8 



NATURE 



[September i, 1921 



soil generally, not with the soils of a particular 

 region. It is written for the practical agricultur- 

 ist and for the student who wishes to farm rather 

 than for the man who desires to become a soil 

 expert, and the illustrations and the tables are of 

 such a kind as will appeal at once to the man 

 interested in the business aspects of the subject. 

 Take, for instance, Table I., which summarises 

 a long and complex series of experiments in Ohio, 

 or the comparison between grain-farming with 

 and without livestock respectively shown in 

 Table II. 



Table II. — Grain-farming v. Stock-farming in maintaining; 

 Soil Fertility. 



It would be difficult to find terser and clearer 

 illustrations of the important part played by lime 

 and livestock as adjuncts to good farming. 



There is an excellent section on ploughs and 

 other implements, and an interesting example of 

 a fraudulent use of soil analysis of a kind we have 

 not met with in this country. We should not 

 agree with the author's unqualified statement of 

 the Law of Diminishing Returns as applied to 

 fertilisers; recent experiments in this country in- 

 dicate that the return increases at first in a greater 

 proportion than the amount of fertiliser used ; not 

 until a certain excess is reached does the return 

 begin to diminish. 



(4) Dr. Harris's book is entirely specialised, and 



deals with one aspect of soil only, viz. alkali, a 



sufficiently important subject, however, to occupy 



one man's whole time and attention. He speaks 



NO. 2705, VOL. 108] 



with great authority; as the Director of the Utah 

 Agricultural Experiment Station he has had 

 unrivalled opportunities for studying the problem 

 at first hand. By alkali is meant any soluble salt 

 that makes the soil solution sufficiently concen- 

 trated to injure the plant; the salts include the 

 chlorides, sulphates, carbonates, and nitrates of 

 sodium, potassium, and magnesium, and the 

 chloride and nitrate of calcium. In the author's 

 view these salts arise from desiccated inland seas. 

 Most of them are actually neutral, but the word 

 "alkali "has so long held the field that it is not 

 likely to be displaced. Some idea of the magni- 

 tude of the problem is conveyed by the statement 

 that more than 9,000,000 acres (or 13 per cent.) of 

 the irrigated land of the United States suffer from 

 this cause. While the author devotes his attention 

 largely to practical problems he is quite alive to 

 the scientific interest of the matter, and he gives 

 numerous references which will allow the student 

 to proceed further in the inquiry. 



There are useful lists of indicator plants and 

 descriptions of some of the most typical of them. 

 Certain of the Atriplex species are the last to 

 abandon an alkali flat. Various methods are 

 described by which the ill effects can be mitigated, 

 but the only permanent cure is flooding, which, 

 however, must be accompanied by adequate 

 drainage or it soon makes matters worse. 



(5) Prof. Jeffery, who was for long in charge 

 of the Soil Department of the Michigan Agricul- 

 tural College, and has now become Land Com- 

 missioner for one of the important States rail- 

 ways, has published the book on drainage for 

 which he was known to possess considerable 

 material. It is intended for the student, and 

 presents the subject in a very comprehensive | 

 form. Some of the experimental demonstrations! 

 are ingenious, and many of the data will prove i 

 of interest to the teacher. In- the United States,^ 

 as in England, the level of the wells is falling,j 

 though usually only slightly, the minimum lower- 

 ing per decade for the entire country beinj 

 0-68 ft. for dug wells and 2-17 ft. for drilled wells;! 

 the maximum recorded is 4-66 ft. for the decade.| 

 The book contains some interesting illustration* 

 of actual drainage problems which cannot fail tc 

 help the student. 



(6) Mr. Doyle's book deals with the specialisec 

 subject of irrigation in its wider aspects anc 

 regarded as the basis of prosperous farming. 

 "The most certain road to profitable production! 

 is by permanent irrigation with good drainage, 

 in an equable climate, free from frost. Underj 

 these circumstances much of the uncertainty ofj 

 farming is eliminated and the best conditions of 



