BOUNTY OF THE SEA

Hawke's Bay Tribune, Volume XXII, Issue 192, 29 July 1932, Page 8

BOUNTY OF THE SEA

WHY BUY PHOSPHATES? RICH WASTE MUDFLATS. DUNE FARMS COMING New Zealand soils are usually deficient in phosphorus and calcium (lime). Yet those New Zealand soils which are naturally rich in phosphorus and calcium are comparatively neglected. To say that a soil is rich in the two main plant-food elements that otner soils lack is not to say that it is inevitably an economic success. But the Chief Chemiat of the Department of Agriculture, Mr. B. C. Aston, evidently holds the opinion that the neglected lands should be developed, and that on present evidence the prospect of their successful development is very bright. These neglected soils are not only rich in phosphates and lime—the supplying of which, in manurial form, to jsew Zealand farms has cost, and is costing, immense sums. The neglected soils are also situated at low levels, and generally in accessible positions. They are water-affected (mostly seaaffected) lands, and that in itself marks them out in most cases for accessibility. These sand dunes and estuarial mud flats, found by sea or river, do not need to be approached by means of tunnels or steep grades. Where they are not served by existing communications, their linking-up with such should not be expensive.

PHOSPHATES WITH LIME. The sea submerges but it also fertilises. When the sea is locked out it leaves wealth of phosphates and lime in its wake. The problem of adapting such a soil to economic production is simpler in the case of sands than in that of clays. The Zuyder Zee yields Holland clay. The soils to be yielded by New Zealand ' dunes, lagoons, and mudflats is estimated to be predominantly sandy. In breaking-in New Zealand’s outback lands, the farmer has leaned on the road engineer. In breaking-iu New Zealand’s water-affected lands, he will lean on the drainage engineer. But in the out-back it was physically possible for the farmer to go out in advance of the road engineer and to isolate himself till the road came to him. Where the barrier is not isolation but water, the pioneer has less liberty of action. Mr. Aston writes: “The large quantity of those elements, phosphorus and calcium (usually so deficient in New Zealand«soils), in lands but recently derived from the sea, is due to the abundance of marine life, which has concentrated in the animal and plant remains the calcium and the phosphorus derived from the sea.” The presence of excessive calcium prevents the reversion of phosphate to a form unavailable as plant food, and even where the sea has ceased to flow for scores of years (perhaps centuries) soil may be found rich in the phosphates which (elsewhere) New Zealand farming inrports at so high a cost. Referring to the Manawatu sand dunes, Mr. Aston states that half a mile from the sea (slowly receding, perhaps a mile in 800 years) analyses of soils have shown “about four times the available phosphate that there is in ordinary New Zealand soil, and I per cent, of calcium, which is more than twice the amount found normally.” Taking sand dune country alone (no* including estuarial mud-flats, lagoons, and mangrove swamps) it is estimated that New Zealand has 300,000 acres available for reclamation. “The examination of only a small part of these has been completed for chemical analyses, but if those areas which have not been examined are as rich in phosphates and lime as those of the Manawatu district, then a great tract of land is available for reclamation, with mineral plantfood present in abundance which would rapidly grow many green-manuring crops for reinforcing the deficient organic matter. Such land has the advantage that it can be worked in all weathers, and, being contiguous to the sea, could be connected up with adjoining occupied areas, fenced, roaded, watered, and bridged at a moderate cost compared with the cost of doing this in most new settlements, which are usually at a distance from rail or harbour.” LITTORAL WEALTH.

As to the estuarial lands and mudflats, these are often “more accessible than the sand-hills, many areas being close to the cities and other densely populated centres. For the same reason that the sand dunes are so rich in mineral matter other than silica—that is, the material has not travelled far and is imperfectly weathered—the estuarial lands have not reached in many cases that stage which is found in Europe under similar conditions, where a stiff soil or clay composes the bed of the type of land now being drained. In New Zealand these lands are composed of sand, silt, clay, and shells in well-balanced proportions, and these components, theoretically ought to make the best of all soils technically known as loams.” Referring to the tendency of public bodies to apply unemployed labour to big scale land-reclama-ations, he observes: “No more fascinating problem has presented itself for years than tho utilisation of these potentially valuable waste lands, now either slightly submerged or abandoned to wild inedible plants, the animal life there finding a congenial home and constantly enriching the area with phosphates. On some of the lands reclaimed from the sea “special crops may have to be grown at first. Most vegetables will grow admirably on light soil with a fair percentage of salt in it, as the ancestors of these vegetables originally inhabited a coastal situation. Thus all the cabbage family is derived from the colewortil a maritime plant, and the beet and mangold from Beta maritima. Nearly all the cross family (Cruciferae), such as mustard, kale, rape, radish, and kohlrabi, are suitable as crops in salty situations, but probably the most payable of all for marketgardening purposes will be asparagus, of which in 1930, 93 tons were imported tinned, mostly from America, valued at £7OOO. Why could not this have been produced in New Zealand, and why could not vegetable produce of all kinds he exported from this country where it is so easily grown? “The Hauraki Plains soils near the sea contain six times the amount of

available phosphoric acid that exists in ordinary soil. Tho Lake Ellesmere (Canterbury) lagoon, occupying 100 square miles, is equally rich in. phosphate. The Nelson (Wakapuaka) mud flats contain about four times the phosphate, the Lake Grassmere (Marlborough) two and a half times, the Blueskin Bay (Otago) four times, and the Napier Ahurin) lagoon three to four times the amount of phosphate normally found in fertile soils. These figures are considerably on the low side where there is much carbonate of lime present which interferes with the method used in spite of corrections made to prevent it.”

It. is anticipated that “the estuarial lands, when drained, will offer no great difficulty in the rapid backing away of injurious sea-salts. ’ ’ —‘ ‘ Post. ’'