BOOKS AND CURRENT LITERATURE 



Soil Aeration and Plant Growth. — The importance of an ade- 

 quate air supplj^ to the roots of plants as a factor in their well-being 

 constitutes the keynote to much of the very extensive field experi- 

 mentation and observation on the behavior of cultivated plants which 

 Howard and his colleagues have carried on for over a decade at Pusa, 

 in the valley of the Ganges, and at Quetta in Indian Baluchistan.^ 

 The results of the work have been presented in^several papers, which, 

 although primarily of agricultural interest, are nevertheless of wide 

 application in the general study of the relation of the growth and 

 activities of roots to the soil environment and to the establishment 

 of the species. 



The work of Howard was carried on in the subtropical climate of 

 northern India, but under widely different conditions as regards rain- 

 fall. At Pusa the rainfall is about 50 inches annually, with 85% oc- 

 curring in June-September, during the monsoon. At Quetta, on the 

 other hand, arid conditions prevail. The annual precipitation is 

 about 10 inches only, most of which is in the cold season. The soil 

 of the Gangetic plain is a fine alluvium which puddles easily. The soil 

 at Quetta resembles that at Pusa but it is loess, sometimes mixed with 

 alluvium, and it also easily runs together on wetting. From these 

 general facts we are not surprised to learn that at Pusa the soil of the 

 valley of the Ganges is saturated with water during the monsoon, and 

 as a matter of fact after every severe storm. A similar but less marked 

 condition occurs at Quetta, where unwise and ill-timed irrigation often 

 causes the same results. It consequently happens that problems associ- 

 ated with the aeration of roots in both regions are of the first importance. 



In general Howard's method may be said to consist in observations 

 on the behavior of crops, including trees already established, during 

 the periods of rains, or under conditions attending irrigation. This 

 is supplemented by field experiments which deal largely with the effects 

 of bettered aeration of the soil. Some of the observations and conclu- 



1 Among the more important papers are the following : Howard, A. and Gabrielle 

 L. C. Howard. Soil Ventilation. Bull. No. 52, Agric. Research Institute, Pusa. 

 1915. Howard, A. Soil Aeration in Agriculture. Id. Bull. No. 61. 1916. 



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