New Zealand Journal of Agricultural Research abstracts

---

Potassium-supplying power of selected Pallic soils of New Zealand 2. Soil testing procedures

A. Surapaneni*
R. W. Tillman^†
J. H. Kirkman
P. E. H. Gregg

Institute of Natural Resources
Massey University
Private Bag 11 222
Palmerston North, New Zealand

A. H. C. Roberts^†

AgResearch
Ruakura Agricultural Centre
Private Bag 3123
Hamilton, New Zealand
*Present address: Institute of Sustainable Irrigated Agriculture, NRE Tatura, Private Bag 1, Ferguson Road, Tatura, Victoria 3616, Australia.
^†Present address: Ravensdown Fertiliser Co-operative, P.O. Box 608, Pukekohe, New Zealand.

Abstract  A previous study showed that there were large differences in the uptake of non-exchangeable K (K_nex) by ryegrass grown in a glasshouse trial between 19 selected Pallic soils from both North and South islands. The present study evaluated a range of soil testing procedures for K for their ability to explain the variability between the 19 soils in both the uptake of total K from the soil and also the apparent uptake of K_nex. A new, simple soil testing procedure, involving extraction of soil K with dilute nitric acid (HNO₃-K), was found to be superior to a number of other published procedures, including estimates of exchangeable K (such as Quick Test K) and reserve K (involving multiple extractions with nitric acid), when correlated with dry matter yield and K uptake. An estimate of step K, calculated as the difference between HNO₃-K and Quick Test K, proved to be better than reserve K in explaining variations in K_nex uptake. The proposed HNO₃ extraction procedure is simple, cheap, and effective. Its validity should be tested under field conditions.

Keywords  nitric acid extractable K; step K; reserve K; Quick Test K; sodium tetra-phenylboron K; yellow-grey earth soils; Pallic soils

A00012 Received 29 February 2000; accepted 22 April 2002
New Zealand Journal of Agricultural Research, 2002, Vol. 45: 123–128
0028–8233/02/4502–0123 $7.00/0 © The Royal Society of New Zealand 2002

PDF file of entire paper: Print-quality (25K)

---

This year's abstracts | Journal home page | All abstracts | Publishing home page