Sub-surface injection of liquid waste

Abstract

The sub-surface injection of sewage sludge in grassland conditions has been investigated showing that injection is a viable alternative technique to surface applications. With the large amounts of existing liquid wastes, either municipal or agricultural, the land required for injection has risen over the available grassland. This study has considered the sub-surface injection of sewage sludge in a growing crop of spring wheat.

The agronomic response of spring wheat has been compared at three different levels of crop development. Five different techniques were used to inject the sludge, and compared with two control situations. Using a three leg injector, with the outside tines bent, and placing gaps between rows for the tines and wheels, the crop showed a better agronomic response at the final levels of development.

Analysing row by row the dry matter production in the injected plots, it was clear that the lower global production per square metre was due to the damage caused in the rows by the legs and traffic.