220 INTRODUCTION TO GENERAL SCIENCE 



d. 1611 : 139-141. Farmyard Manure. 



e. 1611 : 216-226. Handling Manure on the Farm. 

 /. 1612 : 206-215. Barnyard Manure. 



g. 1902 : 69-76. Barnyard Manure and Bacteria. 

 h. 1903 : 306-317. Losses from Barnyard Manure. 



157. RENOVATION OF WORN-OUT SOILS 



Any soil which has ever produced a crop may, with care 

 and patience, be made to produce again, just as bountifully 

 and perhaps more bountifully. Farmers' Bulletin No. 245 

 gives an excellent summary of the whole matter, as well as a 

 general review of many topics which have been studied in this 

 connection. 



References: 



1. Farmers' Bulletin No. 245. Renovation of Worn-out Soils. 



2. Farmers' Bulletin No. 406. Soil Conservation. 



3. Reprint from Yearbook Department of Agriculture, 1908. 



Plant Food Removed by Rain. 



a. 1612 : 282-290. What may be Done to Renovate Worn- 



out Soils. 



b. 1606 : 20-22. Worn-out Land Lacks Humus. 



c. 1902:119-122. Soil Inoculation and the Control of Soil 



Bacteria. 



d. 1903 : 152-154. Maintaining Soil Fertility. 



158. THE LIMING OF THE SOIL 



Lime corrects the acidity of the soil, and since it liberates 

 plant food, it should be classified as an amendment rather 

 than as a fertilizer. See Section 121, Acids, Bases, and Salts. 

 Soil may be tested by blue litmus paper. If it turns red, lime 

 should be applied. It aids the soil organisms in the fixation 

 of nitrogen, and is necessary to obtain the best results from 

 the use of barnyard manures. Some crops need more lime 



