is shown in the attached graph. The graph was made with the SegReg program, see segmented regression. When analysing field data with random variation a proper application of statistical principles like in regression and frequency analysis is necessary. Soil salinity control In irrigated lands, subsurface drainage may be required to leach the salts brought into the soil with the irrigation water to prevent soil salination. Agro-hydro-salinity and leaching models like SaltMod may be helpful to determine the drainage requirement. References External links Website on land drainage : Articles on agricultural land drainage : Frequently asked questions about drainage : Case studies on land drainage : Software on land drainage : Soil science Environmental soil science Hydrology Drainage