SOME EFFECTS OF SOIL WATER CONDITIONS AND SOIL TEMPERATURE ON THE ROOTS OF GRASSES

The effect of irrigation on the weight of roots and on the vertical distribution of roots by weight in the soil profile under grass and grass/clover swards was examined in several field experiments.
The weight of root material was less under irrigated swards than under those which were subject only to natural rainfall; it is postulated that this occurred because dead roots decayed more rapidly in the irrigated swards. There was little evidence to suggest that irrigation had any major effect on the vertical distribution by weight of roots within the soil profile.
There was a significant interaction between nitrogen and irrigation; in the un-irrigated swards, root weight decreased with increased N but on the irrigated swards the highest root weight was at an intermediate level of applied N.