Showing papers in "Crop & Pasture Science in 1952"

A method for unbiased selective sampling, using ranked sets

Abstract: A new method of sampling is described Take the largest in the first of n sets, each of n random items, the second largest in the second set, and so on to the smallest in the nth set The sample of n items selected in this way is an unbiased sample of the population For typical unimodal distributions the mean of such a sample is slightly less than (n + 1)/2 times more efficient than the mean of n items taken at random The application of the ranked sample method to pasture measurement is discussed

The epidemiology of parasitic gastro-enteritis of cattle

Abstract: Observations on parasitic gastro-enteritis of cattle are recorded with particular reference to its epidemiology under conditions existing in Queensland. The most important species of nematodes associated with this disease are Haemonchus contortus, Bunostomum phlebotomum, Cooperia punctata, C. pectinata, and Bosicola radiatus. All of these are serious among dairy cattle, but only H. contortus, Bosicola radiatus, and rarely Bunostomum phlebotomum among beef cattle. Ostertagia ostertagi and Trichostrongylus urei are common, but occur in pathogenic numbers only occasionally. Strongyloides papillosus and Moniezia sp., probably M. benedeni, are also discussed. The incidence and prevalence of these parasites are recorded and also the age of the calf when infestation was first detected. Pathogenic infestations are for the most part confined to young cattle 3 to 24 months of age. In dairy cattle, the most susceptible age is from 4 to 12 months; in beef cattle, the majority of outbreaks occur a few months after weaning. Outbreaks are usually seen during the winter and early spring, although on occasion, losses may commence in the autumn and occur also in early summer. Seasonal fluctuations in the populations of these helminths were followed by means of regular faecal egg counts. It was usual for the egg count of each species to increase to a peak, then to decline fairly rapidly, and to remain on a low level during the remainder of the period the animals were under observation, i.e. up to 18 months of age. The ages at which these peaks occurred are recorded and their relationship to the season of birth of the host is discussed. The influence of temperature and rainfall on the prevalence of these helminths has been studied and some preliminary observations are recorded on the development and behaviour of their preparasitic stages in the dung pad. Evidence is brought forward to show that cattle develop a strong resistance to infestation during the first 18 months or so of life. In young animals this reaction depends on exposure to infestation and is somewhat specific in nature in so far as it may be manifested against one species, but populations of other species may continue to increase. Thus, most animals became resistant to infestation with Cooperia spp. at about five months of age, but not to H. contortus and the other species until several months later. This resistance is considered mainly responsible for the light infestations usual among adult cattle. It appears strongest against B. phlebotomum and weakest against H. contortus, which is the most common and prevalent species among adult animals. Outbreaks of parasitic gastro-enteritis are considered to occur under conditions of high larval prevalence and poor nutrition, when resistance against infestation fails to be effective.

Phosphorus toxicity in Subterranean clover and oats grown on Muchea sand, and the modifying effects of lime and nitrate-nitrogen

Abstract: Phosphorus supplied as mono-sodium phosphate depressed the growth of subterranean clover and oats grown on Muchea sand in pot culture. In both plants the detrimental effects appeared at phosphorus levels equivalent to about 2-4 cwt. per acre superphosphate, provided both nitrogen and lime were in very short supply. Adequate nitrogen, as sodium nitrate, invariably overcame the toxic effects of phosphorus within the range of levels examined. With the clover, nodulation was usually poor, but some evidence is presented in which "heavy" inoculation with Rhizobium markedly increased nodulation and alleviated the toxic effects. Nodule numbers in the clover were increased by addition of lime and in most instances the beneficial effects resulted from enhanced nitrogen supply. Lime was advantageous to the growth of oats, also, wherever applied nitrogen was low. Possible explanations of this are suggested. Phosphorus toxicity symptoms are described for both plants and the relation to percentage total phosphorus in the leaves is discussed. Figures in excess of 1.4 per cent. and 3 per cent. total phosphorus were found in affected leaves of subterranean clover and oats respectively. Identical symptoms were observed in clover with the mono- and dibasic phosphates of sodium, calcium, and potassium.

Observations on the bionomics of the sheep body louse (Damalinia ovisM)

Abstract: Experimental observations are recorded on the bionomics of Damalinia ovis on the sheep and in vitro. The optimal conditions for in-vitro rearing of D. ovis are 36.5°C. and 70-90 per cent, relative humidity when a mixture of skin scurf and baker's yeast is used as food. Under these conditions the life cycle closely approximates the estimated life cycle on the sheep. The incubation period is 9-10 days; the three nymphal instars are completed in 7, 5, and 9 days respectively; the preoviposition period is approximately 3 days, making a cycle of 34 days from egg to egg. The lice and their eggs are very susceptible to changes in temperature. The areas of heaviest infestation are along the mid-dorsal line and down the sides of the sheep. Individual sheep differ considerably in their susceptibility to artificial and to natural infestations. Sheep in poor condition tend to have the heaviest infestations, which are retained throughout the year. There is a pronounced seasonal fluctuation in populations of D. ovis, the heaviest infestation occurring in the period from June to September.

Lime and molybdenum in clover development on acid soils

Abstract: In a study of the factors concerned in the effect of lime on subterranean clover (Trifolium subterraneum L.) on an acid soil where nodulation is defective, it has been found that responses equal to those obtained with heavy dressings of lime can be obtained by the application of molybdenum together with only 2 cwt. of lime per acre at seeding. Marked response to molybdenum was obtained only where low levels of lime were used. Where heavier dressings of lime were applied the clover grew normally and did not then require treatment with molybdenum. Where no lime was used nodulation was defective and, during the first two )ears, response to molybdenum did not occur or was very small. Nodulation subsequently improved on the unlimed soil and response to molybdenum progressively increased over the five-year period of the experiments. In the year of sowing best results were obtained where the inoculated seed was drilled with the lime. The evidence suggests that defective nodulation of subterranean clover may be expected on new land where the soil reactions are less than pH 5.0, and that soils of higher pH but with minimum values less than pH 5.5 are also suspect. The importance of treatment with adequate superphosphate in addition to lime and molybdenum in the development of subterranean clover on this acid soil is stressed. The interpretation and significance of the positive and negative lime-molybdenum interactions obtained are discussed.

The quantitative definition of cattle carcasses.

Abstract: The possibility of defining quantitatively the carcasses of cattle has been investigated and a procedure evolved, based upon “conformation”, “finish”, and “quality”, which are the features appraised by beef-carcass graders. A series of ratios has been used to define “conformation” with respect to shape rather than to dimensional attributes. For example, length, “meatiness”, and compactness, which are attributes of a hind leg, are described by a ratio of which the numerator is the “circumference” measurement at an anatomically fixed point whereas the denominator is a defined length measurement. The trade term “finish” is covered by a percentage assessment of the distribution of subcutaneous fat over the carcass whereas thickness of fat is the mean of two measurements of depth made at points fixed anatomically. The proportion of fat to lean is stated by a ratio of which the numerator is a maximal measurement of the depth of lean meat at a defined situation and the denominator is the mean depth of subcutaneous fat. Attributes of “quality” are colour of fat, firmness of fat, “marbling”, and colour of lean meat. A series of five defined colours has been used to classify colour in a sample of subcutaneous fat rendered by heat. Firmness of fat has been related to a series of iodine numbers of greater or lesser magnitude: Firm, medium, soft, and oily fats were found to be classifiable by the reaction of the rendered substance to slight manual pressure exerted through a blunt probe. The degree of marbling was determined from the size relation of a petrol-ether extract to a sample portion of the carcass taken at a defined situation. Colour of lean meat was classified by reference to a series of defined colours which were given distinctive numbers. Quantitative figures from observations may be recorded for examination by statistical methods or they may be transposed as diagrammatic presentations which may be related to trade standards or to market types for the purpose of judging carcass competitions. The procedure may also be used to provide data from which a “fleshing index” can be determined. Examples of all three possibilities are stated. The procedure has been tested on' three series of animals, from which measurement errors for individual carcasses were calculated and found to be satisfactorily low. However, it has not yet been adequately tested for the comparison of between-group differences in carcasses, principally because no animals suitable for such a test are likely to become available until experimental conditioning is undertaken. The procedure is, therefore, presented tentatively.

The effect of stage of growth on the copper, zinc, manganese, and molybdenum contents of Algerian oats grown of thirteen soils

Abstract: Algerian oats were grown on 13 soils in the glass-house. Plants were harvested at intervals throughout the growing period, and when large enough were divided into leaf, stem, and (in later harvests) flowers or fruits. Copper, zinc, manganese, and molybdenum were determined on the separate plant fractions. Characteristic changes in the trace metal contents of the plant with growth were found for each element. These changes were generally similar irrespective of the soil on which the plants were grown. With the exception of manganese, the availability of the element in the soil did not affect the trend of the changes as the plant matured, but only the amount present. The uptake of each of the four elements continued through the whole period of growth. The total amounts of copper and zinc in both the leaf and the stem decreased after flowering as translocation to the grain proceeded. The amount of manganese in the leaf increased throughout the period of growth, although the rate of increase was less after flowering. The amount of molybdenum in the leaf increased until flowering, after which there was little further change. The rate of uptake of manganese was approximately equal to the rate of production of dry matter, whereas that of molybdenum, copper, and zinc was relatively greater in the early stages of growth. There was no observable influence of soil pH on the availability of copper and zinc, but that of manganese decreased with increasing pH. The availability of molybdenum was affected by the combined influences of soil pH and soil iron.

Growth of wool fibres in sheep.

Abstract: The tips of birthcoat fibres in sheep range in shape from a definite sickle tip to one with no definite shape. The different shapes of tip are related to different types of follicle. The shapes of the tips are explained as the result of competition between follicles. The intensity of competition is not uniform, as follicles enter the follicle population in sequence.

A study of the effect of Chrysomela hyperici Forst. on St. John's Wort in the Mannus Valley, NSW

Abstract: Conditions in those parts of the Mannus Valley, N.S.W., where Chrysomela hyperici Forst. has been liberated appear either unfavourable or just tolerable to the species, which has increased in numbers and spread to a limited extent in the more favourable parts of the area infested with St. John's wort. In the colony site studied intensively, the gradual multiplication of C. hyperici led to great destruction of the weed in places, but this destruction was soon followed by regeneration. Because of this and the way in which the beetles aggregate and move on definite fronts, there has been a history of waves of insects passing back and forth over a small area around the liberation site followed by waves of regeneration of the host plant. Very young and large old crowns of Hypericum were readily destroyed by the insect, but the mortality of mature crowns of moderate size was relatively low. Where few crowns were killed, vegetative reproduction soon resulted in the reoccupation of vacant spaces. Under some conditions, defoliation by the insect appeared to stimulate suckering and thereby produced a stand of higher crown density than the original one. This addition of new crowns must have rejuvenated some stands, and probably increased their resistance to further beetle attacks for a short time. The ability of St. John's wort to maintain its position of predominance in the community in the face of heavy insect damage was due partly to the absence of effective plant competitors. The heavy grazing by rabbits and kangaroos on the plants associated with the weed, and their habit of removing the ground cover by scratching, favoured the regeneration of Hypericum from seed in places where most of the original wort plants had been destroyed.

Bioassay of available trace metals from Australian soils

Abstract: A study was made of various factors influencing the microbiological assay of available iron, zinc, copper, manganese, and molybdenum Aspergillus niger (M) was chosen as the best test organism from a group of 9 fungi, 1 alga, 1 yeast, and 6 bacteria The composition of the basal medium could be altered markedly without affecting the availability figures A new method of purifying the medium with A1203, gave good deficiency symptoms for Fe, Zn, Cu, and Mn, but Nicholas's method was superior for removing Mo It was found necessary to sterilize the soil, preferably by autoclaving The availability of 15 micronutrients was determined by bioassay from 278 surface and 164 subsoil samples from eastern Australia Seven soil groups, viz 3 pedalfers, "red loam", acid humic, and podzol, and 4 pedocals, rendzina and terra rossa, chernozem, red-brown earth, and desert soil, showed more deficiencies than all other soil groups bioassayed Even within these seven groups non-deficient soils also occurred The commonest deficiency detected was that of Zn, followed by Cu, then by Mo, hut deficiencies of Fe and Mn were rarely found Usually surface soils with a well-developed root zone were less deficient than subsoils Fewer deficient samples were obtained from meadow soil, alkaline humic, volcanic tuff, and brown earth than from all other soil groups There was a fair correlation between the availability of Zn, Cu, and Mo to A niger (M) and availability to plants, but none for Fe and Mn The fungus was able to obtain adequate amounts of micronutrients from a variety of insoluble salts or oxides of Fe, Zn, Cu, Mn, and Mo, some of which were known to be unavailable to plants A number of soils, eg red loam, laterite, and desert soil, inhibited the growth of the mould in complete medium This effect was due to active fixation of added micronutrients, especially in soils rich in calcium carbonate and in red loams No evidence was obtained that microbial fixation of trace elements occurred in deficient soils; but most major and minor elements were fixed by microorganisms in very deficient, acid-washed, quartz crystals, with the exception of Ca, which was not significantly affected, and of Fe and Zn, which were released by microbial activity from the minute amounts of contaminants present

Maintenance rations for Merino sheep. 1. A comparative study of daily and weekly feeding on rations containing high proportions of wheat and several proportions of roughage to concentrate.

Abstract: Groups of full-mouthed Merino wethers were given 4.25 lb. starch equivalent (4,550 calories of net energy) per sheep per week, to maintain a low to moderate store condition of 75 lb. body weight, on each of four rations, namely 50:50, 30:60, 20:80, and 10:90 mixtures of wheaten chaff and wheat. Finely-ground limestone was added to these rations to correct calcium phosphorus imbalance. The groups were paired, one of each pair being given the food once a week and the other being given it in daily portions. The weekly-fed groups were brought on to this regime during a preparatory period of 77 days during which they were fed at intervals which were gradually increased from 3 to 7 days. The surviving sheep in the daily-fed groups maintained their mean body weight and general condition as well as did those in the weekly-fed groups but at the end of the experiment the range in body weight in the daily-fed groups was greater: 41.9 per cent. of the daily-fed animals gained in weight during the period of 344 days, whereas only 14.2 per cent. of the weekly-fed animals did so. This difference was due largely to differences in rate of food consumption. The rate of consumption of the food by the daily-fed groups increased during the progress of the experiment. The sheep receiving the larger amounts of roughage took longer to consume the daily ration. The sheep in the weekly-fed groups ate the week's ration in 4 – 4½ days and occasionally took half a day longer. The death rate in the daily-fed groups was 30.2 per cent, compared with 11.8 per cent. in the meekly-fed group. The deaths occurred mainly (72 per cent.) in the sheep which had lost 40 per cent. or more of their initial body weight. Mean wool production from the daily-fed sheep ranged from 6.73 lb. to 6.94 lb. per sheep, and from the weekly-fed groups from 7.19 lb. to 7.57 lb. Regain of body weight after the termination of the experiment on the low diet was studied. Groups which were retained in pens and fed ad lib. gained steadily in weight and maintained a considerable lead over those which had been turned out to graze. In a group of sheep at pasture there was a close positive correlation between the loss suffered in body weight on the experimental low diet and the subsequent improvement at pasture. The rate and magnitude of subsequent regain of weight were not influenced by the proportion of roughage in the experimental diet or by the origin of the sheep from the daily-fed and weekly-fed groups. An inverse relationship between atmospheric temperatures and body-weight changes was observed. The experiments showed that daily feeding of the sheep at levels sufficient for survival was less satisfactory than weekly feeding at the same level. The practical importance of the results is discussed briefly.

A study of two strains of Rhodes Grass (Chloris gayana Kunth.) and of Leucerne (Medicago sativa L.) as components of a mixed pasture at Lawes in South-east Queensland

Abstract: The results of investigations with Rhodes grass and lucerne as components of sown pastures at Lawes in south-east Queensland are reported. Two strains of Rhodes grass, differing very markedly in growth form, rate of maturity, and other characteristics, were shown to be virtually of the same value when grazed by cattle under a system of intermittent grazing at a heavy rate of stocking. It was shown that lucerne could be maintained in a mixed pasture with Rhodes grass, and that the presence of a small population of lucerne, of a density of 2-4 plants per square yard, resulted in Increased growth of Rhodes grass and increased live-weight gains by the steers. Reasons for these increases are discussed.It is considered that the mixture, which can be expected to give improved grazing mainly during the summer months, has possibilities for large areas in south-east Queensland.

Growth of the N-type fleece.

Abstract: The rates of growth of wool fibres are compared between normal and N-type Romney Marsh sheep. The three types of follicles — primaries and first- and second-wave secondaries — form their fibres at rates of the same order in normal Romneys. The N and nr genes cause an increase in the rate of growth of the early, primary fibres, and a decrease in the rate of growth of late fibres, having no marked effect on fibres initiated between these two periods. It is argued that. the primary effect of these genes is to increase the efficiency of competition of the early initiated follicles, resulting in an increased growth rate of their fibres, which, owing to competition between follicles, results in a proportionate decrease in the growth rate of the late fibres.

Studies on fluorosis of sheep. 1. The toxicity of water-borne fluoride for sheep maintained in pens

Abstract: Five groups, each of six sheep, were fed in pens on an adequate diet of chaffed hay and crushed grain for 3½ years. One group was given rain-water to drink, whereas the others were offered similar water to which sufficient sodium fluoride had been added to give final concentrations of 2.5, 5, 10, or 20 p.p.m. F. The mean daily intakes of fluoride, expressed as fluorine, by the four experimental groups were approximately 5, 9, 18, and 37 mg. F respectively during the winter months and 7, 13, 27, and 53 mg. F respectively during the summer months. The ingestion of fluoride appeared to have no adverse effect on general health, food consumption, or wool production. The mean weights of all groups were approximately the same throughout the experiment except at the end of 2½ years, when the weight of the group which received water containing 20 p.p.m. F was significantly less, but only at the 5 per cent. level, than that of either the control group or the groups receiving the lowest two intakes of fluoride. Mottling of the incisors and molars was only slight among the sheep which received water containing 5 p.p.m. F. It was more evident in the 10-p.p.m. group and was marked in the 20-p.p.m. group. Selective abrasion of the molars was pronounced in this last group but was also noticeable in the 10-p.p.m. group. Fluoride intake caused the incisors to erupt at an earlier age. Ingestion of fluoride brought about increases of up to twentyfold in the fluoride content of the bones and teeth. The bearing of these results on enzootic dental fluorosis among grazing sheep in Queensland is discussed.

Competition between skin follicles in sheep.

Abstract: Samples of skin from three sheep (Ryeland, Lincoln, and Merino) were sectioned, and measurements made of the diameters and spatial relationships of the wool fibres. It has been shown that in all three samples a negative correlation occurred between the size of a fibre and the number, size, and distance of the fibres adjacent to it. The analysis demonstrates that the maximum distance over which this correlation occurs is 173 µ for the Ryeland, 283 µ for the Lincoln, and 147 µ for the Merino. I t is suggested that the basis of the correlation is the occurrence of competition between skin follicles for the material from which they synthesize their fibres.

Cytological studies of subterranean clover (Trifolium subterraneum L.)

Abstract: Somatic chromosome number and morphology in certain strains of subterranean clover and in species of several other fairly closely related genera have been observed. Dwalganup, Yarloop, Mt. Barker, Wenigup, Burnerang, and Red Leaf strains have each 16 fairly small chromosomes, the chromosome complexes being similar to one another and to that obtained by Wexelsen (1928) for the species. Palestine and Israel strains have each 12 large chromosomes, bearing no apparent relationship to those of the other strains but being the same in number and of a similar order of size to those found in Vicia sativa. Chromosome number and morphology may explain the failure to obtain intervarietal crosses involving Palestine, but not the low percentage of successful crosses between other strains. It is suggested that perhaps Palestine and Israel may be more correctly classed as strains of a separate species and that, with regard to their origin, Wexelsen's idea of mutational changes in isolated species offers probably the best explanation.

Depression of ruminal digestion in adult sheep by aureomycin.

Abstract: After the consumption by adult sheep of an amount of aureomycin hydrochloride corresponding to 23.6-27.1 mg. per kg. body weight, the ruminal flora had fallen about 75 per cent. within two hours and remained a t this low level for at least two days, the survivors being predominantly Gram-positive rods and cocci. Ruminal fermentation was greatly depressed; the yield of organic acids reached only about 30 per cent. of the normal and was insufficient to lower the ruminal pH significantly. Appetite was lessened and body weight fell, but responded favourably to administration of ruminal fluid and yeast extract.

Studies on the nutrition of pasture plants in the South-west of Western Australia. III. The effect of sulphur on the growth of subterranean clover (Trifolium subterraneum L.)

Abstract: Sulphur applied as calcium sulphate or sodium sulphate significantly increased the growth of subterranean clover on a number of sandy soils in pot culture and also on a gravelly sand under field conditions at Kojonup. In the field trial a significant response was also obtained in the volunteer annual, capeweed.Total sulphur in the tops of both clover and capeweed was markedly increased by sulphur application; the lowest values were observed in one of the pot-culture trials, where deficiency symptoms were most prominent. Some reasons are suggested for the earlier appearance of deficiency symptoms in the field trial, where the deficiency was less severe than in the pot-culture experiments.

The effect of grazing on a perennial veldt grass, subterranean clover pasture

Abstract: The results of a grazing trial with Merino wether sheep on perennial veldt grass with subterranean clover are presented. During the four years 1944-45 to 1947-48 total pasture production under continuous grazing was almost identical with that under rotational grazing (one week's grazing followed by five weeks' rest). No consistent treatment differences were observed in sheep body-weight trends. In each year the weights increased during the growing season, remained stationary during early summer, and declined in late summer. The contribution of the perennial grass (Ehrharta calycina Sm.) declined rapidly with time, though more so under continuous grazing. This was associated with an increase in the proportion of subterranean clover in the sward. The lack of persistence of Ehrharta calycina is attributed to selective grazing, together with susceptibility to drastic defoliation. Alternative schemes for the use of this grass, involving restricted winter grazing, are suggested.

Studies on the carbohydrate metabolism of sheep. 5. The effect of hyperglycaemia and of insulin on the rate of extrahepatic glucose assimilation.

Abstract: Significant increases in the arterio-venous glucose difference have not been observed constantly in sheep either during the hyperglycaemia which follows intravenous glucose injection or during the period in which the blood glucose is falling after insulin administration. It is suggested that the low rate of extrahepatic glucose assimilation at hyperglycaemic levels provides a partial explanation of the relatively slow rate of clearance of injected glucose from the general circulation of ruminants. Blood-glucose curves, obtained after direct administration of glucose into the abomasum, are discussed in the light of these findings, and it is concluded that the rate of glucose absorption from the intestine of the sheep is low compared with the rate in non-ruminants. It is suggested further that hexokinase activity in the extrahepatic tissues of the sheep is relatively low, and that the findings described are conditioned principally by the nature of carbohydrate digestion and metabolism in the ruminant.

The effects of fertilizer treatments on the oestrogenic potency of Trifolium subterraneum L

Abstract: The oestrogenic potency of subterranean clover from plots which received superphosphate together with several other fertilizers did not differ significantly from that of clover from a plot which had received superphosphate only. On the other hand, clover from plots which had received no fertilizer recently was significantly more potent than clover from plots which had received superphosphate.

Studies on the nutrition of pasture plants in the South-west of Western Australia. IV The Growth of Subterranueum Clover (Trifolium subterraneum L.) as affected by lime, molybdenum, and Potassium

Abstract: The results of a pot-culture experiment in which subterranean clover was grown on a coarse siliceous sand slightly acid in reaction are presented. Maximum yields resulted from application of potassium, together with either molybdenum or lime. The lime X molybdenum interaction was almost always negative, but its magnitude varied with time and potassium: in the absence of potassium it diminished in magnitude, but increased markedly in its presence. The lime X potassium and molybdenum X potassium interactions were strongly positive during the later stages of growth, but only in the absence of molybdenum and lime respectively. The effects of treatment on leaf-weight and leaf-area ratio were not closely related to those on relative growth rate. The latter were determined primarily by treatment effects on net assimilation rate. Both relative growth rate and net assimilation rate were increased by potassium. The results provide further support for the findings of Anderson and Oertel (1946) that, in legumes, nitrogen is the primary nutrient concerned in the response to lime and molybdenum, and that the molybdenum concentration gives little indication of the minimum requirements for satisfactory growth. The possible effect of lime on the transport of molybdenum from roots to tops is discussed.

Some aspects of virus Y resistance in the potato (Salanum tuberosum)

Abstract: When the leaves of potato hybrids resistant to virus Y were inoculated, virus development was restricted and within 14 days the virus was inactivated in most instances. There was no evidence to suggest that resistance was due to hypersensitivity. Virus concentration increased gradually in susceptible varieties after inoculation. Four treatments of virus Y inocula were tried; that made with phosphate buffer of pH 7 produced the most lesions on the resistant potato hybrid 11-84. A marked reduction in lesion numbers occurred on 11-84 when sap from virus-free D. stramonium plants or X-infected N. glutinosa plants was added to inoculum of virus Y. Crossbred progenies were developed from two of the resistant hybrids and one of the varieties used to study virus development after inoculation. One progeny contained 68.3 per cent. phenotypes resistant to virus Y and the other had 29.4 per cent. In both progenies there was a strong association between resistance to virus Y and the immune reaction to virus X. The results indicate that immunity and high resistance to virus Y are governed by the nulliplex and simplex conditions of a major gene, while the quadruplex condition controls susceptibility.

Plant responses to nitrogen and sulphur on a heavy clay soil from the Darling Downs, south-east Queensland

Abstract: Pot experiments in connection with investigations into poor establishment of certain pasture species on several heavy clay soils on the Darling Downs have shown nitrogen and sulphur to be the principal elements limiting plant growth. Addition of these nutrients in combination to the soil has resulted in a substantial increase in plant growth associated with an even greater increase in protein production. These increases greatly exceed those obtained with either nutrient singly. Zinc availability in the soil is also discussed.

Some effects of no cultivation on the yield and growth of citrus trees

Abstract: A factorial field experiment is described in which cultural, irrigation, and nitrogen treatments were tested on citrus trees of different stocks and scions. The sod treatment quickly caused decreases in growth of the trees and the yield and quality of the fruit produced. The plots where bare soil was maintained have given large healthy trees with high yields of good-quality fruit, in spite of an observed deterioration of soil structure in these plots. Nitrogen treatments improved the yield and health of the trees in the sod treatments but have had no effect on the other cultural treatments. Root distribution, soil fertility, and leaf analysis studies, undertaken to try to explain the reasons for the yield differences noted, are described and it is concluded that nitrogen effects could explain all differences recorded to date.

Definition of potato virus Y strains by some solangceous species

Abstract: By their differing reactions, Lycium halimifolium, L. rhombifolium, Physalis floridana, and Capsicum annuum distinguished between four strains of potato virus Y, P. floriduna giving the best differentiation. The avirulent strain produced no symptoms in L. rhombifolium and P. floridana, and virus development was restricted in P. floridana. The two varieties of C. annuum were immune to virus Y except for the tolerant reaction of one to a virulent strain. Nicotiana glutinosa indicated virulence of a Y strain when inoculated concurrently with virulent X strain.

The occurrence of sulphur deficiency on a soil of adequate phoshorus status

Abstract: Subterranean clover (Trifolium subterraneum L.) grown on a basaltic soil from Cooma, N.S.W., responded markedly to treatment with sulphur, as sulphate. The sulphur deficiency occurring on this soil was uncomplicated by deficiencies of other elements, including phosphorus. Even when the sulphur deficiency had been corrected the phosphorus status of the soil was adequate for normal clover growth.

Selection for economic characters in Australian Merino sheep. II. Relative efficiency of certain aids to selection.

Abstract: Theoretical consequences of the use of progeny testing, sib testing, and mass selection are examined in a flock of 1,000 ewes producing 700 progeny of breeding age each year. Selection based on a combination of individual merit and merit of half-sibs should result in approximately the same annual improvement as that achieved by optimum use of progeny-tested sires. In large flocks extensive use of outstanding sires by artificial insemination may increase progress for traits with heritability of about 0.3 by a factor of about 1.2 as compared with mass selection. The advantages to be gained by progeny testing and artificial insemination may be outweighed by the dangers of inbreeding, and the cost involved would have to be considered. As most of these advantages should be achieved by combination or even by mass selection, which avoid inbreeding and much of the cost, progeny testing with wide use of progeny-tested sires is unlikely to be the most economical road to flock improvement.

An interpretation of the occurrence of diverse types of soils on basalt in Northern NSW and Queensland.

Abstract: This study is confined to a consideration of the genesis of soil patterns formed on basalt in four districts in northern New South Wales and Queensland. The chief features of five distinct groups of soils -probably of great soil group status -recognized in these soil patterns are described. It is concluded that any interpretation based solely on the present climatic conditions is inadequate. It is submitted that, in the patterns described, the different soil groups represented commenced to form during different climatic eras, on a new basalt flow or. on a new basalt surface exposed by erosion. In each case the newly initiated soil would be in conformity with the pedogenic environment of the era. For instance, under high rainfall the red soils would be initiated; under low rainfall the black soils would be expected to form. These soils tend to persist unless removed by erosion in spite of subsequent changes in the pedogenic environment. This points to the importance of the time factor in the form of past climatic eras and of geologic erosion in the development of these soil patterns. It is suggested that these pedogenic factors may be important in the development of many soil patterns.

The selection of spotted-wilt resistant phenotypes in the potato (Solanum tuberosum)

Abstract: Spotted-wilt-resistant and susceptible phenotypes among potato varieties and hybrids are not determined satisfactorily by hand-inoculation of leaves, but can be selected by stem-tip inoculation of vigorously growing plants at the flowering stage with a strain mixture of the virus. This glasshouse method gives a better differentiation than that obtained in field epidemics. Phloroglucinol staining of infected stems indicated that spotted wilt affects the same tissues as virus Y. Studies on the movement of spotted wilt have shown that varieties like Brownell have a high degree of tolerance, and that the tip blight and necrotic strains of a mixture take part in the early stages of systemic infection in susceptible varieties. A high percentage of the hybrids bred by the authors were resistant to spotted wilt.