In the eastern wheatbelt of Western Australia the yield of barley relative to wheat is influenced by soil type. Field trials studied detailed aspects of growth, development, yield and water use of a range of barley and wheat cultivars on 2 soil types at 2 locations to identify those factors that lead to the differential relative yields. Barley had greater grain yields than wheat on both fine and coarse textured soils. On both soil types barley had a greater number of mainstem leaves which appeared faster than those of wheat and this was associated with greater tillering (6.5 v. 3.5 shoots/plant), higher GAI and greater dry matter production (845 v. 804 g/ m). The difference in yield between the two species was greater on the fine textured soil (15 v. 7 %). Barley also had greater harvest index than wheat (6—15%), and this combined with greater dry matter production on the fine textured soil led to a larger yield advantage over wheat than occurred on the coarse textured soil. Water use efficiency was greater for barley than for wheat on both soils. The greater yield advantage of barley over wheat on the fine textured soil was the result of greater biomass production by barley and greater harvest index. Differences in pattern of water use, and water use efficiency of grain production were associated with greater barley yields but are not themselves considered to be the cause of relative yield differences across soil types. The possible implications of factors such as intrinsic nutrient supply on the 2 soil types in relation to observed yield differences are discussed.

Two newly registered cultivars of triticale, Tiga and Empat, were compared with existing commercial cultivars of triticale, cereal rye and forage oats, for grain yield and dry matter production. Their performance was evaluated at Armidale, New South Wales, over 3 years with varying defoliation regimes (uncut to grain yield, cut in late autumn, cut in autumn and winter, and cut in winter only). Phenological observations confirmed that Tiga and Empat were midseason cultivars, intermediate between Coolabah and Blackbutt oats. Autumn and winter forage production and organic matter digestibility of Tiga and Empat were equal to those obtained from Cooba and Blackbutt oats. Grain yields (up to 4.0 t/ha) of the highest yielding triticale cultivar (Empat) were equal to, or greater than, the best oats cultivar (Blackbutt). Generally, the highest winter growth rates, dry matter yield at maturity and grain yield were recorded from uncut plots, except in the early oats cultivar Coolabah which, in 1 experiment, lodged in spring if left undefoliated through autumn and winter. Cutting only in autumn had small effects (negative) on grain yields, but cutting in both autumn and winter reduced total dry matter yields at maturity by 30% and grain yields by 50%. Cutting only in winter resulted in higher vegetative forage yields than a double cut (autumn and winter), but the single winter cut subsequently produced lowest dry matter yields at maturity. The high grain yields of triticale were linked to rapid spring growth. Harvest indices of triticale cultivars were generally lower than those of the oat cultivars. The results indicate the potential of triticale, especially cv. Empat, as a dual-purpose forage and grain crop.

Summary. This study investigated whether changing phosphatic fertiliser type affects the accumulation of cadmium (Cd) and fluorine (F) in pasture herbage. North Carolina phosphate rock, and partially acidulated fertilisers derived from this rock, generally have higher Cd and F concentrations compared with single superphosphate currently manufactured in Australia. Clover herbage from sites of the National Reactive Phosphate Rock trial was collected and analysed for concentrations of Cd (11 sites) and F (4 sites). A comparison was made between pastures fertilised with 4 rates of single superphosphate, North Carolina phosphate rock, and partially acidulated phosphate rock having Cd concentrations of 283, 481 and 420 mg/kg P respectively, and F concentrations of 170, 271 and 274 g/kg P respectively. One site used Hamrawein (Egypt) phosphate rock (HRP) having a Cd and F concentration of 78 mg Cd/kg P and 256 g F/kg P respectively. To help identify differences in herbage Cd concentrations between sites, unfertilised soils from each site were analysed for total and extractable Cd contents. At one site Cd concentrations in bulk herbage (clover, grasses and weeds) were related to infestation of the pasture by capeweed (Arctotheca calendula L. Levyns). There were no significant differences between F in herbage from plots fertilised with either single superphosphate, partially acidulated phosphate rock or North Carolina phosphate rock, or between sites. Concentrations of F in herbage were low, generally less than 10 mg/kg. However, there were large differences in Cd concentrations in herbage between sites, while differences between fertiliser treatments were small in comparison. The site differences were only weakly related to total or extractable (0.01 mol CaCl2/L) Cd concentrations in soil. Significant differences in Cd concentrations in clover due to fertiliser type were found at 5 sites. North Carolina phosphate rock treatments had significantly higher Cd concentrations in clover compared with single superphosphate at 2 sites. Partially acidulated phosphate rock treatments had significantly higher Cd concentrations in clover compared with single superphosphate at 4 sites. At the site where Hamrawein was tested, this treatment had significantly lower Cd concentrations in clover compared with both single superphosphate and North Carolina phosphate rock treatments.

Summary. The agronomic effectiveness of directly applied North Carolina reactive phosphate rock was determined for 4 years from annual dry matter responses at 26 permanent pasture sites across Australia as part of the National Reactive Phosphate Rock Project. Fertiliser comparisons were based on the substitution value of North Carolina reactive phosphate rock for triple superphosphate (the SV50). The SV50 was calculated from fitted response curves for both fertilisers at the 50% of maximum yield response level of triple superphosphate. The reactive phosphate rock was judged to be as effective as triple superphosphate in the 1st year (and every year thereafter) at 4 sites (SV50 >0.9), and was as effective by the 4th year at 5 sites. At another 9 sites the reactive phosphate rock was only moderately effective with SV50 values between 0.5 and 0.8 in the 4th year, and at the final 8 sites it performed poorly with the 4th year SV50 being less than 0.5. Pasture environments where the reactive phosphate rock was effective in the 1st year were: (i) those on sandy, humic or peaty podsols with an annual rainfall in excess of 850 mm; (ii) those on soils that experienced prolonged winter inundation and lateral surface flow; and (iii) tropical grass pastures in very high rainfall areas (>2300 mm) on the wet tropical coast on North Queensland. The highly reactive North Carolina phosphate rock became effective by the 4th year at sites in southern Australia where annual rainfall exceeded 700 mm, and where the surface soil was acidic [pH (CaCl2) <5.0] and not excessively sandy (sand fraction in the A1 horizon <67%) but had some phosphorus (P) sorption capacity. Sites that were unsuitable for reactive phosphate rock use in the medium term (up to 4 years at least) were on very high P-sorbing krasnozem soils or high P-sorbing lateritic or red earth soils supporting subterranean-clover-dominant pasture, or on lower rainfall (< 600 mm) pastures growing on soils with a sandy A1 horizon (sand component >84%). No single environmental feature adequately predicted reactive phosphate rock performance although the surface pH of the soil was most closely correlated with the year-4 SV50 (r = 0.67). Multiple linear regression analysis found that available soil P (0–10 cm) and the P sorption class of the surface soil (0–2 cm), together with annual rainfall and a measure of the surface soil"s ability to retain moisture, could explain about two-thirds of the variance in the year-4 SV50 . The results from this Project indicate that there are a number of specific pasture environments in the higher rainfall regions of Australia where North Carolina reactive phosphate rock can be considered as an effective substitute P fertiliser for improved pasture.

Summary. This paper examines the response of total annual dry matter production of pastures to a range of rates of phosphate application supplied in fertilisers from various sources. Data from the National Reactive Phosphate Rock Project were used to compare the goodness-of-fit of 2 non-linear regression models, the Mitscherlich and rational functions models, both of which are convex curves lacking an inflection point. These models were fitted to the data from the 2 ‘core experiments’ and tended to give closely equivalent results, with the Mitscherlich model fitting somewhat better in two-thirds of the cases. Generally, both models fitted the data well, with a test for ‘lack of fit’ being non-significant. The models proved capable of fitting all the various responses observed in the 2 experiments, including: (i) the ‘classic’ asymptotic regression response where dry matter production rises gradually with decreasing slope from a baseline at zero added phosphorus to approach an asymptote at very high rates of phosphate application; (ii) a very rapid rise at a low phosphate rate to an almost constant response value with increasing phosphate application; and (iii) an almost linear growth rate with non-zero slope throughout the phosphate application rate range. The Mitscherlich model was generally more stable for the less classical responses, and its parameters were consistently easy to interpret. Hence, the Mitscherlich model is recommended as suitable for describing pasture yield as a function of phosphate application. A new measure of relative fertiliser performance is proposed, based upon the area below the curved line defined by the fitted Mitscherlich curve, which is simultaneously above the horizontal straight line representing the baseline of no added phosphate. The ratio of this area calculated for a test fertiliser to the similarly defined area calculated for a soluble reference fertiliser such as superphosphate serves as a relative performance index. Also, when the area calculated for the reference fertiliser is less than 10% of the total area under the fitted curve, the site is considered to be unresponsive to phosphate addition.