438 ANNUAL REPORT OF THE Off. DoC. 



of decomposition. When this process of decomposition is going on 

 IE the soil, organic snbstances are produced of an acid nature, which 

 when they come in contact with substances of an alliali nature, such 

 as lime, potash and soda, they form neutral bodies or organic salts, 

 called humates, and the process is called humification. The fact 

 that this chemical action takes place in the soil between the humic 

 acid and the potash, has been experimentally demonstrated by 

 mixing known quantities of organic materials, such as green clover, 

 meat scrap, saw dust and farm manure, containing known percent- 

 ages of potash, with soil and allowing humification to go on for a 

 year or two under normal conditions. It was found that the humus 

 produced in this way contained from 4 to 10 per cent, more potash 

 than the original organic substances, and the humus in the original 

 soil. Not only is this the case, but it has been discovered that humus 

 formed from organic matter containing nitrogen is more valuable, 

 not only for its nitrogen content, but because it has the power of 

 combining with, and extracting 2 to 3 per cent, more of the insoluble 

 potash and phosphoric acid than humus from organic substances 

 containing little or no nitrogen; and at the same time putting its 

 original nitrogen nearer the available condition. It has not only 

 been shown that these humates increase the fertility of the soil, but 

 that they put plant food in such a condition that plants can appro- 

 priate it. Oats planted in sand containing no fertilizing elements 

 except that which was added in the form of humus, produced normal 

 crops. 



In order that humification may go on unobstructed and produce the 

 best results, soils must contain a sufficient amount of alkali, such as 

 lime, to produce the neutral humates above referred to. 



The best method of keeping up a supply of humus is by the use of 

 large quantities of farm manure and an intelligent rotation of crops. 

 Loss of humus is always going on in the soil and when a soil is con- 

 tinuously cultivated without the addition of organic matter, and 

 lime, the humus will be greatly reduced and will finally change into 

 the inert form because little of it is left except carbon and oxygen. 

 This reaction takes place more readily in sandy than in clay soils, 

 therefore they are always more in need of humus than clay soils, and 

 show the need of it more. 



We have seen that humus formed from organic substances con- 

 taining nitrogen is more valuable than humus formed from organic 

 substances containing little or no nitrogen; especially is this the 

 case with humus formed from decaying vegetable matter of legu- 

 minous plants. It has been demonstrated beyond a doubt, that the 

 legumes have the power to obtain nitrogen directly from the air, 

 through the agency of an organism which form little nodules on 

 their roots, where it takes up the free nitrogen of the air and con- 



