The Distribution of Mg, P and K in the Split Roots of Subterranean Clover

The aim of these experiments was to determine whether uninhibitedroot growth is possible in a soil lacking Mg, provided thatthe plant is adequately supplied with Mg from another regionwithin the soil. Two experiments were undertaken using splitroot systems in free-draining sand or gravel irrigated dailywith nutrient solution. Magnesium supply to one half of theroot system was varied and root growth in the deficient partof the system was measured. Magnesium redistribution was comparedto that of calcium, phosphorus and potassium. Magnesium content of the roots grown in the compartment withno Mg supply increased, but only when the shoots had an adequateto luxury Mg status. Even under these conditions root growthwas inhibited compared to roots with an adequate external supplyin both compartments. Similarly potassium was transferred tothe roots with no external supply, but root growth was retardedin this compartment. Roots proliferated in the compartment suppliedwith phosphate and did so at the expense of growth in the non-supplycompartment. The shoots had a barely adequate phosphorus statusand there was no transfer of phosphorus to the root with noexternal supply. Magnesium, phosphorus, potassium, root growth, split root systems, subterranean clover, Trifolium subterraneum L.