Sustaining productivity of a Vertosol at Warra, Queensland, with fertilisers, no-tillage or legumes. 9. Production and nitrogen benefits from mixed grass and legume pastures in rotation with wheat

Reduced supplies of nitrogen (N) in many soils of southern Queensland that were cropped exhaustively with cereals over many decades have been the focus of much research to avoid declines in profitability and sustainability of farming systems. A 45-month period of mixed grass (purple pigeon grass, Setaria incrassata Stapf; Rhodes grass, Chloris gayana Kunth.) and legume (lucerne, Medicago sativa L.; annual medics, M. scutellata L. Mill. and M. truncatula Gaertn.) pasture was one of several options that were compared at a fertility-depleted Vertosol at Warra, southern Queensland, to improve grain yields or increase grain protein concentration of subsequent wheat crops. Objectives of the study were to measure the productivity of a mixed grass and legume pasture grown over 45 months (cut and removed over 36 months) and its effects on yield and protein concentrations of the following wheat crops. Pasture production (DM t/ha) and aboveground plant N yield (kg/ha) for grass, legume (including a small amount of weeds) and total components of pasture responded linearly to total rainfall over the duration of each of 3 pastures sown in 1986, 1987 and 1988. Averaged over the 3 pastures, each 100 mm of rainfall resulted in 0.52 t/ha of grass, 0.44 t/ha of legume and 0.97 t/ha of total pasture DM, there being little variation between the 3 pastures. Aboveground plant N yield of the 3 pastures ranged from 17.2 to 20.5 kg/ha per 100 mm rainfall. Aboveground legume N in response to total rainfall was similar (10.6 - 13.2 kg/ha. 100 mm rainfall) across the 3 pastures in spite of very different populations of legumes and grasses at establishment. Aboveground grass N yield was 5.2 - 7.0 kg/ha per 100mm rainfall. In most wheat crops following pasture, wheat yields were similar to that of unfertilised wheat except in 1990 and 1994, when grain yields were significantly higher but similar to that for continuous wheat fertilised with 75 kg N/ha. In contrast, grain protein concentrations of most wheat crops following pasture responded positively, being substantially higher than unfertilised wheat but similar to that of wheat fertilised with 75 kg N/ha. Grain protein averaged over all years of assay was increased by 25 - 40% compared with that of unfertilised wheat. Stored water supplies after pasture were < 134mm (< 55% of plant available water capacity); for most assay crops water storages were 67 - 110 mm, an equivalent wet soil depth of only 0.3 - 0.45 m. Thus, the crop assays of pasture benefits were limited by low water supply to wheat crops. Moreover, the severity of common root rot in wheat crop was not reduced by pasture - wheat rotation.

Temporal and spatial patterns of soil water extraction and drought resistance among genotypes of a perennial C-4 grass

The objective of this study was to investigate patterns of soil water extraction and drought resistance among genotypes of bermudagrass (Cynodon spp.) a perennial C-4 grass. Four wild Australian ecotypes (1-1, 25a1, 40-1, and 81-1) and four cultivars (CT2, Grand Prix, Legend, and Wintergreen) were examined in field experiments with rainfall excluded to monitor soil water extraction at 30-190 cm depths. In the study we defined drought resistance as the ability to maintain green canopy cover under drought. The most drought resistant genotypes (40-1 and 25a1) maintained more green cover (55-85% vs 5-10%) during water deficit and extracted more soil water (120-160 mm vs 77-107 mm) than drought sensitive genotypes, especially at depths from 50 to 110 cm, though all genotypes extracted water to 190 cm. The maintenance of green cover and higher soil water extraction were associated with higher stomatal conductance, photosynthetic rate and relative water content. For all genotypes, the pattern of water use as a percentage of total water use was similar across depth and time We propose the observed genetic variation was related to different root characteristics (root length density, hydraulic conductivity, root activity) although shoot sensitivity to drying soil cannot be ruled out.

Genetic analysis of resistance to root-lesion nematode (Pratylenchus thornei) in wheat

The inheritance of resistance to root-lesion nematode was investigated in five synthetic hexaploid wheat lines and two bread wheat lines using a half-diallel design of F1 and F2 crosses. The combining ability of resistance genes in the synthetic hexaploid wheat lines was compared with the performance of the bread wheat line 'GS50a', the source of resistance to Pratylenchus thornei used in Australian wheat breeding programmes. Replicated glasshouse trials identified P. thornei resistance as polygenic and additive in gene action. General combining ability (GCA) of the parents was more important than specific combining ability (SCA) effects in the inheritance of P. thornei resistance in both F1 and F2 populations. The synthetic hexaploid wheat line 'CPI133872' was identified as the best general combiner, however, all five synthetic hexaploid wheat lines possessed better GCA than 'GS50a'. The synthetic hexaploid wheat lines contain novel sources of P. thornei resistance that will provide alternative and more effective sources of resistance to be utilized in wheat breeding programmes

Rhizoctonia crown and root rot of the pasture legume, sulla (Hedysarum coronarium)

Rhizoctonia solani AG-2-2 was isolated from wilting and dying plants of sulla (Hedysarum coronarium), which is currently being assessed in eastern and southern Australia for its potential as a pasture and forage legume. Infected plants in the field had extensive rotting of the taproot, lateral roots and crown. Koch's postulates were fulfilled using three inoculation methods. The disease may pose a considerable threat to the potential use of H. coronarium in the dryland, grazing farming systems of Australia, with resistance offering the most viable option for minimising its impact.

Effect of seasonal conditions on fleece weight and its components in merino sheep grazing Mitchell grass pasture in North West Queensland

SUMMARY Seasonal conditions in the pre to post natal period and selected periods before and during wool growth were described using climatic measures and estimates of the quality and quantity of pasture on offer derived from a validated pasture production model (GRASP). The variation in greasy and clean fleece weight, yield, staple length, fibre diameter, neck and side wrinkle score of Merinos grazing Mitchell grass in north west Queensland was explained in terms of these pasture and climatic measures and animal characteristics such as reproductive status, age and skin area. Multiple regression equations predicting clean and greasy fleece weight from the proportion of days in the wool growth period that the green pool in the pasture was less than one kg/ha, the percentage utilisation of the pasture, age, reproductive status and skin area of the ewes explained 87% and 79% of the variation respectively. Equations with similar predictors explained 58-85% of the variation of the other components. The inclusion of pasture conditions in the pre to post natal period did not significantly improve the predictions of the animal’s later performance. 22nd Biennial Conference.

Milk Production Responses to Oversowing a Portion of Tropical Grass Pasture with Summer Crop Legumes on Sub-tropical Dairy Farms

Northern Australian dairy farms have a large area of tropical dryland grass pasture available for use as summer pastures. Late summer-autumn in sub-tropical Australia is traditionally a difficult period in which to produce milk because of the decline in both quality and quantity of tropical grasses (Ehrlich et al. 1994). Options to improve autumn feed on dairy farms include introducing forage crops and conservation, increasing concentrate feeding and introducing legumes. Perennial tropical legumes have not been successful at this time of year because of their inability to sustain stocking rates above one cow/ha. This experiment, conducted on farms, was designed to test if annual crop legumes could be successfully oversown into tropical grass areas using minimal till methods to measure the subsequent impact on milk production on farms. Previous experiments using annual legumes in plots at Mutdapilly Research Station had demonstrated yields up to 10 t/ha can be achieved using annual tropical legumes with protein levels as high as 20% in the whole legume plant. Animal production for a consuming world : proceedings of 9th Congress of the Asian-Australasian Association of Animal Production Societies [AAAP] and 23rd Biennial Conference of the Australian Society of Animal Production [ASAP] and 17th Annual Symposium of the University of Sydney, Dairy Research Foundation, [DRF]. 2-7 July 2000, Sydney, Australia.

Using Alkanes to Predict Voluntary Intake, Faecal Output and Digestibility of Buffel Grass Hay Fed to Steers

The cuticular waxes of forage plants contain long chain n-alkanes with odd carbon chain lengths in the range C25-C37 which are quantitatively recovered in faeces. When these concentrations are used with the concentrations of administered synthetic even chain length alkanes, the voluntary intake (VI), faecal output (FO) and digestibility (DMD) of forages can be estimated (Dove and Mayes 1991, 1996).

Response By Dairy Cows Grazing Tropical Grass Pasture To Barley or Sorghum Grain Based Concentrates and Lucerne Hay

This study investigated the responses by dairy cows grazing Callide Rhodes grass (Chloris gayana cv. Callide) pasture to supplementation with barley or sorghum based concentrates (5 grain:1 cotton seed meal) or barley concentrate plus lucerne (Medicago sativa) hay. It was conducted in summer - autumn 1999 with 20 spring calved cows in 4 treatments in 3 consecutive periods of 4 weeks. Rain grown pastures, heavily stocked at 4.4 cows/ha, provided 22 to 35 kg green DM and 14 to 16 kg green leaf DM/cow.day in periods 1 to 3. Supplements were fed individually twice daily after milking. Cows received 6 kg concentrate/day in period 1, increased by 1 kg/day as barley, sorghum or lucerne chaff in each of periods 2 and 3. The Control treatment received 6 kg barley concentrate in all 3 periods. Milk yields by cows fed sorghum were lower than for cows fed equivalent levels of barley-based concentrate (P<0.05). Faecal starch levels (14, 18 and 17%) for cows fed sorghum concentrate were much higher (P<0.01) than those of cows fed similar levels of barley (2.1, 1.2 and 1.7%) in each period respectively. Additional supplementation as lucerne chaff did not increase milk production (P>0.05). Increased concentrate supplementation did not alleviate the problem of low protein in milk produced by freshly calved Holstein-Friesian cows grazing tropical grass pasture in summer. Animal production for a consuming world : proceedings of 9th Congress of the Asian-Australasian Association of Animal Production Societies [AAAP] and 23rd Biennial Conference of the Australian Society of Animal Production [ASAP] and 17th Annual Symposium of the University of Sydney, Dairy Research Foundation, [DRF]. 2-7 July 2000, Sydney, Australia.

Supply capability of sheep on the Mitchell grass downs of North and Central West Queensland

While, in the past, sheep have been predominantly reared and grazed in western Queensland for wool, interest in the sheep meat industry increased when wool prices became depressed. For north west and central west Queensland producers, opportunities may exist to participate in live sheep and meat export to Asia. The capability of the Mitchell grass downs to provide sufficient numbers of export quality sheep under the variable climatic conditions while sustaining the land resources has been simulated. Sheep numbers were found to be insufficient to maintain a consistent supply for live export. However, raising marking rates and lowering mortalities effectively increased reproductive performance to a level at which a surplus for export could be sustainable. Other practices might be required for the liveweight specifications to be met. 24th Biennial Conference. Adelaide, South Australia.

Simulation of the supply capability of sheep on the Mitchell grass downs of north west Queensland

Sheep in western Queensland have been predominantly reared for wool. When wool prices became depressed interest in the sheep meat industry, increased. For north west Queensland producers, opportunities may exist to participate in live sheep and meat export to Asia. A simulation model was developed to determine whether this sheep producing area has the capability to provide sufficient numbers of sheep under variable climatic conditions while sustaining the land resources. Maximum capacity for sustainability of resources (as described by stock numbers) was derived from an in-depth study of the agricultural and pastoral potential of Queensland. Decades of sheep production and climatic data spanning differing seasonal conditions were collated for analysis. A ruminant biology model adapted from Grazplan was used to simulate pregnancy rate. Empirical equations predict mortalities, marking rates, and weight characteristics of sheep of various ages from simple climatic measures, stocking rate and reproductive status. The initial age structure of flocks was determined by running the model for several years with historical climatic conditions. Drought management strategies such as selling a proportion of wethers progressively down to two-tooth and oldest ewes were incorporated. Management decisions such as time of joining, age at which ewes were cast-for-age, wether turn-off age and turning-off rate of lambs vary with geographical area and can be specified at run time. The model is run for sequences of climatic conditions generated stochastically from distributions based on historical climatic data correlated in some instances. The model highlights the difficulties of sustaining a consistent supply of sheep under variable climatic conditions.

Protein supplementation and growth enhancer strategies in successive years to maximise growth of Brahman cross steers grazing sown grass pastures on brigalow lands

A strategy comprising a winter/spring protein supplement, rumen modifier and hormonal growth promotant (Compudose 400) was used in either the first year (Tl), second year (T2), or in both years (T1+2) following weaning in Brahman cross steers as a means of increasing liveweight gain up to 2.5 years of age. T2 produced the heaviest final liveweight (544.7 kg) and highest overall liveweight gain (366.7 kg), but these were not significantly different from T1 (538.6 kg; 360.9 kg), or T1+2 (528.7 kg; 349.3 kg). However, final liveweight and overall liveweight gains of T1 and T2 but not T1+2 were significantly greater than for untreated (C) steers (504.9 kg; 325.2 kg, both P < 0.05). Regardless of the strategy imposed, liveweight and liveweight gain were enhanced, however final liveweights in each treatment were below the preferred minimum target liveweight (570-580 kg) for premium export markets. Treatment in both years gave no benefit over treatment in 1 year only. 19th Biennial Conference. 5-9 July 1992. LaTrobe University, Melbourne.

Transcriptome analysis of Neotyphodium and Epichloë grass endophytes

Large-scale gene discovery has been performed for the grass fungal endophytes Neotyphodium coenophialum, Neotyphodium lolii, and Epichloë festucae. The resulting sequences have been annotated by comparison with public DNA and protein sequence databases and using intermediate gene ontology annotation tools. Endophyte sequences have also been analysed for the presence of simple sequence repeat and single nucleotide polymorphism molecular genetic markers. Sequences and annotation are maintained within a MySQL database that may be queried using a custom web interface. Two cDNA-based microarrays have been generated from this genome resource. They permit the interrogation of 3806 Neotyphodium genes (NchipTM microarray), and 4195 Neotyphodium and 920 Epichloë genes (EndoChipTM microarray), respectively. These microarrays provide tools for high-throughput transcriptome analysis, including genome-specific gene expression studies, profiling of novel endophyte genes, and investigation of the host grass–symbiont interaction. Comparative transcriptome analysis in Neotyphodium and Epichloë was performed

Resistance of selected strawberry cultivars to root-knot nematode species (Meloidogyne spp.)

Strawberry runner production areas in Queensland are assessed for the presence of Pratylenchus vulnus (lesion nematode) and Meloidogyne hapla (root-knot nematode) as part of the approval process for sites used in runner production under the approved runner scheme. M. hapla is known to infest strawberry. The ability of three other Meloidogyne species occurring in Queensland to infest this host was investigated. The species M. arenaria, M. incognita and M. javanica, in addition to M. hapla, were able to reproduce on strawberry roots of the cultivar 'Joy', which sustained higher nematode reproduction rates than 'Jewel' and 'Sweet Charlie'. The ability of species other than M. hapla to infest strawberry needs to be recognised in site selection for runner production, and in screening cultivars for resistance to nematodes.

Biological control of parthenium (Parthenium hysterophorus) in Australian rangeland translates to improved grass production.

Biological control of parthenium, a major weed in grazing areas in Australia, was initiated in the mid 1970s. Since then, nine species of insects and two rust fungi have been introduced. Evaluation using pesticide exclusion at two sites (Mt. Panorama and Plain Creek) in Queensland, Australia, revealed that classical biological control had a significant negative effect on the target weed, but the impact varied between years. In this study, I quantified the effects of biological control of parthenium on grass production. Grass production declined with the increase in parthenium biomass. Significant increase in grass production due to biological control was observed, but only in 1 of 4 yr at Mt. Panorama and 2 of 4 yr at Plain Creek. At Mt. Panorama, there was a 40% increase in grass biomass in 1997 because of defoliation by Zygogramma bicolorata and galling by Epiblema strenuana. At Plain Creek, grass biomass increased by 52% in 1998 because of E. strenuana and by 45% in 2000 because of combined effects of E. strenuana and the summer rust Puccinia melampodii. This study provides evidence on the beneficial effects of biological control of parthenium in areas under limited grazing.

Resistance of Brassicaceae plants to root-knot nematode (Meloidogyne spp.) in northern Australia

Brassicaceae plants have the potential as part of an integrated approach to replace fumigant nematicides, providing the biofumigation response following their incorporation is not offset by reproduction of plant-parasitic nematodes on their roots. Forty-three Brassicaceae cultivars were screened in a pot trial for their ability to reduce reproduction of three root-knot nematode isolates from north Queensland, Australia: M. arenaria (NQ1), M. javanica (NQ2) and M. arenaria race 2 (NQ5/7). No cultivar was found to consistently reduce nematode reproduction relative to forage sorghum, the current industry standard, although a commercial fodder radish (Raphanus sativus) and a white mustard (Sinapis alba) line were consistently as resistant to the formation of galls as forage sorghum. A second pot trial screened five commercially available Brassicaceae cultivars, selected for their biofumigation potential, for resistance to two nematode species, M. javanica (NQ2) and M. arenaria (NQ5/7). The fodder radish cv. Weedcheck, was found to be as resistant as forage sorghum to nematode reproduction. A multivariate cluster analysis using the resistance measurements, gall index, nematode number per g of root and multiplication for two nematode species (NQ2 and NQ5/7) confirmed the similarity in resistance between the radish cultivar and forage sorghum. A field trial confirmed the resistance of the fodder radish cv. Weedcheck, with a similar reduction in the number of Meloidogyne spp. juveniles recovered from the roots 8 weeks after planting. The use of fodder radish cultivars as biofumigation crops to manage root-knot nematodes in tropical vegetable production systems deserves further investigation.