The development of a hydraulic seeding technique for unstable sand slopes. 1. Effects of fertilizers, mulches and stabilizers.
Hydraulic sowing is used to establish vegetation on steep slopes, but the technique is not reliable. 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 were examined. The inclusion of fast-release NPK compound fertilizer in the hydro-sowing mixture (75% perennial ryegrass cv. S23 + 25% white clover cv. S184) at rates >125 kg/ha seriously inhibited germination and establishment, especially of legumes. N and P 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. Peat mulch at 0.8 t/ha increased establishment more 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 N.-facing slopes. The date of sowing and the prevailing weather conditions determined the total establishment and determined which spp. 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 sowing of sand waste is given.