H.—29.

CHEMISTRY SECTION. REPORT OF B. C. ASTON, F.1.C., F.N.Z.INST., CHIEF CHEMIST. Mineral Content of Pastures Investigation. .Now that so much information has been accumulated regarding the composition of improved and unimproved pastures of all types and at all seasons, in many parts of New Zealand, mainly through the investigations undertaken by the Chemistry Section, attention is being turned very largely to the remedying of the mineral deficiencies revealed, through the agency of compounds in lick form or other forms of supplementary mineral feeding. Perhaps the most important feature of the year's work has been the remarkable demonstration of the efficacy of finely ground limonite (hydrated iron oxide) in preventing and curing bush sickness in sheep. With the knowledge that breeding-ewes can be maintained in perfect health and can produce a normal percentage of high-class lambs, which in turn can be fattened, or reared for flock purposes at trifling increased cost and trouble, the final bogey of bush sickness has been laid low. A powerful weapon is also placed at the disposal of settlers in the affected pumice areas where ragwort and other weeds controllable by sheep have hitherto proved a serious obstacle to dairying, which could otherwise be carried on with the methods recommended by the Department, of which the chief was periodical drenching of stock with a solution of iron and ammonium citrate. It is not practicable to drench sheep as a farming practice to prevent or cure bush sickness ; the adoption of a limonite lick should render it possible to run sheep in districts hitherto used solely for cattle, which, cannot keep ragwort under control and which are more susceptible to the plant poison than are sheep. Atiamubl Pumice Lands Experiment (Sandy Silts). A large - scale and highly successful experiment has been carried out using limonite — obtained from a commercial firm who are mixing, and grinding the soft ore which occurs near Whangarei— mixed in equal proportions with salt as a lick for breeding-ewes and lambs. Attention was diverted to limonite, as the native carbonate of iron which had previously given very promising results was becoming expensive, difficult to obtain, and irregular in quality. As the result of inquiries and experiments, three firms are now supplying limonite in very finely-ground form for use as a stock lick, Analyses of samples have been made both for fineness and hydrated iron oxide, with very satisfactory results. From a flock of two thousand ewes, four groups of fifty were selected, of age between two and three years ; all had. been on the property for at least two years. On this property at Atiamuri the hill slopes are healthier than the pumice flats on which the experiment was conducted. The groups were treated as follows : No. 1, control, no lick ; No. 2, lick containing iron and ammonium citrate and salt; No. 3, lick containing Whangarei hydrated iron oxide (limonite) and salt; No. 4, lick containing spathic iron ore and salt. All groups grazed the same paddocks in rotation. Possibly owing to the taste, the iron-ammonium-eitrate lick was only sparingly consumed, but the iron-oxide lick was taken, freely. The spathic-iron lick was unsuccessful, probably on account of poor quality so that the effective supply of iron from this source may have been very small. In each group twelve ewes were selected for weighing at monthly periods. On 20th February, a farmers' field day was held. All the lambs of the control and citrate groups were dead. Of the iron-oxide group forty-four lambs from forty-five ewes were well developed, robust, and with a healthy bloom on the wool, while the ewes were bright and healthy. The total cost of the treatment for nine months was about 5-4 d. per head. Only sixteen of the control ewes had survived, in poor condition, while twenty-four surviving citrate ewes were rather better than the controls. On post mortem, a lamb from the oxide group was reported by the Veterinarian to be healthy and free from parasites, while one from the main mob was poor and " full of worms " (parasitic infection). Apparently the iron oxide treatment of the ewes had enabled the lambs to resist parasitic invasion. Results may be tabulated as follows : —

Experiments with the incorporation of limonite in ensilage have been continued. In one case several cows which had refused to take an iron lick and had consequently sickened were readily cured when fed the treated ensilage. Excellent results have been obtained from feeding limonite to dairy cows and calves, and it has been shown to be highly efficient when used as a drench for sick animals. The collection of pasture and soil samples for analysis and the care and sampling of pure pasture species in the grass garden on Mr. E. H. Brain's property, at Kaharoa, have been continued. The experimentally green-manured paddocks have been stocked and some observations recorded. Cows milk better when on these paddocks than when on others similarly top-dressed, and also show

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Ewes' Weight. Lambing. Average ; Weight of Group of Ewes. . . Ewes' Fleece, 5th May, 8th Feb- . - R . . When Surviving at 2 0th Febru1931. ruary, 1932. At Bllth ' marked. ary, 1932. lb. lb. Per Cent. Per Cent. lb. Limonite .. .. .. 120 128 100 90 88 8| Iron ammonium citrate .. 112 92 62 16 Nil. 7 Control .. . . .. 114 72 76 50 Nil. 6|