The Development of a Hydraulic Seeding Technique for Unstable Sand Slopes. I. Effects of Fertilizers, Mulches and Stabilizers

Abstract

SUMMARY Hydraulic seeding is used to establish vegetation on steep slopes, but the technique is not reliable. This paper examines the effects of individual components of the technique on the germination and establishment of grasses and legumes on the sand waste left after china clay extraction. The inclusion of fast release compound fertiliser in the hydro-seeding mixture at rates above 125 kg ha- 1 seriously inhibited germination and establishment, especially of legumes. Nitrogen and phosphorus salts had the most inhibiting effect. The effect was reduced by the application of a mulch, which improved moisture levels around the surface-lying seed and increased germination, especially under dry conditions. Seedling establishment was greater on coarse than on fine sand. A peat mulch (0.8 t ha- ') increased establishment nore than did the application of most chemical stabilizers. Certain stabilizers actually inhibited germination, increased sand erosion and reduced the benefits of mulching. Seedling establishment was best on north-facing slopes. The time of sowing, and the prevailing weather conditions, determined the total establishment and determined which species became established. It was concluded that the normal practice should be modified, but that the technique should be flexible to suit the conditions prevalent at sowing. An outline of the components required and the rates of application for the effective hydraulic seeding of sand waste is given.