Impact of infield irrigation management by Botswana cabbage farmers on soil salinity

Abstract

Some vegetable farmers in the semi- arid Botswana are struggling or closing down their enterprises citing the cost of irrigation and salty water as the problem. Irrigation with water from the salt-laden underground water is known to be the main sources of salts for arid and semi-arid agricultural land. Crops grown in saline environments show symptoms similar to those shown by drought-affected crops hence more irrigation is needed therefore increasing the irrigation cost. Research from other semi arid areas shows that water with high salinity levels can be used for irrigation without increasing soil salinity to values beyond critical levels. A lot of studies have been done which show that the impacts of saline irrigation water depend on the irrigation management. This study therefore aims at recommending infield irrigation management practices to be used by cabbage farmers in Botswana without increase in soil salinity to levels that will affect crop yield. A survey was conducted to identify the infield irrigation management practices presently used by cabbage farmers in Botswana. Rootzone salinity trend due to the identified infield irrigation management was simulated for 20 years using WaSim simulation model. Recommendations on irrigation management practices were made for those soil salinity trends that reached critical levels. It was realised that there are no common infield irrigation management used by farmers. The way farmers manage infield irrigation could not be identified with the factors involved in irrigation scheduling. Infield irrigation management by the farmers contribute to the soil salinity increase in their fields and some of the farmers are already using saline soils. Most farmers are not aware of the saline conditions they are farming on and those who know do not know about the soil salinity measures. The study recommends a need to educate farmers on irrigation under saline environments and also a need for farmers to include soil salinity control in their irrigation planning.