Characterisation of farming systems in southern Rwanda

III.2.4. data collection

In order to have fair or accurate information and to be able to verify our hypotheses the following methods and techniques were used.

III.2.5. Methods and techniques

Descriptive method: This method helped us to characterize the production systems. For this we made recourse to the documentary technique. We consulted the documents available related with our study and compile an extensive literature review. The technique of direct observation was also used when farmers could not answer correctly certain questions like those concerning the acreage (cultivated area), farm size, the application of some cultural practices, etc. We went on ground to observe in order to collect reliable information about our study.

Survey method: A structured questionnaire was used to collect the essential information from farmers on their farms.

Technique of soils sampling: Topsoil (20cm) samples were taken directly with an auger at five points per plots according field variability from all the production units (closest, middle, remote field) identified in the farms visited after farmer interview, A composite sample of approximately 0.75kg from each field was taken to the laboratory for soils analyses. Soils samples were air dried, sieved through 2mm and 0.5mm and then stored at room temperature.

The soils analyses method: The major chemical elements, namely N P K as well as organic carbon and pH were analyzed:

v Organic carbon was determined using the method of Schlichting, Blume (1966), consisting of humid oxidation of organic matter. The combustion is done by K₂Cr₂O₇ in the presence of H₂SO₄ concentrated and the carbon rate is measured by reading on spectrophotometer of 60 nm length (Baize, 2000).

v Total nitrogen was determined by the method of Kjedhal which encompasses mineralization of organic nitrogen by H₂SO₄ concentrated, distillation and titration of ammoniac by H₂SO₄ N/70 (Baize, 2000).

v Exchangeable Potassium was extracted by NH₄AC at soil pH of 7. Its content in solution was determined on spectrophotometer of atomic absorption (Juo, 1978).

v Available phosphorous was determined by Bray 1 method consisting of extraction of phosphates by ammonium ions (Baize, 2000)

Results analysis and interpretation: results were analyzed using excel to check eventual errors and SPSS for further analysis that allowed us to get coherent answers. Tables and pie charts were used to represent average values of different wealth groups; Data at plot level were also presented to indicate variability of soil fertility within farm. The statistical means between field types for nutrient status in the soils was assessed using Excel to compare soil fertility of different farms and different fields within farm.