Calibration of a lime requirement buffer for site-specific lime applications in South-Eastern Australia

1999

R.A. Viscarra Rossel and A.B. McBratney
Australian Centre for Precision Agriculture, McMillan Building A05, The University of Sydney NSW 2006, Australia.

In J.V. Stafford (ed.) Precision Agriculture '99, Vol. I, pp. 429-440.

ABSTRACT

The reliability of lime requirement maps for site-specific management depends on the inherent soil variability, the sampling strategy used, the accuracy and precision of the analytical procedure and the spatial methods used for continuous-map production. This paper deals with the development of a statistical calibration method for the SMP (Shoemaker, McLean & Pratt) buffer procedure for determining lime requirement (LR), which may be suitable as a component of a decision support system (DSS) for Precision Agriculture. The accuracy and precision of the buffer with response surface-type calibration is compared to standard incubation-determined lime requirements. We show that the SMP buffer and response surface calibration produce accurate and precise results, giving the procedure versatility to the choice of target pH without the need of excessive specific target pH calibrations. Lime requirement maps derived using this calibration and its 95% confidence intervals show the reliability and precision of the procedure. The maps produced by block kriging, also illustrate the spatial distribution of limits for the lime requirement to target pH 6.5 data, the field showing little variability. Finally, two maps were produced to illustrate the economic and agronomic benefits of site-specific lime applications.