bluuebunny/crossref_metadata_2025 huggingface dataset:
Variation in the response of Lolium genotypes to defoliation
Authors: Fulkerson WJ , Slack K , Lowe KF
Published: November 2004

A glasshouse study was undertaken to determine the effect of defoliation frequency (three times at one leaf stage or once at three leaf stage of the regrowth cycle) and height (20, 50 or 120 mm) on regrowth, plant water soluble carbohydrate (WSC) reserves and root growth of seven Lolium perenne and two Lolium multiflorum cultivars. The sensitivity to defoliation was in decreasing order: biennial, PI perennials (cv. Ellett, AN2327, LP30, LP31), P2 perennials (cv. Kangaroo Valley, Yatsyn, Pacific). The effect of frequent, compared to infrequent, defoliation was to suppress regrowth by l00%, 95% and 80%; stubble WSC (mg/plant) by 97, 89 and 81%; root DM (g/plant) by 76, 60 and 6%, for biennial, P1 and P2, respectively. The effect of defoliation height accentuated this response, with biennials defoliated frequently at 20 mm stubble height all dying. Under defoliation conditions producing optimal yield, the yield was positively related to sensitivity to defoliation, giving regrowths of 2.90, 2.68, 1.53 g DM per plant for biennial, P1 and P2 plants, respectively. In view of the marked defoliation by cultivar interaction, response to defoliation should be considered as a possible selection criterion in any evaluation process.
Reduced growth and yield of wheat with conservation cropping. II. Soil biological factors limit growth under direct drilling
Authors: Kirkegaard JA , Munns R , James RA , Gardner PA , Angus JF
Published: November 2004

Wheat was grown in intact cores of soil removed from a field experiment in which seedlings had grown more slowly in direct-drilled soil than in cultivated soil. Experiments were conducted in controlled environments to resolve (1) whether shallower sowing of direct-drilled crops caused slower growth, (2) whether the soil factors causing the slower growth were physical or biological and (3) if biological, whether Rhizoctonia solani was the major pathogen. The conditions of the experiments removed possible constraints of water and nutrient supply but otherwise simulated the environment of wheat seedlings in southern Australia. Shallower sowing led to faster emergence and increased seedling growth, but irrespective of sowing depth, direct-drilled plants grew more slowly than plants in cultivated soil. Shoot growth of direct-drilled plants was 25-65% less than that of cultivated plants. These growth reductions were largely overcome by sterilizing the soil with y radiation or by fumigation with methyl bromide, indicating that biological factors were primarily responsible. Rhizoctonia was implicated as the cause of the reduced shoot growth when infection was severe (>3 on a 0-5 scale). There was no correlation between infection severity and shoot growth at moderate levels (<3) and significant reductions in shoot growth occurred in the absence of Rhizoctonia. These reductions were evident on the first leaf suggesting a direct influence on shoot growth rather than one mediated through inadequate uptake of water or nutrients. Infection of the germinating seed by Pythium spp. or the effects of phytohormones produced by inhibitory bacteria on the roots are possible causes of reduced shoot growth of direct-drilled seedlings. The dominant role of biological factors in determining plant response to soil management indicates the need for further studies to identify the organisms responsible, to determine the mechanism by which they influence shoot growth, and the effect of management on their populations and activity.
Bean yellow mosaic potyvirus infection of alternative hosts associated with subterranean clover (Trifolium subterraneum and narrow-leafed lupins (Lupinus angustifolius): field screening procedure, relative susceptibility/resistance rankings, seed transmission and persistence between growing seasons
Authors: McKirdy SJ , Jones RAC
Published: November 2004

A field screening procedure was devised to determine relative susceptibility and resistance rankings for hosts of bean yellow mosaic potyvirus (BYMV) using BYMV-infected Trifolium subterraneum plants transplanted at eack end of single row test plots. Natural spread of BYMV by aphids resulted in BYMV symptoms in test lines. Four test lines were ranked as highly resistant, nine were resistant, seven were moderately resistant, eight were susceptible and two were highly susceptible to BYMV infection. Disease progress curves plotted for each test line assisted in the ranking process. Relative rankings were independent of flowering date and presence of host alkaloids. Acrythosiphon kondoi, Myzus persicae and Rhopalosiphum padi were the predominant aphid species caught in traps associated with field screening plots. Seven plant species tested were new BYMV host records. Seed of four plant species systemically infected following sap inoculation with BYMV was tested, and seed transmission detected in Melilotus indica (0.5%). When seed of 19 alternative host species that became systemically infected through natural spread was tested, seed transmission was found in Medicago polymorpha (0.9%), Medicago truncatula (0.3%), M. indica (1%), T, arvense (0. 1%), T. campestre (0.2%) and T. glomeratum (0.05%). No seed transmission was detected in T. subterraneum. It is concluded that under broadacre agriculture in the Mediterranean climate of Western Australia, seed-borne infection in naturalized M. polymorpha, T. arvense, T. campestre and T. glomeratum growing in T. subterraneum pastures probably provides the principal means by which BYMV persists over the dry summer to act as primary sources for subsequent spread. The species most likely to contribute to BYMV spread within T. subterraneum pastures and from them to Lupinus angustifolius crops were L. cosentinii, T. campestre, T. dubium and T. subterraneum itself.
The role of allelopathy in legume decline in pastures. II. Comparative effects of pasture, crop and weed residues on germination, nodulation and root growth
Authors: Halsall DM , Leigh JH , Gollasch SE , Holgate M
Published: November 2004

Sterile cold water extracts of a range of residues from pasture, crop and weed species have been shown to exert allelopathic effects on subterranean clover and other species of pasture legumes, resulting in reduced germination, stunted growth of the radicle and reduced root growth and nodulation. Roots exposed to the extracts became discoloured and shortened with distorted and scant root hair formation which may result in reduced nodulation. Seedlings exposed to these allelopathic compounds were smaller, less robust and slower growing than the control seedlings and hence more susceptible to attack by plant pathogens.
The growth of Lupinus species on alkaline soils
Authors: Tang C , Robson AD , Longnecker NE , Buirchell BJ
Published: November 2004

Lupinus angustifolius L. grows poorly on alkaline soils, particularly those that are fine-textured. This poor growth has been attributed to high concentrations of bicarbonate, high clay content and/or iron deficiency. In field studies, we examined the growth of 13 lupin genotypes reliant on N2 fixation, or receiving NH4N03, at four sites with various combinations of soil pH and texture. Plants grown on an alkaline clay and an alkaline sand showed iron chlorosis at early stages, and had a slower shoot growth than those grown on an acid loam or an acid sand. Species varied greatly in the severity of iron chlorosis and also in growth and seed yield, with L. angustifolius, L. luteus and L. albus more affected than L. pilosus, L. atlanticus and L. cosentinii. Rankings of growth and seed yield of the lupin genotypes on the alkaline clay correlated well with the rankings on the alkaline sand soil. Plants which had severe iron chlorosis in alkaline clay also had severe chlorosis in alkaline sands. However, correlation between the severity of iron chlorosis and early shoot growth was poor. The results suggest that high pH and/or high bicarbonate are more likely than soil texture to be the primary factors restricting the growth of commercial lupins.
The reaction-diffusion (RD) theory of wool (hair) follicle initiation and development. II. Original secondary follicles
Authors: Nagorcka BN
Published: November 2004

In an accompanying paper it was shown that a spatial prepattern mechanism based on a biochemical reaction referred to as a reaction-diffusion (RD) system is able to account for many aspects of the initiation and development of primary (P) wool follicles. In this paper the same RD system is applied to the initiation and development of original secondary (SO) follicles. Prepatterns are generated by solving the equations describing the reaction and diffusion of the chemical components of the RD system in early stage follicles. It is demonstrated that the prepattern mechanism can account for the loss of a sweat gland causing a change from P follicle initiation to SO follicle initiation. The RD system equations are also solved in the epidermis. The time sequence of prepatterns obtained in the epidermis account for the tendency of SO follicles to group with P follicles, by initiating in-between members of the trio group of P follicles as well as in between existing SO follicles. The prepatterns obtained did not account for the tendency of secondary follicles to initiate on the posterior side of the trio group. Good agreement was obtained between the predicted increase in total follicle density and the increase in follicle density observed during follicle initiation by Carter and Hardy (1947), provided full account was taken of the interaction between existing follicles and each new future generations of follicles. The prepattern mechanism provides a fundamental basis for an inverse genetic correlation between total P and SO follicle density and fibre diameter.
Relative resistance, associated yield losses and phyto-oestrogen production from fungal foliar diseases in new and old annual Medicago cultivars
Authors: Barbetti MJ
Published: November 2004

The relative resistance, associated herbage and seed yield losses and phyto-oestrogen production from fungal foliar diseases in two new annual Medicago cultivars, viz. M. sphaerocarpos cv. Orion and M. truncatula cv. Caliph, were compared with those of four old cultivars, viz. M. murex cv. Zodiac, M. polymorpha var. brevispina cw. Santiago and Circle Valley, and M. truncatula cv. Cyprus. Orion was much more resistant to Phoma stem disease than Circle Valley and Santiago, but was more susceptible than Zodiac. However, Orion was the most susceptible cultivar to Phoma leaf disease. Orion and Caliph were susceptible to Leptosphaerulina stem disease, resembling Santiago, but much more susceptible than Circle Valley and Zodiac. Caliph was comparable with Cyprus with moderate susceptibility to both Phoma and Leptosphaerulina on stems. Both Caliph and Cyprus were resistant to Pseudopeziza. In mid-October and early November, foliar diseases reduced overall herbage yield of the six varieties by 16.2 and 20.3% respectively, compared with the fungicide-treated plots of the same cultivars. Foliar diseases reduced seed yield by 37.3%, and mean seed weight by 13- 7% compared with fungicide treated plots. Foliar disease in the disease block increased the content of the phyto-oestrogen coumestrol in stems from 230 to 500 ppm and in pods from 30 to 130 ppm, compared with the fungicide block. There was a positive correlation between the severity of Phoma on stems and leaves and the level of coumestrol in stems and pods. Orion produced large amounts of coumestrol in stems and pods in response to foliar diseases (e.g. 470 ppm in stems) but less than Zodiac. Caliph also produced large amounts of coumestrol in stems and pods in response to foliar diseases (e.g. 230 ppm in stems), and was similar to Cyprus but had less coumestrol than all other cultivars tested (stems) or Zodiac, Circle Valley and Santiago (pods). Orion carried the highest level of P. medicaginis seed contamination (28%), followed by Santiago (15%), Cyprus (11%), Circle Valley (l0%), Zodiac (10%) and Caliph (6%).
N application increases pre-anthesis contribution of dry matter to grain yield in wheat grown on a duplex soil
Authors: Palta JA , Fillery IRP
Published: November 2004

The effect of fertilizer N on the growth, post-anthesis water deficits and remobilization of dry matter in spring wheat was measured on a duplex soil at East Beverley, Western Australia. Nitrogen was applied at 15, 30 and 60 kg N ha-1 with half being applied at seeding and the remainder at 35 days after sowing (DAS), immediately before the onset of tillering. The applied N generated differences in early growth (76-117 g m-2) and dry matter at anthesis (410-693 g m-2), mainly through the effect of N on tiller number (120-171 m-2) and tiller size. It also generated differences in the water deficit, particularly after flowering. During the first 21 days after anthesis, midday flag leaf water potential fell at rates of 0.04, 0.07 and 0.13 MPa day-1 at 15, 30 and 60 kg N ha-1 respectively. Grain yield at 60 kg N ha-1 was increased by 20% relative to that of 15 kg N ha-1. The increase in grain yield resulted from an increase in the number of ears and grain number per ear. The high N treatment probably induced the increase in the number of fertile tillers (tillers with an ear), but reduced the grain size by 16% relative to the low N treatment. Contribution of preanthesis dry matter to grain yield was 193 g m-2 for the wheat receiving 60 kg N ha-1, 71 g m-2 for wheat which received 30 kg N ha-1 and only 16 g m-2 for wheat which received 15 kg N ha-1. This indicates that at high N supply, grain growth was substantially supported by pre-anthesis stored assimilates.
Water-soluble carbohydrates and in vitro digestibility of annual ryegrass (Lolium rigidum Gaudin) sown at varying densities
Authors: Smouter H , Simpson RJ , Pearce GR
Published: November 2004

An experiment is described in which the tiller density of microswards of Lolium rigidum was varied by altering planting density. The treatments were expected to alter the interplant competition for light and thus affect the concentration of water-soluble carbohydrates (WSC) of the grass swards. Swards were grown at planting densities of 100 (low density), 500 (medium density) and 5000 (high density) plants m-2. Mainly because of compensatory tillering in the low and medium density swards, all swards had equivalent dry matter yields by 13-15 days after anthesis. The concentrations of material soluble in neutral detergent (NDS) and of WSC, in particular, varied in response to the treatments, and the yield of WSC in the low density sward was 30-50% higher than in the other swards. The yield of WSC reached a maximum at anthesis in all treatments with large losses of WSC occurring as the grass senesced. Fructans were the major type of soluble carbohydrate in all plant parts (50-99% of WSC). At anthesis, the in vitro dry matter digestibility (IVDMD) of the low density sward was higher than that of the high density sward (60.7% and 54.3% respectively). When dead, whole plant IVDMD had declined to 40.8% in the low density and 37.9% in the high density sward. The higher digestibility of the low density grass sward was a result of higher digestibility in almost all component plant parts. Opportunities may exist to improve the feeding value of senescing grass pastures if mobilization of WSC can be delayed or regulated to ensure higher retention of NDS.
Cultivar and environmental effects on malting quality in barley
Authors: Eagles HA , Bedggood AG , Panozzo JF , Martin PJ
Published: November 2004

Improvements in malting quality are important if barley from south-eastern Australia is to remain competitive on export markets. Grain is desired that will produce high levels of malt extract and diastatic power but has moderate levels of grain protein. To examine cultivar and environmental effects, especially nitrogen (N) fertilizer, on levels of malting quality parameters and their correlations, seven cultivars of barley were grown in a fallow and pea stubble rotation with five levels of N fertilizer in the Wimmera region of Victoria in 1990 and 1991. The first season was relatively dry and warm, while the second was wetter and cooler. Grain yield and malt extract were markedly lower in 1990 than 1991, and grain protein concentration, grain screenings and diastatic power were significantly higher. Grain protein and diastatic power increased almost linearly with increasing N application, with a higher rate of increase in 1990 than in 1991. Malt extract declined almost linearly with increasing N application, but the change in rate of decline between seasons was less than the change of rate of increase of grain protein. Environmental correlations between protein concentration and malt extract, and between malt extract and diastatic power, were negative. They were close to -1.0 when the environmental factor varying was restricted to N fertilizer, but were of a smaller absolute magnitude when seasons and rotations were also allowed to vary. In contrast, genotypic correlations were of intermediate magnitude. Broad-sense heritabilities for malt extract and diastatic power were relatively high, even with such contrasting seasons. This indicates that it should be possible to develop cultivars for south-eastern Australia which have high malt extract and high diastatic power at low protein levels. However, applications of N fertilizer that raise grain protein concentration will reduce malt extract, with the effect much greater in drier, warmer seasons.
Studies on weather damage in mungbean. III. Development of a system for measuring genotypic variation in resistance to weathering
Authors: Williams RW , Lawn RJ , Imrie BC , Byth DE
Published: November 2004

Mungbeans are susceptible, following rainfall, to weather damage which reduces their value for food uses. Cultivars differ in their resistance to weathering, but selection for resistance based on field response has been unsuccessful. Three controlled experimental systems (immersion in water, exposure to simulated rainfall, and exposure to cyclic wetting and drying in a mist chamber) were evaluated for their ability to reproduce the symptoms of weather damage and to differentiate among the responses of cultivars known from field experience to differ in resistance. When seeds were immersed, the susceptible green gram cv. Berken absorbed water faster and had less impermeable seed than the resistant black gram cv. Regur. The green gram cv. Celera showed an intermediate response consistent with its intermediate resistance to weathering. The rainfall simulator produced more realistic conditions for weathering than seed immersion, and symptoms typical of weather damage were produced. However, the responses of cultivars were relatively poorly differentiated and the method showed poor repeatability. The exposure of podded racemes to wetting and drying cycles under controlled conditions of temperature and humidity in a mist chamber provided the most reliable method for simulating weather damage. The degree of damage increased with duration of exposure and the relative resistance of cultivars was consistent with field observation. The extent of weather damage was best measured as reduction in seed viability and as change in the appearance and permeability of the testae of seeds following exposure. The combined use of the mist chamber and these measurement criteria constitute a successful system for the selection and breeding of mungbeans for resistance to pre-harvest weathering.
Variation in the morphology and flowering time of cluster clover (Trifolium glomeratum L.) and its relationship to distribution in southern Australia
Authors: Smith FP , Cocks PS , Ewing MA
Published: November 2004

Cluster clover is a widely distributed and ecologically successful introduced legume in southern Australia. In an attempt to understand the role of genetic variation in this success, morphological and physiological traits were measured in 94 accessions from southern Australia and 6 from the Mediterranean basin. Flowering time ranged from 105 to 185 days after sowing, but was not strongly correlated with annual rainfall or length of growing season at the site of collection. Variation in other traits partitioned the populations into two morphs which, apart from flowering time and leaf marker, were largely homogeneous. The morphs differed significantly in floret number per inflorescence (22 v. 32-37) and seed mass (379 8g v. 523 8g), had different growth habits and strong within-morph associations between leaf markers and stipule and petal coloration. The morphs differed in their distributions within southern Australia and the pattern of distribution was related to summer maximum temperatures, winter minimum temperatures and spring rainfall. These results demonstrate that genetic variation has been important to the success of cluster clover and suggests that the variation is organized. The pattern of variation observed and its relationship to ecogeography is consistent with findings for other highly inbreeding species. A map of the species distribution in Western Australia is presented.
The role of allelopathy in legume decline in pastures. III. Tolerance of subterranean clover lines to the allelopathic compounds released from Phalaris residues
Authors: Leigh JH , Halsall DM , Muller WJ , Oram RN , Edlington JP , Geissler AE
Published: November 2004

The tolerance of 126 lines of subterranean clover (Trifolium subterraneam L.) to allelochemicals released in cold water leachate from dry herbage of phalaris (Phalaris aquatica L. cv. Australian) was examined and compared. The lines were 112 accessions from grassy associations in the Mediterranean region and 14 Australian cultivars. Measures of germination, radicle length, nodulation and root length in seedlings exposed to three concentrations of extract relative to those obtained from seedlings exposed to distilled water only were obtained. A performance index for each line was derived from these measures. Large differences between lines for these four parameters were evident. On the basis of these comparisons, scope exists to select and recommend lines of subclover which are tolerant to these allelochemicals and thus are capable of higher production and greater persistence in long-term perennial phalaris pastures.
High Ca is not the primary factor in poor growth of Lupinus angustifolius L. in high pH soil
Authors: Tang C , Robson AD , Adams H
Published: November 2004

Poor growth of Lupinus angustifolius L. on alkaline soils has been suggested to be due to effects of both high calcium concentrations and high ionic strength in soil solutions on growth. This glasshouse study investigated the effect of calcium supplied as either CaCO3 or CaSO4 to an acid soil on the growth of N-fertilized and N2-fixing plants of L. angustifolius cv. Gungurru, and compared responses of L. angustifolius and Lupinus pilosus Murr., an alkaline-tolerant species, to high ionic strength in high pH solutions. Increasing CaCO3 application increased soil solution pH, and decreased shoot and root growth and chlorophyll concentration in the youngest fully expanded leaflets of both Na-fixing and N-fertilized plants of L. angustifolius. The effect of CaCO3 in decreasing root length was prior to and more pronounced than that on shoot weight and chlorophyll concentration. Adding CaSO4 increased calcium concentration in soil solution by 1.7-6.6 fold and calcium concentration in leaves by 10-30%, but did not markedly decrease the growth of plants grown at any rate of added CaCO3. Increasing pH in nutrient solution from 5 2 to 7.0 decreased shoot weight of L. angustifolius, but slightly increased that of L. pilosus. Plant growth of both L. angustifolius and L. pilosus was slightly decreased as solution ionic strength increased. The effect of high ionic strength was similar whether CaCl2 or KCl was the source of ions. The results suggest that poor growth of L. angustzfolius relative to L. pilosus on some alkaline soils is not caused by excessive calcium or high ionic strength, rather high pH effects on root extension appear to be the major cause of the poor growth.
Responses and feeding damage of redlegged earthmite (Acarina: Penthaleidae) to seedlings of resistant and susceptible subterranean clover varieties
Authors: Ridsdill-Smith TJ
Published: November 2004

Responses of redlegged earth mite (Halotydeus destructor) to seedlings of three resistant and four susceptible varieties of subterranean clover (Trifolium subterraneum) were measured after 7 or 14 days in pot experiments in the glasshouse. With a single variety/pot, mites on resistant varieties (DGI007, EP145SubD and Rutherglen B) produced 45% of the progeny that were produced by mites on the susceptible varieties (89838G, Dalkeith, Junee and 70088B). Number of stages completed and survival were little affected by varieties. Feeding damage (silvering of cotyledons) on resistant varieties averaged 45% of that on susceptible varieties with a single varietylpot. H. destructor fed less on resistant varieties in choice than in single variety experiments. On Junee and 89838G seedlings, feeding damage was similar to that on other susceptible varieties, but there were about half as many H. destructor progeny as on Dalkeith and 70088B. Mites laid more eggs on soil away from Junee plants, compared to the other three susceptible varieties. Different factors adversely affected the number of progeny produced on resistant varieties and on Junee.
The effect of nitrogen and protein supplementation on feed intake, growth and digestive function of steers with different Bos indicus, Bos taurus genotypes when fed a low quality grass hay
Authors: Hennessy DW , Kohun PJ , Williamson PJ , Brown DA , Nolan JV
Published: November 2004

Two studies were undertaken at Grafton, NSW, to determine the effects of supplementing a subtropical hay diet with a mixture of non-protein nitrogen (urea) and protein (protected casein), on the feed intake and growth of 20 steers of four genotypes (Study I), and on the digestive and metabolic functions of 16 of the steers that were fistulated in the rumen (Study 2). All steers were reared in the one subtropical environment. They consisted of backcross Hereford (H) (H x BH), backcross F1 (BH x BH) and backcross Brahman (B x BH), all of 50% heterosis, and a first-cross F1 of 100% heterosis (BxH). Steers in both studies were confined in pens and offered a basal diet of chaffed pasture hay (digestibility 52f 1.4% and nitrogen [N] content of 6.1 � 0.2 g/kg dry matter [DM]) supplemented with minerals only (low N diet; 8 steers) or with urea or formaldehyde-treated casein and cottonseed meal (high N diet; 12 steers) for 49 days. There were eight steers, for each of the two diets in Study 2, which were fed for 30 days. There was a diet x genotype interaction (P < 0-05) in the daily DM intake (DMI) of hay by steers in Study 1. The mixed N supplement increased ( P < 0.05) DM1 (per kg liveweight) by 14% in HxBH and by 13% in BxBH steers, but there was no significant effect of the supplement on the DM1 of BxH and BHxBH steers. Daily liveweight change was increased (P < 0.05) by the supplement from -30 to 250 (s.e.d � 40) g/steer and there was no significant difference between genotypes. N supplementation increased ( P < 0.05) rumen volume (63 to 87 � 7.6 L) and fluid residence time (491 to 822 � 76.9 min) (P < 0.05) in BHxBH steers, but the increases in other genotypes were not significant. Rumen ammonia concentration (30 to 61 � 3 7 mg N/L) and plasma urea concentration (56 to 94 � 6-0 g N/L) were increased (P < 0.05) by supplementation. Total protozoa density in rumen fluid was greater (P < 0.05) in BxBH than HxBH steers but did not differ significantly between supplemented and unsupplemented steers. The HxBH steers had the lowest density of small entodiniomorph protozoa when N-supplemented, which was less (P < 0.05) than that in BxBH steers which had the greatest density. Supplementation increased (P < 0.05) N retention but only B x BH steers had a positive N balance. These experiments indicated that there are some physiological differences between genotypes. The BxH genotype with the high hybrid vigour had a high DM1 on the low digestibility hay diet without the N supplements and it transferred more urea from the plasma pool to the gut. The backcross steers (HxBH and BxBH) had low DM1 which increased when supplemented. The high content B. indicus steers (BxBH) had positive net retentions of N, but the results indicated that rumen protected proteins may be more usefully fed to steers with a lower B. indicus content.
Soil carbon fractions based on their degree of oxidation, and the development of a carbon management index for agricultural systems
Authors: Blair GJ , Lefroy RDB , Lisle L
Published: November 2004

Increasing population pressure is increasing the demand on agricultural systems in many parts of the world and this has often led to the degradation of the soil resource. Soil carbon (C) is a major determinant of sustainability of agricultural systems and changes can occur in both total and active, or labile, C pools. A procedure is presented to determine the degree of lability of soil C. By treating a ground sample of soil with 333 mM potassium permanganate (KMnO4) to oxidize a proportion of the carbon and by determining the total carbon by combustion, two fractions of C can be measured. These fractions represent carbon of different lability, with fraction I representing the Labile C (CL), which is oxidized by 333 mM KMnO4, and fraction I1 representing the non-labile C (CNL), which is not oxidized by 333 mM KMnO4. On the basis of changes in total carbon (CT), a Carbon Pool Index (CPI) is calculated and, on the basis of changes in the proportion of labile C in the soil between a reference site and those subjected to agricultural practice or research treatments, a Lability Index (LI) is determined. These two indices are used to calculate a Carbon Management Index (CMI), with CMI = C Pool Index (CPI) xLability Index (LI) x 100. Analyses of paired samples (cropped and uncropped) from three sites in northern and central New South Wales, Australia, have shown a decline in CPI, a greater decline in LI and hence a decline in the CMI with cropping. Introduction of a legume into a wheat cropping system restored the CMI from 22 to 37 at the Warialda site. Analyses of paired samples from a sugarcane area in north Queensland have shown a decline in CMI in systems dominated by trash burning, but an increase in CMI in systems dominated by green cane trash management. Similar data from Brazil showed no increase in CT with mulching but a 48% increase in CMI due to an increase in the lability of C in the soil. The fractionation procedure and CMI outlined can be used to determine the state and rate of change in soil C of agricultural and natural systems.
Growth and development of potatoes under salinity and water deficit
Authors: Heuer B , Nadler A
Published: November 2004

The agronomic and physiological responses of potato to salinity and to water deficits were determined. The experiment consisted of five treatments: three salinity levels and two restricted amounts of water. Plant height, leaf area and fresh weight accumulation were significantly affected by the salinity and moisture treatments. Stem number, leaf elongation and the content of dry-matter in leaves, stems and tubers were hardly affected. Harvest index, an important agronomic trait, was markedly improved by the different treatments.
Potential for increasing rate of grain growth in spring wheat. I. Identification of genetic improvements
Authors: Whan BR , Carlton GP , Anderson WK
Published: November 2004

Cultivars that can fill their grain quickly may have an advantage in environments with short, hot, dry grain-filling periods, but this hypothesis needs to be tested by selecting in breeding populations. The rate and duration of grain growth of 13 introductions and three local, standard cultivars were measured in nine environments over 3 years to identify new germplasm with faster grain growth and shorter durations of grain growth. Duration of grain growth was calculated from the cumulative daily average temperatures between anthesis and physiological maturity, and rate of grain growth was calculated from the mean kernel weight and duration. The loss of green colour from the peduncle was used as an indicator of physiological maturity. The aim was to identify parents to use in a subsequent breeding program. Genotypes were identified with improvements in grain growth characters over the standard cultivars. Kansu No. 32, SA 42, NIAB 75-509 and Maya 74 had the fastest rates of grain growth, e.g. 75, 84, 79 and 70 8g/kernel �C day respectively, compared with 64 for Aroona, the best standard cultivar, at sites with short periods of grain growth. Kansu No. 32 developed heavy kernels quickly, and differed from other genotypes in that it had a short duration of grain growth that was consistent regardless of environmental conditions. SA 42, NIAB 75-509 and CEP 8058 also developed grain quickly, with the flexibility to develop grain in a shorter time than the standard cultivars in hot grain-filling conditions, but similar time in favourable conditions. These four genotypes had less kernels/m2 associated with the increased grain growth rate. Yu Mai 7, Maya 74 and V763-251 had smaller increases in rates of grain growth, but only a slight reduction in kernel numbers. Rate of grain growth is more important than duration as a selection criterion to improve kernel weight and grain yield in Western Australian conditions, as duration is influenced to a much greater extent by environment. Growth rate was negatively associated with number of kernels/m2, so these two characters must be considered simultaneously in selection, to ensure grain numbers are maintained while improving rate of grain growth.
Applying nitrogen to grain sorghum in central Queensland: residual value and effect of fallowing and tillage practice
Authors: Armstrong RD , Halpin NV , McCosker K , Standley J , Lisle AT
Published: November 2004

In the northern cereal belt of Australia, farmers are reluctant to apply nitrogen (N) fertilizers because of a perception that if N is added to the soil and no crop is subsequently planted due to lack of rain, the N is 'lost'. An experiment was conducted on a cracking clay soil over three seasons to compare the response of grain sorghum to N applied to the current crop v. N applied the previous season which was then either planted or left fallow (to simulate a missed planting opportunity). Recovery of 15~-labelled fertilizer by the crop and that remaining in the soil were simultaneously determined in microplots. The effect of tillage practice [zero (ZT) and conventional (CT)] was also examined. Sorghum grain yield responded to fresh applications of N in 1993 and 1993194 but not 1992, reflecting the importance of timing of rainfall rather than the total amount received within the season. Applications of N to the current crop always improved yield more than equivalent amounts of N applied to the previous crop. Grain yields of plots that were previously fallowed (fallow-sorghum rotation) were higher than the combined yields of sorghum-sorghum rotations, although fallowing was an inefficient means of accumulating both water and mineral N. Recovery of applied 1 5 ~ by sorghum varied from 48% in 1992 to 36% in 1993 but was not related to the overall N responsiveness of the crop. Sorghum recovered a similar proportion of 1 5 ~ from plots which had been fertilized and then fallowed the previous year compared to fresh applications to the current crop, despite the fallow plots having less 1 5 ~ in them due to losses from the previous season. Losses of 1 5 ~ from the soil/plant system varied markedly with year and appeared to be related to the pattern of rainfall occurring and its possible effect on denitrification. Tillage practice did not affect grain yields or PAWC, had minimal effect on the amount of mineral N present, and little influence on the fertilizer N requirements of sorghum per se. This study suggests that there is only a small residual value to subsequent sorghum crops of fertilizer N if added initially to a successful crop. However, if N is applied pre-plant and the crop is not planted, for example due to lack of planting rain, a large proportion of this N can remain available to the following crop depending on the nature of the subsequent rainfall.
Amelioration of coarse-textured acidic soils used for macadamia production. II. Effects of surface applied lime on subsoil properties
Authors: Aitken RL , Stephenson RA , Moody PW , Gallagher EC
Published: November 2004

The chemical properties of the soil at depths of 0-5, 5-10, 10-20, 20-30 and 30-50 cm at two field sites with established macadamia trees were monitored for 5 years following the surface application of various rates of lime (0-1200 g/m2). The effects of annual applications of N and N plus lime were also studied at one site. Both sites received >I700 mm annual rainfall and had strongly acidic, sandy soils. A residual effect of increased pH in the surface soil (0-5 cm depth) was evident after 5 years for lime rates 2200 g/m2. Differences in the nature of the residual effect at each site are discussed in relation to soil acidification, lime dissolution and leaching. High lime rates (>300 g/m2) applied to the soil surface increased pH and reduced extractable A1 in the 10-20 cm depth interval after 12 months. Three years after application, the soil pH at depths of 20-30 and 30-50 cm had been significantly (P < 0.05) increased by surface applications of 600 and 1200 g lime/m2, respectively. The results of this study show that surface application of lime at economic rates (300 to 600 g/m2) can reduce subsoil acidity in coarse-textured soils in high rainfall areas.
Constraints to the modelling of diet selection and intake in the grazing ruminant
Authors: Dove H
Published: November 2004

The interaction of grazing animals and their pasture generates substantial income for Australia, so that an interest in modelling the processes involved can be justified readily. Based on a brief review of the factors influencing diet selection, it is suggested that, from the point of view of modelling the process, a major constraint has been the availability of accurate and convenient methods for estimating the botanical composition of the consumed diet. It is also suggested that there is a need in future work to define more adequately the available herbage in botanical, physical, chemical and spatial terms, and to conduct experiments in which factors influencing selection are examined in an unconfounded way. It is further suggested that, while the idea of fixed preference or selection coefficients for particular species is attractive from a modelling standpoint, available evidence does not support the concept. Factors influencing herbage intake are then discussed, particularly in relation to the interaction between the degree of rumen fill and the animal's capacity to use energy. The manner in which this interaction has been used in the modelling of intake is then described briefly and the modeling of diet selection and intake within the decision-support system GrazFeed is presented by way of example. Finally, the constraints associated with model validation are discussed briefly, especially in relation to the need in future work to define more adequately the characteristics of the pasture on offer.
Recovery in plants and soils of 15N applied as subsurface bands of urea to sugarcane
Authors: Vallis I , Catchpoole VR , Hughes RM , Myers RJK , Ridge DR , Weier KL
Published: November 2004

The recovery of fertiliser N by sugarcane crops is low in comparison with most other field crops. Application of urea in subsurface bands instead of by broadcasting can greatly reduce loss of fertiliser N due to ammonia volatilisation, but the fertiliser N is still susceptible to loss from leaching or denitrification, which could be affected by soil internal drainage, trash management, or tillage practice. The recovery of fertiliser N in crops and soil from 15N-labelled urea applied as subsurface bands was measured in ratoon crops in southern Queensland and northern New South Wales. Two soil types, with contrasting internal drainage, were used in each region. In Queensland, the cultural practice was either trash burnt with inter-row cultivation or trash retained on the surface ('trash blanket') with no cultivation. In northern New South Wales, where the trash was burnt prior to harvest, the practice was either inter-row cultivation or zero tillage. Crop recovery of fertiliser N was nearly always in the range 20-40% of the amount applied. Residual fertiliser N in the soil at crop maturity ranged from 13 to 42% (average 26%). Total recovery of fertiliser N in the soil-plant system ranged from 35 to 76% (average 52%) at 6 months after application, and from 35 to 96% (average 56%) at crop maturity. Urea fertiliser supplied only 20-40% of the crop N uptake in a given season. Neither crop recovery nor loss of fertiliser N from the soil-plant system were related to the soil type or cultural practice used, indicating that compensatory effects occurred.
Natural resistance to bean yellow mosaic potyvirus in subterranean clover
Authors: Ferris DG , Jones RAC
Published: November 2004

Seed of 31 named cultivars and 11 other genotypes of Trifolium subterraneum (subterranean clover) was sown in 3 major and 3 smaller scale field experiments. In these, bean yellow mosaic virus (BYMV) was spread from infector plants to test rows by naturally occurring aphids. The numbers of clover plants developing BYMV symptoms in each row were counted at different times. Based on the results from at least 2 field experiments, different genotypes were assigned to 1 of 5 BYMV infection categories (A-E), ranging from greatest (A) to least (E) infection. Category A was found to contain genotypes that were latest maturing while, except for cv. Rosedale (ssp. brachycalycinum) which was in E despite being of intermediate maturity, category E contained earliest maturing genotypes. Except for cv. Rosedale, when the percentages of plants with BYMV symptoms in the 3 main experiments were plotted against days to flowering previously established for each genotype, the two were closely related. However, when young plants of cultivars in categories D or E were aphid-inoculated with 2 BYMV isolates, they became infected to a similar extent to young plants of 2 late-maturing cultivars from category A. This suggests that, except for cv. Rosedale, the extent of BYMV infection obtained in the field was determined by plant physiological age, plants of late-maturing genotypes being easier for viruliferous aphids to infect with BYMV than plants of early-maturing genotypes of the same age but physiologically older, a phenomenon known as 'mature plant resistance'. When plants of cv. Rosedale were aphid-inoculated with 7 different isolates of BYMV, a systemic hypersensitive reaction developed with 5 isolates but not with two others. This suggests that cv. Rosedale has 'strain specific hypersensitive resistance' to BYMV. No systemic hypersensitive reaction developed when the same 7 BYMV isolates were aphid-inoculated to cv. Dwalganup and named selections Pink Flowered and Northam Early, genotypes previously reported to react hypersensitively to potyvirus infection. The field screening procedure employed is suitable for use by T. subterraneum breeding programs seeking to develop new cultivars with resistance to BYMV. Cultivar Rosedale may prove a suitable source of resistance to use as a parent in crossing programs aimed at producing cultivars with natural BYMV resistance.
Short-term patterns of seed softening in Trifolium subterraneum, T. glomeratum and Medicago polymorpha
Authors: Smith FP , Cocks PS , Ewing MA
Published: November 2004

The short-term (within-year) dynamics of the softening of hard seeds in a number of accessions of Trifolium subterraneum L., T. glomeratum L., and Medicago polymorpha L. were monitored in the field. There were distinct differences in the patterns of seed softening between and within species and between years. Seed softening was accurately described by logistic curves with calculated half-lives of hard seeds (within a given year) a good indicator of differences in the softening patterns between species and accessions. T. subterraneum cv. Nungarin softened most rapidly over summer, ceasing by March (half-life in the first year 45 days), whereas M. polymorpha cv. Serena and 2 accessions of T. glomeratum softened mainly during the autumn (half-lives of 126, 104, and 136 days, respectively) First year half-lives of 4 other accessions of T. subterraneum ranged from 64 to 79 days. The results showed that large seeds were more likely to soften in the first year than were small seeds. The different patterns can be explained using Taylor's 2-stage model of seed softening. The implications of different patterns are discussed in terms of adaptation to a Mediterranean environment. T. glomeratum and M. polymorpha cv. Serena are considered to have a short-term pattern of seed softening well adapted to an environment where false breaks to the growing season are likely. The pattern of T. subterraneum is considered to be less well adapted to such an environment. However, variation within the species indicates the potential for selection of better adapted varieties. The inclusion of the short-term seed softening pattern as a selection criterion for pasture legumes is recommended.
The leaf infection process and resistance to Pleiochaeta setosa in three lupin species
Authors: Yang HA , Sweetingham MW , Cowling WA
Published: November 2004

In field experiments in Western Australia, Lupinus albus cv. Kiev Mutant was very susceptible, L. angustifolius cv. Yorrel was susceptible, and L. luteus cv. Motiv 369 was resistant to brown spot caused by Pleiochaeta setosa. The process of leaf infection by P. setosa was examined on these 3 Lupinus species and cultivars. Field infection occurred on young plants almost exclusively on the lower side of leaves from conidia splashed from the soil. More conidia per cm2 leaf surface were deposited on Kiev Mutant than on Yorrel or Motiv 369. In humid chambers at 15�C, 94-98% of conidia germinated on all species after 24 h. On all species, appressorial formation began 6 h after inoculation, but fewer appressoria were formed on Motiv 369 (27% of germinated conidia) than on the other 2 species (average 55%) after 24 h. Leaf penetration was directly through the cuticle via appressoria with few stomata1 penetrations. Efficiency of lesion formation (expressed as the number of lesions produced per 100 conidia deposited) was greater on Kiev Mutant and Yorrel (8.3 and 7.2%) than on Motiv 369 (2.3%). More lesions per cm2 leaf area were produced on Kiev Mutant (2.4) than on Yorrel (0.7) or Motiv 369 (0.3), but average lesion size was similar in each variety. Lesions expanded from 200-250 8m at 3 days to > 500 8m radius at 16 days after inoculation. During lesion expansion, P. setosa hyphae grew 50-200 8m beyond the border of necrotic lesions on Kiev Mutant, remained at the border of lesions on Yorrel, and were 100-200 8m inside the border of lesions on Motiv 369. Lesions on the susceptible cultivars Kiev Mutant and Yorrel (but not Motiv 369) were surrounded by a large chlorotic halo up to 2 mm from the outside necrotic lesion border. More lesions per cm2 leaf area were required to cause defoliation in Motiv 369 than in Kiev Mutant and Yorrel. Brown spot resistance in Motiv 369 is expressed as a reduction in defoliation. This appears to result from reduced attachment of conidia, reduced efficiency of infection and lesion formation, restricted growth of mycelia in lesions, reduced chlorosis, and delayed leaf senescence. Fewer conidia were produced on defoliated leaves of Motiv 369 in field plots.