Abstract: A novel method of studying root interactions in mixtures of small crops (eg. cereals and peas is discussed. The technique involve the measurements of root activity using lithium, a non-radioactive tracer and using a mixture of cereal and peas as an example of a mixed crop where the technique is applicable. Results of studies on root activity of cereals and peas by Tofinga, Tofinga and Snaydon and Tofinga were used in the discussion and to explain how the technique works. The total lithium uptake by cereals was tenfold that of peas and for both species, the uptake decreased with placement depth. Semi-leafless peas absorbed more lithium than leafy peas, by about sixteen times. Lithium uptake by peas was significantly more in monoculture compared with mixtures, in cereals.