PASTURE PROBLEM

Evening Post, Volume CXV, Issue 15, 19 January 1933, Page 3

PASTURE PROBLEM

PART PLAYED BY IRON

THE HEALTH OF STOCK

Mr. T. Eigg, Dr. H. O. Askew, and Miss E. B. Kidson at the Cawthron Institute have for some time past been conducting investigations into the part played by iron in the soil on the growth and . development of pastures, and upon stock health. While the investigations are not yet completed, and a great deal remains to be done before a full understanding of the part played by iron in stock health and nutrition is concerned, yet useful progress has.been made which throws interesting light upon a number of New Zealand farm problems.

As a result of the work of Mr. B. C. Aston and others, it has long been recognised that a deficiency of iron in the soil is connected with the production of stock anaemia, known as "bush-sickness," which occurs very commonly in the bush areas of the central part of the North Island, in the vicinity of Botorua, and exteuding to tho Bay of Plenty. The soils of this area and of large'portions of the North Island have a volcanic origin, having been ejected from volcanic cones in past ages. The same disease"- is also found in other parts of New Zealand, and occurs on soils derived from granito rocks near Glenhope in the Nelson province. :

Chemical analysis of the volcanic soils shows that the nature of the material which has been ejected at different times, from different craters, varies considerably in its composition. Some of the showers possess a very low iron cpntent, while others do not. A review of the results which have been secured to date indicated,that all. localities which are .definitely associated with bush-sickness have, comparatively low amounts of available iron, present in their composition. These percentages are much lower than those found over volcanic soils w^hieh are known to be free from bush-sickness. Reviewing the iron contents, and grouping them, the soils of New Zealand which have..already, been examined range as follows: — Pakihi soils, 0.07 per cent.; guniland soils , 0.14; Kaharoa shower, 0.49; Taupo, 0.67; Glenhope granite soil, 0.57; other volcanic showers, 1 to 2.25; alluvial volcanic soils, 1.8 to 2; healthy soils in volcanic areas, 2.8; Nelson nonvolcanie loam soils, .1.1 to 9 per cent. It is significant to note that the stock anaemia, trouble is associated with the group of soils whose iron content is less than 1 per cent., and does not occur on the .pakihi and gumland soils with the .low iron percentage content of less than 0.1 per cent. From these figures it seems..- reasonable to draw the conclusion thati^absenee of iron is associated to some-extent with the occurrence of. bush-sickness, but that iron is.not. the only contributing factor, as is evidenced by:the fact that stock on the pakihi and gumland soils do not suffer from the malady. Farmers in the ■ bush-sick'- areas have considered that by turning Jtheir stock into-the bush the -resulting recovery could be attributed to the fact that the animals fed on certain native plants. If iron is the material necessary for effecting a cure ;of this trouble, it was thought that probably the consumption of bush foliage effected a cure on account of its higher iron content. Consequently, analyses of the foliage of a number of native plants growing on bush-sick areas were made, and determinations of the iron and manganese contents worked, out. With the exception of one, Carmichaelia, or native broom, the iron percentage of none of these native plants exceeds 0.01 per cent., and in general they are very much lower. Whatever is the curative effect, of the animals grazing in native bush it seems that this cannot be attributed to their securing supplies of iron thereby.