Showing papers on "Soil organic matter published in 1971"

Simplified Colorimetric Determination of Soil Organic Matter

Abstract: SIMPLIFIED COLORIMETRIC DETERMINATION OF SOIL ORGANIC MATTER JAMES SIMS;VINCENT HABY; Soil Science

Soil and Water

Abstract: Soil and Water : Physical Principles and Processes By Daniel Hillel (Physiological Ecology: a Series of Monographs and Treatises) Pp xiv + 288 (Academic: New York and London, January 1971) $14; £655

An effective water extraction method for the determination of plant-available soil phosphorus

Abstract: A new variant of the water-extraction method for the assessment of soil phosphorus availability to the plant was recently developed by Van der Paauw and Sissingh. The correlation between the water-extractable soil phosphate (Pw value) and the response of the plant, measured in most cases by the P2O5 content of dry matter, was high on Dutch soil types and was not affected by differences in such soil factors as organic matter content, particle size content, CaCO3 content, pH, phosphate-fixation capacity and other factors related to the origin of the soil. In other words, the relationship was the same for all soil types investigated.7 In order to investigate whether an equally good result would be obtained with soil types from widely diverging origin and properties, the method was evaluated in a pot experiment with potato (tops) and spring wheat grown successively on different soil types of European, American and Australian origin. A high correlation between Pw value and the P2O5 content of spring wheat was found, which explained 88% of the variance. All soil types of different origin could be represented by one regression line. The dry-matter yield of wheat was also closely correlated with Pw value, although the yield was also influenced by the pH of the soil. With potatoes a high correlation between water-extractable P and P2O5 content of the tops was found in the series of European soils, but on part of the American and Australian soils the P2O5 contents of plants were higher than those on European soils with corresponding Pw values. This difference could not be explained. In general it may be stated that the Pw value provides a reliable estimate of the availability of soil phosphorus to the plant in a wide variety of soil types.

Decomposition and binding action of polysaccharides in soil

Abstract: In recent years more attention has been given to the polysaccharide fraction of the soil humus and some progress has been made toward an understanding of its nature and function in the soil. There is good evidence that it does contribute to soil aggregate stabilization. Its presence in the soil in relatively large amounts indicates relative resistance to decomposition. Methods for extracting and determination of total polysaccharides have improved but undoubtedly, still yield low results. Progress has been made in enumerating and quantitizing different structural units but it is not known whether (1) the soil polysaccharides consist of a mixture of numerous relatively simple plant and microbial polysaccharides at all stages of decomposition which are resistant to decomposition as such or become resistant through reactions with inorganic and organic soil constituents or, (2) whether the soil polysaccharides are new, highly complex polymers, consisting of numerous structural units, and which are naturally resistant to decomposition or become resistant through reaction with other soil constituents. Careful studies requiring new approaches and great ingenuity are needed to obtain more meaningful information on the structure, mechanisms of formation, and relationship to other soil constituents of the soil polysaccharide polymers. One rewarding area of research related to decomposition and binding action would be concerned with the recovery of soil polysaccharides (Finch et al., 1966). Relatively unaltered preparations should be obtained and freed from ash components. Further separation could be based on molecular weight distribution and relative concentration of uronic acid units. The preparations could then be used for binding or aggregation, adsorption and decomposition studies involving clays, soils, metal ions and humic acid preparations.

Soil analysis by means of a 1:2 volume extract

Abstract: The use of the 1:5 weight extract in soil analysis presents some difficulties. Conductivity determinations as a means of assessing the salt status are unreliable for those soils containing appreciable amounts of gypsum, and it is also desirable that the soil organic matter content be known when interpreting the analytical data.

The maintenance of soil organic matter under continuous cultivation at Samaru, Nigeria

Abstract: Treatment effects on levels of soil carbon and nitrogen in four long-term experiments at Samaru are reviewed in relation to an expected change in the future away from a bush-fallowing agricultural system towards an intensive mechanized system of permanent agriculture.Where different rates of farmyard manure were applied to the soil annually for nearly 20 years marked differences in soil organic matter contents developed. The mean soil carbon (0·82 per cent) of plots that received 12·5 tonnes ha-1 annum-1 is now almost four times as great as the mean content (0·22 per cent) of control-plot soils. Phosphate applications tended to encourage higher levels of soil organic matter, but where mineral fertilizers (N, P and K) were applied with farmyard manure lower soil organic matter levels and C:N ratios than those of manure-only plots resulted. Apparent retention in the soil of carbon and nitrogen applied as farmyard manure was of the order of 12–15 and 30% respectively. A groundnut shell mulch, applied for 9 years, produced significantly higher levels of soil organic matter than control plots.In a rotation experiment in which three years of cropping alternated with either 2, 3 or 6 years of planted Gamba grass (Andropogon gayanus) fallow, large differences in soil organic-matter status and rate of turnover existed between the three rotations. In particular the 3-year fallow showed an annual rate of soil organic-matter increase over twice that of the 2-year fallow. Soil nitrogen build-up exceeded 50 kg ha-1annum-1 in the 3-year fallow.Shortage of farmyard manure and the relatively poor return from systems that include unproductive fallows suggest that in future soil organic matter must be maintained by the return to the soil of all crop residues.

Atrazine-Soil Organic Matter Interactions'

Abstract: Adsorption capacities of Walla Walla silt loam soil for 2-chloro-4-(ethylamino)-6-(isopropylamino)-s-t r i a z i n e (atra- zine) were determined after each extraction with ethyl ether, ethyl alcohol, and hot water. The results suggested that the ether and alcohol-extractable components of the soil organic matter, i.e. fats, oils, waxes, and resins, had a negligible capacity to adsorb atrazine but that hot-water-extractable materials, i.e. polysaccharides, had a small adsorptive capacity. Of the com- pounds chosen to be representative of some soil organic matter components, polysaccharide types had low affinities, a protein and a nucleic acid had intermediate affinities, and humic acid, lignin, and quinizarin had high affinities for atrazine. Compari- son of adsorption isotherms of atrazine to lignin and humic acid at- 25 aiid 62 C suggested that a weak chemical bond may contribute to retention of the herbicide by soil organic matter. Nearly quantitative desorption of atrazine from native and calciurn saturated soils was affected by repeated water ex- traction. extent to which several extractable fractions of the soil organic matter adsorbed atrazine. Preferential removal of parts of the organic matter was made by a series of ex- tractions with ethyl ether, ethyl alcohol, and hot water (proximate analysis); and the quantity of atrazine ad- sorbed after each extraction was determined. Organic chemicals were selected to represent model compounds of the soil organic matter and adsorption was measured on these materials. Preliminary studies were conducted into the type of bonding mechanism accounting for the ad- sorption of atrazine on lignin and humic acid.

Free-living nitrogen-fixing bacteria in egyptian soils and their possible contribution to soil fertility

Abstract: Azotobacter and nitrogen-fixing clostridia are ubiquitous soil inhabitants in Egypt, Iraq and probably in all of the Near East. They occur in high numbers except where barrenness, NaCl accumulation or other depressing factors exist. The soil environment has proved favourable for their development since their response to supplementation with energy materials is quite marked. The organisms are resistant to drought, but optimal activity of Azotobacter is around 60% W.H.C. while that of clostridia is at 100%. Azotobacter as well as clostridia show optimal activity around 30°C, higher temperatures favour clostridia while lower ones favour Azotobacter. Gains of soil nitrogen are linked to the growth of Azotobacter rather than to that of Clostridium. The amounts of nitrogen gained and fixation efficiency are affected by the nature of the substrate, being greatest in clay, then in sand and calcareous soils and least in liquid media. Phosphate is essential, favouring nitrogen fixation firstly by satisfying the high phosphate requirement of Azotobacter and secondly by increasing the rate of decomposition of otherwise unavailable material. Gains of combined nitrogen and fixation efficiency are also affected by the type of organic matter added. A wide C/N ratio and susceptibility to decomposition are specially beneficial properties. Plant residues enrich the soil with nitrogen, partly by enhancing nitrogen fixation and partly by causing immobilization of mineral nitrogen which would otherwise be leached out of the soil by irrigation.

Availability of Cu, Zn and Mn in soils: I.—Influence of soil pH, organic matter, and extractable phosphorus

Abstract: Samples from Ap horizons of 36 cultivated Wisconsin fields were tested for concurrent availability of Cu, Zn and Mn. The effects of soil pH, organic matter, and available P were evaluated by using four chemical extract ants. Oats were used as the test crop and were grown using a self-watering pot-culture technique in a plant-growth room. The divergent soils had the following averages: pH, 6–4; organic matter, 2–6%; available P, 37 ppm; total Cu, 20 ppm; total Zn, 35 ppm; and total Mn, 631 ppm. Concentrations of the micronutrient elements in plants and soils were determined by atomic absorption spectrophotometer. NPK fertilisation resulted in greater plant uptake of Cu, Zn and Mn. Significant interactions between the soil properties and the different chemical fractions influenced the plant uptake of each micro-element; interactions between Cu, Zn and Mn in the same chemical fraction also influenced their individual uptake. Copper uptake was best predicted by inclusion particularly of soil pH, or the same chemical fractions of Zn and Mn in the regression equation; Zn uptake by inclusion of soil organic matter and available P, Mn uptake, or the chemical fractions of Cu and Mn; and Mn uptake by inclusion of available P, Cu chemical fraction, or Zn uptake in the equation. The extractants N ammonium acetate (pH 7) 10 · 01 M EDTA and 0·1 N-HCI show promise in soil tests for the simultaneous availability of Cu, Zn and Mn.

A study on the decomposition of organic matter in an alluvial soil: CO2 evolution, microbiological and chemical transformations

Abstract: Three different types of organic materialsviz berseem hay, farm yard manure and wheat straw at two different rates were applied to an alluvial sandy loam soil and incubated at 30 MoC to investigate their rate of decomposition as well as their effect on the development of soil microflorai.e. bacteria, actinomycetes, fungi and Azotobacter. Berseem hay decomposed rapidly in the initial stages but after 30 days wheat straw + N and wheat straw alone released more CO2. FYM showed an uniform and steady rate of decomposition. Microbiological changes showed a fluctuating trend. In general, maximum increase in bacterial, actinomycete and fungi population was observed at 30 and 90 days period, followed by the lowest activity at 60 and 120 days. However, again an increasing trend was observed after 120 days of incubation period. Berseem hay showed the highest zymogenic effect in the initial stages. FYM had marked influence on the fungal population while wheat straw with and without nitrogen showed a decreasing trend. Azotobacter population was appreciably increased by the addition of wheat straw alone. Other treatments including wheat straw + N recorded a slight effect. Chemical analysis at the end of the experimental period indicated favourable effect of organic materials on humic acid content, organic carbon, total nitrogen and available nutrientsviz nitrogen, phosphorus, and sulphur. FYM increased organic carbon by 77% over control followed by wheat straw 75%. This suggests that the addition of FYM and crop residues has a positive effect on the maintenance of organic matter in the soil. The effect of different levels of organic materials showed only quantitative difference. In general, no marked variations were observed on the pattern of CO2 evolution, microbiological and chemical changes.

The influence of living plants on mineralization and immobilization of nitrogen

Abstract: Changes in the pattern of distribution of the nitrogen of the soil and seedling grass plants have been investigated when the grass plants were grown in pots of sandy soil, from a pasture, at pH 5.7. Net mineralization of soil nitrogen was not observed during an experimental period of one month in the absence of added nitrogenous fertilizer (Table 2).

Nitrate and ammonium contents of Wisconsin limestones.

Abstract: IT has been suggested1,2 that a number of environmental problems may be associated with high levels of nitrates and other nitrogenous compounds in waters. These problems relate to deleterious effects on human and animal health, crop quality and yields, and eutrophication of surface waters. Nitrate in the environment may be derived from nitrogenous fertilizers, organic wastes, soil organic matter, precipitation, and biologically fixed nitrogen. According to Feth3, however, geological sources of nitrate have been largely ignored, and he has suggested that high levels of nitrate in water may be associated with limestones. We therefore measured the nitrate content of Wisconsin limestones.

Reaction of surface-applied superphosphate with soil. II. Movement of the phosphorus and sulphur into the soil

Abstract: Phosphate moving into moist soil from particles of surface-applied superphosphate penetrated a hemispherical zone beneath the particle. The size of this zone and the distribution of phosphate through it were governed by the phosphate sorption capacity of the soil, the size of the particle, and the soil moisture. In calcareous soils the calcium carbonate content was important in determining phosphate penetration. Phosphate from superphosphate particles penetrated rapidly into moist (100 cm tension) soil during the first 5 or 6 days after contact and continued to move through the soil at a decreasing rate throughout the whole of an 8-week period. Movement of sulphate from surface-applied superphosphate into soil was governed by the particle size of the fertilizer and the soil moisture, both of which influenced the rate of solution of the calcium sulphate. The distribution of the sulphate through the soil was influenced by the sulphate sorption capacity of the soil. The rate of penetration of sulphate from surface-applied superphosphate into calcareous soil was considerably less than when the superphosphate was applied to acid soils. Leaching influenced the movement of both phosphorus and sulphur into the soil. It caused distortion of the hemispherical distribution of phosphate beneath superphosphate particles, resulting in deeper penetration of phosphate below the particles and smaller horizontal movement away from them. It also greatly enhanced the solution of sulphate, especially from small particles. The results indicate that the optimum particle size of superphosphate will vary from soil to soil, but a 2.5 mm diameter particle is likely to satisfy a wide range of soil and environmental conditions.

Reaction of surface-applied superphosphate with soil. I. The fertilizer solution and its initial reaction with soil

Abstract: The phosphorus and calcium contents of the fertilizer solution from surfaceapplied superphosphate in contact with moist soil were shown to be similar to those of the metastable triple-point solution (MTPS) produced when an excess of monocalcium phosphate is shaken with water. The average phosphorus, calcium, and sulphur concentrations of saturated aqueous extracts of superphosphate at 20°C were 4.0M, 1.5M , and 0.023M respectively. The pH of these extracts ranged from 1.60 to 1.92 (0.15-0.47 units higher than that of MTPS). The sulphur content of the fertilizer solution was generally one-fiftieth to one-hundredth of the phosphorus content. In the absence of leaching both diffusion and capillarity were involved in the movement of phosphate from superphosphate particles into moist soil. The fertilizer solutes entered the soil mainly by diffusion but on soils of low moisture content the increase in pore size of the fertilizer particles, which resulted from the dissolution of monocalcium phosphate, led to a reversal of the suction gradient between soil and particle which caused movement of some of the fertilizer solution into the soil by capillarity. Leaching of superphosphate applied to dry soils by rainwater is likely to yield fertilizer solutions which have higher pH, lower phosphorus and calcium contents, and higher sulphur contents than the saturated solutions arising from superphosphate particles in contact with moist soil. When synthetic fertilizer solution reacted with acid soils the rate of removal of phosphate and calcium from solution depended upon the phosphate sorption capacity of the soil. In calcareous soil the calcium carbonate played a major part in phosphate precipitation. Appreciable amounts of iron and particularly aluminium were dissolved from each of the soils studied by the synthetic fertilizer solution to give solutions which, on standing, readily formed precipitates of phosphate. Both sulphate and organic sulphur compounds were displaced from the acid soils by the fertilizer solution but, in the calcareous soil, sulphate was coprecipitated with the phosphate.

Young secondary vegetation and soil interactions in Izabal, Guatemala

Abstract: A study of the relationships of soils and vegetation was undertaken in the humid tropical region of Lake Izabal, Guatemala, Central America. Soils and associated 10-month-old secondary growth were analyzed for N, P, K, Ca, and Mg. In addition, organic matter, Al and pH were determined in the soil samples and plant biomass for the secondary growth were calculated. The secondary growth biomass averaged 9,710 kg/ha for the 10-month growth period. Total nutrient content of the vegetation increased linearly with the biomass, except for Mg. The antagonism of Mg on K and Ca nutrition was quite significant when Mg exceeded Ca in the soil under shifting cultivation. Pure stands ofHeliconia sp. andGynerium sp. appeared to be more efficient in accumulating P than stands of mixed vegetation. Chemical composition and dry matter production of native vegetation may provide additional information to evaluate soil fertility in the humid tropics.

Bromine in wheat grown on soil fumigated with methyl bromide

Abstract: Patches of discoloured ("scorched") plants developed on winter wheat growing in a field that had been fumigated with methyl bromide. Scorching was most marked round the methyl bromide injection sites and was associated with bromine uptake by the plants: the above‐ground parts of the scorched plants contained up to 0.61% bromine. In one scorched area, the first, second and third wheat crops after fumigation contained 0.42, 0.25 and 0.09% bromine respectively, so that three years was not sufficient to leach all the residual bromine from the soil. The greater the organic content of a soil, the more bromine remained after fumigation with methyl bromide. Thus a soil containing 2.81% organic carbon contained 63 ppm bromine after fumigation in the laboratory, whereas an otherwise similar soil with 0.93 organic carbon contained only 25 ppm. The residual bromine from methyl bromide fumigation could be extracted with N potassium sulphate, whereas the native soil bromine could not.

Soil-plant nutrition studies on tropical rice: III. The Effect of Soil Fertility Status of Nitrogen and its Liberation upon the Nitrogen Utilization by the Rice Plants in Bangkhen Paddy Soil.

Abstract: The lowland rice depends comparative1y more on the nitrogen supply by the soil resources than the other upland crops. Usually, the rice plant utilizes much more native soil nitrogen than the applied fertilizer nitrogen(1). Accordingly, the paddy soil fertility is usually regarded as a nitrogen supplying potentiality of the soil in a narrow sense. Many studies(2) on the soil fertility proplems have been focused on the availability and the recovery of this organic nitrogen. Decause the yield of rice are primarily determined by the liberation of this organic nitrogen.