VALUE OF RICE GRASS.

New Zealand Herald, Volume LXIX, Issue 21098, 4 February 1932, Page 14

VALUE OF RICE GRASS.

USE ON TIDAL FLATS. AID IN RECLAMATION. The uso of Spartina Townsenilii, or rico glass, in tlio reclamation of tidal flats lias a particular significance in Now Zealand, where, in the northern districts especially, considerable areas of this nature exist. For the last seven or eight years the economic possibilities of the grass in the rehabilitation of lands subject to sea erosion have been diligently investigated both in Holland and in Essex, England, and progress has been such that some effort to apply the new knowledge in appropriate New Zealand areas seems highly desirable. Perhaps tlio most striking results to date have been secured in Holland, bold and large-scale experiments in Zeeland and in Uie estuary of the Scheldt having been carried out with signal success by the Dutch reclamation officers. The results in the Eloedam area, particularly, have been referred to by experts as a classic example of a pioneering effort in an entirely new reclamation technique. Here, in 1928, four years after the commencement of planting, the ground round the tufts of Spartina was relatively bare, but by August of last year it had been covered everywhere at maximum density with self-grown seedlings of the grass together with a,dense and luxuriant growth of various halophytes. Stabilising Soft Mud.

V Spartina lias an almost magical touch in stabilising soft muds, and where it has entered other plants can follow," says Professor F. W. Oliver, of the Egyptian University, Cairo, in commenting on the Sloedam results. " Put even more striking was the impression that the original plants had sunk into the mud. The impression was illusory, since actually it was due to the fact that the soil had everywhere risen under the joint silting of the different plants concerned —risen so fast, indeed, that the Spartinas appeared to have lagged behind." Those in charge of the operations have expressed the conviction that the extensive Sloedam area will be ready within the next three or four years for polderising, that is, banking 111. Another Zeeland area under treatment is the Verdranken land higher up the Scheldt at Saeftinge. This is representative of much ground which was lost centuries ago by inroads of the sea, and has never reclaimed itself. Here the plantations of Spartina are extraordinarily luxuriant, and the spread of self-sown seedlings very conspicuous, it being evident, so the investigators say, that under rice grass the recovery of such land is shaping well. It is considered that the employment of the Spartina method of reclamation is accelerated where climatic conditions favour a good output of seed tliree years out of five, as, by self-sowing, Nature rapidly continues the work commenced by man. Professor Oliver considers it a method which is destined to add hundreds of thousands of square miles to the cultivable area of land. Essex Experiments.

The Essex experiments with the grass were commenced in 1925. Prior to 1929 the operations consisted of testing a comparatively small number of plants in a variety of situations, but with the knowledge gained from this work experiments 011 a larger scale, involving thousands of plants, have now been instituted, the immediate object being to prevent erosion along a given length of coast line. Briefly, the Essex investigations have shown that Spartina Townsendii can be grown successfully under the following conditions: — (1) From high-water mark of spring tides down to eight feet below that level, involving periods of immersion from a few minutes on the highest levels to four hours 011 the lowest, with corresponding, variations in water pressure; (2) on mud of varying consistency, from the firmest on which the foot hardly leaves an impression to the softest where one sinks to the heels or further; (3) on mud containing varying proportions of sand, gravel and organic matter, the latter in different stages of decomposition, (hydrogen sulphide, very evident in some sands, does not appear to be toxic to the plants) ; (4) on mud which is quite bare, and among the natural vegetation of both high and low saltings, where rice grass may quickly become dominant, its most serious opponent apparently being the perennial Glyceria maritima of the high saltings. One important point brought out by the Essex experiments was that the speed of the ebb tide may affect the success or otherwise of establishment, and investigations are being designed to determine whether or not a correlation exists between the speed of tidal currents and the growth of rice glass. In the event of positive results from these, it is considered that it should (hen be possible to state tlie chief requirements for the successful growth of rico grass, and also to make recommendations as 'to the, suitability of any given situation, and on the best disposition of the plants to compete with excessive scour.