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 (Knex) 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 Knex. 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 Knex 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)
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