MANURING POTATOES.

Otago Witness, Issue 2914, 19 January 1910, Page 20

MANURING POTATOES.

The Tasmanian Government agricultural expert, Mr H. J. Colburn, in an article dealing- with the- manuring of potatoes, speaks favourably of the- vylue of sulphate of dr on as a manure and germicide. H. O says : “I have been impressed by the vigorous condition and- healthy appearance of a, patch of early potatoes grown by Mi- E. Bonnett, of Upper Macquarie street,, Hobart, who applied a top-dressing- of greenvitriol (sulphate of iron) to the- surface of tho ground soon after the potatoes were planted. _ Sulphate of iron in excess, especially n-n. the subsoil, is a, poison to plants, but used- in the proper quantity— from half to lowt per acre—as a top dressing, a. ctm-eide-rablo increase in the yields , of almost all kinds of crops has been obtained. Tbs application, to Mr Bennett’s potatoes amounted to 4cwt per acre, but the tops

looked beautifully green and vigorous, while from the specimens: dug the crop of tubers promises to be heavy if allowed to proceed to full (maturity. The reason why sulphate of iron is beneficial in proper quantity as a top-d'rossing is that, it readily decomposes when in contact ..with air and moisture, rendering up its iron, in a. very available form for abtoriitlpn,'by the roots of the growing crops, ' wlibnce it passes upwards with the flow of sap’.to, the leaves, where it, performs an important part in increasing the activity of too. chlorophyll cells, which are the chief agents in the fixation of starch, a substance of special importance in the case of tha-..potato—since starch forms the bulk of the. tuber apart from the water contained. “The promotion of a healthy, vigorous growth renders a plant more resistant of disease. Besides, as Professor Griffiths (who was a strong advocate for the use of sulphate of iron to crops) remarks, ‘Sulphate of iron is an antiseptic agent capable of destroying the vegetable and parasitic diseases which attack farm crops.’ He further adds that. ‘ soluble iron compounds are necessary for the formation of green chlorophyll. Therefore,' if a soil is deficient in soluble .iron, although it may ‘contain an abundance of insoluble iron compounds, farm crops and plants generally must suffer, the plants not yielding full crops, or becoming diseased.’ ” Experiments carried out by Professor Griffiths gave the following results: —Three plots, each 1 aero, of well-drained land, were chosen, the soil of good quality. Plot A was left unmanursd. Plot B was manured with lewt kainit, lewt nitrate of soda, gowt sulphate of iron, and 2cwt suporp hasp hate. Plot C was manured with the above constituents minus the iron sulphate. On each plot was sown 7cwt of good potatoes. At the end of the season the following results were obtained:

The above results show that the crops grown with the addition of iron sulphate to the ordinary- artificials yielded 8g tons of potatoes. That grown with the_ artificials, but without sulphate of iron, yielded only 6£ tons ; while the unmanured yielded only 3 tons. In another experiment upon plots one-eighth of an acre in extent 14-lb (lewt per acre) of sulphate of iron was applied when the potato tons were bin above ground, the manure being placed between the plants on the tops of the drills. At harvest the yields were:—The tubers from the one-eighth acre manured with iron sulphate weigh'd 52371 b. The plot without sulphate yielded 48911 b. The application of the sulphate is best made after the crop is above ground, and after a rainy day, if possible. Quantity, iewt to lowt, more than this being dangerous. The iron sulphate should be and mixed with some material to bulk it, as soil or ashes. Sulphate bf iron, which is sometimes called Copperas, must not be confused with copper sulphate or blue vitriol.

Tubsrs Haulm - " Plot A. lb. .. 6.720 .. 2,125 Plot B. lb. 19,040 6,231 Plot C. lb. 14,023 4,917 Total 8,845 25,271 18,940