164 INCOMPATIBLES 



soil, or sifted ashes are often used for this purpose. The manure, 

 thus diluted, can be distributed, either broadcast or by special manure 

 drills. In some cases, drills, which sow both seed and manure at the 

 same time, are employed. 



As a general rule, separate application for each artificial manure would 

 probably be best for their utilisation, but often, in order to save trouble 

 and cost, they are mixed before application and sown in one operation. 



In mixing artificial manures there are certain points which should 

 be borne in mind or losses and damage may be sustained. 



Sulphate of ammonia, for example, should not be mixed with any 

 manure containing free alkali. Basic slag, lime, or wood ashes would, 

 in contact with sulphate of ammonia, lead to evolution of free am- 

 monia and thus loss of nitrogen. 



Acid manures, superphosphate or double superphosphate or dis- 

 solved bones, if mixed with nitrate of soda or nitrate of lime, evolve 

 nitric acid vapours, which act corrosively on brass or metal work and 

 lead to losses of nitrogen. 



The addition of lime, basic slag, basic nitrate of lime, or wood ashes 

 to superphosphate or dissolved bones, leads to the conversion of the 

 soluble acid calcium phosphate of the latter into insoluble forms, with 

 consequent injury to the ready distribution, through solution in water, 

 which is the great advantage of the latter manures. 



Even the addition of any form of tricalcium phosphate, e.g., bone 

 flour to superphosphate, should not be done except just before the 

 mixture is sown, or the soluble phosphates of the latter will undergo 

 reversion to the less valuable " reverted phosphate ". 



Another point to be borne in mind in using concentrated artificial 

 manures, is that direct contact of a considerable quantity of any sol- 

 uble saline matter with the roots of a growing plant is dangerous, since 

 it is liable to induce plasmolysis in the root-cells and thus kill the 

 plant (vide Chap, xi., p. 226). Cases have come under the writer's notice, 

 where large numbers of transplanted tobacco -plants have been killed 

 outright by ignorance of this fact, and where a small quantity of a con- 

 centrated soluble manure was placed in each hole, in direct contact 

 with the roots of the plant. Solutions of above a certain concentration 

 will destroy a plant when in contact with its roots, whatever be the 

 nature of the dissolved substance. 



Nitrogenous Manures. (a) Nitrate of soda. Abundant supplies 

 of nitrates tend to prolong the period of growth of most plants and to 

 favour the formation of foliage rather than seed. They also tend to 

 favour the production of large, succulent roots in the case of root-crops, 

 which, weight for weight, are of much lower feeding value than the 

 same roots grown with a less abundant supply of nitrates. Caution 

 therefore is necessary in the use of this manure, especially in cases 

 where early ripening of seed or fruit is of importance. 



On pastures or meadows, applications of nitrates favour the growth 

 of graminea at the expense of leguminosce and may in this way, if 

 used in excess, injure the herbage and thus damage the quality, though 

 greatly increasing the quantity of the crop. 



