NPP Grassland: Towoomba, South Africa, 1949-1990


[PHOTOGRAPH]
Photograph: General view of study site at Towoomba (click on the photo to view a larger image from this site).

Data Citation

Cite this data set as follows:

Scholes, R. J. 1998. NPP Grassland: Towoomba, South Africa, 1949-1990. Data set. Available on-line [http://www.daac.ornl.gov] from Oak Ridge National Laboratory Distributed Active Archive Center, Oak Ridge, Tennessee, U.S.A.

Description

Productivity of an artificially-established grass savanna was monitored at the Towoomba study site, under a long-term experiment to test the long-term effect of fertilizer application. Peak above-ground biomass was monitored for each treatment, from 1950 to the present.

The Towoomba agricultural research station (24.90 S 28.35 E) is situated 100 km north of Pretoria, near the town of Warmbaths. The savanna-fertilizer experiment is several hectares in extent, with 5 levels of nitrogen and 3 levels of phosphorus laid out in a randomized block design on an area from which all trees were removed. The ammonium sulphate and superphosphate fertilisers were added during November (50% of total), January (25%) and February (25%). The response to N fertiliser saturated at higher levels, so data from only six (3 x 2) of the 15 possible treatment combinations are presented here.

Biomass data are available for every year from 1950 to 1980, except 1976 and 1977. Since above-ground biomass was sampled by mowing to 5 cm height, it is assumed that 50 g/m2 is left in the field, plus an additional 5% of the mown dry weight. Soil nutrients were measured in 1962, 1980 and 1990, and 1949 estimates were inferred in 1990 from undisturbed savanna adjacent to the experiment.

Over 30 years, mean above-ground net primary production (ANPP) was estimated at 198 g/m2/yr (mown weight = 141 g/m2) for the control non-fertilised plots, rising to 607 g/m2/yr (mown weight = 530 g/m2) for plots fertilised annually with 151/167 kg N/ha and 37.7/52.7 kg P/ha (P2N3 treatment). Some uncertainty exists over the precise fertiliser application rates, according to the plot sizes assumed.

Contact Information

Contact: Dr. R. J. Scholes
Forestek
CSIR
P.O. Box 395
Pretoria 0001
SOUTH AFRICA

Telephone: +27 (12) 841-2045
Fax: +27 (12) 841-2689
E-mail: bscholes@csir.co.za

Click on the following linked phrase to view references and summaries.