January, 1909.] 



65 



Scien hfte A gri 'culture, 



world will reach common ground in 

 relation thereto. Animal physiology, 

 including human physiology, has been 

 making rapid strides, through the last 

 two or three decades, largely because 

 of its investigation along industrial and 

 economic lines. So far as the work has 

 been left to the medical fraternity, un- 

 happily, they have not been able to 

 develop much that is new ; they, as a 

 rule, being not only overworked, but 

 underpaid in their ordinary vocation. 

 The investigations of animal life by our 

 scientific agricultural institutions have 

 done much to aid humanity. 



All of this, however, left plant physio- 

 logy in the background and, as we now 

 stand, we hardly know how plants live, 

 breathe, drink, eat and die, as apparent- 

 ly they all must do, and probably simi- 

 larly to all other living beings. In a 

 recent issue of the West India Agricul- 

 tural News there is reprinted from the 

 Memoirs of the Department of Agricul- 

 ture in India an article entitled -'The 

 Toxic Substances Excreted by the Roots 

 of Plants." We reprint this in another 

 column in this issue, but desire to cast 

 our opinion against the accuiaey of its 

 conclusions, even if we have to use the 

 Scotch verdict of " not proven." [Given 

 in the last issue, page 563.] 



The general tenor of the argument 

 used is that some crops are found to do 

 very poorly after certian other crops, 

 when grown upon the land the follow- 

 ing year. The inference is that the pre- 

 vious crop has secreted some toxic ele- 

 ment in the soil inimical to the more 

 recently planted crop. The first refer- 

 ence is made of cotton crops grown in 

 Egypt, in which a certain grass was 

 permitted to grow as a weed. It is 

 recognized everywhere that grasses are 

 inimical to the best growth of our so- 

 called hoed crops. Just why this is, it is 

 difficult to determine with the data we 

 have, but we are led to believe that the 

 grasses growing in with other crops 

 consume the air, moisture and plant 



nutrients of the soil and, generally, 

 being indigenous, they are quite hardy 

 and difficult to extirpate and survive in 

 the contest that they are making with 

 the cultivated crops, unless positively 

 hoed out. 



Why one crop following the other 

 should be bettered or injured because of 

 the previous crop, is not so well under- 

 stood. It is understood that a legumi- 

 nous crop enriches the soil and that any 

 crop following it will probably be much 

 benefited thereby. Sweet potatoes are 

 not leguminous and yet we know that 

 sugarcane will generally do very well 

 in land that has been in sweet potatoes 

 the previous year. We presume that 

 this is owing to the fact that the 

 sweet potatoes occupy the ground 

 to some depth, and in their planting, 

 cultivation and harvesting the soil will 

 receive a degree of tilth not ordinarily 

 given to standard crops like sugarcane 

 and cotton. We are very much inclined 

 to think that the author of the article in 

 question is guessing at his conclusions, 

 and this particularly as given in the 

 fourth statement that the substance 

 excreted by all crops is probably iden- 

 tical. All plant analyses show that the 

 plants consume different quantities of 

 the mineral constitutents of the soil. 

 If the plant absorbs all of its nutrition 

 mineral constitutents included, through 

 its roots and in solution with water, 

 then the excretion is, we belive, sent 

 into the air through the leaves. And 

 we believe that the apparently toxic 

 effects of previously grown crop, on 

 given lands have their origin in the 

 exhaustion of the lands by the growth 

 of such crops rendering them less fit for 

 the successful production of subsequent 

 crops. Everyone interested in scientific 

 agriculture will do well to read the 

 article herein referred to, as it comes 

 from what is persumed to be a scientific 

 agricultural authority in Bombay, Bri- 

 tish East India, — The Louisiana Planter 

 and Sugar Manufacturer, Vol. XLI., 

 No. 8. August, 22, 1908. 



