TUSSOCK GRASSLAND

New Zealand Journal of Agriculture, Volume 89, Issue 4, 15 October 1954, Page 397

TUSSOCK GRASSLAND

EXPERIMENTAL work in depleted tussock grassland follows a definite pattern. Nursery rows indicate what species of grasses and clovers are adapted to the particular soil and environment. Then come plot ; sowings which provide information about the best time to sow, how much to sow, and compatibility among species to afford cover and/or production. At this stage the grazing animal is introduced, but so far the studies have been purely observational and the measuring rod has been the survival of the grass when grazed by sheep.

LARGE-SCALE TRIALS

AFTER this information has been secured the next stage is relatively large-scale trials to make sure that the results on a small area

can be related to the improvement of the depleted country as a whole. In Central Otago most of this basic information has come from the Cockayne plots (sown 1920 to 1922) and from the Pisa Experimental Area. By 1948 a large-scale trial was considered necessary. The difficulty lay in the choice of a suitable site, the main requirement being freedom from rabbits. In addition, seed of the species to be sown was in short supply. The area finally selected was on the property of Mr D. J Kane near Hawea Flat. It consists of some 80 acres containing both exposed and shady faces and ranging from about 1200 ft. to 2000 ft. in altitude. Most of the block was depleted, with scabweed as the dominant vegetation on the sunny faces and sorrel and bidi-bidi on the dark faces.

Half of the block was left as a control and the remainder was divided into three, on the basis of aspect, and different seed mixtures were sown by hand on these in March 1949. Apart from a few rabbits the area remained unstocked until May 1953, when 42 fine-wool hoggets were put on for 5 months.

RESULTS OF TREATMENTS

For the first 2 years there was only a slight response to oversowing. On the sunny slopes some plants became established, but

these seemed to be barely existing and provided little growth. On the moderately sheltered and dark faces a better establishment was obtained, but again there was little growth. However, in the third and fourth years the picture changed. Wherever there was any depth of soil sown species made vigorous growth and set seed. The following summarises results so far:—

On exposed sunny faces there has been poor, patchy establishment of tall oatgrass and Danthonia pilosa. Only where there is any depth of soil is there evidence of seeding of these. On the lower slopes there has been a recovery of native species, particularly plume grass and blue wheatgrass. Over most of these areas, however, improvement as measured in terms of increase in perennial grasses has been slight.

On shady slopes with a fair to good soil cover and enjoying some protection from wind and sun there have been two distinct responses to the treatments applied. In the most sheltered sites the response has been a dense and vigorous establishment of sown species, mainly tall oatgrass with cocksfoot, sheep’s burnet, yarrow, sweet vernal, and browntop. There is a carpet of tall oatgrass seedlings, and the resultant sward has largely crowded out the original cover of sorrel, bidi-bidi, and Canadian thistle. On less sheltered sites, however (and this is more noticeable with increasing altitude), the response has been recovery of native tussock species. At the time of sowing, these plants appeared to be dead or almost so, but spelling has permitted their regrowth and oversowing has resulted in only slight establishment and then only where there is more than about a square yard of bare ground. Recovery of the natives has involved good growth of hard tussock, blue wheatgrass, and blue tussock.

PRESENT CONCLUSIONS

On bare, exposed slopes with little or no soil cover no exotic species have been found which can establish and thrive after

oversowing. It may be that the use of native species and strains would give better results, but the problem is difficult. Wherever there is an open, friable surface and some soil there are species which will grow and set seed, but the cover will take a long time to thicken up. On dark faces there is quite a range of species which will establish and which will rapidly provide a dense, useful sward. Wherever there is an existing cover of tussock, whether this is vigorous or merely recovering from ill treatment, oversowing of introduced grasses has been disappointing. In all cases, however, it must be stressed that proper management is essential if any improvement is to be effective and permanent. Species must be spelled at regular intervals to permit reseeding and a proper intensity of utilisation maintained.

—J. M. HERCUS * * * . *

-..me,,,,,,.,OVERSOWING SUBTERRANEAN CLOVER

IN most districts autumn sowings finally result in a better density of clovers, though early spring may give a greater strike. There is always the risk with

subterranean clover that this annual plant will not have the opportunity to flower and set seed if sown in spring. In two time of sowing trials, one in the Hamilton district and one in the Wellington district, 1 the sowings of subterranean clover made in May and August gave the highest numbers of germinated clovers. In the Hamilton trial a January sowing was also made, and though the number of clover plants was as high as that of the May sowing, the wet 1953 summer was favourable to the initial growth of subterranean clover. From results of a time of sowing trial at Invermay' Research Station it can be recommended that subterranean clover should not be sown later than February in districts where severe frosts occur or frost lift will cause a low survival of seedlings. 'c? / !

—S. M. MACLEAN