Showing papers in "Australian Journal of Experimental Agriculture in 1990"

A review of the use of phosphate rocks as fertilizers for direct application in Australia and New Zealand.

Abstract: Field trials in New Zealand have shown that reactive phosphate rocks (RPRs) can be as effective as soluble P fertilisers, per kg of P applied, on permanent pastures that have a soil pH 800 mm. Whereas RPRs such as North Carolina, Sechura, Gafsa and Chatham Rise have been evaluated on permanent pastures in New Zealand, most Australian field trials have examined unreactive PRs such as Christmas Island A and C grade, Nauru and Duchess, using annual plant species. Only in recent experiments has an RPR, North Carolina, been examined. Except on the highly leached sands in southern and south-western Australia, both reactive and unreactive PRs have shown a low effectiveness relative to superphosphate. In addition to chemical reactivity, other factors may contribute to the difference in the observed agronomic effectiveness of PRs in Australia and New Zealand. Generally, PRs have been evaluated on soils of lower pH, higher pH buffering capacity (as measured by titratable acidity) and higher P status in New Zealand than in Australia. Rainfall is more evenly distributed throughout the year on New Zealand pastures than in Australia where the soil surface dries out between rainfall events. Dry conditions reduce the rate at which soil acid diffuses to a PR granule and dissolution products diffuse away. Even when pH and soil moisture are favourable, the release of P from PR is slow and more suited to permanent pasture (i.e. the conditions usually used to evaluate PRs in New Zealand) than to the annual pastures or crops used in most Australian trials. Based on the criteria of soil pH 800 mm, it is estimated that the potentially suitable area for RPRs on pasture in New Zealand is about 8 million ha. Extending this analysis to Australia, but excluding the seasonal rainfall areas of northern and south-western Australia, the potentially suitable area is about 13 million ha. In New Zealand, many of the soils in the North and South Islands satisfy both the pH and rainfall criteria. However, suitable areas in Australia are confined mainly to the coastal and tableland areas of New South Wales and eastern Victoria, and within these areas the actual effectiveness of RPR will depend markedly on soil management and the distribution of annual rainfall. Further research on RPR use should be focused on these areas.

Effects of conservation tillage farming on soil microbial biomass, organic matter and earthworm populations, in north-eastern Victoria

Abstract: A long-term field experiment was set up in 1981 in north-eastern Victoria to determine the effects of conservation tillage farming on agronomic and soil properties. Conventional cultivation was compared with direct drilling, and stubbles retained from the previous crop were compared with burning under direct drilling. Wheat was grown continuously over the 7 years of the experiment. Organic carbon (C), total nitrogen (N), soil microbial biomass and earthworm populations were measured. When samples were taken incrementally down the soil profile, there was a significant concentration gradient of organic matter under direct drilling. In the surface 2.5 cm, biomass C and N, and N mineralisation were 35, 30 and 62% greater, respectively, than under conventional cultivation. Direct drilling into retained stubble did not significantly increase organic C or total N. Of the estimated 7.8 t C/ha added to the soil from conserved crop stubbles, 4% was retained in the top 7.5 cm at the time of sampling. Organic C, total N and biomass C and N decreased with depth in both treatments. Microbial biomass varied considerably with season. The biomass of earthworms in the top 10 cm, under direct drilling, was more than twice that of conventional cultivation, while total worm numbers increased significantly (P<0.05), from 123 to 275/m2, when wheat stubble was retained with direct drilling compared to stubble burning.

Acidification under grazed annual and perennial grass based pastures.

Abstract: Soil samples to a depth of 60 cm were collected from adjacent, 39-year-old, phalaris-based and annual pasture fields on an acid soil at Rutherglen, north-eastern Victoria. The fields had similar histories of fertiliser application and stock enterprise. Minimum net acid addition rates were determined under both pasture types, and the soil under annual pasture showed greater acidification. Carbon cycle acid addition contributed 1.3 1 and 1.36 kmol H+/ha.year to net acid addition on annual and phalaris pastures, respectively. Because slow alkaline soil reactions in the field contribute to buffering capacity on an acid soil and lead to underestimation of net acid addition rate and nitrate leaching, estimates of such reactions were made for both pasture types. If correct assumptions were used nitrate leaching was substantial under both pasture types but was reduced by 1.01 kmol H+/ha.year under phalaris pasture. This suggests that perennial grass based pastures can be used to reduce acidification on pastoral soils. Alkali addition to counteract net acidification may be necessary on acid soils to maintain management options for growing aluminium-sensitive species.

Soil acidification under subterranean clover (Trifolium subterraneum L.) pastures in north-eastern Victoria

Abstract: Summary. Eleven paired soil samples to 60 cm depth were collected from grazing properties in north-eastem Victoria. Soils were naturally acid and most were red or yellow podsolics. At each site unfertilised soils (unimproved) and soils which had received regular superphosphate applications (improved) were sampled from either side of a fenceline. The percentage of organic carbon was higher on improved sites but pH was usually lower. Using pH and pH buffering capacity data, the rate of soil acidification under improved pasture, relative to unimproved pasture, was estimated. The improved pastures, on average, required 39 kg CaC03ka.year to balance the net acid accumulated. The estimated rates of acidification are much lower than those reported previously for similar environments and soil types in New South Wales. There was a relationship between initial profile pH and net acid addition, lower measured net acid addition being associated with low initial soil pH. This paper demonstrates the need for both standardisation of soil pH buffer capacity measurements, and more direct assessment of the role of soil mineral dissolution processes in buffering the pH of strongly acid soils. Until such data exists it will be very difficult to provide convincing information to primary producers regarding the long term alkali input requirements needed for sustainable farming systems.

The importance of the carbon cycle to acidification of a grazed annual pasture.

Abstract: Soil samples to a depth of 60 cm were collected from 3 fields of a 73-year-old experiment in north-eastern Victoria. One field (unfertilised) had never received fertiliser, whereas, the other 2 fields (fertilised) had received 4.5 t/ha superphosphate. One of the fertilised fields also had a lime application history (fertilised and limed). The fields were particularly useful for estimation of the amount of acid added by the carbon cycle as records of lamb, wool and hay removal over a long period were available. The soil pH of the fertilised field had declined relative to the unfertilised field to a depth of at least 30 cm. The field receiving fertiliser and lime had a similar pH profile to that of the unfertilised field. Pasture improvement resulted in much higher stocking rates and consequent product removal (hay, wool and meat) from the fertilised and limed fields compared with the unfertilised field (68, 72 and 12 kmol H+/ha, respectively). Carbon and nitrogen cycle acidification accounted for 65 and 35%, respectively, of the net acid addition on the fertilised field. The acidification rates for the fertilised, fertilised and limed, and unfertilised fields over the 73-year period were 1.42, 2.37 and 0.16 kmol H+/ha.year. These acid addition rates are likely to be underestimates because the laboratory pH buffering capacity method used did not account for slow buffering reactions in the field (Ridley et al. 1990).

Rooting depth of wheat in the Victorian Mallee

Abstract: In 1986 and 1987 wheat was sown in an experiment at the Mallee Research Station, Walpeup, at 2 times of sowing and with 3 rates of applied nitrogen. Soil cores were taken and trenches excavated to 1.5 m to measure wheat root growth and depth of rooting. Wheat roots penetrated to a maximum depth of 104 cm in crops sown in May, the optimum time of sowing for maximum yield, while delayed sowing reduced total root biomass and limited rooting depth to 73-83 cm. The application of nitrogen fertiliser did not affect either the rooting depth or growth and yield. Significant changes in total soil water content between sowing and harvest only occurred in 1987 with the early and late sown crops reducing the total soil water content by 47 and 99 mm respectively. In 1986, above average rainfall during the growing season caused the early sown crop to accumulate more water below 50 cm than the late sown crop. While total water use was increased only in 1986 with early sowing, crop water use efficiency and yield was greater in both years. The addition of nitrogen had no effect on crop water use or water use efficiency. A survey of wheat crops carried out in 1988 on 10 Mallee farms also found that shallow rooting is widespead. The field experiment and survey data show that, irrespective of sowing time, roots did not penetrate as far down the profile as might be expected, given reported rooting depths commonly in excess of 200 cm on similarly textured soils. This was shown to be associated with high soil pH and salt content. Poor rooting depth of wheat in this environment will restrict the use of stored water and accordingly, calls the practice of fallowing into question.

Field evaluation of tissue-cultured bananas in south-eastern Queensland.

Abstract: Field performance is described for tissue cultured plants and conventional propagules of planting material of banana cultivar 'New Guinea Cavendish' (Musa sp., AAA group, Cavendish subgroup). Tissuecultured plants were produced by either regeneration of plants from callus culture or by micropropagation of plants following the release of dormant buds at the leaf axils of explants. The conventional material consisted of suckers and 'bits' (lateral buds and associated corm material). Tissue-cultured plants established more quickly, were taller, and had a shorter time to bunch emergence and harvest of plant crop than conventional planting material. They had significantly (P<0.05) higher yields in terms of bunch weight, which was a function of greater numbers of fingers and hands. These advantages did not extend to the ratoon crop. Sucker production on tissue-cultured plants was significantly (P<0.01) higher up to 8 months after planting, equal to conventional material from 8 months to harvest, and then significantly lower. Twenty-two per cent of the plants derived from callus were off-types compared with 3% in the line produced by axillary bud proliferation. No off-types were observed in conventional planting material.

Polysaccharide composition of Australian wheats and the digestibility of their starches in broiler chicken diets.

Abstract: The polysaccharide compositions of 20 wheat varieties from New South Wales and Western Australia were determined. Mean pentosan and â-glucan contents ranged from 5.7 1 to 8.18% and from 0.61 to 0.87% respectively, on a dry matter basis. Starch contents ranged from 61.5 to 68.9% and the wheat starches were between 21.1 and 31.8% amylose. The starch digestibility of the wheats was found to be independent of the levels or composition of the polysaccharides when assayed using 5-week-old broiler chickens.

Influence of an acid soil on the herbage yield and nodulation of five annual pasture legumes.

Abstract: Balansa, persian and subterranean clover and barrel and murex medic were grown in acidic sandy loam in pots in a glasshouse. Four lime treatments (0, 1, 2, 3.5 t/ha) resulted in pH levels of 4.2, 4.7, 5.1 and 6.0 (1:5 CaCl2). After addition of plant nutrients, total exchangeable cations in the nil lime treatment averaged 2.197 cmol(+)/kg, increasing to 4.738 cmol(+)/kg at pH 6.0. With increasing pH, aluminium saturation of the soil exchange was 38, 14, 4 and 3%. The effect of soil acidity on dry matter production was compared between legumes by determining relative yield (yield/maximum yield) responses over the pH range. Subterranean clover was the most tolerant legume, followed by murex medic and balansa clover (similar), persian clover and then barrel medic. All legumes except barrel medic produced at least 90% of maximum yield at pH 4.7; only subterranean clover produced more than 90% of maximum yield at pH 4.2. Establishment of nodules was more sensitive to acidity than indicated by relative yields of dry matter, especially in murex medic and persian clover. Average nodule weight usually increased at lower pH. The dry matter yields of murex medic and persian clover at lower pH were probably reliant on compensatory increases in nodule volume as nodule number declined with increasing acidity.

Effect of seed weight, and seed phosphorus and nitrogen concentrations on the early growth of wheat seedlings.

Abstract: Wheat seeds of uniform weight selected from 3 batches of seed with phosphorus (P) concentrations of 0.14, 0.17 and 0.19% were sown in soil with a range of applied P treatments. Seedling emergence was more rapid the higher the seed P. By 25 days after sowing all plants grown at the highest concentration of applied P were similar in size, but with lower applied P, plants from seed with higher P concentrations had an advantage. A range of weight classes was selected from 2 batches of seed raised at low or high concentrations of P. There were 11 groups ranging in mean seed weight from 28 to 58 mg and in seed P from 0.13 to 0.37%. Seedlings from the high P batch had larger first leaves, a higher dry weight, and longer roots than those from the low P batch when grown in a highly P-deficient sand culture system. Within each batch, heavier seeds produced larger leaves, heavier plants and longer roots. The yield differences between batches were largely accounted for if the seed P content (¦g P/seed) was considered rather than either percentage P or seed weight alone. Differences in seed nitrogen concentration or content did not consistently account for differences in seedling growth.

Maternal behaviour in Border Leicester, Glen Vale (Border Leicester derived) and Merino sheep

Abstract: Ewe and lamb behaviour in traditional Border Leicesters, Glen Vale Border Leicesters of the NSW Agriculture and Fisheries, Glen Vale x Border Leicester crosses and medium-fine-wool Merinos, all running in paddocks of 3-4.5 ha, were compared in spring 1983 at Glen Innes, N.S.W. Twenty-eight aspects of behaviour with a known or reputed influence on lamb survival, especially of multiples, were examined in undisturbed and contrived situations. The Glen Vales and their crosses were superior to the Border Leicesters and Merinos in behaviour and lamb survival, particularly behaviour concerned with the ability of ewes to keep their lambs together. The study indicates that contrived twin-care tests could form the basis of a selection program to improve maternal care and survival of multiples.

Yield response of barley germplasm to field variation in salinity quantified using the EM-38

Abstract: Five field trials to screen a range of barley germplasm for tolerance to saline soil conditions were conducted on irrigation farms in southern New South Wales, in areas affected by secondary salinisation from shallow watertables. Three trials were located on heavy grey clay soils and 2 on red-brown earth soils. An electromagnetic soil conductivity meter (EM-38) was used to quantify the salinity of individual field plots. Cultivars were compared in terms of their grain yield response to soil salinity. Yields were significantly reduced by soil salinity at all sites except 1 on red-brown earth. Both genetic and site differences in salinity response were identified. The reduction in yield per unit increase in electrical conductivity of the saturated paste (EC,), averaged across sites, varied from 4.7% for Forrest to 6.6% for Schooner. However, the yield reduction per unit increase in EC,, averaged across cultivars, varied from 4.1% in a red-brown earth to 6.4% in heavy clays.

Effect of nitrogen on the growth, yield and grain protein content of barley (Hordeum vulgare)

Abstract: Barley (Hordeurn vulgare) cvv. Grimmett, Galleon and Corvette were grown under irrigated conditions at The University of Queensland, Gatton College. to determine the effects of nitrogen (N) rates (0-200 kg N/ha) on plant growth, yield and grain protein content. Nitrogen delayed maturity in all cultivars, especially in Galleon. Total tiller number and fertile tiller number were increased by N and there was a significant cultivar x N rate interaction. Similar trends were evident in total dry matter at maturity and grain yield, with Galleon producing the highest yields. Fertile tiller percentage was reduced by increasing N rate. Grain protein content increased with the increasing N rate, with differences in the nature of the response between cultivars (i.e. linear in Corvette, quadratic in the other 2 cultivars). Total and fertile tiller numbers were explained by quadratic regressions, with maximum values at 150 kg N/ha (except fertile tillers in Grimmett, maximum value at 100 kg N/ha). The declines in fertile tiller percentage were explained by quadratic equations except in Grimmett, which showed a negatively linear response to increasing N rate. Dry matter yield and grain yield showed quadratic responses to N in Grimmett and Galleon (predicted maximum values near 200 kg N/ha) and linear responses in Corvette, over the experimental range of N rates. The response in grain protein content was explained by quadratic equations for Grimmett and Galleon, with minimum grain protein content occurring at close to 0 and 55 kg N/ha respectively. Corvette showed a linear increase in protein content in response to increasing N rate. It is concluded that plant breeding programs should consider variation in grain yield and protein content in response to N supply and select for efficiency of utilisation of N. Recommended N rates for irrigated barley could be 150-200 kg N/ha. Lower rates will promote strong yield responses, but protein content would remain low.

Composting based on moderately thermophilic and aerobic conditions for the production of commercial mushroom growing compost.

Abstract: Mushroom compost was prepared using an enclosed, environmentally controlled composting (ECC) method, designed to promote rapid substrate decomposition and subsequent establishment of ecological conditions favourable to mushroom culture Composting aerobically usually at 54¦C early in processing followed by 47¦C for the majority of processing produced a compost ready for spawning in 6-8 days Final compost had a bulk density of 486 kg/m3 (range 440-510 kg/m3) at 704% moisture (range 66-75%) and produced average fresh mushroom yields of 194 kg per bed m2 (range 227-173/m2), or 066 kg per kg dry compost, in a 3 flush cropping cycle Disease, or growth of competitive fungi, was not observed Composting odours were greatly reduced compared to traditional methods The processing control and uniformity of the ECC method offer much potential for detailed investigation into compost production and ecological and chemical factors in mushroom nutrition

Effect of additions of nitrogen and sulfur to irrigated wheat at heading on grain yield, composition and milling and baking quality

Abstract: The effects of adding nitrogen (N) and sulfur (S) to wheat (Triticum aestivum L. cv. Matong) at heading on the concentrations of nutrients in the plant, on grain and flour composition and milling and baking quality were studied. The crop was grown on a red- brown earth in the Goulburn Valley irrigation area of northern Victoria. There were 2 application rates of urea, 0 and 50 kg N/ha combined factorially with 2 application rates of calcium sulfate, 0 and 20 kg S/ha.Additions of N increased the concentrations of both N and S in the grain and increased protein level, but grain N:S ratio remained unaffected. Sulfur application had no effect on grain composition or on flour or dough properties. A standard range of baking tests showed that the extra protein synthesised was functional protein contributing to the dough properties in an additive manner. The N treatment lowered the hot paste viscosity and the brightness of the cold paste suggesting that there was a qualitative effect on the starch component as well as a lowering of starch content as the protein increased. There was no indication of any deleterious effects on quality arising from the late application of N as has been found by other workers.

Effect of plant density on grain yield and yield stability of sorghum hybrids differing in maturity.

Abstract: The extent and significance of the maturity x density interaction in dryland grain sorghum, and its implications for yield stability, were examined for 3 hybrids over 6 locations. Site mean grain yield ranged from 0.44 to 4.96 t/ha. Early maturity was superior in environments truncated by water stress, while late maturity was superior in favourable environments. Mid-season maturity provided greater stability of grain yield. Maximum yield by each hybrid at each yield level did not differ significantly from yield at a density of 75 000 plants/ha. The highest grain yields should be obtained with plant densities of 50000-100000 plants/ha under rainfed conditions, where yield expectations range from 0 to 5.0 t/ha. The results demonstrate the stability of sorghum grain yield over a wide range of plant density and crop maturity. Regression analysis aided data presentation and interpretation.

Growth and carcass fatness of ewe, wether, ram and cryptorchid crossbred lambs reared at pasture: effects of weaning age.

Abstract: The effects of weaning age and sex on growth, the carcass fatness and dressing percentage were studied in grazing Dorset x (Border Leicester x Merino) lambs. Entire male (ram and cryptorchid) lambs grew significantly (P<0.001) faster from marking to slaughter than did either wethers or ewes. They were also leaner than wethers, which were in turn leaner than ewes (mean ¦ s.e. GR tissue depth: 11.4 ¦ 0.16, 13.9 ¦ 0.22 and 16.3 ¦ 0.23 mm, respectively, at a carcass weight of 19.7 kg). Across all sex groups, the GR measurement increased 1.2 ¦ 0.03 mm per kg increase in carcass weight. An earlier weaning (at 13-15 weeks of age) reduced (P<0.001) liveweight gains. There was also a small reduction (P<0.05) in the GR measurement associated with the earlier weaning, particularly in ewe and wether lambs. The dressing percentage of wethers increased with increasing liveweight over the entire range of weights. However, in ewes and entire males, there was little change in dressing percentage with increasing liveweight above 40 kg. An earlier weaning was associated with a small reduction in dressing percentage.

Nitrogen fertiliser response of wheat in lupin-wheat, subterranean clover-wheat and continuous wheat rotations.

Abstract: Response of wheat to 7 rates of nitrogen (N) fertiliser was compared in clover-wheat (CW), lupin-wheat (LW) and continuous wheat (WW) rotations, in 4 alternate years on a grey gravelly sand over ironstone gravel at Badgingarra, during the period 1980-87. Nitrogen fertilisers significantly increased wheat grain yields in all assessment years (1981, 1983, 1985 and 1987). There were significant (P<0.05) interactions between rotation and N fertiliser in all years except 1983, with response to N fertiliser on wheat least in the LW rotation. The apparent average increases in N available in wheat dry matter, without added N, were 10.9 kg/ha from clover and 13 kg/ha from lupins. The contributions from clover and lupins in grain N were 10 and 12.3 kg/ha respectively. Organic carbon and total N levels in the soil were similar in the LW and WW rotations but were less than in the CW rotation. The levels of organic carbon in the LW and WW rotations decreased with time. Despite the difference in soil organic carbon and total N, grain yields were similar for the CW and LW rotations in the absence of N fertiliser but were higher than in the WW rotation. It was concluded that a LW rotation (in this environment) would be as effective, at least over a 6-year period, as a CW rotation in maintaining wheat yields due to the contribution of N from readily decomposible residues from the lupin crop. However, highest yields overall where obtained when N fertiliser was added to the CW rotation.

Growth and yield characteristics of dwarf off-types recovered from tissue-cultured bananas

Abstract: Summary. Dwarf off-types recovered from a tissuecultured line of banana cultivar New Guinea Cavendish (Mum sp., AAA Group, Cavendish subgroup) were used to quantify some of the changes associated with dwarfism, the most common off-type associated with tissue-cultured Cavendish bananas, and to determine the relative stability of the trait. The off-types were significantly (P<0.01) shorter than true-to-type plants and retained their dwarf stature over 5 generations. The dwarfs were characterised by small fruit with closer packing of the hands on the bunch. Choking, when the bunch fails to emerge fully from the plant, was a characteristic of the dwarfs but not observed in true-totype plants. Dwarfism appears to be a relatively stable genetic trait and not a transient (epigenetic) change produced in vitro. By contrast, a thin-leafed off-type reverted to normal morphological characteristics 3-4 months after field establishment.

Comparative phosphate requirements of yellow serradella (Ornithopus compressus) burr medic (Medicago polymorpha var. brevispina) and subterranean clover (Trifolium subterraneum)

Abstract: The phosphate (P) requirements of burr medic (Medicago polymorpha) on marginally acidic, medium-textured soils and yellow serradella (Ornithopus compressus) on acidic, light-textured soils in the low rainfall (<400 mm) wheatbelt of Western Australia are not known. The hypothesis that yellow serradella, subterranean clover (Trifolium suhrerraneum) and burr medic have the same external requirement for applied P was tested in a glasshouse trial on 2 P-deficient soils. Species were compared on an equal total seed weight and similar maturity length basis. It was found that yellow serradella required less soil applied P to achieve 90% maximum shoot production or total plant (shoots + roots) growth and had a greater curvature co-efficient from fitted Mitscherlich functions than either subterranean clover or burr medic. Burr medic was the most responsive to applied P and had the largest external requirement for applied P. These differences in external P requirements were related to differences in ability of the 3 legumes to absorb P and to transport it to their shoots and were not due to differences in internal efficiency of the shoots. Yellow serradella was able to take up more P (total plant P content) per g roots than subterranean clover, and subterranean clover more than burr medic. The same relationship applied to the translocation of absorbed P from roots to shoots.

Effect of nitrogen on the yield and quality of irrigated onions (Allium cepa L.) cv. Cream Gold grown on siliceous sands

Abstract: Summary. The effect of nitrogen (N), at rates up to 590 kg N/ha, on the yield and quality of Cream Gold onions grown on siliceous sands was investigated in field experiments conducted during 1987-88 (1 site) and 1988-89 (2 sites). As the rate of applied N increased there was a significant (P<0.001) increase in the fresh weight of tops harvested when the largest bulbs were 25-30 mm in diameter. Fresh weight of tops was significantly (P<0.001) correlated with final marketable yield of bulbs. Nitrogen application accelerated top senescence. Nitrogen-deficient plants had erect green tops at harvest. Marketable yield was significantly (P<0.01) increased and the yield of culls (unmarketable bulbs) was significantly (P<0.01) decreased as the rate of N increased at all sites. Nitrogen rates in the range 299-358 kg N/ha were required for 95% of maximum yield. Scale thickness increased significantly (P<0.05) and glucose and fructose concentrations decreased significantly (P<0.05) at 2 sites as the rate of applied N increased. Soluble solids and dry matter of bulbs were not affected by N. Bulb size increased as the rate of applied N increased, however, the magnitude of the effect varied between sites. Number of days to 10% sprouting during storage at 15 f OS°C was significantly increased as the rate of applied N increased up to 40 kg N/ha at 2 sites. We have concluded that for the cv. Cream Gold grown on siliceous sands, the high rates of fertiliser N required to maximise marketable yield and bulb size were not detrimental to quality.

Effect of reproductive status, body condition and age of Bos indicus cross cows early in a drought on survival and subsequent reproductive performance.

Abstract: A herd of 802 Brahman cross cows, managed under extensive conditions (7000 ha paddock with twice-yearly handling) in a dry tropical environment, was studied during the severe drought of 1982-83. Twenty-one per cent of the cows died. Cows more advanced in pregnancy and those in poorer condition in the early stages of the drought had lower (P<0.05) survival probabilities. Cows aged over 7 years also generally had a reduced (P<0.05) probability of survival. Calf loss between confirmed pregnancy early in the drought and weaning after the following wet season was 31%. Calf loss from surviving cows was not higher than is usual in non-drought years. All deaths of lactating cows were associated with calf deaths. The practical use of these results in cost-efficient management for survival of cows in drought was then evaluated in a second study in which 293 cows were drafted into high- and low-supplement-requirement (HSR and LSR) groups in the early stages of the 1987 drought. Survival feeding in the HSR group commenced about 6 weeks earlier than would have been necessary in the LSR group. In both studies, reproductive status in the early drought period was a significant determinant of both body condition and conception rates early in the following year. Cows more advanced in pregnancy early in the drought were in poorer condition after the following wet season (P<0.05), but remained further advanced in pregnancy (P<0.05). Both body condition in the early part of the drought and age had minimal effects on performance in the following wet season, although younger cows tended to be lighter and have the lowest conception rates. Cows in better condition after the wet season had higher (P<0.05) pregnancy rates.

Distribution of field birth-sites of lambing ewes

Abstract: Summary. This paper reports on birth-site distribution of Merinos and some British breeds in 34 lambing paddocks in a major study over 5 lambing seasons at Armidale New South Wales, and in minor studies during single lambing seasons, 2 in New South Wales and 3 in the United Kingdom. The observed distribution of birth-sites is related to topographic and other environmental features of the paddocks. In level, or nearly level paddocks, Merinos tended to lamb in a random pattern, but in sloping paddocks their birth-sites were consistently aggregated in the areas of greatest elevation. British breeds (Suffolks and Cheviots in New South Wales, and Welsh Mountain, Scottish Blackface, North Country Cheviots and Greyface in the United Kingdom) showed a pronounced tendency to lamb near the margins of paddocks, and a less marked preference for an elevated site. It is suggested that lamb mortality could be significantly reduced by the use of paddocks that provide shelter at preferred elevated positions, or along and within the paddock margins.

Responses in cotton yields to nitrogen and phosphorus fertilisers in the Emerald Irrigation Area, central Queensland

Abstract: The poor growth of cotton in the Emerald Irrigation Area of central Queensland was investigated in fertiliser experiments from 1978 to 1980. The need for large amounts of phosphorus (P) and nitrogen (N) fertilisers was demonstrated. In a glasshouse nutrient-omission experiment, N, P, potassium, sulfur (S), zinc, copper, manganese, boron (B) and molybdenum were tested for effects on cotton growth on the soil surface fraction (low in P and S) of a black cracking clay at Emerald. Plant growth indicated that P, N and S were extremely deficient. Other nutrients, except B, were marginally deficient. Slow growth was reflected in low shoot concentrations of N, P and S. In subsequent field experiments at 5 sites on 3 different soils, yield responses were only obtained to applications of P and N. Phosphorus at a rate of 40 kg/ha was required on a shallow, basaltic, dark cracking clay (Bug) soil. Yield responses to P were not obtained on an alluvial, dark cracking clay (AUg) or on a deep, basaltic, dark cracking clay (TbUg), but soil P concentrations were generally higher at these sites. For high value cotton crops where soil P analyses are low (i.e. <12 mg/kg bicarbonate-extractable P at 0-10 cm), high P fertiliser rates are recommended to maintain the soil P status. Nitrogen at a rate of 120 kg/ha produced heaviest yields on the Bug soil, but there were symptoms of N deficiency in plants early in the season. Irrigation frequency treatments produced no significant differences in yield.

Increasing wheat yields in a high rainfall area of Western Australia.

Abstract: Average commercial wheat yields in the southern, high rainfall area of Western Australia have seldom exceeded 1.5 t/ha and wheat is not widely grown. However, the average annual rainfall and length of growing season (>400 mm and >6 months) are conducive to much larger yields. Thirteen factorial experiments with mid and long season cultivars (Aroona and Osprey), 2 levels of applied nitrogen (N) (40 and 80 kg N/ha), 2 seed rates (50 and 100 kg/ha) and with or without fungicide were conducted at 8 sites over 2 seasons. The experiment was done to investigate combinations of cultivar and agronomic practices suitable for increased wheat production in long season environments in Western Australia. Largest grain yields (>4 t/ha) were obtained where wheat followed a grass-free break crop, and the mid season cultivar was used with 80 kg N/ha and 100 kg/ha of seed. Increases due to cultivar and seed rate were more consistent than those due to N, and increases from application of fungicide were less consistent. It is suggested that the optimal wheat production 'package' will include sowing in May in rotation with a grass-free break crop, seed rate of about 100 kg/ha and, when all other factors are optimal, N rates of over 40 kg/ha. The greatest yield increases were associated with the sites where wheat followed a grass-free crop. Increases due to other factors were relatively smaller. Hectolitre weight and percentage of small grain (<2 mm) often reached levels that would have entailed downgrading in commercial deliveries. However, in the most productive crops where root and leaf diseases were minimal, these quality parameters were seldom deficient and grain protein contents exceeded 10% at yields of up to 4 t/ha.

Evaluation of herbicides for control of summer-growing weeds on fallows in south-eastern Australia

Abstract: Eighteen herbicides or herbicide tankmixes were evaluated over 3 years (1987-89) for their control of 11 important summer-growing weeds on fallows in southern New South Wales and the Wimmera area of Victoria. Each of the weeds was effectively controlled by at least 1 herbicide. The tank-mixes of glyphosate plus metsulfuron (270 + 4.2 g a.i./ha) and glyphosate plus 2,4-D ester (270 + 320 g a.i./ha) were the most effective treatments, each giving an average of 68% control of all species. Hogweed (Polygolzunz avicu1ar.e L.), prickly paddy melon (Cucumis myriocarpris Naudin), spear thistle [Cirsium vulgare (Savi) Ten.] and skeleton weed (Chondrilla juncea L.) were the species most tolerant of these 2 tank-mixes. When these species were exluded, glyphosate plus metsulfuron and glyphosate plus 2,4-D ester gave an average of 90 and 88% control, respectively, of the remaining species [common heliotrope, Heliotropiunz europaeum L.; camel melon, Citrullus larzatus (Thunb.) Matsum. and Nakai var. lanatus; prickly lettuce, Lactuca serriola L.; sowthistle, Sonchus spp.; clammy goosefoot, Chenopodium pumilio R.Br.; caltrop, Tribulus terrestris L.; stink grass, Eragrostis ciliatiensis (All.) E. Mosher]. Hogweed was most effectively controlled by 2,4-D amine plus dicamba (750 + 100 g a.i./ha) or 2,4-D ester (800 g a.i./ha); prickly paddy melon by 2,4-D amine plus triclopyr (750 + 96 g a.i./ha); spear thistle by 2,4-D amine plus dicamba (750 + 100 g a.i./ha) or glyphosate plus clopyralid (270 + 60 g a.i./ha); and skeleton weed by 2,4-D amine plus clopyralid (750 + 60 g a.i./ha). A pot experiment confirmed field observations that, as common heliotrope ages, glyphosate and glyphosate plus metsulfuron become less effective for its control.

Effect of brief pre-marketing holding of bananas in nitrogen on time to ripen

Abstract: Bananas obtained from more than 20 plantations in 3 seasons and stored in nitrogen at 20°C for 3 days soon after harvest took about 27 days to ripen in subsequent air storage, compared with untreated fruit which ripened after about 19 days. However, skin injury was found on about 4% of fruit, with the affected areas principally being previously damaged areas. When nitrogen treatment was delayed, the inhibition of ripening was lost and skin injury became more severe. While there were some differences in chemical composition found between nitrogen treated and untreated fruit, taste tests showed that this had no noticeable effect on eating quality.

Yield losses in wheat caused by stripe rust (Puccinia striiformis West.) in northern New South Wales

Abstract: Three field trials were established at Tamworth in northern New South Wales to quantify the effect of stripe rust on the yield of wheat The yield parameters were total grain yield per plot, 1000-grain weight, number of grain produced per head tiller number and grain yield per plant In addition, grain protein and dough and flour quality were determined The total yield losses were found to be dependent on the cultivar, the timing of the epidemic and the yield potential of the crop In most cases, early stripe rust epidemics had a greater effect on yield than late epidemics Total grain yield and 1000-grain weight were most often affected Long season epidemics affected all the yield parameters, with losses of up to 50% in grain yield being recorded in susceptible cultivars The quality of dough and flour was unaffected by the fungicide treatments The results suggest that the levels of resistance of the currently recommended wheat cultivars were sufficient to protect them from yield losses from stripe rust epidemics in most years

Field calibration of a neutron-gamma probe in three agriculturally important soils of the Lower Macquarie Valley

Abstract: A neutron-gamma probe was field calibrated in a grey clay, a grey-brown clay and a red-brown earth near Trangie, New South Wales. These are the main soils used for irrigated agriculture in this region. Accurate but simple calibrations and sampling procedure\ are required by commercial irrigators and researchers. Bias in the estimation of soil water content was minimised by using separate calibrations for each soil and depth where equations were significantly different. Precision tended to be higher where an equation combining all depths and soils was used. but the introduction of large bias at some depths suggests that soil-specific equations should be used where possible. Calibration error generally was a smaller component of total error than location error, particularly where the combination equation was used. The errors associated with commercial sampling methods are discussed. The relationship between gamma count rate ratio and soil wet bulk density was poor, particularly in the grey and grey-brown clays, and this technique was considered to be inadequate for the measurement of bulk density in the field.

The effect of two forms of nitrogen fertiliser applied near anthesis on the grain quality of irrigated wheat

Abstract: In 1976, the feasibility of using nitrogen (N) fertiliser to raise the protein levels of irrigated wheat was investigated using 3 rates of fertiliser (0, 40 and 80 kg N/ha) applied either at anthesis or 3 days later to the soil surface (ammonium nitrate), or as a foliar spray (urea). Each 40 kg/ha increment in N applied as ammonium nitrate or urea produced a 1.1% increase in grain protein. Ammonium nitrate produced significantly (P<0.01) higher protein levels than urea. The relationships between grain protein level and several grain quality criteria (farinograph absorption, extensibility, loaf volume, bake score) were examined to determine whether protein quality was maintained when protein levels were increased by late application of N fertiliser. All the criteria examined indicate that protein quality was maintained. Although it is possible to raise protein levels with N fertiliser, large price premiums for high protein would be necessary to make the practice economic.