SOIL FERTILITY ANALYSIS RESULTS

The following tables record the results of laboratory analyses on series of soil samples collected in the Wola region. Some of these soil analysis data feature in the investigation of soil fertility under cultivation (see Chapter 12).

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Explanation of the Tables

All of the soil samples are composites. Subsamples of soil were collected at random across the sites (from 0 to 10 cm depth for topsoils, and from whatever depth the horizon started for subsoils, on average at a depth of between 15 and 20 cm). Between 10 and 20 spots were sampled at each location (depending on swidden size), while walking about it. The soil collected was mixed up, and a coned and quartered sample bagged after drying in the sun. The samples were subsequently ground to pass a 2 mm sieve before analysis (Anderson & Ingram 1993). All of the soils were analyzed for the principal fertility indicators – pH, phosphorus, exchangeable cations, organic carbon and nitrogen – and some of them were tested for other measures – such as boron, base saturation, aluminium and sodicity.

The experimental procedures followed in analysing the soil samples are detailed in notes 6 to 23. According to Macfarlane & George (1987), the soil tests used here for the major nutrients of nitrogen, phosphorus and potassium correlate well with yield and nutrient uptake by glasshouse grown maize, in soils similar to those investigated here, from the Mendi valley in the Southern Highlands Province (although Floyd et al. 1987:19 report that soil analyses were poor indicators of differences in crop response).

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