REVIEW.

New Zealand Journal of Agriculture, Volume XXXV, Issue 1, 20 July 1927, Page 65

REVIEW.

“PLANT NUTRITION AND CROP PRODUCTION.” Sir John Russell, Director of the Rothamsted Experiment Station, Harpenden, England, was the fifteenth annual lecturer selected to deliver the Hitchcock lectures at the University of California, U.S.A., in 1924. These lectures have now been published (University of California Press, Berkeley, California, and Cambridge University Press, England, 1926) under the title Plant Nutrition and Crop Production.” . It goes without saying that the book is intensely interesting to students of agriculture. Sir John Russell has the happy knack of treating historical matter with freshness and originality, and when he takes one back to 600 b.c. or to a.d. 1620, or to other experiments of the seventeenth, eighteenth, and nineteenth centuries, it is all with the purpose of showing how the theories now held were laboriously built up, and each illustration fits beautifully into the scheme of his ordered instruction to his American audience. Treated in the lecturer's easy style the description of the development of the theories concerning agricultural chemistry centring round the great names of Liebig, Lawes, Gilbert, and Boussingault makes eminently good reading. The rise of the artificial-manure industry, and particularly that of the great superphosphate trade,, reads like a fairy-tale. Sir John concludes : “It is not too much to say that the discoveries and developments of artificial fertilizers have been one of the great factors in the making of modern Europe.” MllTo review the whole field of his subject the lecturer has, in 115 octavo pages, succeeded beyond expectation. Sir John has much to say on nitrogen and soil bacteriology worthy of close attention, but on the questions of special interest to New Zealand students he must be fully quoted : “ Probably the most dramatic effects, however, are those produced by minute quantities of certain elements, iron, boron, manganese, and a few others, on the growth of plants supplied with a complete nutrient solution. Small quantities of manganese were found by Bertrand to be essential to plant growth. Boron is being studied at Rothamsted, the investigation. having originated in an observation made when the entomologists were adding various poisons, including borax, to soil in which broad beans were growing, in the hope of making the plant unsuitable to the Aphis. Borax markedly increased the plant growth, and when the botanical staff took the matter up they found that the old ' complete ’ nutrient solution would not allow beans to develop unless a trace of borax was supplied. Maze, of the Institut Pasteur, Paris, has added other elements, iodine, zinc, aluminium, &c., to this remarkable list. The subject is under investigation by Dr. C. B. Lipman. The analogy with vitamins is obvious, but analogy is the most treacherous method in science.” BISThe difficulties of the investigator in getting his theories translated into farm practice are thus touched upon : “We shall find this to be the usual course of events. The first workers obtained much knowledge rapidly; then comes a period when progress apparently ceases and confusion reigns instead. Suddenly the generalization appears, and sooner or later thereafter the practical application. Then comes the large-scale test, the criticisms, and the curious and inexplicable observations of the practical grower. And although we who are working in the experimental stations may sometimes be tempted to feel that these observations, being unknown to us, cannot possibly be 'true, nevertheless, they often are true, and contain the germ of highly interesting scientific problems, sometimes, indeed, the key to further progress. We shall see in later lectures how history is repeating itself in other branches of science. But progress is always slow, and we can never see the whole of anything in nature ; as Browning said, ' We explore with a taper and not with a torch.’ ” Finally, the lecturer summarizes . what .is known regarding soils and their classification. Soils contain two phases : (1) mineral, from the rocks ; (2) organic, from the decay of plants. In humid, cool conditions, as in New Zealand, the silicates of the rocks break down to form soils rich in silica ; but in wet tropical conditions the silica is washed out, leaving only aluminium and iron oxides ; and under still wetter conditions the aluminium is also washed away,

leaving the laterite red soil (chiefly iron compounds) of the tropics. The nature of the organic matter is determined by the vegetation from which it arose and the kind of decomposition to which it is subjected, both of which are dependent on the climate. Hence the soil is very much the child of the climate. An actual confirmation of this has been effected by American investigators who transported a soil from one district to another with different climate. In seven years considerable alteration was found in its composition. The first great division of soils is therefore into the laterite and silica soils. The second great division is determined by the presence or absence of reactive calcium. “In the realm of nature it is remarkable how exceedingly important certain elements are in comparison with others. Probably no single element plays a greater part in the soil economy than does calcium. The whole flora of a soil, its agricultural possibilities, and therefore the comfort and well-being of the agricultural community that dwells upon it,- are all profoundly affected by the consideration whether it does or does not contain reactive calcium. A third great soil division depends on the fate of the organic matter ; ,in the normal case it mingles with the soil, being drawn in by earthworms, ants, or other animals ; but when mingling agencies are absent it lies on the surface and forms peat, fen, or muck soils.” The lecturer proceeds : ” Time does not allow of consideration of the laterites, the peats, or the fen soils. We are concerned mainly with a great middle region . where the decomposition products have persisted so that colloidal substances are present; where there may or may not be much reactive calcium, but where there is invariably organic matter, the remains of older generations of plants, which have decomposed so far as to reach the steady state . . Reference has already been made to the fact that some of the soil constituents are in the jelly-like or colloidal condition. The soil particles are pictured as being coated with jelly just as if they had been steeped in it. The study of the soil colloids is one of the triumphs of modern times, and is furnishing the explanation of many important soil .properties which had previously been wholly inexplicable.” The lecturer’s scheme of soil classification is illustrated by a very interesting chart. ' The book is well printed, and the illustrations are admirable, but the absence of an index is a distinct blemish. B. C. A.