Root penetration of Lolium perenne on colliery shale in response to reclamation treatments.
Perennial ryegrass cv. S23 was grown on 13 shales in a glasshouse and at 3 field sites with 0, 125 or 625 kg 17-17-17 (NPK) fertilizer/ha (field) or 625 or 1250 kg 10-10-10 (NPK) fertilizer/ha (glasshouse). In a 3rd experiment at 1 site, 50 kg N, 20 kg K and 0-100 kg P/ha as analytical reagent were applied. Limestone was applied at 2.5-12.5 t/ha. Increasing levels of fertilizer increased root penetration considerably, while limestone had a smaller effect. In the field, pH had little effect whereas in the glasshouse root penetration was adversely affected at pH <4.1. In the 3rd trial maximum root penetration coincided with maximum shoot growth; root penetration in this experiment was poorer and this was considered to be related to the lower level of N used. It was considered that there may be a direct stimulation of root growth by the presence of nutrients at a particular depth, and deep incorporation of fertilizers was recommended.