Calculation of hydraulic conductivities of horizons in some major soils in Wisconsin

Hydraulic conductivity between saturation and a tension of 100 cm water was calculated with moisture-retention data for nine soil horizons and compared with results from in situ measurements with the crust test. Agreement was good for sandy, apedal soil horizons with simple packing voids but only if matching factors were used. Results were unreliable in clayey, pedal soil horizons in which a few relatively large planar and tubular pores determine K in the measured tension range, whereas the greatest fraction of total porosity is composed of fine pores inside peds that hardly contribute to flow. Varying the number of pore classes (n) and the water-filled porosity at saturation made no significant difference in the calculations for the apedal soils, but drastically changed the shape of the calculated curves for the pedal soils. Matching factors based on K_sat measurement had to be used for all studied soil horizons, indicating that Marshall's pore-interaction model never predicted K_sat accurately.     

THE EFFECT OF AUTUMN MANAGEMENT ON WINTER DAMAGE AND SUBSEQUENT SPRING PRODUCTION OF SIX VARIETIES OF LOLIUM PERENNE GROWN AT CAMBRIDGE

Six perennial ryegrass varieties which were known to differ in winter hardiness were subjected to ten managements comprising two N rates and fire autumn cutting treatments. Autumn yields and soluble carbohydrate contents were measured, also the amount of winter damage in February and subsequent spring yields. The winter was mild, herbage damage was slight and no plant deaths were recorded, but significant differences were found between cutting treatments and varieties. The amount of winter damage increased with the length of the autumn rest period and with the degree of winter dormancy of individual varieties, indicating that natural senescence was a more important causative agent than frost action. Spring yields were affected by the amount of winter damage but there were considerable interactions between varieties and environments. The results are discussed in relation to autumn management practices, choice of variety for different locations and measurements of winter hardiness. The induction of winter dormancy by day length or low temperature reactions is considered in the breeding of varieties for maximum production in different parts of the country.     

THE EFFECT OF NITROGEN, STOCKING RATE AND GRAZING METHOD ON THE OUTPUT OF PASTURE GRAZED BY BEEF CATTLE

An experiment was conducted in 1971 and 1972 to study the effects of two levels of fertilizer N (50 and 504 kg/ha) on the productivity of pastures grazed by young beef cattle. Two stocking rates were imposed at the lower N level and three at the higher. In addition to rotational grazing, set-stocking and an integrated grazing-conservation system were included. The responses/kg N were approximately 1 kg live-weight gain, 19–24 Meal ME and 8–9 kg DM. Maximum yields of 1200–1300 kg live-weight gain/ha and 25,000–27,000 Meal ME/ha were recorded. Productivity of set-stocked pasture was similar to rotational grazing at the high N level, but lower at low N. The integrated system yielded comparable results to high-N rotational grazing. Performances and herbage intakes per animal reflected the stocking rates imposed.     

Adsorption and activity of chitinase on kaolinite

Chitinase is adsorbed on kaolinite below the isoelectric point of the enzyme, pH 6.8. Maximum adsorption is reached below pH 4.6. The amount of chitinase adsorbed to kaolinite depends on the concentration and on the ratio of enzyme to kaolinite. Adsorption results in reduction of chitinase activity. the extent of which depends on the amount of kaolinite present, on pH, and on the length of exposure time. Upon sorption of chitinase on kaolinite the optimal pH for activity is increased from pH 4.7 to 5.7.     

Microbial degradation of several acetamide,acylanilide, carbamate,toluidine and urea pesticides

Soil enrichment was used to isolate soil microorganisms capable of degrading isopropyl carbanilate (propham), 3′,4′-dichloropropionanilide (propanil), 3′-chloro-2-methyl-p-valerotoluidide (solan), and methyl 3,4-dichlorocarbanilate (swep) in a muck and a silty clay loam. Degradation of the pesticides in enrichment solutions, and by pure cultures of effective microbial isolates was demonstrated by the production of the corresponding aniline, chloride ion liberation and disappearance of the parent compound. Degradation products were identified by gas-liquid and thin-layer chromatography.Organisms isolated include Pseudomonas striata Chester, Achromobacter sp., Aspergillus ustus (Bain) Thorn and Church, A. versicolor (Vuill. Tirabaschi), Fusarium oxysporum Schlecht, F. solani (Martius) Appel and Wollenweber, Penicillium chrysogenum Thorn, P. janthinellum Biourge, P. rugulosum Thorn and Trichoderma viride Pers. Each organism demonstrated a unique substrate specificity and was capable of degrading other aniline-based pesticides of the acetamide, acylanilide, carbamate, toluidine and urea classes.     

The chemistry of humic and fulvic acids extracted from argentine soils—I. Analytical characteristics

Five humic and three fulvic acids were extracted from Argentine Chestnut, Brunizem, Solod and Solonetz soils and analysed by electrometric, spectroscopic and spectrometric methods. There were great similarities in elementary analysis, functional group content, absorption characteristics in the visible region and in the IR, and in the ESR measurements between the humic acids and, similarly, between the fulvic acids. There were distinct differences between the humic and fulvic acids in C, H, N and O content, distribution of oxygen in functional groups, E₄/E₆ ratios and free radical content.     

The redox characteristics of four peat profiles

In several previous observations on peat soils, redox potentials appeared to vary with season and depth. To clarify this variation, a systematic study was made over 1 yr at four peat sites, including wet and dry areas at high and low altitude in northern England.The coefficients of linear regressions of redox potential on seasonal temperatures became progressively more negative with increasing depth at all four sites. These observations support an hypothesis that increased aeration accompanying increased temperature played a role at the surface, but was of less importance in the deeper layers, where the reducing conditions that result from microbial activity were dominant.By using orthogonal polynomials, it was possible to demonstrate the existence of redox minima in the profiles at all sites. There were rather more minima present using this method at the lowland sites that at the upland ones where trends of redox with depth were otherwise linear or non-significant. Although the mean redox potentials over whole profiles were lower in the wetter sites than the drier, the mean depths of the redox minima were similar. These mean depths were poorly defined however having standard deviations of 30–50 per cent of the means calculated from the year's observations.Finally, it was shown that although the potentials were measured 60 s after closing the circuit, very similar conclusions would have been reached if the readings had been taken after 10 s.     

The arthropods associated with the decomposition of some common grass and weed species in the soil

The arthropod fauna associated with the decomposition of herbage of various species on the surface of the soil was studied. Litter of Rumex, Urtica, Ranunculus, Senecio and Lolium disappeared rapidly at first and thereafter at a slower rate. Dactylis disappeared more slowly than the other litters over the first 6$\text{1}\text{2}$ months but its rate of disappearance thereafter was greater than that of the other species. There were quantitative and qualitative differences between the microarthropod communities associated with the various litters. Highest populations of microarthropods were recorded from Dactylis. Dactylis and Lolium were the most similar in the species composition of their faunas. Changes occurred in the relative abundance of various arthropod groups and species during the course of decomposition in all litters.     

Electron microscopical studies of chlamydospores of Fusarium solani F. cucurbitae formed in natural soil

Macroconidia of Fusarium solani f. cucurbitae were placed into natural soil, incubated for various times, recovered and examined by light and transmission electron microscopy. Lysis of macroconidia and formation of chlamydospores were studied and the fine structure of these propagules and their associated microflora was investigated. The two most obvious features of chlamydospore morphology were the sloughing of outer wall layers and the accretion of micro-fibrillar elements adjacent to the plasmalemma. Chlamydospore formation was partially suppressed by addition of nitrogenous compounds to the soil.