different levels of tagged gypsum (Ca⁴⁵SO₄.2H₂O) and calcium carbonate (Ca⁴⁵CO₃) (i.e. 0, 25, 50, 75, and 100 per cent of gypsum requirement) were mixed thoroughly in 3.5 Kg of a non-saline alkali soil (ESP, 48.4; ECe, 2.68 millimhos/cm). Dhaincha (Sesbania aculeata) — a legume and barley (Hordeum vulgare L.) — a cereal were taken as test crops. Increasing levels of gypsum caused a gradual increase in the yield of dry matter, content of Ca and K in the plant tops and Ca:Na and (Ca+Mg):(Na+K) ratios in both the crops. Application of calcium carbonate caused a slight increase in the dry matter yield, content of Ca and Mg and Ca:Na and (Ca+Mg):(Na+K) ratios in barley, however, in case of dhaincha there was no such effect. Gypsum application caused a gradual decrease in the content of Na and P in both the crops. Total uptake of Ca, Mg, K, N and P per pot increased in response to gypsum application. The effect of calcium carbonate application on the total uptake of these elements was much smaller on dhaincha, but in barley there was some increasing trend.Increasing application of tagged gypsum and calcium carbonate caused a gradual increase in the concentration and per cent contribution of source Ca in both the crops, although, the rate of increase was considerably more in dhaincha. The availability of Ca from applied gypsum was considerably more than that from applied calcium carbonate. Efficiency of dhaincha to utilize Ca from applied sources was considerably more (i.e. about five times) than that of barley     

Bacteriostasis in soils sterilized by gamma irradiation and in reinoculated sterilized soils.

An agar-disc method was used to compare the bacteriostatic properties of five soils with those of samples of the same soils sterilized by gamma irradiation. For three of the soils, bacteriostasis was removed either partially or entirely by sterilization. Bacteriostasis was completely restored to sterile soil by reinoculating it with natural soil. All the reinoculation treatments restored the level of bacteriostasis equally effectively, whatever the origin of the soil used as inoculum.     

The soils

The soils of Lake Prespa can be distinguished according totheir degree of development, drainage condition,texture, content of coarse fragments, topography,degree of erosion and the presence of impermeablelayers. A generalized land evaluation was carried outaccording to which land suitability was assessed formajor uses including arable farming, pasture,forestry, wildlife, and recreation and tourismdevelopment. Furthermore, the soils were classified indifferent groups for environmental protection by meansof both the protection of areas with high ecologicalvalue against any agricultural activity and thedelineation of the lands susceptible to degradationsuch as soil erosion, through intensive arablefarming, and groundwater contamination, throughintensive irrigation and the application of highamounts of fertilizers and pesticides.     

Carbon for soils,not soils for carbon

The role of soil organic carbon (SOC) sequestration as a ‘win-win’ solution to both climate change and food insecurity receives an increasing promotion. The opportunity may be too good to be missed! Yet the tremendous complexity of the two issues at stake calls for a detailed and nuanced examination of any potential solution, no matter how appealing. Here, we critically re-examine the benefits of global SOC sequestration strategies on both climate change mitigation and food production. While estimated contributions of SOC sequestration to climate change vary, almost none take SOC saturation into account. Here, we show that including saturation in estimations decreases any potential contribution of SOC sequestration to climate change mitigation by 53%–81% towards 2100. In addition, reviewing more than 21 meta-analyses, we found that observed yield effects of increasing SOC are inconsistent, ranging from negative to neutral to positive. We find that the promise of a win-win outcome is confirmed only when specific land management practices are applied under specific conditions. Therefore, we argue that the existing knowledge base does not justify the current trend to set global agendas focusing first and foremost on SOC sequestration. Away from climate-smart soils, we need a shift towards soil-smart agriculture, adaptative and adapted to each local context, and where multiple soil functions are quantified concurrently. Only such comprehensive assessments will allow synergies for land sustainability to be maximised and agronomic requirements for food security to be fulfilled. This implies moving away from global targets for SOC in agricultural soils. SOC sequestration may occur along this pathway and contribute to climate change mitigation and should be regarded as a co-benefit.     

Decomposition of cellulose in soils

1. Cellulose decomposition in forest and orchard soils was investigated by studying the breakdown of boiled and washed cellophane in the soils and in vitro. Decomposition occurred from quick to slow in the order: orchard on clay soil, forest on clay soil, forest on sandy loam, and in the latter in the order: calcareous mull, acid mull and mor. 2. In the different forest soils which were investigated the rate of decomposition was parallel to their water capacity. It slowed down considerably when the water content of the soil decreased, especially after the wilting point was reached. 3. Of the fungi isolated from these soils, those from orchard soil — 5% to 50%Fusarium spp. — were among the fastest decomposers of cellulose. This agrees with, and may explain the high rate of decomposition in orchard soil. 4. Decomposition in pure culture is quicker than in soil. As filtersterilized soil extract checked the decomposition in pure culture, but heat-sterilized soil extract did not, an extractable but heat-sensitive substance may be one retarding factor.     

Azotobacter bacteriophages in Czechoslovakian soils

Summary Azotobacter bacteriophages were studied using liquid as well as solid enrichment cultures. The study included 16 samples representing the soils of Ruzyn, Prague. The effect of long-term application of mineral fertilizers (N, P, K) and organic manure (straw enriched by inorganic nitrogen) to the soil on Azotobacter and their phages was investigated. Liquid enrichments yielded phages in fairly high titers, and phages were found in most of the soils while solid ones only gave low titers in occasional soils. On the basis of plaque morphology 4 different phage types were obtained. Electron micrographs showed that the phages belong to the groups with long non-contractile, contractile, and short contractile tails. Host specificity assay showed that the majority of the strains of A. chroococcum, A. vinelandii, and one strain of A. beijerinckii were lysed by phage, while none of A. macrocytogenes, A. agilis and A. insignis strains were lysed. Phage inactivation and neutralization was carried out with homologous antisera. re]19741128     

Nitrate distribution in tropical soils

Summary The downward movement of the nitrate ion in the top 5 ft of Tippera clay loam was followed by applying sodium nitrate at the rate of 2000 pounds per acre to bare fallow soil after different rain intervals during the 1957/58 wet season. At the end of the season soil samples were collected at 6-inch intervals and compared with samples from adjacent plots that received an equivalent anion quantity of sodium chloride after the same rain intervals. After 23.7 inches of rain the distribution of nitrate and chloride anions the soil profile was nearly identical and it was concluded that the anions are equally mobile in this soil.The mean movement of the anion was 1.075 inches for each inch of rainfall. A high positive correlation of 0.946 was obtained between mean movement and rainfall. The downward movement of both anions out of the topsoil appeared to be enhanced by channels left by partly decomposed roots.Application of sodium chloride on sandier soils revealed a much higher mean movement of anions on Blain sand than on Tippera clay loam after equal amounts of rain, but on Florina sand with a high silt content in the topsoil the mean anion movement approached that of the clay soil. The difference is explained in terms of low infiltration rate into the Florina soil.The practical implications of leaching of nitrate in Tippera soil are briefly discussed.     

Methanogenic activities in alpine soils

Uncontrolled microbial methane production is playing an important role in global warming. In the present study, we showed that water content and incubation temperature increase the potential for methane formation in the two alpine soils under investigation. Beside these factors, the grazing of cows and thus the amendment of methanogenic microorganisms by cattle dung is the most important factor determining the potential of methane production in those soils.     

Biogenic ecotoxicants in urban soils

A pool of biogenic ecotoxicants on urban lawns is considered. The toxobity of cultivated plant seeds in snowmelt and in filtered culture fluids of microorganisms is estimated. Harmful fungi, bacteria, and insects are found, pathological modifications of cyanobacteria are revealed, and the microbiological activity of soil at the sod base and outside it is determined.