PAPA ROCK AS A SOIL – DRESSING.

New Zealand Journal of Agriculture, Volume XII, Issue 4, 20 April 1916, Page 303

PAPA ROCK AS A SOIL - DRESSING.

The following report on trials with • crushed papa rock as a soildressing has been made by Mr. G. de S. Baylis, Fields Instructor (North Island). The trials were undertaken at the instance of the Dominion Conference of the Farmers’ Union :

With a view to making some trials as to the possible benefits to be derived from papa, samples were procured from various places. Analyses which were made by the Department’s Chemist of many samples gave indifferent results, the lime-content being low and phosphoric acid only a trace. A sample was eventually procured from Mangaweka showing calcium carbonate 4'538 per cent. This was handy to the railway and at a convenient place for quarrying.

Considerable difficulty was experienced in getting anybody to grind the papa in order that it might be evenly distributed by means of a drill, and owing to breakdowns in the machinery it was very late in the season before the material was delivered.

At Ashhurst, on a clay loam with a stiff clay subsoil, the following trial was put in, with oats and vetches as the crop : Plot 1,2 cwt. basic slag; plot 2, 2,000 lb. limestone; plot 3, nil; plot 4, 2 cwt. of a mixture of superphosphate,- bonemeal, dried blood, sulphate of potash, and sulphate of ammonia. A strip across the top of each plot was dressed with papa at the rate of 8,000 lb. per acre.

Owing to very heavy rains in the early part of the season the crop did not do so well as it promised at first. There was, however, a superior growth on the portion to which papa had been applied. The best growth was made on the slag section. These plots are now to be put down in grass, and observation will show if any future benefit is derivable from the application of papa to this soil.

A sample of papa was obtained already ground from the brickworks at Patea, „and forwarded to Mr. Blackhall, of Lepperton. This was applied at the rate of 4 tons per acre. A crop of swedes was sown with the usual. freezing-works manure mixture. An equivalent area was also sown with the same manure on land not previously dressed with papa. Mr. Blackhall noticed no difference in the swede crop, “ but the following crop for green manure/’ says Mr. Blackhall, “ stood out with marked advantage in favour of the papa dressing, giving much heavier weight and being of a better colour. The soil to which papa had been applied was also, when ploughed, of a better texture than that of the ‘ nil ’ plot. lam of opinion that, provided one could apply, say* 6-tons of papa per acre, or more, it would give good results.”

Last year ground papa was applied at the rate of 2 tons per acre to a small plot at Marton. The crop was Thousand-headed kale. The crop on the land dressed with papa was noticeably of a better colour than that on the no-lime plot, but the limed plots were superior to the crop on the papa plot.

It is hoped to pursue experiments with papa by treating a plot with a heavy dressing and leaving a check-plot alongside of it. A preliminary plot will then be grown to assist to mix the papa well with the soil, after which the land will be laid down in grass-and-clover mixture for observation purposes. Although there are deposits of papa to be found having a fairly good lime-content, the average papa does not contain a high percentage. It would appear to me that to reap any real advantage papa would require to be heavily applied—say, in lots of 4 tons and considerably over. The cost of cartage and carriage . would therefore prohibit its use, save where it is handy to the land to which it is to be applied. The application of papa should improve the soil by its content' of lime and what traces of phosphoric acid it possesses, and it should help, when applied in large quantities, to make the Soil more absorbent and more retentive of moisture. It would probably need, like lime, to be applied some months before any real benefit would be likely to accrue from its use.

Lucerne usually does well on deep loams with rubbly papa subsoils, and where lime is not available a heavy dressing of papa, applied the previous season and well worked into the soil, would probably be found beneficial.

Papa might be quarried and left for twelve months in small heaps exposed to the atmosphere : it would then readily break up upon being applied to the soil. The better method, however, would be to apply it to grass lands, say, twelve months before same were ploughed. Another use for papa would be as drier for manures. If ground into grit size like bonedust and then artificially dried, it would form a splendid make-weight or drier, and help to make the manure run better through the drill. When gypsum, which is largely used for this purpose, is high in price it is probable that papa artificially dried would answer the same purpose at probably a lower figure.