A study was carried out to examine distribution of salt affected soils by types and extent in the Ndungu Agricultural Development Project (NADP) area of Tanzania. The objective was to generate information to guide salt-affected soil management for sustainable rice production. Conventional methods including use of mini-pits and profile pits, coupled with farmers’ experiences were used to characterise soil. A total of seven randomly selected soil profile pits located in major soils were dug and described. Soil was sampled from natural horizons for laboratory analysis. In addition a total of 158 topsoil (0 – 20 cm depth) composites soil samples were randomly collected from 90 sites of NADP project area for laboratory analysis. Results showed that a few blocks (block is a piece of farm of 6 to 12 acres) had high exchangeable sodium percentage and high levels of bicarbonates, indicating salt-affected soils. Soil pH, exchangeable sodium percentage (ESP), and electrical conductivity of soil paste extract (ECe) values as high as 9.06, 28.7 cmol(+)Nakg-1, and 14dSm-1 were measured. Out of 90 blocks, 10 blocks (11%) showed slight to strong salt effects. Two blocks (2%) has been abandoned, and in some cultivated blocks zero yields were recorded due to salt content. The different levels of salinity development in the project area suggest site-specific remediation and appropriate management options be developed to improve crop production. These include rehabilitation of the irrigation infrastructure, use of farmyard manure as a soil amendment and growing salt-tolerant rice varieties. Furthermore, it is important to create awareness among farmers of the problem of salt-affected soil on rice productivity.
Hydraulic conductivity in response to exchangeable sodium percentage and solution salt concentration
