This paper describes a method that can be used by individual cotton growers and/or cotton consultants to estimate the potential deep drainage. To do this the initial work undertaken was to identify the minimum number of observations that need to be taken to in a cotton field to give a good estimate the potential deep drainage (Figure 1). Once the number of observations needed was known the next stage involved estimating the sub-soil hydraulic conductivity using the falling head lined-borehole technique (FHLBT). To calculate the potential deep drainage also requires an estimate of how many days the sub-soil is saturated for, which growers can determine by knowing the soil moisture after irrigation using their C-probe data (Figure 1). The data generated by the growers is managed by the user-friendly Potential and Required Deep Drainage Interface housed in Microsoft EXCEL. To make the estimate of potential deep drainage more meaningful growers are also asked about the quality of their irrigation water and the crops that are to be grown during the season. This information is used to by the Potential and Required Deep Drainage Interface to determine the leaching requirement that is needed to prevent excess salts build up in the sub-soil that may affect crop yield.