Growth of Potatoes.

An investigation into the respective effects of potash phosphates and nitrogenous salts was quite as interesting and significant in its results. A lantern slide was shown depicting the crops obtained with these chemical manures near Paris, the conclusion formed there being that potash was the most essential manure for potatoes. With us, or the contrary, a series of plots planted at Oamaru, Waikouaiti, Puketeraki, Seacliff, Waitati, Wakari, and Southland showed potash to be practically unnecessary as a potato manure in those localities. On the other hand, phosphates proved of great value, and in some localities more than doubled the crop. At Waitati ground that without manure yielded only 3 tons of poor potatoes to the acre gave 9 tons of good quality with a dressing of artificial manures costing about £2 10s per acre. At Waitati and Wakari doubling the dressing of potash actually diminished the crop; yet sulphate of potash costs £15 per ton, and superphosphates only £5 per ton. Our soil in the districts named contained enough potash and was short in phosphates. However, potash should rarely be entirely omitted when making up a compound manure. In the localities named it could be reduced to a minimum, so far as the farms tested were concerned, whereas, in some other localities, potash would page 66 prove to be the main desideratum. Such facts were of cardinal importance for the farmer and the country, and showed the absurdity of imagining that chemical mixtures labelled "potato manure" or "turnip manure" could be satisfactorily compounded without reference to the special local ingredients of the soil. By planting only a gross of potatoes in an experimental plot the children of any country school could discover for themselves in a single season something of real value to their district. The experience would be as important to them in training their powers of observation and stimulating interest, and in giving them faith in the practical value of scientific precision, and in developing their reasoning faculties, as it would be valuable to their parents from a direct pecuniary point of view. Add to these advantages the fact that such knowledge comes by way of recreation, and it may seem that we could afford to exchange it for some superfluities at present required for examinations. The boy whose future lay in town would gain enough from such pursuits to make the matter worth his while, and the benefit to the future farmer and to the country would be inestimable.^*