268 SOILS AND FERTILIZERS 



cline in the nitrogen content of soils? 131. What is nitrification? 

 132. What are the conditions necessary for nitrification? and 

 what are the food requirements of the nitrifying organism ? 133. 

 Why is oxygen necessary for nitrification ? 134. How does tem- 

 perature, moisture, and sunlight influence this process? 135. 

 What part does calcium carbonate and other basic compounds take 

 in nitrification ? 136. How is nitrous acid produced? 137. What 

 is denitrification ? 138. What other organisms are present in soils 

 besides those which produce nitrogen pentoxide, nitrogen trioxide, 

 and ammonia? 139. What chemical products do these various or- 

 ganisms produce ? 140. Why are soils sometimes inoculated with 

 organisms? 141. Why does summer fallowing of rich lands cause 

 a loss of nitrogen ? 142. What influence have deep and shallow 

 plowing, and spring and fall plowing upon the available soil 

 nitrogen? 143. Into what three classes are nitrogenous fertilizers 

 divided? 144. How is dried blood obtained? What is its compo- 

 sition, and how is it used? 145. What is tankage? How is it 

 used, and how does it differ in composition from dried blood ? 

 146. What is flesh meal ? 147. What is fish scrap fertilizer, and 

 what is its comparative value ? 148. What seed residues are used 

 as fertilizer ? What is their value ? 149. What method is em- 

 ployed to detect the presence of leather, hair, and wool waste in 

 fertilizers? Why are these materials objectionable? 150. How 

 may peat and muck be used as fertilizers? 151. What is sodium 

 nitrate ? How is it used, and what is its value as a fertilizer? 152. 

 How does ammonium sulphate, as a fertilizer, compare in value 

 with nitrate of soda ? 153. What is the difference between the 

 nitrogen content and the ammonia content of fertilizers? 154. 

 What is fixation ? Give an illustration. 155. To what is fixation 

 due? 156. What part does humus take in fixation ? 157. Why do 

 soils differ in fixative power ? Why are nitrates not fixed ? 158. 

 Why is fixation a desirable property of soils? 159. Why is it 

 necessary to study the subject of fixation in the use of manures ? 

 160. Why are farm manures variable in composition? 161. What 

 is the distinction between the terms stable manure and farm-yard 

 manure? 162. About what per cent, of nitrogen, phosphoric acid, 

 and potash is present in ordinary manure? 163. Coarse fodders 

 cause an increase of what element in the manure? 164. What four 

 factors influence the composition and value of manure? 165. 

 What influence do absorbents have upon the composition of 

 manures? 166. What advantages result from the use of peat and 

 muck as absorbents? 167. Compare the value of manure produced 

 from'clover with that from timothy hay. 168. How may the value of 

 manure be determined from the nature of the food consumed ? 

 169. To what extent is the fertility of the food returned in the 

 manure? 170. Is much nitrogen added to the body during the 



