Evaluation of techniques for quantitative detection of Phytophthora cinnamomi

Three baiting techniques and a sieving technique were evaluated for the quantitative detection zof Phytophthora cinnamomi Rands. Baiting with seedlings of Lupinus angustifolius L. (blue lupins), cotyledons of Eucalyptus sieberi F. Muell. and pear fruits cv. Packham's Triumph, detected one chlamydospore introduced into 50 g of either sand or soil. Sieving detected one chlamydospore in 50 g sand and also in 5 g soil. In naturally-infested soil, diluted with a similar non-infested soil, P. cinnamomi was detected at dilutions of $\text{1}\text{8}$ and $\text{1}\text{128}$ by the sieving and the baiting techniques, respectively. In general, pears were the most satisfactory bait for the detection and isolation of P. cinnamomi. The potential of baiting techniques for estimating numbers of propagules of P. cinnamomi in naturally-infested soil is discussed.     

Current status of two endangered Caribbean rodents

Living rodents of the genus Geocapromys of the hutia family have been known during this century on three Caribbean islands (Walker, 1968). Visits were made in 1974 to Jamaica and Little Swan Island to check the current status of two of these endangered populations. It appears from these field investigations that the Swan Island hutia, Geocapromys brownii thoracatus, has been exterminated from Little Swan Island. The main cause may have been predation by cats introduced in the late 1950s and after. The Jamaican hutia, G. b. brownii, remains in three remote areas of Jamaica. It exists at low population levels which have been much reduced from those occurring 30 years ago. The Jamaican hutias are shy and secretive in habits compared to the undisturbed Bahamian hutias, G. i. ingrahami, of East Plana Cay, Bahama Islands.     

The use of a comparative particle size distribution index for the numerical classification of soil parent materials: application to mollisols of the argentinian pampa

A method to estimate the magnitude of discontinuities or similarities in parent materials having equivalent mineralogical composition is proposed. It is based on a particle size distribution index which compares for two samples the weight percentages of all fractions taken between selected size limits.The indexes form a matrix and are used to construct a dendrogram which illustrates the clustering into groups. The calculations are carried out by computer using a Fortran programme.The technique was applied to a set of soil samples of Mollisols in the humid undulating pampa in Argentina and good agreement with field observations was obtained.     

Substances interfering with the gas-liquid chromatographic determination of T-2 mycotoxin.

Two substances interfering with the gas-liquid chromatographic (GLC) detection of T-2 mycotoxin were identified as 1-glyceryl-monooleate and 1-glycerylmonolinoleate. These monoglycerides are natural products formed by species of Fusarium growing on cereal grains and are also additives contained in liquid vegetable and animal fats added to the feed mixture. The monoglycerides can be removed from the analytical sample by resolution by thin layer chromatography prior to separation by GLC. Trimethylsilyl ether derivatives of the monoglycerides and T-2 toxin have almost identical retention times on 3% OV-1 columns, whereas the trifluoroacetyl and pentafluoropropionyl derivatives give baseline separation on the same column. The monoglycerides can be misidentified as the T-2 toxin in analyses involbing GLC.     

Sodium bicarbonate as an extractant for soil phosphate III. Effects of the buffering capacity of a soil for phosphate

An index of the buffering capacity for phosphate of a group of soils was obtained by measuring adsorption of phosphate from dilute solutions of calcium chloride. The effect of buffering capacity on the amount of phosphate initially displaced by solutions of sodium bicarbonate and on the amount of secondary adsorption from bicarbonate was then studied. These two effects were separated using a regression procedure in which the soil: solution ratio was the independent variable.As buffering capacity increased the amount of phosphorus initially displaced decreased and the amount of secondary adsorption increased. Both these changes resulted in a decrease in the amount of phosphate in the extract. The effect of buffering capacity was greater with the Olsen method (soil : solution ratio 1 : 20; 30 min) than with the Colwell method (soil : solution ratio 1 : 100; 16 h). The relation between phosphorus extracted and buffering capacity was of a similar shape to that between effectiveness of fertilizer and buffering capacity. However, the first relation depends on the conditions of extraction and the second on the kind of plant grown and on the conditions of growth. Hence the two relations do not necessarily coincide.The effect of buffering capacity on the proportion of added phosphate initially displaced from the soil became more marked as the period of incubation prior to extraction was increased. Bicarbonate soil tests would therefore indicate that, on soils of low buffering capacity, the decrease with time in availability of applied phosphate would be smaller than on soils of high buffering capacity. This effect differs from that observed with plants.     

Detection of O,O-diethyl-O-(2,5-dichlorophenyl) phosphorothioate and O,O-diethyl-O-(3,6-dichloro-2-pyridyl) phosphorothioate in meat fat.

Two previously unreported organophosphorus residues have been detected in meat fat. The first, O,O-diethyl-O-(2,5-dichlorophenyl) phosphorothioate, apparently results from the debromination of bromophos-ethyl, while the other, O,O-diethy-O-(3,6-dichloro-2-pyridyl) phosphorothioate, presumably arises by the monodechlorination of chlorpyriphos. Mass spectral evidence is presented in support of the assigned structures and gas-liquid chromatographic retention data for the residues and their oxygen analogs are provided.     

Economic trade-offs to limit nonpoint sources of agricultural pollution

A national model has been built which allows analysis of physical and economic trade-offs as soil loss per acre is limited to specified levels in each major land group of the nation. Crop variables with their associated conservation practices are developed for each of 1891 land groups in 223 agricultural producing regions and 51 water supply regions. The regions and soil groups are made interdependent through regional commodity demands and a transportation submodel. Hence, changes in cropping systems and erosion control practices in one region are simultaneously expressed in effects on other regions. Soil loss limits are set at 10, 5, and 3 t per acre. The 10 t limit does not have a large impact on interregional production patterns and farm comodity prices. However, the 5 and 3 t limits, either singularly or in combination with different export levels, cause rather marked increases in commodity prices. Also at limits of 5 and 3 t, considerable shifts take place among regions in the crops grown and the erosion control methods used. Regions with erosive soils sacrificed in reduced income; regions with level soils can crop more intensely and gain greater income. Conservation practices such as reduced tillage increase the amount of pesticides needed in some regions and pose special environmental problems. The South Atlantic region is affected most by soil loss limits to control nonpoint pollution. The Great Plains regions with more level land and limited rainfall are affected least.     

Determination of amphetamine by Schiff base formation and quantitative gas-liquid chromatography.

A procedure was developed to determine amphetamine salts in solid dosage forms. Amphetamine was extracted from the solid matrix with dilute hydrochloric acid and reacted with cyclohexanone in a strongly basic aqueous methanolic solution. The Schiff base reaction product was extracted with hexane for gas chromatographic determination. Reaction time and optimum conditions were studied. Phenethylamine, similarly treated, was used as an internal standard. Results compared favorably with those obtained by using USP methods.     

Some genetic characteristics of the freely drained soils of the ettrick association in East Scotland

This paper describes the interrelated characteristics of the freely drained soil series of the Ettrick Association. These soils are extensively developed in the Southern Uplands of Scotland on glacial drift derived from greywacke.At the present day the soils of the Linhope series are acid brown soils whereas the Minchmoor and Dod series include podzols and peaty podzols. Subalpine podzols and alpine soils are included within the Merrick series. It is concluded that the soils of the Linhope, Minchmoor and Dod series were all formerly brown forest soils under deciduous woodland. They have evolved to their present status after forest clearance which gathered momentum after the widespread establishment of monastic institutions in Scotland in the twelfth and thirteenth centuries A.D. The evolutionary outline of profile development is described and discussed.