New Zealand Journal of Agricultural Research abstracts
Effects and interactions of phosphorus and sulphur on a mown white
clover/ryegrass sward
2. Concentrations and ratios of phosphorus, sulphur, and nitrogen in clover
herbage in relation to balanced plant nutrition
A. G. SINCLAIR
J. D. MORRISON
L. C. SMITH
K. G. DODDS
AgResearch
Invermay Agricultural Centre
Private Bag 50034
Mosgiel, New Zealand
Abstract Phosphorus (P), sulphur (S), and nitrogen (N)
concentrations were measured on white clover herbage from a fertiliser field
trial on a mown white clover/ryegrass sward involving 5 rates of P by 5 rates
of S in a factorial design. Samples were analysed from two harvests in
Year 1 and three harvests in Year 2 of the trial. P fertiliser markedly
increased % P and slightly reduced % S in white clover, whereas S fertiliser
had corresponding effects on the percentages of S and P in white clover. % N in
white clover was increased by P fertiliser in Year 1 and by S fertiliser in
both years, with S fertiliser having much the larger effect. By relating
herbage chemical composition to white clover DM yield response patterns, S/P
ratio in white clover herbage corresponding to balanced nutrition was
calculated to be 0.63 in Year 1 and 0.72 (at high fertiliser rates) in Year 2.
When calculations were based on white clover N uptake instead of white clover
DM, S/P ratio for balanced nutrition was 0.04-0.06 higher, whereas calculations
based on total DM gave a lower balance ratio than those using white clover DM.
Because S fertiliser costs much less per kg of nutrient than P fertiliser,
white clover S/P ratios arising from economically optimal fertiliser S:P ratios
were higher than those for balanced nutrition. It was calculated that white
clover S/P ratios could range by 0.05 on either side of the economic optimum
without significant economic effects and it was concluded that for a
well-balanced fertiliser policy white clover S/P ratios should be within the
range 0.70-0.80. During the year following fertiliser application, initially
high S/P ratios in white clover herbage declined but low ratios remained
relatively unchanged.
Keywords balanced nutrition; economics; fertiliser; nitrogen;
nutrient ratios; pasture; plant analysis; phosphorus; sulphur; white clover
New Zealand Journal of Agricultural Research, 1996, Vol. 39: 435-445
0028-8233/96/3903-0435 $2.50/0 (c) The Royal Society of New Zealand
1996
PDF file of entire paper: medium quality (1101K); (scanned from paper original: notes about this process)
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