New Zealand Journal of Agricultural Research abstracts
The availability of native and applied soil cobalt to ryegrass in relation
to soil cobalt and manganese status and other soil properties
Z. Li
R. G. Mclaren*
Soil and Physical Sciences Group
P.O. Box 84
Lincoln University
Canterbury, New Zealand
A. K. Metherell
AgResearch
c/o Soil and Physical Sciences Group
P.O. Box 84
Lincoln University
Canterbury, New Zealand
*Author for correspondence
Abstract A glasshouse pot trial was conducted using 18
New Zealand grassland soils to assess the effects of soil manganese (Mn) and
cobalt (Co) status, Co fertiliser and soil moisture conditions, on the plant
availability of soil Co. The uptake of native and applied Co by ryegrass was
measured, and attempts made to determine the main factors influencing plant
Co concentrations. There were highly significant relationships between ryegrass
Co concentrations and total soil Mn, and EDTA-extractable and CaCl2-extractable
soil Mn; ryegrass Co concentrations decreasing in a curvilinear fashion with
increasing soil Mn levels. Similar relationships were observed between ryegrass
Co concentrations and Mn determined in individual soil fractions as determined
using a sequential fractionation technique. It was therefore clearly demonstrated
that soil Mn status plays a crucial role for soil Co availability. Soils with
high Mn contents have a high probability of strong fixation of soil Co and
showed negligible responses to Co fertiliser treatment. For the soils in
this study, which had a large variation in Mn status, soil Co extractants
were poor predictors of Co availability to plants. However, soil Co fractionation
data suggests that Co in the organic-bound fraction is probably one of the
important sources of supplying Co in soils for plant uptake.
Keywords cobalt; manganese; ryegrass; soil moisture
A02058; Received 2 September 2002; accepted 7 August 2003; online publication
date 26 February 2004
New Zealand Journal of Agricultural Research, 2004, Vol. 47: 33-43
0028-8233/04/4701-0033 © The Royal Society of New Zealand 2004
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