Predicting the response of wheat (Triticum aestivum L.) to liquid and granular phosphorus fertilisers in Australian soils

Abstract

Liquid forms of phosphorus (P) have been shown to be more effective than granular P for promoting cereal growth in alkaline soils with high levels of free calcium carbonate on Eyre Peninsula, South Australia. However, the advantage of liquid over granular P forms of fertiliser has not been fully investigated across the wide range of soils used for grain production in Australia. A glasshouse pot experiment tested if liquid P fertilisers were more effective for growing spring wheat (Triticum aestivum L.) than granular P (monoammonium phosphate) in 28 soils from all over Australia with soil pH (H2O) ranging from 5.2 to 8.9. Application of liquid P resulted in greater shoot biomass, as measured after 4 weeks’ growth (mid to late tillering, Feeks growth stage 2–3), than granular P in 3 of the acidic to neutral soils and in 3 alkaline soils. Shoot dry matter responses of spring wheat to applied liquid or granular P were related to soil properties to determine if any of the properties predicted superior yield responses to liquid P. The calcium carbonate content of soil was the only soil property that significantly contributed to predicting when liquid P was more effective than granular P. Five soil P test procedures (Bray, Colwell, resin, isotopically exchangeable P, and diffusive gradients in thin films (DGT)) were assessed to determine their ability to measure soil test P on subsamples of soil collected before the experiment started. These soil test values were then related to the dry matter shoot yields to assess their ability to predict wheat yield responses to P applied as liquid or granular P. All 5 soil test procedures provided a reasonable prediction of dry matter responses to applied P as either liquid or granular P, with the resin P test having a slightly greater predictive capacity on the range of soils tested. The findings of this investigation suggest that liquid P fertilisers do have some potential applications in non-calcareous soils and confirm current recommendations for use of liquid P fertiliser to grow cereal crops in highly calcareous soils. Soil P testing procedures require local calibration for response to the P source that is going to be used to amend P deficiency.

Predicting availability of mineral elements to plants with the DGT technique: a review of experimental data and interpretation by modelling

“…To our knowledge, there is only one study that assessed the critical DGT concentration for the P deficiency of plants grown under field conditions. [98] A critical c DGT of ∼3.2 µM, above which no response of wheat to P application was observed in field trials, was derived, whereas the critical c DGT for the same plant species under laboratory conditions was ∼1.2 µM, [74] which supports our hypothesis of lower critical DGT concentrations for field conditions.…”

“…The DGT method also well predicted responsiveness of wheat to liquid P fertilisers, with a critical c DGT of ∼1.2 µM (c E ∼16 µM), for a range of acidic and neutral soils. [74] Similarly, the DGT method well predicted wheat responsiveness to applied P in a growth cabinet experiment, with a critical c DGT of ∼1 µM (S. Mason, R. Hamon, J. Anderson and H. Zhang, unpubl. data).…”

“…[73,74] Ferrihydrite is then used as binding agent instead of Chelex. Ratios of c DGT to P concentration in a stirred solution were unaffected by varying pH (pH 3-9) and by increasing concentrations of chloride, sulfate and nitrate, while bicarbonate decreased c DGT , but only at very high concentrations that are unlikely to occur in soil solutions.…”

“…Triticum aestivum Cd, Zn, Pb: shoot concentrations well correlated with DGT and soil solution [3] concentrations; Cu: shoot concentration best correlated with total Cu, weakly correlated with DGT concentration P 2 4 Lycopersicon esculentum, Triticum aestivum P deficiency assessed by yield response to P fertilizer; DGT provided [73,74] excellent separation of responsive and non-responsive soils A The 28 samples from four sites at various Zn levels (field contaminated or laboratory spiked).…”

World Phosphorus Use Efficiency in Cereal Crops

“…They studied P availability in calcareous soils and compared granular and fluid P fertilizers, and that confirmed P being more available to plants when applied as a liquid. McBeath et al (2007) also recommended liquid P over granular forms, and their effectiveness for wheat in calcareous soils. Foliar P fertilization is recommended in dry environments, soils with elevated P-fixing capacity, and soils that are marginally deficient in an effort to avoid pathways that promote loss of soil P. Relatively low rates are used for foliar applications; therefore, foliar P fertilization normally improves PUE.…”