WATER SOILS. 92V> 



evaporation. A rather large di-sh should be used and the evaporation caj-ried on 

 slowly until the aleohol is completely volatilized. There i.s left a large residue of 

 iininioniuni chlorid, which should be well diluted with water, and 2 or 3 cc. of nitric 

 acid are abided. The dish should be covered at first and warmed very gently to 

 avoid loss by spurting. After the salt has been decomposed, the evaporation may 

 be completed. The residue is taken up with water and a few drops of nitric 

 acid, and the determination of phosphorus pentoxid made according to the usual 

 molybdate methoil, titrating the yellow precipitate." 



The results by Dyer's 1 per cent citric-acid method agreed (piite closely with those 

 of the crop tests in regard to potash, but there were wide iliscrepancies in the phos- 

 phoric acid. The phosphoric-acid soluble in ^'^ normal hydrochloric acid agreed 

 very closely with that removed from the soil by 3 successive crops of oats. 



In order to gain some insight into the amount of plant food rendered assimilable 

 in the soil during the growth of the crop "40 pots, holding about 1 pint each, were 

 filled with the same soil, and in each pot, 18 grains of corn were planted. At the end 

 of 2 weeks 6 pots were emptied, the corn plants and their roots freed of soil, all 

 the soil put together as one sample, and all the plants and roots made into one sam- 

 ple. The roots were separated very easily, washed in a minimum quantity of water, 

 the washings concentrated and mixed through the soil, which was then allowed to 

 assume an air-dried condition before its moisture-free weight was obtained. The 

 corn plants with their roots were then ashed and analyzed," /. e., potash and phos- 

 i:)horic acid soluble in hydrochloric acid varying in strength from y^^ normal to 

 2 normal were determined. The same observations were repeated at 3 other periods 

 thereafter at intervals of one week. The plants and roots contained practically the 

 same percentages of phosphoric acid at each period, and in no case Avas it equal to 

 that added in the seed. There was a steady increase of potash in the plants until 

 about 4 times as much was removed l>y the plants as had been added in the seed. 

 The results in general indicate "a condition wherein the mineral compounds are 

 constantly undergoing a change into more soluble compounds, and with a tendency 

 to revert before the compounds reach the point where they would leach out in drain- 

 age water. It is not seen how so great a change in the solubility of minerals can be 

 brought about through so weak an acid as is contained in the sap of plants. In this 

 case, a 5 weeks' growth so affected the more insoluble minerals as to bring 182 

 parts per 1,000,000 of the potash compounds into the range of solubility of 2-normal 

 acid. As a mere question of solution, the weak acid of the sap could not possibly 

 exert so strong a solvent effect as that shown. It is easier to believe that the 

 changes in the mineral compounds of the soil are due to the action of bacteria, which 

 are stimulated by the excretions from the roots. 



"The complete chemical and mechanical analyses have no bearing on the.imniedi- 

 ately available plant food, in so far as the writer is able to interpret." 



In .sampling soils for analysis "a succession of similar depths should be taken in 

 order to ascertain how deep the available food existed, and with this [should be] 

 compared the depth to which the feeding roots of the intended crop are known to 

 penetrate. For actual practice, the writer has constructed a very simple form of 

 samj)ling cylinder, made out of 7-in. wrought-iron pipe. The pipe is cut 6 in. in 

 length, an<l turned down to a thickness of ^r, in-i leaving a collar on one end, to 

 strengthen and drive upon, while the cutting edge is turned at the other end. This 

 makes a strong cylinder weighing al)OUt 4 lbs. The cylinder is driven down to the 

 top, and the inclo.«ed soil taken out. The soil is dug from around the sides of the 

 cylinder as it is driven down for the second (i in., and so for a third ti in. The sep- 

 arate portions are weighed and subsampled for analysis. . . . The more divisions into 

 which a soil sample can be divided the more data there will be for study. . . . 



