A non-destructive technique for studies of root distribution in relation to soil moisture

The minirhizotron technique is simple, non-destructive and can give detailed information on root growth dynamics. This method can easily be used to monitor the number of roots at several depth levels and in several experimental treatments. It was used in a field experiment on clay soil where winter wheat was subjected to different irrigation/fertilization combinations. Soil water content around the rhizotrons was measured at 6-cm depth intervals using a capacitance probe, which was gradually lowered into the minirhizotrons. The same depth intervals were used for making root observations, and moisture was measured shortly after making the root counts, resulting in a data set with a one-to-one correspondence between root counts and soil water content. Estimates of soil water content were corrected for the soil cracking that occurred at low water contents. Other variables, e.g. changes in moisture over time and soil water tension, were calculated. Correlation and regression techniques were applied to variable pairs of the whole data set and subsets thereof. Potential applications, improvements and expansions of the technique are discussed.