CAWTHRON INSTITUTE

Otago Daily Times, Issue 22356, 1 September 1934, Page 3

CAWTHRON INSTITUTE

BULLETINS ON FARMERS’ PROBLEMS IX. NUTRITION OF FRUIT TREES With a view to making known the results of it* numerous trials and experiments in economic botany and insect and pest control, the Cawthron Institute is issuing periodical bulletins. The ninth to be published in these columns deals with the subject of nutrition in fruit trees. It has been compiled by Mr T. Rigg, M.A., M.Se., F.R.S., N.Z. (director of the Cawthron Institute). INTRODUCTION. It is only in recent years that investigators have realised the complexity of the many factors which operate in tho production of high yield and high quality of fruit. It is now known that root stocks, soil types and climatic conditions, in addition to methods of pruning and orchard management, affect tho performance of apple trees in respect to growth, yield, and quality of fruit. More and more emphasis has been placed by students of fruit tree culture on a careful study by the orchardist of individual trees in his orchard, and the regulating of his manurial programme in accordance with the appearance and record of the trees.

It has been shown that quality of fruit is influenced greatly by manurial treatment, and although improvement in quality can frequently be effected by judicious manuring, yet the excessive use of nitrogenous manures may prove highly detrimental to the keeping quality of certain varieties in cool storage. ENGLISH INVESTIGATIONS.

In England important contributions to our knowledge of tree nutrition have been made by Dr T. Wallace, of the Long Ashton Fruit Station. Ho has shown that apple trees require all the common plant foods for normal tree growth and fruit production. Deficiency of any of the important plant foods affects tree* in definite and frequently in different ways. Trees on a‘ deficient nitrogen supply show retardation in the opening of blossom and leaf buds; restriction of foliage development is pronounced, and premature defoliation invariably takes place. Fruit from trees with a deficient nitrogen supply are good keepers, both in common and cool store, and in the case of coloured varieties a very high colour is obtained. Under conditions of low phosphate supply, somewhat similar symptoms in tree characteristics develop ag those noted for nitrogen deficiency. The leaves of the trees, however, frequently show bronzing effects instead of the pale yellow tint characteristic of nitrogen deficiency. Fruit from trees on a low phosphate diet is soft and lacks colour. In the case of trees maintained on a low potash supply, the opening of blossom and leaf buds is frequently hastened. Dieback of shoots is very marked and fruit bud formation appears to be greatly favoured. One of the characteristic symptoms of potash deficiency is a scorching of leaf edges and a reduction in the size of leaves.

Fruit grown under these conditions is of poor quality, lacks colour, and is subject to internal breakdown in cool store. Considerable success has already been obtained in England as a result of the work done by Dr Wallace in diagnosing deficiencies of plant foods in commercial orchards. The occurrence of leaf-scorch has been noted in many orchards located on clay soils in the south of England, and liberal potassic manuring has been shown to give marked improvement in tree vigour and quality of fruit. AMERICAN INVESTIGATIONS. In the United States of America, the great importance of nitrogenous manures, particularly for orchards in sod has been confirmed in several experiments. More recently Hoagland and his colleagues in California have demonstrated that the dieback and death of prune trees is caused by the high potash deficiency in these Californian soils. Zinc salts have been used with success in combatting rosette of fruit trees, but it is not known whether zinc is required by the trees as an essential plant food, or whether the zinc salts act in an indirect way, removing harmful compounds in the sap. Although phosphatic manures are employed in the commercial orchards of England, U.S.A., and other fruit-producing countries, no satisfactory proof has yet been obtained that apple trees on average orchard soils actually require phosphatic manures for optimum fruit production. NELSON INVESTIGATIONS.

Conditions in the commercial orchards of the Nelson district diifer markedly from those prevailing in either England or the U.S.A. The use of the Northern Spy stock with its less vigorous and more superficial rotting system prevents any wide application to New Zealand orchards of the results of manurial experiments conducted in other countries where different apple stocks are used. Experimental tests in New Zealand conducted on typical soils will alone give the information which is required for putting the manurial programme of New Zealand growers on a satisfactory basis. Another feature of great importance in any consideration of the manurial treatment of apple trees lies in the fact that such a large area of the Nelson apple industry is located on the Moutere Hills soil which is so poorly supplied with nitrogen, organic matter, lime and phosphate. The experiments of the Cawthron Institute and the Government Research Orchard at Appleby have already shown the great importance of manurial treatment in increasing apple production and in improving quality of fruit on this soil type. In the experiments of the institute at Upper Moutere, where certain blocks have received manurial treatment for a period of 12 years, the yield of fruit in the case of trees receivin'' complete treatment of phosphate, potasn, and nitrogen, supplemented by cover crops, is now almost double that from the untreated blocks whith have been maintained without manurial treatment. The accompanying table 1 shows the remarkable effect of

manurial treatment in the ease of the Upper Moutere experiments in increasing yield from Jonathan trees.

Table J: Manorial experiment, Jonathans, Upper Moutere.

Block 3A, 41b super., lib sulphate of potash nod lib dried blood per tree. Block 3B as 3A, but 31b dried blood per tree. Block 5A as SB, but am, sulphate replaces dried blood; sulphate of potash omitted in 1934 season. Block 5B as 6A, but 41b sulphate of potash per tree each year, since 1928 Block 6, untreated till 1927, then 6lb dried blood per tree in 1928, 1929, 1930, and 31b am. sulphate per tree in 1931, 1932, 1933. It Is interesting to note that the yield from the untreated block 4 hag been sationary over the last four years. Block 3A receiving only lib of dried blood in addition to superphosphate and potash, is now increasing in yield very slowly and has fallen markedly behind Block 3B or SA, in which 31b of nitrogenous manure per tree have been used along with standard amounts of superphosphate and potash. Block 6, which has received nitrogenous manures without phosphate and potash during the last six years, is of great interest. The yield of this block is still increasing, but the appearance of the trees does not suggest that nitrogen alone is sufficient for satisfactory vigour, high production and quality of fruit. _On this block a number of trees are suffering from die-back, despite the liberal nitrogenous manuring. The yield in the case of Block 58, which has received 41b of potassie manures per tree each year for the last six years, is of interest, in that very little improvement appears to have been effected when compared with the adjoining Block 6A, which has received only lib of potassxo manure per tree each year. The result of this Upper Moutere experiment on Jonathans shows clearly the great importance of manorial treatment on Moutere Hills soil for optimum fruit, production. The result of this experiment has been confirmed in so far as the Coxa Orange variety is concerned by a supplementary investigation at Waimea West, where the use of 3lb of nitrogenous manure per tree has shown to a very great advantage over the use of 11b per tree. In this experiment superphosphate and sulphate of potash were applied at standard rates over both blocks which were located on a poor type of the Moutere Hills soil. In the case of other Nelson soils of higher natural fertility than that of the Moutere Hills, indications are not lacking that maintenance of growth and yield when trees come into heavy cropping is dependent on suitable manuring. At the Annesbrook orchard of the institute, Dougherty trees maintained for 14 years without manurial treatment have during the last four or five years shown pronounced die-back and a falling-on of performance. In this experiment, little difference between manured and untreated blocks were noted over the first period of eight years. With increasing yields as the trees matured, growth on the untreated blocks became weaker and weaker, until actual die-back of shoots and branches occurred. The beat result was obtained with a complete manure consisting o: super., potash and nitrogen, but trees supplied solely with super, and potash have up to the present done remarkably well, and although growth is very small, are not associated with any symptoms of die-back so characteristic of trees without manurial treatment. The results of this experiment suggest that manurial treatment's desirable for many average orchard soils in the Nelson district. GENERAL RECOMMENDATIONS. The experiments which have been carried out in Nelson orchards show conclusively the great importance of manurial treatment in maintaining orchards in a high state of/ productivity. The programme recommended by the Cawthron Institute in the case of the Moutere Hills orchards has included the use of cover crops—-so necessary for the enrichment of the soil in organic matter and nitrogen-—the use of phosphates and potassie manures for the manuring of the trees, and the use of nitrogenous manures at the rate of 21b per tree about the third week in September. In addition the use of ground limestone has been recommended at the rate of one ton per acre every four or five years. This programme has been used with success in many orchards of the Moutere Hills, and the results of the experiments of the institute at Upper Moutere testify to its general value in the improvement of crop production. The manurial programme has included _ the three common plant foods in quantities based on the general experience of the institute in connection with this soil. The experiments have clearly shown the great importance of nitrogenous manures for all orchards on this type of soil, but the position of phosphate and potash manures in improving orchard yields and quality of fruit has not been satisfactorily defined. In the early years, owing to the exceedingly low supply of phosphate in the top-soil, it was highly desirable to give liberal applications of super, or other phosphatic manures to ensure the free growth of cover crops. The exact role of phosphate in regard to tree performance is not known, and there is good reason to suspect that in those cases where liberal quantities cf phosphatic manures have been applied oyer a period of years, that a reduction in the amount of this fertisiler could be made with safety. In the case of potassie manure again, its inclusion undoubtedly has exerted a highly beneficial effect on the free growth of cover crops, but the part it has played in improving or maintaining yield and quality has not been satisfactorily settled. In both cases it is probable that larger applications of these two manures used periodically for ploughing under would give better results than annual small applications. Although financial stringency may‘involve a reduction in the manurial programme of many orchardists, it must be emphasised that the omission of phosphate and potash cannot be recommended as standard practice. Our knowledge of the role of these plant foods in fruit production and in quality on soils such as the Moutere Hills is as yet very limited and their influence may well be much greater than is apparent from casual observation. Much additional information from the chemical investigations of the Cawthron Institute and the manurial experiments of the Government Research Orchard should become available during the next two years, enabling a more complete statement to be made concerning the value of these fertilisers for orchards in the Nelson district. Already definite indications have been obtained in the Cawthron Institute investigations that “ dieback ” in apple trees is sometimes associated with a low potash status of the trees. IMPORTANCE OF NUTRITIONAL INVESTIGATIONS. In view of the fact that manurial treatment of apple trees has been shown to exert a marked influence on yield of fruit over such a large area of the orchards of Nelson, it is most important for the success of the industry that as complete knowledge as possible should be obtained concerning the role of individual' plant foods on both tree performance and quality of fruit. Investigations are required dealing with the penetration of phosphates and potash

in orchard soils f» order to ascertain whether improvement can be effected in our methods of applying these manures. The nitrogen status of the soil jn typical orchards should be studied throughout the whole year in order to secure information concerning the decomposition of cover crops and the liberation of available nitrogen for use by the trees. In formation on this point is urgently required in order to secure optimum benefit from the use of cover crops. The valuable work which has been dona by Dr Wallace at the Long Ashton Fruit Station should be applied to Nelson orchards with a view to ascertaining the valuo of chemical analyses of fruit and leaves in indicating deficiency of particular plant foods. Cool storage tests of fruit quality must be undertaken in all manurial experiments and the results of these tests must be correlated with fruit production and chemical composition of fruit. With more knowledge of the role of individual plant foods in connection with yield and quality of fruit, it is practically certain that large savings could be made by many growers of New Zealand in the purchase of fertilisers, and a higher quality of fruit obtained at the same time. Furthermore, if the investigations are planned on broad lines information must be obtained concerning factors affecting “ cracking ” of fruit, russeting of fruit, incidence of drought spot, cork, bitterpit, and other ailments of apple trees. Such information may well provide the basis for the successful control of these ailments. In the experimental blocks of the Cawthron Institute and of the Government Research Orchard, material of the greatest value is available for the conduct of these investigations outlined above. The continuance of these experiments is of the greatest importance to Nelson and New Zealand as a whole, for in no other part of New Zealand do equal facilities exist for the conduct of correlated investigations in fruit tree nutrition, and in no commercial orchard district of the world is better value likely to be obtained than in that of the Nelson area.

Average yield fruit lbs per Year. 3A tree. Blocks 3B 4 5A 5B 6 1931 , 112 130 80 120 121 91 1932 .. .. 128 141 82 130 130 90 1933 . 118 131 74 138 138 102 1934 , 129 154 83 170 182 117 Totals for 4 seasons 487 656 Ci CO 550 571 400