The use of stable isotopes to quantify nutrients uptake efficiency from compound fertilizers

Transcription

1 The use of stable isotopes to quantify nutrients uptake efficiency from compound fertilizers B. Ajiboye, T. McBeath, F. Degryse, J. Kirby, S. Stacey, and M. McLaughlin The University of Adelaide, AUSTRALIA

2 Fertilizer, an essential input A must for the production of food, fibre and biofuel Slide 1

3 Maximizing fertilizer use efficiency 4R principle right source right time Measuring efficiencies Improve recommendations Refine fertilizer formulations right rate right application method + _ Slide 2 Indirect difference method

4 Enriched stable/radioisotope labeled fertiliser Direct method with isotopes Harvest shoot Determine % plant nutrient derived from fertilizer Efficiency of fertilizer Slide 3 Unavailable Available

5 Stable isotope, an alternative Stable isotopes in use: 34 S 67 Zn 65 Cu 10 B 97 Mo Slide 4

6 Sulfur fertilizer efficiency S⁰ oxidation depends on: Soil temperature Soil moisture Particle size of S⁰ S⁰ SO 4 2- Microbial oxidation H + SO 4 2- SO 4 2- SO 4 2- Slide 5

7 MAP labeling with enriched 34 S Slide 6 Total S (%) = 10.9 ± 0.2 SO 4 -S (%) = 5.4 S (%) = S = atom-% Particle size within range reported for % oxidation in a 1-yr best case scenario

8 Pot trials.. Growth conditions : 20 C/15 C day/night temp 14 h photoperiod 5 Growth periods: 6, 8, 10, 12, 14 wk Slide 7

9 34 S analyses and calculations Atom-% of 34 S measured by CF-IRMS % plant S derived from fertilizer Allowed for direct calculation of efficiency Slide 8 Continuous flow isotope ratio mass spectrometer (CF-IRMS)

10 Cumulative S uptake from 34 S Cumulative 34 S added taken up (%) st Crop - Canola ES Efficiency Cumm. total S uptake 2nd Crop- Canola 3rd Crop - Wheat Time since application (weeks) Cumulative S uptake (mg/pot) Slide 9

11 Ongoing field trials Slide 10

12 Zinc fertilizer efficiency Slide 11 Cakmak Life Impact et al. The 2010 University of Adelaide

13 Pot trials with enriched 67 Zn DAP granule coated with 3µL of 67 Zn 4 soils x 3 fertilizers 1. Control Zn labeled 3. Unlabeled Zn Soils Labile Zn (mg kg -1 ) Kandosol 0.4 Hypercalcic Calcarosol 1.9 Red Sodosol 4.9 Red Chromosol 12.7 Slide 12

14 Field trial with 67 Zn Plant harvested at mid-tillering maturity Slide 13

15 67 Zn: 66 Zn ratios measurement Argilent 7500ce ICP-MS Collision gas: He Flow rate: 4 ml min -1 Concentration: 40µg/L Double charged species minimized (m z & 140) < 2% Slide 14 Interference of 134 Ba ++ up to 500 µg Ba L -1 with 67 Zn was ca. 2.9 % and corrected for.

16 % Zn derived from fertilzer Zn derived from fertilizer Kandosol Calcarosol Sodosol Chromosol Labile soil Zn (mg/kg) Slide 15

17 Zn precipitation in granules 90% Zn remained in granule Zn diffusing into soil Zn still in granule 5 mm Slide 16 Hettiarachchi Life Impact et al. 2008: The Soil University Sci. Soc. of Amer Adelaide J.

18 Conclusion Tracing method with stable isotopes allows for measurement of fertilizer efficiency over several seasons.. Fertilizer with elemental S has a high residual efficiency Zn coated fertilizer showed a very low efficiency With this method, efficiencies of different fertilizer formulations/design can be compared Slide 17

19 Acknowledgement Funding: Technical Assistance: Claire Wright, Sarah Noack, Margaret Yam and Caroline Johnston for analyses and to David Chittleborough for soil classification Slide 18

20 Thanks for your attention For further enquires: Dr Babasola Ajiboye Slide 19