SOILS. 



133 



It is obviously of interest to consider whether 

 or not there is evidence of decline in the amount 

 of nitrogen as nitric acid annually formed in 

 the soil over that period. As the drainage 

 water was not systematically sampled and 

 analysed until the year 1877, accurate estimates 

 of the amount of nitric acid in the drainage 

 water of the first seven years of the experiment 

 cannot be made; but the indication is that it 

 averaged more over the earlier than over the 

 subsequent years. Examination of the results 

 given below for the three five-yearly periods of 

 the eighteen years 1877 to 1895 shows that the 

 average annual loss of nitrogen in the drainage 

 was over 40 lbs. per acre, equal to a loss of 

 about 280 lbs. of nitrate of soda; over the second 

 five years about 32 lbs. of nitrogen, equal to 

 say 200 lbs. of nitrate of soda; the third five 

 years showed a loss of nitrogen of about 30 

 lbs., which is equivalent to rather less than 

 200 lbs. of nitrate of soda; whilst in the last 

 three years, 1892 to 1895, the annual loss of 

 nitrogen was more than 32 lbs., equal to 206 lbs. 

 of nitrate of soda. Taking the average loss for 

 four-monthly periods and the total harvest years 

 extending over the same period of eighteen 

 years, it is seen from the following table that 

 from September to December there was a loss 

 of nitrogen equivalent to 126 and 111 lbs. of 

 nitrate of soda respectively; from January to 

 April a loss of 50 lbs. and 63 lbs.; and from 

 May to August 51 lbs. and 44 lbs. The whole 

 harvest year thus shows a total loss by drainage 

 of 227 lbs. and 218 lbs. of nitrate of soda per 

 acre. The loss of nitric acid, that is of soluble 

 plant-food, is found to be very obviously depen- 

 dent on the amount and on the distribution of 

 the rainfall and of the drainage from the land. 



Table showing the Loss of Nitrogen as Nitric Acid, and its 

 equivalent as Nitrate of Soda, per acre from Uncropped 

 and Unmamired Soil at Rothamsted, Hertfordshire. 





Reckoned as 

 Nitrogen. 



Reckoned as 



Nitrate of 



Soda. 





Soil 

 20 ins. 

 deep. 



Soil 



60 ins. 

 deep. 



Soil 

 20 ins. 

 deep. 



Soil 

 60 ins. 

 deep. 



5 years 1877-8 to 1881-2, ... 

 5 years 1882-3 to 1886-7, ... 

 5 years 1887-8 to 1891-2, ... 

 3 years 1892-3 to 1894-5, ... 



lbs. 

 44-37 

 32-26 

 31-55 

 33-57 



lbs. 

 42-45 

 31-67 

 30-01 

 30-87 



lbs. 

 284 

 206 

 202 

 215 



lbs. 

 271 

 202 

 192 



197 



Sept. 1 to Dec. 31, 



Jan. 1 to April 30, 



May 1 to August 31, 



19-72 

 7-89 

 8-04 



17-34 

 9-80 

 6-93 



126 

 50 

 51 



111 

 63 

 44 



Total harvest year, 



35-65 



34-07 



227 



218 



It may be well to note that the whole of the 



nitrogen that is shown to be lost by drainage 

 from our soils is not all available to ordinary 

 plants, for the reason that many of these only 

 assimilate the spring or early summer formed 

 nitrates, the principal growth and power of 

 assimilation having ceased by the month of 

 July. Thus we find that the greatest loss 

 occurs from September to December, and the 

 least loss from May to August. Root-crops 

 such as potatoes, beet-root, carrots, onions, tur- 

 nips, &c, may still get hold of summer-formed 

 nitrates, but the nitrates produced in the autumn 

 and winter are of little use to plants. The 

 spring nitrification alone is, as a rule, quite 

 insufficient for the requirements of the crops 

 then starting into rapid growth, hence the need 

 for and value of increasing quantities of artifi- 

 cially supplied manure. 



Deherain being anxious to ascertain if it was 

 possible to excite in our cultivated soils during 

 the period of spring-time a sufficiently active 

 nitrification of the organic matters, so as to 

 avoid the great expense of nitrogenous artificial 

 manures, instituted a series of experiments with 

 soils obtained from different districts of France 

 in order to determine the point. From the re- 

 sults obtained the following conclusions were 

 drawn: — Trituration or pounding of the soil is 

 a powerful method of causing active nitrification. 

 In making preparation for the winter season, 

 soils should be dug or ploughed, and left in a 

 rough state, with the clods unbroken. There 

 ought to be no trituration if the soil is to remain 

 uncovered during the winter months, the break- 

 ing up of the soil particles causing active nitri- 

 fication, which must be absolutely hurtful; the 

 nitrates formed being dissolved, carried into the 

 drains by rain, or into the lower subsoil, and 

 thus lost. With the return of spring, seed-sow- 

 ing begins. Trituration should then be as com- 

 plete as possible, all known methods for pulver- 

 izing and crumbling of the soil being adopted. 

 During the growth of the crops the hand-hoe 

 and horse-hoe should be vigorously used, for it 

 was found in these experiments that the weight 

 of beet-roots obtained was in proportion to the 

 number of cross-ploughings the land had re- 

 ceived 



It may be mentioned, further, that in three 

 soils at Eothamsted, Hertfordshire, in fair agri- 

 cultural condition, and cultivated as bare fallow 

 since the harvest of the previous year, the amount 

 of nitrogen as nitric acid per acre was found in 

 September and October, to a depth of 27 inches, 

 to be as follows: — No. 1, 56-5 lbs.; Xo. 2, 

 58-8 lbs.; and No. 3, 59*9 lbs. Again, the soils 



