bluuebunny/crossref_metadata_2025 huggingface dataset:
Ecology of the cattle tick (Boophilus microplus) in subtropical Australia. I. Introduction and free-living stages
Authors: Sutherst RW , Sutherland ID , Bourne AS , Maywald GF , Stegeman DA
Published: November 2004

An experiment is described which compared the fluctuations in the numbers of cattle tick, Boophilus miicroplus, that resulted from direct climatic effects or from changes in host resistance. Four herds of cattle, matched for tick resistance and with different Bos indicus (zebu) content, were grazed at each of two locations, one in central Queensland (23� S.) and one in southern Queensland (28� S.), from November 1977 to May 1982. Natural tick populations were counted regularly, and host resistance was measured using artificial infestations, either twice or six times a year. Concurrent exposures of engorged ticks in pastures were used to measure the success of the ticks in producing larvae and to partition mortality during development. Two later papers report other aspccts of the experiment. These include observations on the resistance of cattle to ticks and on the relationship between tick numbers on the cattle on one hand, and the availability of larvae on pasture and survival of parasitic stages on the other. Engorged ticks produced more larvae throughout the year in central Queensland, despite laying fewer eggs. The colder and longer winter in southern Queensland greatly reduced tick reproduction. Failure of engorged ticks to survive predation and find a favourable oviposition site, egg mortality and loss of larvae in the pasture accounted for most of the reduction in the potential number of larvae produced. Reduced oviposition was also important in wintcr.
Soil acidity and Rhizobium: their effects on nodulation of subterranean clover on the slopes of southern New South Wales
Authors: Evans J , Hochman Z , O'Connor GE , Osborne GJ
Published: November 2004

Rhizobium trifolii and root nodulation were compared in acid and limed soil to investigate mechanisms by which current soil acidity on the slopes of southern New South Wales may reduce the growth of Trifolium subterraneum. Increasing soil pH increased both the rate at which Rhizobium trifolii colonized soil and the frequency of nodules/g root (NF). Thus, numbers of R. trifolii were greater in carbonate-treated soil throughout autumn and winter compared to unlimed soil. In limed soil R. trifolii were measured at 104-105/g soil as early as seedling germination, 40-200 x more than in unlimed soil. Despite this, by spring, the numbers of rhizobia in soil without lime reached large and even similar levels as occurred in limed soil. Subsequently, with the drying of soil in summer, the numbers of R. trifolii declined markedly in both untreated and limed soil. Maximum NF could not be achieved with addition of Ca without increase in pH. From the field observations and other research, a hypothetical model is proposed to explain how differences in the rates of change in rhizobial numbers due to acidity may determine nodulation (NF). Thus, it is suggested that, when there is a repetitive decline in numbers of R. trifolii to low levels in summer, their subsequent rate of increase in the following autumn influences nodule abundance. The production of DM in an acidic soil appeared to be limited by symbiotic N2 fixation since added N fertilizer removed lime response. The limitation to N2 fixation did not appear to be due to lower occupancy of nodules by Rhizobium strains with less potential for N2 fixation than those in limed soil. It is possible that the effect of acidity on NF influences DM, though sampling limitations made it difficult to generalize in this regard.
The effect of weight stasis on the non-carcass components of crossbred sheep
Authors: Murray DM , Slezacek O
Published: November 2004

A study was made of the non-carcass components of 16 crossbred wethers (progeny of Dorset Horn rams and Border Leicester x Merino ewes) maintained at 30 kg liveweight for either 0,25, 50 or 75 days. Animals were individually penned and fed a pelleted ration of 80% lucerne chaff and 20% cereal grain (89.3% dry matter, 14.8% crude protein and 18.27 kJ/g gross energy). The weight of hooves increased significantly (P < 0.05) during weight stasis, while the weight of the liver decreased significantly (P < 0.001) as did the weight of the kidneys (P < 0.01). Neither head, skin, heart, lungs, spleen, pancreas nor total alimentary tract fat weight was influenced by weight stasis. The separate parts of the alimentary tract did not respond to the weight stasis treatment in the same manner. The weight of the rumen-reticulum, small intestine and large intestine each showed a significant reduction (P < 0.001) in weight. In contrast, neither omasum nor abomasum weight was affected by weight stasis. Total alimentary tract weight was significantly reduced (P < 0.001) by weight stasis. An evaluation of the weights of digesta in the separate parts of the alimentary tract showed that the weight of omasal contents increased significantly (P < 0.01) during weight stasis, while small intestine contents weight decreased significantly (P < 0.01). The weight of contents in either the rumen-reticulum, abomasum, large intestine or total alimentary tract was not influenced by weight stasis.
Fate of urea nitrogen applied in solution in furrows to sunflowers growing on a red-brown earth: transformations, losses and plant uptake
Authors: Smith CJ , Freney JR , Chalk PM , Galbally IE , McKenney DJ , Cai GX
Published: November 2004

Nitrogen transformations and transfers were investigated after applying a urea solution to a crop of sunflowers by ponding in furrows. The fertilizer was applied 24 days after sowing. Distribution of the applied nitrogen (N) in the soil, N uptake by plants, and losses by ammonia (NH3) volatilization and denitrification were measured. This method of fertilizer application resulted in concentration of the applied N in the furrow and shoulder zone of the soil beds; little of the applied N moved across to the centre of the beds. Inorganic N was not leached into the clay B horizon, but was retained by the surface 0-200 mm layer. A 15N mass balance showed that 28 kg of the 80 kg N ha-1 applied (35%) was lost during the experiment. Less than 5 kg N ha-1 (6% of the applied N) was lost as NH3 and the remainder (22 kg N ha-1 or 29% of the applied N) appeared to be lost by denitrification. The 15N balance data suggest that c. 4.6 kg ha-1 fertilizer N were lost after each irrigation up to 44 days after fertilizer application. The study indicates that N loss could be markedly reduced by delaying the bulk of the application to coincide with the period of rapid uptake.
Clinical footscald and footrot in a New Zealand Romney flock: phenotypic and genetic parameters
Authors: Skerman TM , Johnson DL , Kane DW , Clarke JN
Published: November 2004

Phenotypic and genetic parameters for clinical footscald and footrot were investigated in a pedigree flock of New Zealand Romney sheep inspected during outbreaks over six years. At inspections, each sheep's overall status with regard to footscald and footrot was summarized on a combined severity scale (Rating). Sheep were also categorized in terms of two binomial variables specifying the presence or absence of footscald or footrot (FI) and the presence or absence of footrot only (FR). A trinomial variable specified no infection, infection limited to footscald, or footrot with or without footscald (FSR), all variables being derived from the Rating value. Notwithstanding marked annual variations in prevalence of FI, F1 prevalence increased with age among ewes, and a higher prevalence of FI among male than female lambs was noted. Birth rank, birth date and dam's age had no significant effect on Rating in lambs. Repeatability of ewe Rating over successive annual inspections was low. Heritabilities of Rating, FI, FR and FSR, estimated by half-sib analyses were 0.14, 0.28, 0.17 and 0.25, respectively. Heritability of Rating estimated from dam-offspring regression was 0.12. Production traits did not appear to be genetically associated with liability to footrot. Selection of the top 5% of progenytested sires for breeding could be expected to reduce the prevalence of FI by approximately 45% per generation.
Effect of spot-type net blotch (Drechslera teres (Sacc.) Shoem) infection on barley yield in short season environment of northern cereal belt of Western Australia
Authors: Khan TN
Published: November 2004

The effect of spot-type net blotch (Drechslera teres (Sacc.) Shoem.) on yield was studied in fourteen field experiments located at two sites over seven years in the area where the disease occurs; the northern cereal belt of south-west Western Australia. An overall reduction of 26% in grain yield occurred associated with spot-type net blotch infection. The yield losses varied depending upon season, date of sowing and cultivar. Disease was found to reduce 100 grain weight and number of ears/m2, but number of grains/ear were not affected. Regression analysis supported the above negative effect of disease on yield in general, but in a few cases disease and yield were positively correlated. The Area Under Curve (AUC) model was considered most appropriate and percentage yield loss (L) was estimated as L = 0.0233 AUC. Using this relationship, potential losses in yields of cvv. Beeeher and O'Connor were estimated to be 34% and 29%, respectively. The application of this relationship is suggested to be limited to short season environments similar to the northern cereal belt of Western Australia. A need to understand factors which modify the yield response to this disease is highlighted.
Fungi associated with root and hypocotyl diseases of seedling lupins in Western Australia
Authors: Sweetingham MW
Published: November 2004

Pleiochaeta setosa, Pythium irregulare, Fusarium spp. and Rhizoctonia spp. were frequently isolated from root lesions on lupin seedlings growing at 18 locations in the temperate south-west of Western Australia. P. setosa was isolated from all 13 sites where lupins had previously been grown (average isolation frequency 90%) but from none of the 5 sites with no lupin history. P. setosa was pathogenic in pot experiments using colonized millet or conidia as inoculum. Certain isolates of P. irregulare and Rhizoctonia spp. were pathogenic, but all Fusarium isolates appeared very weak or non-pathogenic. In a fungicide drench field experiment Rovral� reduced the isolation of P, setosa from roots by 97% and reduced root rot by 42%, providing complementary evidence for the importance of P. setosa as a root pathogen in Western Australia.Rhizoctonia solani was isolated from characteristic reddish-brown hypocotyl lesions and reproduced these symptoms in pathogenicity tests.
Studies in uterotrophic activities in strains of subterranean clover
Authors: Davies HL
Published: November 2004

Uterotrophic responses in ovariectomized ewes when fed or grazed on Mount Barker, Yarloop or Dwalganup varieties of subterranean clover are reported. The high formononetin varieties Dwalganup and Yarloop always elicited a uterotrophic response. The low-formononetin, high-genistein and biochanin A variety, Mount Barker, stimulated a uterotrophic response, using a 5-day bioassay, when fed at 200g/day or 800g/day, but little or no response when grazed. When chopped lucerne hay was offered with 200 g of the Mount Barker the uterotrophic response was suppressed and the mean uterine weight was not significantly different from that of the negative controls (P= 0.57). The uterine weight of sheep eating 200 g/day of Yarloop and offered lucerne chaff or pellets in one experiment was lower (but not significantly lower) than the unsupplemented group. This trend may be worthy of further investigation.
The effect of chlorsulfuron on the uptake and utilization of copper and zinc in wheat
Authors: Robson AD , Snowball K
Published: November 2004

The effect of the herbicide chlorsulfuron on the uptake and utilization of copper and zinc by wheat was examined in a series of glasshouse experiments. Application of chlorsulfuron induced symptoms of both copper and zinc deficiencies, and decreased copper and zinc concentrations within shoots. Chlorsulfuron accentuated deficiencies of copper and zinc by decreasing uptake of the micronutrients rather than by affecting their utilization within the plant. Effects of chlorsulfuron in decreasing uptake of copper and zinc did not appear to be due to effects on root weight or root length. However, chlorsulfuron appeared to decrease water uptake by roots, indicating that chlorsulfuron may have decreased copper and zinc uptake by effects on root morphology or root physiology.
Pigmented fibres in white-skirted fleece wool from Piebald Merino sheep
Authors: Fleet MR , Smith DH
Published: November 2004

White-skirted fleece wool from 68 piebald Merino sheep was divided into four portions that were sampled and measured for pigmented fibres. The piebald sheep were identified by the presence of pigmented fibre spots (usually one), varying in size from 2 mm diameter to over 50% of body surface area, and their location conformed to no particular pattern. The majority of samples for each portion (72-82%) had no detected pigmented fibres. There were 14.7% of piebald sheep with a concentration of isolated pigmented fibres (PFC) of at least 1 per 10 g scoured staples (taken to be the threshold of commercial importance) for their white fleece wool. While most PFC values were below the commercial threshold, there is a risk that some pigmented areas on piebald sheep may be missed during shearing. Of the various records taken for macroscopic pigmentation on the piebald sheep, only the scores for pigmented fibres at the horn sites (HSF) were significantly correlated (r=0.37; P<0.01) with PFC. The HSF scores were significantly correlated (P<0.05) with several other types of non-fleece pigmentation.
Forage tree legumes. I. Productivity and N economy of Leucaena, Gliricidia, Calliandra and Sesbania and tree/green panic mixtures
Authors: Catchpoole DW , Catchpoole DW , Blair GJ , Blair GJ
Published: November 2004

A field experiment was conducted at Gowa, S. Sulawesi, Indonesia, to assess the productivity of 4 tree legumes. The experiment consisted of an establishment phase of 6 months, a tree only phase of 8 months, followed by a tree/grass phase of 14 months. After the initial cutting to 1 m, trees were lopped to 1 m when they reached heights of 1.5, 2.0 and 2.5 m above the soil surface. Leaf production was unaffected by cutting at the various attainment heights. Over the 14 month establishment and tree phase, yields totalled 2 1.8 t DM ha-1 in leucaena, 19.2 t DM ha-1 in gliricidia, 18.2 t ha-1 in calliandra and 6.7 t ha-1 in sesbania, which did not survive cutting. Stem production increased as attainment height increased. Yield of the understorey grass (Panicum maximum cv. Riversdale) in the 14 month tree/grass phase was unaffected by tree attainment height and was highest in the grass monoculture plots (12.0 tha-1), and lowest under leucaena and gliricidia. Nitrogen yields totalled 103 kg ha-1 in the grass monoculture and 901 kg ha-l in the tree monoculture and tree/grass mixtures. There was little N transfer from the tree legume to the grass.
The effects of dietary inclusion of narbon beans (Vicia narbonensis) on the growth of broiler chickens
Authors: Eason PJ , Johnson RJ , Castleman GH
Published: November 2004

The narbon bean (Vicia narbonensis) is a grain legume which shows agronomic potential in southern Australia. In the present study narbon beans (50 and 100 g kg-1) were compared with lupins (Lupinus augustifolius) and field peas (Pisum sativum) (100 g kg-1), in starter diets for broiler chickens. There were two control diets one which contained soybean meal (1 10 g kg-1) and a second which contained meat and bone meal (65 g kg-1) as the major protein supplement. The diets were fed from 1 to 2 1 days, each to 48 male chickens. There were no significant effects (P< 0.05) of dietary inclusion of narbon beans at either 50 or 100 g kg-1on feed intake, liveweight, liveweight gain or feed conversion ratio of broiler chickens when compared with the other protein sources.
Competition among three agronomic types of the Eragrostis curvula (Schrad.) Nees complex and three temperate pasture grasses on the Northern Tablelands of New South Wales
Authors: Robinson GG , Whalley RDB
Published: November 2004

Three agronomic types of the African lovegrass (Eragrostis cuwula (Schrad.) Nees) complex were established in a replacement series with three temperate pasture grasses to determine their relative competitiveness over three years in the field on the Northern Tablelands of New South Wales. The curvula agronomic type was more competitive than Consol or the chloromelas type which were similar in competitive ability. Festuca arundinacea Schreb., Dactylis glomerata L. and Pharlaris aquatica L. were each able to reduce the forage production of the curvula type in spring, but were in turn subject to suppression during summer and autumn. The relationships among Consol, the chloromelas type and the temperate grasses followed a similar pattern, but differences in their relative competitiveness were smaller. F. arundinacea was the most competitive of the temperate grasses, but this ability declined over time; D. glomerata was equally competitive during early assessments, but its ability declined more rapidly, while P. aquatica was the least successful competitor with any of the E. cuwula types. Differences in competitiveness among species over time (particularly the decline in competitiveness of the temperate species) suggest that management practices aimed at minimizing the impact of invasions by the E. cuwula complex should be investigated.
Comparison of some pea seed-borne mosaic virus isolates and their detection by dot-immunobinding assay
Authors: Ligat JS , Cartwright D , Randles JW
Published: November 2004

Five isolates of pea seed-borne mosaic virus (US, S4, S6, Q and T) were compared by host range and symptomatology on 16 Pisum sativum cultivars and lines, 21 lines of Lathyrus and Lens spp. and several indicator species. All selections of Pisum sativum, except cv. Greenfeast, were susceptible to all isolates, but Greenfeast was susceptible to the US isolate. All isolates except T infected the Lathyrus and Lens spp. through mechanical and aphid transmissions. Chenopodium amaranticolor and Vicia faba reacted similarly to all isolates, Phaseolus vulgaris cv. Hawkesbury Wonder reacted to none. The North American isolate (US) was distinguished from the Australian S4, S6, Q, and T isolates by infecting Nicotiana clevelandii and Greenfeast pea. In all cases the highest rate of seed transmission occurred in the largest seed (82-91%) and the lowest was in the smallest seed (27-40%). Infected seed in the largest size classes was lighter in weight than the corresponding uninfected seed. Infected seed in all classes had a significantly lower germination rate than uninfected seed although the greatest reduction in germinability was in the smallest seed. In each size class uninfected seed was heavier than infected seed and germinated better. Two-dimensional immunodiffusion tests showed that precipitin lines between all the isolates and either the US and S6 antisera were confluent with no evidence of spurs. A rapid and sensitive indirect dot-immunobinding assay on nitrocellulose membrane for PSbMV was developed in which non-specific reactions were eliminated by using mannose and glucose in buffers, and healthy plant sap as a blocking agent. The limit of detection of antigen was about 32 ng per sample. Both of the antisera detected antigen in sap extracted from peas infected with the 6 PSbMV isolates, originating from the USA, Australia, New Zealand and Denmark and all isolates were detected at similar antiserum dilution endpoints.
Effect of palatability on voluntary feed intake by sheep. II. The effect of altering the palatability of a wheaten hay on long-term intake and preference
Authors: Gherardi SG , Black JL , Colebrook WF
Published: November 2004

The effect of either an increase or a decrease in palatability on both long-term intake and preference for a wheaten hay was studied using two groups of sheep. Quantitative assessments of palatability confirmed that it was possible either to increase the palatability of 17 mm length hay by treating it with a combination of butyric acid plus monosodium glutamate or to decrease the palatability of 6 mm length hay by treating it with MgO. The voluntary intake of hay treated with butyric acid plus monosodium glutamate was 10% higher than that of the untreated hay when offered singly to sheep over 25 days. The increase in intake of the treated hay was associated with an increase in the apparent fractional rate of digestion in the rumen. There was no difference in voluntary intake between hay treated with MgO and untreated hay, even though there was a reduction in the apparent digestibility of the treated hay. The addition of MgO resulted in a decrease in the apparent fractional rate of digestion in the rumen which was compensated for by an increase in rumen digesta load. The palatability of a forage did affect its long-term preference, as determined by offering treated and untreated forages together in separate containers for 25 days. The sheep demonstrated a preference for hay treated with butyric acid plus monosodium glutamate (77 cf. 23%) and an aversion to hay treated with MgO (23 cf. 77%). The results indicated that palatability had little effect on the voluntary intake of a wheaten hay when it was offered as the sole forage to sheep. However, when offered a choice between forages, animals consumed significantly more of the more palatable forage.
Vesicular-arbuscular mycorrhizae (VAM) improve phosphorus and zinc nutrition and growth of pigeonpea in a Vertisol
Authors: Wellings NP , Wearing AH , Thompson JP
Published: November 2004

In a glasshouse trial, pigeonpea (Cajanus cajan) was grown in a Vertisol from the Darling Downs, Qld. The experimental design included two rates of inoculation with vesicular-arbuscular mycorrhizal (VAM) fungi (nil and inoculated), three rates of phosphorus (P) application and two of zinc (Zn), and inoculation (nil and inoculated) with a recently discovered pathogen of pigeonpea, Phytophthora drechsleri Tucker (Pdr). lnoculation with the pathogen was included in the factorial design to investigate any effect of VAM on root rot. Plants responded to inoculation with VAM fungi, showing that the growth of pigeonpea is highly dependent upon mycorrhizal colonization of its root system. The mycorrhizal plants yielded, on average, 3.3 times the dry weight of the non-mycorrhizal plants. Shoot dry weight and Zn concentration of the shoots were both exponentially related to per cent VAM colonization of the root length ( R2 values of 0.904 and 0.644 respectively) and P concentration was linearly related to VAM colonization (R2 = 0.888). VAM increased P concentration, P uptake, Zn concentration, Zn uptake and P/Zn ratio, indicating enhanced growth through improved P and to a lesser extent Zn nutrition. Zinc fertilizer (15 mg kg-1 soil) without Phytophthora inoculation was fungitoxic to the mycorrhizae, decreasing per cent VAM colonization and depressing plant growth. lnoculation with Pdr did not result in infection and root rot symptoms. However, it did overcome the Zn toxicity, possibly through organic chelation effects, and thereby enhanced VAM colonization. Greatest VAM colonization and best plant nutrition and growth were obtained with the combination of VAM inoculation, Pdr inoculation, Zn (15 mg kg-1) and P (10 mg kg-1). Our results indicate the importance of maintaining adequate levels of VAM fungi in soil through appropriate agricultural practices in order to maximize pigeonpea growth.
Agronomic studies on soybean (Glycine max (L.) Merrill) in the dry season of the tropics. II. Interaction of sowing date and sowing density
Authors: Mayers JD , Lawn RJ , Byth DE
Published: November 2004

An analysis was undertaken of the development, growth and seed yield of irrigated soybean crops grown during the dry season in the semi-arid tropics of north-western Australia, to establish whether constraints to seed yield induced by precocious flowering could be overcome agronomically by manipulating sowing date and/or sowing density. Three agronomically improved cultivars and a later-flowering landrace cultivar were tested using irrigation, fertility and pest management practices designed to minimize constraints to yield. Maximum seed yields were 3.5-4.0 t ha-1, with large genotype x sowing date x sowing density interaction. Analysis of vegetative growth showed that higher sowing densities stimulated more rapid leaf area development and earlier canopy closure, and enhanced total biomass production. However, very high sowing densities were needed to maximize yields of most genotypes, while lodging precluded high yield being realized from the greater biomass production of high density sowings of the landrace genotype. Delaying sowing from April to June delayed flowering, increased biomass production and marginally enhanced yields, but not sufficiently to offset potential problems caused by maturation into hot dry conditions prior to the wet season. It was concluded that agronomic strategies alone were insufficient to overcome the constraints to yield of present soybean genotypes in the dry season.
Epidemiology of Puccinia striiformis f.sp. tritici on wheat in southern New South Wales
Authors: Ellison PJ , Murray GM
Published: November 2004

Development of stripe rust was observed on wheat cultivars that differed in reaction to the disease at the post booting stage of growth over 4 years (1984-1987) at Yanco and Wagga Wagga in southern New South Wales. In 1984, the epidemic began in August and the disease affected up to 20% of leaf area by the booting stage. The disease then ceased to develop in cultivars with moderately resistant or resistant adult plant reaction (APR) to stripe rust, but in susceptible wheats up to 82% of leaf area was affected by early milk stage of growth. The early onset in 1984 was associated with the highest rain in the previous summer-autumn (January-April) of the 4 years. In the other 3 years, the epidemics began laer. Stripe rust did not develop on cultivars with resistant APR, but it affected up to 97% of leaf area of the highly susceptible cultivar Avocet by early milk. The disease was more severe on later sown than early sown Avocet. The apparent rates of infection both before and after booting ranged from 0.02-0.41 per day. In each experiment, the rate was less on wheats with higher levels of APR while in 1984 the rate on all cultivars decreased from the pre-booting to the post-booting stage of crop growth. After booting, the apparent rates of infection on susceptible and moderately susceptible cultivars were postively correlated with the mean temperature during the period over which the rate was calculated, for the range 12.9-16.2�C. Over this range, the apparent rate of infection of susceptible wheats increased at 0.095 per day per �C while that of moderately susceptible wheats increased at 0.045 per day per �C. From 16.2-203�C the rate of susceptible wheats was negatively correlated with the mean temperature, and declined at 0.043 per day per �C. There was no significant relationship between apparent rate of infection and temperature for moderately resistant wheats after booting, or for rates before booting in 1984. Development of wheat, measured on the Zadoks scale, was linear from first appearance of the flag leaf (GS 37) to mid milk (GS 75) at both sites over the four years.
Pathogenic variation of powdery mildew of barley in Western Australia
Authors: Chan KC , Boyd WJR
Published: November 2004

The identity and estimated frequency of genes for virulence in natural field populations of Endsiphe grarninis f.sp. hordei is reported in Western Australia. Fifteen genes were identified, five of which occurred at relatively high frequency. Only two of those identified (Vk and Vg) can be accounted for on the basis of natural selection due to the presence of corresponding resistance genes in commercial barley cultivars. Implications for breeding for host resistance in Western Australia are discussed.
Sweet corn responses to basal and top-dressed rates and sources of nitrogenous fertilizers
Authors: Salardini AA , Sparrow LA , Holloway RJ
Published: November 2004

Sweet corn (Zea mays L. var. rugosa cv. Jubilee) was grown on a fine loamy clay krasnozem soil with banded nitrogen fertilizer at rates up to 200 kg N ha-1 from (NH4)2SO4 and 50 kg N ha-1 from each of NH4NO3 and urea. Some treatments were top-dressed with one or two applications of 50 kg N ha-1. The highest yield of both cobs (23.1 t ha-1) and fresh shoots (93.8 t ha-1) and the highest concentration of N in cobs and shoot dry matter was attained with 100 kg basal N ha-1 and two subsequent topdressings of 50 kg N ha-1 each, applied as (NH4)2SO4. From banded dressing alone, 150 kg N ha-1 produced the highest cob yield and the highest accumulation of N in cobs and shoot dry matter. Top-dressed N increased the yield of cobs and the yield and N concentration in shoots, but did not influence the N concentration in cobs. As N rates were increased, there was an increase in the weight of primary cobs, the weight and number of secondary cobs and more significantly, in the number of tertiary cobs. The source of N did not have any effect on the yield or most yield related components except yield and number of tertiary cobs, which were higher in the ammonium sulfate treatments. The contribution of nitrogen uptake efficiency NUPE and nitrogen ultilization efficiency NUTE to variations in nitrogen use efficiency NUSE was calculated and discussed.
Effect of plant age on the critical inorganic and total phosphorus concentrations in selected tissues of subterranean clover (cv. Trikkala)
Authors: Lewis DC
Published: November 2004

Subterranean clover (cv. Trikkala) was grown in field and glasshouse experiments to calibrate the critical concentrations of inorganic P in selected plant tissues, for maximizing vegetative growth. Critical concentrations of total P in the various tissues were also calibrated from the field experiment. Critical concentrations of inorganic P derived in the glasshouse, for both youngest open leaf (YOL) and next oldest leaf (YOL+1), were similar at any one sampling time, but declined markedly with plant age, i.e. critical concentrations for YOL declined from 196 mg kg-1 at the first sampling to 96 mg kg-1 1 month later. Similarly, critical inorganic P concentrations for YOL derived in the field declined with time, i.e. from 187 mg kg-1 to 124 mg kg-1 from the first to second sampling. Critical inorganic P concentrations for YOL+1 were less age dependent, though much lower at any one sampling time. As such, inorganic P is not recommended for diagnostic laboratory use. Critical concentrations of total P for YOL and YOL+1 did not decline significantly over the sampling period, while those for whole plant tops (WT) declined from 0.35 to 0.30% over the same period. In the YOL tissue, the proposed critical nutrient range for total P is 0.40-0.45% while that for WT, sampled early in the growing season, is 0.35-0.40%. Results from this study support the use of total P in diagnostic plant testing services.
Irrigation using groundwater for watertable control: a model of water and salt balance limitations
Authors: Slavich PG
Published: November 2004

One of the land management practices for alleviating irrigation waterlogging and salinity in S.E. Australia is groundwater pumping from aquifers to lower shallow watertables. Pumped groundwater may be mixed with channel supply waters to obtain an acceptable water quality then used for irrigation. A model was developed to determine the effect of irrigation using saline groundwater, diluted with channel waters, on nett recharge i.e. the quantity of deep drainage minus the quantity of pumped groundwater. The model was used to assess nett recharge in rice and pasture based landuse by reviewing field studies on groundwater use. Combined with crop salt tolerance data and a leaching requirement model, the nett recharge model enabled both water and salt balance limitations to groundwater pumping to be assessed. Nett groundwater recharge was expressed as a function of the salinity of the groundwater, surface water, and the applied water using two empirical relationships which relate the leaching fraction and the infiltration amount to the salinity of the applied water for given soils and crops. In its simplest form the model equates nett recharge to the difference between the leaching fraction and the relative salinity of the applied water. For low salinity channel water (0.1 dS/m), the analysis for rice indicated that zero or negative nett recharge would only occur if at least half the applied water was pumped from low salinity aquifers (<2dS/m). For white clover based summer pastures, on permeable fine sandy loam soils, more than half of the irrigation water must be pumped from relatively low salinity aquifers (2-4 dS/m). For white clover summer pasture on a relatively impermeable clay loam, an aquifer salinity up to 5 dS/m could be used at high dilution and zero nett recharge achieved.
Wool growth in sheep fed diets based on wheat straw and protein supplements
Authors: Coombe JB
Published: November 2004

Wool growth of sheep fed wheat straw and various nitrogen (N) supplements was studied in two experiments lasting 16-20 weeks. In experiment 1, penned Crossbred wethers were fed wheat straw supplemented with urea (36 g kg-1 straw) and starch, or equivalent (N basis) amounts of formaldehyde-treated (F) casein (FCAS), rapeseed meal (RSM) or F-treated RSM or sunflower meal (FRSM and FSFM), all at the same total DM intake of c. 1240 g day-1. They produced from 7.9 to 13.9 g clean dry wool (CDW) day-1, and gained from 40 to 100 g day-1 for the urea and FCAS diets respectively. Mean digestibilities of organic matter (OM) and cell wall constituents were 0.53 and 0.42, with few differences between diets, while N digestibility of the FRSM diet (0.76) was significantly (P < 0.05) lower than all others (mean 0.89). During 1-6 h post-feeding, mean rumen pH and volatile fatty acid levels (6.43 and 55.2 mM respectively) were similar for all diets, whereas rumen ammonia levels were significantly (P < 0.01) higher with the urea and RSM supplements compared with the F-treated supplements. In experiment 2, penned Merino wethers fed 770 g DM day-1 of the urea-supplemented diet produced 5.0 g CDW day-1 and lost 50 g live weight day-1. In other sheep, fed at the same DM intake on wheat straw plus increasing levels (c. 70-350 g sheep-1 day-1) of an FRSM supplement, wool growth was quadratically related to supplement-N intake, with a maximum of 10.1 g CDW day-1 at a N intake of 15.6 g day-1. Digestibility of OM and N balance were significantly (P < 0.05) reduced at FRSM levels < 127 g sheep-1 day-1, while mean rumen ammonia levels during 6 h post-feeding remained < 70 mg N L-1 at FRSM levels < 183 g sheep-1 day-1. It was concluded that protein supplements resistant to ruminal degradation will substantially increase wool production in sheep fed straw diets at approximately maintenance levels.
Effect of formaldehyde-treated sunflower meal on the milk production of grazing dairy cows
Authors: Hamilton BA , Ashes JR , Carmichael AW
Published: November 2004

Forty-five Friesian cows grazing kikuyu pastures in the first 3 months of lactation were fed pasture alone or pasture supplemented with cracked barley or cracked barley mixed with sunflower meal untreated or treated with 0.5 or 0.7% formaldehyde. All supplements were isoenergetic and differed only in the level of formaldehyde treatment of the protein meal. The experimental rations were given for 8 weeks. The milk production of cows fed sunflower meal treated with 0.5% formaldehyde was significantly higher (P.< 0.05) than that of cows fed either barley or untreated sunflower meal and it was suggested that the level of formaldehyde added to protein meals may be important for optimum responses. The feeding of untreated sunflower meal did not significantly increase the protein content of milk above that of the pasture-fed control group. The feeding of barley and sunflower meal treated with both levels of formaldehyde significantly increased the protein content of milk above that of controls (P.< 0.05). The fat content of milk from cows receiving supplements did not differ significantly between treatment groups, but all were significantly lower than from cows in the control group fed pasture (P.< 0.05). All supplemented groups gained weight over the period of the experiment whereas the pasture-fed control group lost weight. Pasture intake of individual cows was estimated with controlled release chromic oxide capsules. The rate of substitution of pasture by supplement was 0-16 kg/kg concentrate eaten and this is below the rates observed for cows grazing temperate pastures.
Thermal requirement for germination and seedling growth of wheat
Authors: Addae PC , Pearson CJ
Published: November 2004

Two cultivars of wheat, Hartog (a spring type) and Rosella (winter) were sown at 2, 5, 8, 10, 15, 20 and 25�C on porous sand medium held at constant soil matric potential. The thermal times required for germination, onset of coleoptile elongation and emergence were similar, 27, 35 and 130�C days respectively, for the two cultivars over the temperature range of 2-25�C. By extrapolation, the base temperature for germination and coleoptile elongation was 1�C and for emergence 0.4�C. The rate of seedling elongation and emergence of both cultivars increased linearly with temperature between 5 and 25�C. Final percentage germination, final coleoptile length and total emergence of both cultivars were independent of temperature between 8 and 25�C but were smaller at 2�C. Differences between the two cultivars were confined to response to low temperature (2OC) during germination and to high temperature (25�C) during coleoptile elongation.
Digestibility of senescing annual ryegrass following application of glyphosate
Authors: Armstrong RD , Simpson RJ , Pearce GR , Radojevic I
Published: November 2004

The effect of time of spraying glyphosate on a sward of annual ryegrass (Lolium ridigum Gaudin) was examined. Glyphosate (180 g a.i. ha-1) was applied at weekly intervals between 21 days prior to anthesis and 14 days after anthesis. The resulting physiological and chemical changes were monitored to assess the contribution of plant components to digestibility during senesence. When applied before anthesis, glyphosate delayed the loss in digestibility of senescing annual ryegrass. However, glyphosate applied at, or after anthesis did not alter the decline in digestibility of the grass compared to the control (unsprayed) treatment. Glyphosate applied before anthesis significantly reduced the development of the grass ear, and delayed the loss of materials soluble in neutral detergent (NDS) from the stem for up to 35 days after anthesis. In control plants, soluble carbohydrates comprised up to 90% of the NDS in the stems, 66% in leaf sheaths, and 25% in leaf blades but were lost almost entirely during senescence. Glyphosate applications before anthesis delayed the loss of soluble carbohydrates until 35 days after anthesis. However, soluble carbohydrate loss occurred after this period and by 66 days there was little difference between control and treated plants. The IVDMD of the neutral detergent fibre (NDF) declined in all parts of the unsprayed grass during senescence. When plants were sprayed with glyphosate, the digestibility of the NDF was maintained or declined only slowly after spraying. Application of glyphosate prior to anthesis resulted in higher stem and sheath nitrogen concentrations. By contrast, glyphosate had little effect on leaf nitrogen concentration. Conservation of feeding value in senescing grass pasture was achieved only by application of glyphosate before anthesis. However, some losses of soluble carbohydrates, and thus digestibility, could not be avoided.
Broad sense heritability and genotype × environment interaction for carbon isotope discrimination in field-grown wheat
Authors: Condon AG , Richards RA
Published: November 2004

Carbon isotope discrimination (-) has been proposed as a possible selection criterion for greater water use efficiency in breeding programs for water-limited environments because it provides an integrative assessment of genotypic variation in leaf transpiration efficiency. Considerable genotypic variation for - has been demonstrated in wheat, but environmental factors may cause even larger changes in the value of - measured in plant dry matter, which could compromise the effective use of - in breeding programs. In this study we assess broad-sense heritability of - and the significance of genotype x environment interaction for - in field-grown wheat. Another objective was to identify the most effective growth stage or plant part to characterize genotypic variation in -. Experiments were done using several large sets of genotypes (between 8 and 40, usually c. 20) grown in a range of field environments spanning the southern Australian wheat-belt. Carbon isotope discrimination was determined on unreplicated grain samples from seven Interstate Wheat Variety trials grown in 1983 and 1984 and on several plant parts taken from replicated experiments conducted at four locations in south-west New South Wales from 1985 to 1988. From these replicated experiments broad-sense heritabilities for - were calculated on a genotype mean basis h2-M) and on a single-plot basis (h2-P). In dry matter sampled from several environments, site-mean - ranged from 21.0 x 10-3 to 18.9 x 10-3 for early-formed dry matter and from 16.4 x 10-3 to 13.4 x 10-3 for grain. When followed in a single environment, the value of - fell from c. 20 x 10-3 in early-formed leaves to 15.4 x 10-3 in the grain. Variation among genotypes in - of different plant parts was always significant, and was typically c. 2 x 10-3 . Among Australian wheats, low values of - (implying greater transpiration efficiency) were strongly associated with the WW15 genetic background. Estimates of broad-sense heritability for - averaged over 95%, on a genotype mean basis, in experiments where common genotypes were grown in numerous environments. In individual trials, heritability was lowest for plant material sampled near anthesis (average value for h2-M, 83% and for h2-p, 62%) and greatest for dry matter laid down before or during early stem elongation (average value for h2-M, 95% and for h2-P 88%). Even though heritability for grain - was also relatively high (average value for h2-M, 92% and for h2-P, 79%), genotypic differences in grain - are difficult to interpret because of the likelihood of some changes in genotype ranking for - resulting from differences among genotypes in the degree of water stress encountered during grain filling. As well, the contribution of remobilized carbon to grain - may vary between environments and genotypes. We conclude that, for wheat, assessment of genotypic variation in - should be most effective under well-watered conditions using dry matter laid down early in plant development.
Effects of nitrogenous fertilizer on the growth, grain yield and grain protein concentration of wheat
Authors: McDonald GK
Published: November 2004

The responses of wheat to applications of nitrogenous fertilizer were examined between 1988 and 1990 at 10 sites in South Australia which were considered to be marginally deficient in N. Nitrogen rates ranged from 0 kg N/ha to 150 kg N/ha and the experiments were sown after a range of crops and pastures. Nitrogen often increased early crop vigour and subsequent vegetative growth but significant increases in grain yield occurred at three of the 10 sites only; at the remaining sites there was no significant response or there was a reduction in yield at the highest rates of N. Kernel weights fell and grain protein concentration increased at most sites as the rate of N increased. The total amount of N per kernel was relatively constant across the N treatments at each site and across the 10 sites it varied less than the starch content per kernel. Grain protein concentration therefore was affected more by the amount of starch deposited in the grain than by the total amount of nitrogen. The amount of dry matter remobilized post-anthesis, calculated from changes in dry weight, was high and at the majority of sites was increased with applications of nitrogenous fertilizer. Despite the generally large amount of dry matter remobilized, this appeared to be used inefficiently during grain filling and there was little evidence that it greatly contributed to grain growth and grain protein concentration. The relationship between starch content per kernel and N content per kernel varied between sites: in some cases starch and N were negatively correlated, while in other instances there was a positive correlation or no correlation. The data suggest that high grain protein concentration at high levels of N are not a direct consequence of increased mobilization of dry matter and greater translocation of N to the grain. Dry matter production at anthesis was correlated with the amount of growth after 10 weeks but generally this increased dry matter production was of no benefit to yield. It is concluded that in the medium rainfall areas of the state, there is no advantage to be gained from improved early vigour, except perhaps where poor early growth is due to inadequate management.
Variations in the strength of wool fibres - A review
Authors: Reis PJ
Published: November 2004

This review outlines the factors that may influence the strength of wool fibres and the associated changes in structure and protein composition that have been observed in weakened fibres. The strength of a wool staple is dependent on the intrinsic strength of the fibres that it contains and the total cross-sectional area of fibre being tested. The minimum fibre diameter and the rate of change of diameter along a staple are important determinants of strength. Different sheep kept under similar conditions show a large range of staple strengths. Estimates of heritability for staple strength are sufficiently high (0.17 to 0.49 in Merinos; 0.20 to 0.58 in Romneys) to prompt the establishment of selection programmes in both breeds. A variety of physiological and environmental factors influence the strength of wool fibres. Nutrient supply exerts a major influence via effects on fibre diameter. In addition, there are specific effects of some amino acids (methionine and lysine), trace elements (copper and zinc) and vitamins (folic acid). Seasonal effects are important in breeds which exhibit a large annual rhythm of wool growth, e.g. Romneys, but not in Merinos. Pregnancy and lactation influence fibre strength through competition for essential nutrients but hormonal factors may also be involved. Fibre strength may also be influenced by stress involving excessive secretion of glucocorticoids and by various parasites and diseases which can influence nutrient supply and cause stress. No clear association has been established between the strength of wool fibres and the proportions of the constituent proteins. The content of high-tyrosine proteins in the matrix of weak fibres is frequently, but not invariably, reduced. Likewise, fibre strength has been associated with the proportions of components of the high-sulfur proteins in some studies, but not in others. Thus in Romneys, but not Merinos, tender (weak) wool contained a higher proportion of orthocortex than sound wool, and hence contained less ultra-high-sulfur proteins. Weak fibres produced by specific nutritional treatments in adult sheep and lambs show a loss of cuticle scale pattern and malformed or degraded fibres.