Effects of regeneration burning on the properties of forest soils in southern Tasmania: Comments on recent study by Elliset al. (1982)

Summary Important methodological factors which should be considered when attempting to measure and interpret the effects of hot slash fires on the properties of forest surface soils are briefly discussed. Soil properties cannot be assumed to be similar, prior to cutting and burning of forest, on coupes located several kilometres apart in dissected terrain. In order to study the effects of forest treatment on soil properties, sites should either be closely adjacent or preferably measurements should be taken before and after treatment on the same experimental area.It is argued that the conclusions reached by Elliset al. regarding the effects of regeneration burning on soil properties in southern Tasmania are unjustified because of the use of inappropriate experimental methods.     

Multivariate analysis of multispectral remote sensing data on grasslands from different soil types

Summary From an area of 60 sq. km in East-Flanders (Belgium), two sets of stereoscopic aerial photographs were taken. After selection of 13 soil types, 58 grasslands (mainly permanent ones) were localized. Data on species composition (S1 taxa) were quantitatively sampled with a double meter.Density values were obtained from both emulsions and using three filters. Using the densitometric varishles (extended to 22) or taxa variabies. Minimum Variance Clustering (MVC) and Principal Component Analysis (PCA) were applied. The recognition of different grasslandtypes and their relative position in both new sample point spaces was discussed as well as their relation to soil type. The results obtained by both Canonical Analyses (CCA and CVA) were examined and where necessary compared to the searce applications in vegetation ecology.Finally, the possible reasons for the meagre results were briefly discussed.Nomenelature follows De Langhe e.a. (1973).     

Effect of urea placement on leaching losses of nitrogen from flooded rice soils

In an effort to provide an explanation for the reported variability in fertilizer N efficiency from deepplaced urea on flooded rice, a set of controlled experiments was conducted to evaluate the effect of water percolation on fertilizer loss and plant uptake from¹⁵N labeled urea supergranules. Three soils of different texture (silt loam-clay) were subjected to various percolation rates (0–20 mm/day) while planted to rice which was harvested after approximately 40 days.The results indicate that moderate to high percolation through silt loam soil will lead to significant fertilizer N losses and drastically decrease the fertilizer uptake by plants. The permeability of the clay soil was too low for any leaching to take place. It is therefore concluded that deep placement of urea supergranules not be recommended in soils where percolation rates may exceed 5 mm/day, particularly if the cation exchange capacity of the soil is low. This experiment points to the need of evaluating and reporting the percolation rates in soils where experiments with supergranular urea are conducted.Contribution from the Agro-Economic Division of the International Fertilizer Development Center (IFDC), Muscle Shoals, Alabama 35660.     

The measurement of mean temperatures in plant and soil studies by the sucrose inversion method

Summary A polarimetric procedure is described for determining exponential mean temperatures (_e) from the rate of inversion of sucrose solutions buffered at pH values between 1 and 3. An equation is given for calculating the pH values appropriate for various temperature ranges and time scales. The procedure used for monitoring air and soil temperatures over a 5 year period at a network of sites in Aberdeenshire was to expose 5 ml volumes of sucrose solution at pH 2.06 in sealed polythene tubes. Each month the changes in optical rotation were measured with a sensitive automatic polarimeter and fresh tubes exposed. The values of _e were 2°C higher than arithmetic means obtained from standard thermometric devices. Observations at elevations between 275 and 686 m a.s.l. demonstrate the lapse of temperature with altitude and illustrate the usefulness of _e measurements.     

Sorghum-sudan green manure; Its effect on nursery stock

Summary The use of sorghum-sudan green manure has recently attained popularity among nurserymen because of the assumption that toxic excretions of these hybrids control root-rot fungi. Greenhouse trials of 2-year duration have revealed that green manure of sorghum-sudan inflicts severe damage of tree seedlings, largely by eradication of mycorrhiza-forming fungi. Early plowing under of green manure, periodic watering, and late fall seeding of nursery crop may alleviate phytotoxicity of the sorghum-sudan residues, but the biocidic properties of these plants defeat the primary purpose of using green manure in contemporary nurseries, namely the biodegradation of toxic compounds.Research supported by the College of Agricultural and Life Sciences, University of Wisconsin, Madison, and the Wisconsin Department of Natural Resources.     

Trace elements in the hydrologic cycle of a forest ecosystem

Summary Concentrations of Cu, Fe, Mn, and Zn were measured in bulk atmospheric precipitation, throughfall, stemflow, and soil solutions at 10−, 15−, 25−, and 30-cm depths, in aEucalyptus globulus forest in the Berkeley hills, California, during the 1974–75 wet season after each main storm event. Litter and plant samples were analyzed. There was some similarity in the behavior of Cu, Fe, and Zn, but Mn behaved differently. Mn and Zn are largely deposited on the forest canopy by impaction during dry-deposition episodes, whereas most of the Cu and Fe input occurs in rain. For the hydrologic components measured, concentrations of Cu and Fe increase in the order: precipitation<throughfall<stemflow <soil solutions. For Zn the order is: precipitation<stemflow<throughfall<soil solutions. Concentrations of Cu, Zn, and Fe in the soil solution fluctuate with downward movement of wetting fronts and are negatively correlated with pH. Concentrations of Fe in soil solution are about 10 times greater than those of throughfall and stemflow; the corresponding relative differences for Cu and Zn were much less. Plant uptake of Mn exceeds that of Cu, Zn, and Fe. The increases in Mn concentrations from precipitation to throughfall and stemflow are much greater than those for Cu, Zn, and Fe because precipitation has very low Mn concentrations. The concentration series for Mn is: precipitation<soil solutions<throughfall<stemflow. Concentrations of Mn in the soil solution are negatively correlated with pH. During the dry summer Mn accumulates in the soil, but is quickly flushed by early rains of the wet season.     

Effect of lime and phosphorus applications on concentrations of available nutrients and on P,Al and Mn uptake by two pasture legumes in an acid soil

Summary Effects of increasing rates of lime and phosphorus addition on concentrations of available nutrients in soil and on P, Al and Mn uptake by two pasture legumes, lotus (Lotus pedunculatus Cav.) and white clover (Trifolium repens L.), were studied in a pot experiment using a highly leached acid (pH 4.2) soil.Liming resulted in an increase in exchangeable Ca and thus in percentage base saturation, with concomitant decreases in levels of exchangeable Al, Fe and Mn. The relationship between exchangeable Ca and Al was linear and negative with a gradient of almost unity. Liming had no consistent effect on measured CEC values. Increasing lime rates significantly reduced concentrations of Mg, K and Na in saturation paste extracts but had no effect on exchangeable Mg, K and Na levels.With increasing lime additions, available phosphate indicesviz water soluble, resin-, Morgan-and Williams-extractable all decreased significantly, Truog-extractable was unaffected, while Brayextractable generally increased. Fractionation revealed that lime additions caused a decrease in easily soluble, Fe-bound and to a lesser extent Ca-bound phosphate fractions, had no effect on reductant soluble phosphate, but resulted in an increase in the Al-bound fraction. P uptake and yield of both legumes increased with lime and P additions.Correlations between available phosphate indices and yield of both legumes were weak or nonsignificant. However, high, significant positive correlation coefficients were found between available phosphate and plant uptake of P. Indices of available Al and Mn were not generally significantly correlated with plant uptake of Al or Mn but significant negative correlations were found between available Al and Mn and yield of both species.     

Assay and properties of alginate lyase and 1, 3-β-glucanase in intertidal sands

Summary Alginate lyase and 1, 3--glucanase activity were detected in intertidal sands below decomposing seaweeds (Fucus sp. andLaminaria sp). Linear relationships between activity and sand weight; length of incubation and substrate concentration, were established for both enzymes. Other properties of these enzymes in intertidal sands are reported.     

Fungistatic activity of different Indian soils againstFusarium udum Butler

Summary The fungistatic activity of different Indian soils againstF. udum, causing wilt disease of pigeon-pea, has been assessed in relation to soil pH and organic matter. Correlation co-efficient between soil characteristics and fungistasis has been calculated to evaluate relationship. High fungistatic activity was exhibited generally by the soils having low pH but high organic matter. The soils exhibiting high fungistatic activity againstF. udum have low incidence of wilt disease of pigeon-pea. There was no definite correlation between volatile and non-volatile fungistasis and, therefore, the origins of volatile and non-volatile fungistasis are different. In the usual biological limit pH had insignificant impact on fungistasis.     

Changes of pH across the rhizosphere induced by roots

Summary Plants that absorb nitrogen as NO₃ ^– tend to raise the pH in the rhizosphere. Those absorbing nitrogen as NH₄ ⁺ or N₂ lower the pH. The change in pH near the root surface may be calculated approximately from the H⁺ or HCO₃ ^– efflux and radius of the root; and the pH buffering capacity, moisture content, initial pH and p_{CO 2} of the soil. An accurate equation, solved numerically, also takes account of root hairs, mass flow and slow acid-base reaction in the soil. The pH at the root surface will often differ from the pH a few mm away by 1–2 units.