New Zealand Journal of Agricultural Research abstracts

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Sustainability of New Zealand high-country pastures under contrasting development inputs. 5. Nutrient pools and balances

D. SCOTT

AgResearch
P.O. Box 60
Lincoln, New Zealand

Abstract  The nutrient fluxes, pools, and balances for N, S, P, and Ca were estimated for two sheep-grazed mixed species studies on a Pukaki/Tekapo high-country soil from measurements during the 10-15th years following initial development. One compared 30 combinations of 5 superphosphate rates (0-500 kg ha^-1 yr^-1) x 3 stocking rates x 2 stocking methods x 2 spatial replications; the other compared 27 combinations of P and S fertiliser (0-100 kg element ha^-1 yr^-1). The stock off-take under zero fertiliser was 1.1, 0.1, 0.2, and 0.4 kg ha^-1 yr^-1 for N, S, P, and Ca, respectively. Fertiliser inputs exceeded stock off-takes by 4-100-fold in fertiliser treatments. The 10-year stock off-take was similar to the 1-year spring shoot pool. C and N were principally in the soil fraction. Estimated N fixation was 150-223 kg N ha^-1 yr^-1 in the fertilised treatments. Increases in the components of the S pools in the shoots and soil to 40 cm accounted for 46-56% of the applied S in the dryland fertilised treatments and 21% in the irrigated high fertiliser treatment. Residual elemental S accounted for 11-21% of applied S. Much of the P and Ca were in the coarse organic matter pools. P and Ca pools did not increase in proportion to fertiliser rates. There was an apparent loss of total P to levels similar to double the applied fertiliser rates, possibly from change in datum sampling depth due to measured soil expansion. There was less than 2% movement of nutrients into sheep camps.

Keywords  New Zealand; high country; Ca; sustainability; nutrient balance; N; S; P

New Zealand Journal of Agricultural Research, 2000, Vol 43: 415-438

0028-8233/00/4303-0415 $7.00/0 (c) The Royal Society of New Zealand 2000

PDF file of entire paper: medium quality (4735K); (scanned from paper original: notes about this process)

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