tit.—34.

Two heavy dressings of potash, followed by light dressings in subsequent seasons, have proved economic over the six-year period of the experiment to date, the yield increasing by 229 lb. per tree for an outlay of ss. on potash ; the colour grading of the fruit was improved at the same time. Sturmer : Outlay on fertilizers has proved highly economic with this variety, particularly as regards the PN combination, in which, for an expenditure of approximately 3s. 4<i., the yield has been increased by 560 lb. per tree over the seven years since treatments began. The extra Is. Bd. per tree spent on potash in the PNK plots has scarcely been recouped in yield up to the present, but the trees arc in distinctly healthier condition. It has again been found that the combination of phosphate and nitrogen has produced a yield increase considerably higher than the sum of the two separate increases. Cawthron Institute. —The long-term manurial experiments on the Jonathan variety at Upper Mo'utere were continued during the 1939 season. In addition, treatments were maintained on individual trees which formerly received no treatment. The results are similar to those noted in the last .annual report, in which the PNK trees were superior to either the PN trees of the NK trees, Average yields (pounds per trees) for the 1938 and 1939 seasons show the value of the complete fertilizer in maintaining crop production:— Untreated. N PN PNK PNK with extra K. 44 69 109 128 147 Trees treated with nitrogen only are going back rapidly, and the fruit is poor in quality and small in,size. The importance of potassic manures is clearly shown in the yield data. r , Rootstock Experiments. » Research Orchard.- The trees are still in the juvenile stage and at the present time there are no developments to report. ' : Cawthron Institute —-Records continue to support the observations noted in last annual report that Northern Spy Was superior to two seedling types for Cox's Orange, and that seedling types were better than Spy for Jonathan and Sturmer. With Jonathan, the Epp's Seedling stock continues to prove rather better than Double Vigour. Plant Diseases Division. —In trial blocks of East Mailing stocks established in 1934 in the main fruitgrowing centres of the Dominion, differences in tree growth and crop are now more in evidence, though it is apparent that the behaviour of any one stock may vary appreciably with different scion varieties. Analysis of the records kept from time of planting indicates the following stock-scion influences: —

Stocks of Northern Spy were not included in trials with Jonathan and Cox's Orange, as no trees were .available at the time the plots were laid down. Trials of these,varieties on Northern Spy and East Mailing ,stocks iiave been established at the Plant Diseases Division at Owairaka, but, owing to the check received by the trees after transplanting from Palmerston North, differences are much less juarked than in the trials reported above. .Trees of Gravenstein and Delicious worked to their own roots continue to make growth superior to that of comparable trees on Northern Spy stocks. Gravenstein on their own roots have also been planted out in the experimental area at Havelock North to ascertain if they would remain free from the gnarling to which the variety is commonly Subject when worked on Northern Spy roots in this country. Inarching Experiments. At Haupai Orchard, operated by the Plant Diseases Division, vigorous clonal stocks were inarched into stunted Jonathan trees, but there has not yet been any indication of increase in vigour over untreated trees. At Appleby a replacement set of one-year-old, M.XVI stocks has been planted in readiness for a repetition of the inarching test there. Varietal Investigations. Work on the strains of apple varieties has been continued by the Plant Diseases Division, and trees grown from budwood secured from twenty-six localities and worked to M.IX dwarfing stock are now cropping freely at Owairaka. With the Delicious variety one object is to find a strain that is not subject to mouldy-core. Five out of twenty-one types that had fruited were free from the disorder,

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Rootstock. Scion Variety. Very Vigorous. Vigorous. j Inferior. Stunner . . . . . . XVI, XV, XII Northern Spy, XIII I Delicious .. .. .. XVI, XV, XII . Northern Spy, I XIII Granny Smith.. .. .. XVI, Northern Spy XV, XIII, XII I Statesman .. .. .. Northern Spy, XVI, XV, I XIII Jonathan .. .. .. XII, XVI, XV XIII I Cox's Orange XII, XVI, XV .. I