Assessment of selected soil nutrients and irrigation water quality in the dryland area of Chivi district, Zimbabwe

Abstract

The levels of selected nutrients in soils and chemical composition of irrigation water were investigated in 16 villages from the dryland areas of Chivi District in Zimbabwe. The objective was to generate a biophysical knowledge base on the soil fertility status across different villages, and to relate it to site history, management and quality of surface and groundwater used for irrigation. Soil samples were collected from the fields, gardens, cultivated vleis, and virgin land while irrigation water samples were collected from rivers, vlei and shallow wells used to irrigate horticultural crops. Results revealed medium to deficient levels of nitrogen (N) and phosphorus (P) (>75% of the sampled units), and to a lesser degree, potential soil acidity problems on selected fields. The considerably higher soil pH and exchangeable bases in the irrigated gardens and vleis than in the fields and virgin land reflected the impact of management and land utilization. The chemical quality of the sampled water used for irrigation of horticultural crops all showed high chloride hazard. There was need to ascertain the magnitude of crop productivity against applied soil fertility inputs to establish the level and rate of nutrients mining from the soils. Key words: Soil, fertility, dryland, desertification, irrigation.