Vol. XII KEBRU ARY 11, 1918 No. 6 



JOURNAL OF 



AGRICULTURAL 

 RESEARCH 



CONTE^NXS 



T^mfi 



Water Eztractions of Soils as Criteria of their Crop^Pro- 



ducing Power -------- 297 



JOHN S. BURD 



(Contribution tram California Agricultural Experiment Station) 



Effect of Season and Crop Growth in Modifying the Soil 



Extract - - - - - - - - - 311 



GUY R. STEWART 



(Contribution from California Agricultural Experiment Station) 



The Freezing-Point Method as an Index of Variations in 



the Soil Solution l)ue to Season and Crop Growth - 369 



D. R. HOAGLAND 



(Contribution from California Agricultural Experiment Statton) 



PUBUSHED BY AUTHORHy OF THE SECRETARY OF AGRICULTURE. 



WITH THE COOPERATION OF THE ASSOCUTION OF AMERICAN 



AGRICULTURAL COLLEGES AND EXPERIMENT STATIONS 



WASHINGTON, D. C- 



'.'A^HINaTO^<:oOVERNUENTPmKTIf<a OFFICE ; lOr; 



