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3. Effect upon different crops (176). 



4. Other conditions influencing the action of alkali 



(177). 

 d. Reclamation of alkali land (178). 



1. Irrigation and alkali (179). 



2. Under-drainage (180). 



3. Correction of black alkali (181). 



4. Retarding evaporation (182). 



5. Cropping with tolerant plants (183). 



6. Other methods (184). 



7. Alkali spots (185). 



VII. Manures 319 



a. Early ideas of the function of manures (186). 



b. Development of the idea of the nutrient function of 



manures (187). 



c. Classes of manures (188). 



1. Commercial fertilizers (189). 



(a) Function of commercial fertilizers (190). 



(b) Fertilizer constituents (191). 



(c) Fertilizers used for their nitrogen (192). 



(1) Sodium nitrate (193). 



(2) Ammonium sulfate (194). 



(3) Calcium cyanamid (195). 



(4) Calcium nitrate (196). 



(5) Organic nitrogen in fertilizers (197). 



(d) Fertilizers used for their phosphorus (198). 



(1) Bone phosphate (199). 



(2) Mineral phosphates (200). 



(3) Superphosphate fertilizers (201). 



(4) Reverted phosphoric acid (202). 



(5) Double superphosphates (203). 



(6) Relative availability of phosphate fer- 



tilizers (204). 



(e) Fertilizers used for their potassium (205). 



(1) Stassfurt salts (206). 



(2) Wood-ashes (207). 



(3) Insoluble potassium fertilizers (208). 



