W9 



about the iniportanco of these matters. Imt I hflieve there is a jroUleii oppor- 

 tunity for some one. 



There is another matter which has suggested itself to me. We have all been 

 irying for a long time to tind a solvent which will lell us in regard to the 

 assiniilability of the phosphoric acid in tlie soil, and as yon well know. c(>rtain 

 (Jermans at an earlier date and Professor Hall recently have worked at 

 analyzing i)lants to see if some hint can not he gained from their composition 

 as to the recpiirement of the soil where they have been grown. We have <lone 

 similar work in the jtast year in Rhode Island by way of several preliminary 

 tests. I wish to emithasize that we do not wish to say that we have anything 

 absolutely definite ^r positive, but it is at least suggestive. We find that the 

 ordinary flat turnip, when grown upon certain soils, contains twice as much 

 phosphoric acid as when grown upon others, and there was a close relationship 

 between the ph(»sph()ric acid in the tnrniii and tlie .iiiiomit of irop produced. 

 All I can say at the |)resent time is that we have no conclusion to offer, but 

 it is suggestive that possibly the ordinary fiat turnip may be grown upon a soil, 

 and by its snbseiiuent an.ilysis we <-an draw conclusions as to whether the soil 

 is well stocked with assimilal)le ijliosjihoric acid or not. We hope to ascertain 

 what there is in this matter and do not wisli to i.i-oliil)it others from making 

 similar trials. 



Another line of investigation of interest has been suggested by our experiments 

 with sodium and iwtassium salts. We have found like others before us that ci-r- 

 tain kinds of i)lants are very grasping in their i»roi»ensities in so far as c(mcerns 

 taking up potash. In other words, they will take (Uit of the soil more |iotasb 

 than they seem to reiinire. In fact. I think .Jordan and .Tenter showed In an 

 instance of crops of the same size that ten times as much potash was removed 

 from the soil in one case as in the other. Now. we lind th.it where soda Is pres- 

 ent certain idnnts take uii large amounts of it. In other words, they satisfy 

 their demand for alkali with soda and take out very nmch less potash. Sodium 

 seems, therefore, to conserve the potassium supply in the soil. If we are right 

 in this, it seems to me of the utmost importance that an extensive and thorough 

 >,tudy should be made to find out in connection with what varieties of plants 

 sodium can conserve the potassium supply. With the i)otato plant it is probably 

 not possible to any practical extent, and with the cereals and possibly with 

 millet the same may be true, but when we grow at least certain root crops there 

 is no question but what if we apply sodium salts liberally there will be left in 

 the soil much potassium which would otherwise have been taken out. This is 

 another fruitful field for investigation, and I think it is an important one. We 

 propose to do something with it in Rhode Island, but we are not intending to 

 usurp it. and I mention this so that if any of you are interested you will take it 

 up and pursue the question further. 



Another thing has been suggested by I'rofessor Loew. If he is right, some 

 soils contain so nmch lime and so little nuignesia and others so little lime in pro- 

 portion to the magnesia that the best results are unobtainable. It seems to me 

 very important to test the question and see if there are such ill relationships 

 actually existing in our soils as one might infer from his writings, for if so we 

 ought certainly to take the matter more frequently under consideration. Per- 

 sonally, I think that in some instances the ditliculty attributed to such ill rela- 

 tionships of lime and magnesia was really due to other causes. Yet I have no 

 doubt there may be very much in it, and what there is ought to be found out. 



Finally. I wish to seize this opportunity to enter a protest against the use of 

 the word " humus " without (lualiflcation. One reads in text-books, bulletins, 

 and in the agricultural press that soils need humus. Now, I may be mistaken, 

 but I think I have seen soils that had too much humus and which were neverthe- 



