In the Canterbury Mountains of South Island, New Zealand, revegetation trials were established at two eroded mountain sites to study establishment, growth and survival of four native tussock grass species when sown with or without cover nurse crop species.
At Porter's Pass (975 m) on 20 October and Craigieburn (990 m) on 25 October 1967, five cover treatments (non-native species) with four replicates were sown (broadcast) in plots (size not given) at a rate of about one seed per square inch (2.5 x 2.5 cm):
1. No seeding (control);
2. Inoculated white clover Trifolium repens (Huia cultivar);
3. Chewing’s fescue Festuca rubra commutata;
4. common bent (browntop) Agrostis tenuis;
5. Yorkshire fog Holcus lanatus.
Twenty seeds of each of four native tussock species (mountain danthonia Notodanthonia setifolia, blue tussock Poa colensoi, hard tussock Festuca novae-zelandiae and silver tussock Poa laevis) were planted just beneath the soil surface. Within each plot a total of 80 seeds of the four species were sown (400 seeds within each replicate; 1,600 seeds/site). Fertiliser was applied to each plot.
At Porter's Pass, tussock seedling survival and growth was recorded in December 1967, May 1968, September 1968 and April 1969, and at Craigieburn in May 1968 and May 1969.
Mountain danthonia seedling emergence was very low (3% germination). The other three species did better: blue tussock (Porter's Pass 35%, Craigieburn 14%) hard tussock (Porter's Pass 54%, Craigieburn 27%) and silver tussock (Porter's Pass 53%, Craigieburn 34%). Highest tussock seedling emergence occurred in controls, with a trend towards lower emergence the higher the cover crop density.
However, tussock seedling survival over the first 18 months was positively related to the amount of cover present e.g. in 1969 at Craigieburn average percent survival (and % cover): control: 98% (54%); clover: 77% (41%); fescue 89 (54%): bent: 96 (85%); Yorkshire fog: 89% (59%).
Growth of tussock seedlings was slow. Tiller number (range 2.7-13.5 in 1968) tended to be greatest in plots with least cover species. This is attributed to less competition for nutrients leading to greater tillering (and larger tussocks), but countered by lower survival in the controls. Most tussocks decreased in size during the second growing season. The results of the trials were considered disappointing; low seedling numbers were caused in part by bad weather (especially at Craigieburn where snow and a rapid thaw caused severe surface wash and erosion).
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