278 SOILS AND FERTILIZERS 



soils? 127. To what extent is nitrogen returned to the soil in 

 rain-water? 128. How may the ratio of nitrogen to carbon vary 

 in soils? Of what agricultural value is this ratio ? 129. Under 

 what conditions do soils gain in nitrogen content ? 130. What 

 methods of cultivation cause the most rapid decline in the nitro- 

 gen 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 temperature, 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 pro- 

 duce nitrates, nitrites, and ammonia? 139. What chemical 

 products do these various organisms produce ? 140. Why are soils 

 sometimes inoculated with organisms? 141. Why does summer 

 fallowing of rich lands cause a loss of humus and 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 composition, 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 employed to detect the presence of 

 leather, hair, and wool waste in fertilizers ? Why are these ma- 

 terials 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 sul- 

 phate, as a fertilizer, compare in value with nitrate of soda? 153. 

 What is the difference between the nitrogen content and the am- 

 monia content of fertilizers ? 



CHAPTERS V AND VI. 



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 manure? 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. W 7 hat 

 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 



