Composition of Walnut Trees as Affected by Certain Salts

Abstract

1. The effects of saline irrigation water upon walnut trees have been studied with reference to the effects upon behavior and growth, and upon the relationship between the inorganic constituents. 2. The continued application of saline irrigation water, to tanks of soil planted to walnut trees, has resulted in a reduced size of the leaves with occasional leaf burn, but no indications of mottle leaf or of walnut "yellows." 3. There exists a gradient in the ash content of the dry matter of walnut trees, which in good soil has its minimum in the rootlets but in saline soil has a minimum near the level of the surface of the soil. 4. The production of a new cycle of growth brings about changes in the relationships of the inorganic constituents of the water-soluble and insoluble fractions of the dry matter. 5. Although the sodium, potassium, and calcium contents of the drainage water of artificially made saline soil, in which walnut trees were grown, were much greater than the magnesium content, yet the woody portion and leaves of the trees contained less sodium, potassium, and calcium but more magnesium than the corresponding parts of control trees in good soil. 6. Walnut trees may absorb large amounts of chlorine and sulphur, much of which may be in organic combination. Persimmon leaves, and citrus leaves and fruit, as well as walnut leaves and fruit have been shown to be able to absorb large amounts of chlorine and sulphur, and to place much of it in organic combinations. The dry matter of leaves of walnut trees growing in soils rich in chlorine may lose one-half or more of its chlorine upon gentle ignition, whereas practically none is lost in the case of badly burned mature walnut husks. 7. Saline soils affect not only the inorganic constituents of the trunk, shoots, and leaves, but also those of the husk and kernel. 8. The effects of the artificially made saline soil upon walnut trees and their fruit are not confined alone to accumulations of chlorine or sulphur, but involve equally important changes in the relationships between the bases within the tissues. 9. When a soil was artificially made saline in controlled tank cultures of walnut trees, the effect of salinity of the soil solution was in the direction of reducing rather than increasing the ash content in the portions of the plant above the soil level, as compared with homologous portions of suitable control trees. 10. The effect of direct sunlight upon walnuts is to bring about an increase in the ash constituents of the dry matter. Such effects, when extreme temperatures also occur, may be so destructive in their action as to cause burning of the husks with its consequent effects upon the marketability of the nuts. 11. Absorption from salt solutions by short shoots with walnuts attached, while the kernels were still in the liquid condition, resulted in a considerable increase in sodium in the kernel portion. Although a considerable amount of chlorine and sulphur was absorbed by the shoots into the walnuts, only the increased sulphur of the husks was retained upon ignition. 12. The ash content of walnut husks increases most rapidly from July to late summer. Mature husks are extremely rich in bases, but the importance of such high concentrations in the physiology of the husk is very little understood. The water solubility of the inorganic constituents of husks changes considerably according to the nature of the soil solution bathing the tree roots. 13. The pH of the juice of young walnut kernels still in the liquid condition was about 5.2. Such juice was extremely rich in inorganic constituents.