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more recent work entitled Aj;n'iculture,lia.s mnrli to say of the effect of the 

 physical properties of tlie soil as related to ]>laiit jirowth, and of the 

 physical effect of fertilizers and manures on the soil. Praetieally, how- 

 ever, this has been neglected in all of onr fertilizer work, and the old 

 theory of fertilization still holds, that soils vary in their power of snjjply- 

 ing food to crops and that the chief use of fertilizers is to supply the 

 deficiency of available plant food in the soil. 



It is beginning to be realized that sufficient iini)ortance has not been 

 given to the physical properties of the soil as a controlling cause in the 

 fertility of the land, and it now appears that the chief value of coniiner-* 

 cial fertilizers and manures may be in their physical effect on the soil. 

 That the interest in this subject is growing may be seen from tlie fact 

 that several of the experiment stations have provided tor investiga- 

 tions of the physical properties of soils. At tlu' recent conference of 

 the agricultural colleges and experiment stations held in Washington 

 in August, 1891, a resolution was adojjted asking that the work of the 

 Weather Bureau "shouhl be enlarged to include the physics, condi- 

 tions, and changes of agricultural lands." 



It may be interesting to outline a general ])lan upon which these soil 

 investigations should be carried out. Tiie investigations are based u|)on 

 tin' following geiieralizations: The local <listiilMition and development 

 of i)lants are largely dependent up(tn the circulation of water within 

 the soil and the ease with which the i)roper Water sn]»i>ly may b(^ 

 maintained within the soil for the crop, and U]»on the relatiiui of the 

 soil to heat. Soil exhaustion is due to a <-hange in the arrangement of 

 the soil grains, changing the relation of the soil to moist in e :iud heat. 

 The chief value of commercial fertilizi'is and manures is in thcii' jthysieal 

 etiect on the texture of the soil or the airangenu'iit of the soil giains. 

 which changes the iclatiou of tlicsoil to moisture and heat. 



The oltjecls of the work are to study the iclation <tf soils to nntisture 

 and heat, to lind out the con<liti<uis which determine the htcal dis- 

 tribnti<m and dcvclopnu'iit of plants in the great soil fornniti(ms,and to 

 see how these c(Miditi(Uis gradually change in the detcri«»ratiou of loc:il 

 soils. 



Soils should be classified according ta their geological origin, and. 

 until soiue better nu-thod is devised, accortliiig to their ]>resent agri- 

 cultural value. The lattt-r should not only include the familiar classi- 

 lication into wheat, <'orn. tobacco, and tiuck lands, but the natural 

 herbage should also be determined, as showing what conditions jirexail 

 in the soil best ada])ted to the nee<ls of a particular class of plants. A 

 better systiMn of classification can ]>robably be W(»rl<e<l out lati'r from 

 the mechanical analysis of the soils, and a few general types be estab- 

 lished for comparison with soils of local value. 



Localiti<\s fairly reiuvsenting the normal conditions in these typo 

 soils should be carefully selccttMl tor tin' inv<'stigation of the comlitions 

 of moisture and heat peculiar to the great soil tnimations. IJecords 



