Multiple forms of acetyl-naphthyl-esterase activity in soil organic matter

Acetyl-naphthyl-esterase activity has been identified and characterized in organic matter extracted from an A₁ horizon of an Alpine podzol. The temperature optimum of the esterase is about 75° C and its activity rises with increasing pH, without reaching a maximum value in the tested range. The Michaelis constant has been determined as Km = 2.950 mM. Pronase does not disrupt esterase activity. Electrofocusing in acrylamide gel shows several peaks of enzyme activity, which correspond with humic isoelectric bands. The location of acetyl-esterase activity in organic matter is discussed.     

Studies on soil fumigation—III: Effects on enzyme activities,bacterial numbers and extractable ninhydrin reactive compounds

Fumigation of a field soil with chloropicrin and methyl bromide, either singly or in combination, differentially decreased soil enzyme activities and viable bacterial numbers and increased the amounts of ninhydrin reactive compounds extractable with acidified Tris buffer. Chloropicrin treatment was more effective than methyl bromide.The rates of hydrolysis of both an amide and a peptide derivative were decreased by chloropicrin treatment and remained relatively low despite changes in activities over 325 days. By contrast, caseinase activity initially was decreased by both chloropicrin and methyl bromide fumigation, but activities of the fumigated soils recovered to exceed those of untreated soils. Thereafter, caseinase activities of fumigated and untreated soils exhibited relatively large fluctuations, which were partly associated with seasonal drying of the soils in the field.Chloropicrin but not methyl bromide fumigation markedly depressed the viable bacterial populations, which subsequently increased to be above those of the untreated soils. There was no consistent relationship between the release of ninhydrin reactive compounds following fumigation and changes in bacterial numbers or changes in enzyme activity. Autolytic reactions are probably important in the early stages of amino-nitrogen release in fumigated soils. Net gains in caseinase activity may be partly due to the production de novo of extracellular proteases by microorganisms or to the release of intracellular proteases from killed cells.     

Studies on soil fumigation—I: Effects on ammonium,nitrate and phosphate in soil and on the growth,nutrition and yield of wheat

Fumigation of field soil with chloropicrin alone or followed by methyl bromide, each at 220Kg·ha^?1, released 20–30 parts/10⁶ NH⁺₄-N which persisted for 75 days; such fumigation also doubled the amount of bicarbonate-extractable phosphate 28 days after fumigation. Soil fumigation increased both the vegetative and grain yields as well as increasing the content of N in the grain and the content of K and Cl in the tops at ear emergence. Root growth and the phosphate uptake activity of the roots were increased by soil fumigation.     

The effect on young beef cattle of supplementing hay with dried grass or concentrates

Forty-eight Friesian steers with an average live-weight of 168 kg were given hay ad libitum supplemented with 0, 0.6, 1.2, 1.8, 2.4 and 30 kg artifically dried grass or concentrates. In vitro dry matter digestibility of hay was 55%. Liveweight gain increased with each successive increase in the level of supplementation. The intake of hay decreased but the total DM was greatest at the higher level of supplementation. The results suggest that dried grass pellets combine well with hay and may be used to replace concentrates. It was shown that 1 kg of either dried grass or concentrates given as a supplement to hay fed ad libitum, will increase the live-weight gain by 0.16 kg d^?1 and decrease hay intake by 0.25 kg d^?1.     

Pathogens occurring on ten varieties of ryegrass at Rothamsted in 1973–74

Six varieties oi Loliumperenne, three of L. multiflorum and one hybrid (L. multiflorum × L. perenne) were assessed for diseases over two harvest years. Crown rust (Puccinia coronata) and mildew (Erysiphe graminis) occurred on some varieties in 1973. Leaf spotting (Drechslera spp.) was common, but slight on most varieties, in both years. Ryegrass mosaic virus (RMV) and its mite vector, Abacarus hystrix were present on all varieties in the second year. The relative susceptibility of varieties to RMV was similar in the field and in glasshouse tests.     

The effect of delayed autumn harvest on the survival of varieties of perennial ryegrass

The reactions of five early and five late varieties of perennial ryegrass to stimulation of bulky autumn growth and deferment of harvesting were compared in terms of spring growth and subsequent recovery during three winters. Winterkill was marked in 1971–72, particularly when harvesting was deferred to late November, in early varieties S24 and Presto Pajbjerg and in the late variety S23. Least affected among early varieties were Premo and Barvestra (tetraploid) and among late varieties, Perma and Barpastra (tetraploid). All varieties showed rapid recovery. The results are discussed in terms of the significance of winterkill, and the effects of age of sward, variety susceptibility and deferment of autumn defoliation. It is concluded that the form of winterkill which occurs in the west of Scotland can have serious consequences to farm productivity in severe winters. Autumn growth left standing into November can also lead to winterkill. Under good management, varietal differences are unimportant. In a severe winter, no varieties of perennial ryegrass are reliable.     

Detection of twelve mycotoxins in mixed animal feedstuffs, using a novel membrane cleanup procedure.

A multimycotoxin thin layer chromatographic screening method is described which is applicable to most animal feedstuffs. Interference from nonspecific lipid, pigment, and other components of simple and mixed feeds is reduced to a minimum by using a membrane cleanup step. Aflatoxins B1, B2, G1, and G2, citrinin, diacetoxyscirpenol, ochratoxin A, patulin, penitrem A, sterigmatocystin, T-2 toxin, and zearalenone may be reliably detected. The sensitivity of the method is generally low for mixed feeds but even so aflatoxin B1 can be detected at a level of 3 ppb and ochratoxin A at 80 ppb. While the basic method is less sensitive for sterigmatocystin (330 ppb), patulin (600 ppb), zearalenone (1000 ppb), and the trichothecenes (1000-4000 ppb), it may be adapted so as to reduce the above detection limits when the presence of these toxins is suspected. Lower levels may be detected in extracts of simple feeds.     

The effects of dredging operations on the benthic community of a chalk stream

Sampling of the benthic fauna showed that dredging operations produced relatively short-term effects on invertebrate population levels. The behaviour of the animals was immediately affected, the differences between species were noted and the implications of dredging at different times of year are discussed.     

Conservation and the low population density of invertebrates inside neotropical rain forest

Counts of invertebrates by sweep-netting and beating the stratum of rain forest vegetation between 6 in (15 cm) and 6 ft (1·8 m) have been made during rainy season conditions in N. Brasil and on Barro Colorado Island, Panama Canal, the latter from measured volumes of habitat. This work has been repeated on BCI during the dry season. The average population densities of total catches were 0·97 m³ for rainy season and 1·09 m³ for dry season. Species diversity was very high, therefore numbers per species extremely low. It is suggested that such low population density brings hazards of local extinction, and that the maintenance of such a system depends on the existence of extensive habitat from which recolonisation can occur. If this is so, reserves in rain forest will have to be very large, to ensure long-term survival of many of the invertebrate species.     

Investigation,evaluation, and priority ranking of natural areas

Texas experience suggests that amateur naturalists will be heavily involved in preliminary ecological surveys of natural areas, hence a simple key for identification of community-types is presented. Line intercept transects are suggested for amateur use in providing standardised quantitative data on the physiognomy of natural areas. A scheme for the evaluation of each area utilises the weighted values of climax condition, educational suitability, species significance, community representation, and human impact through multiplicative scoring to give a natural area score. With the weighted values-multiplicative scoring scheme, natural areas are clearly distinguished in priority for acquisition.