68 
On the Rain and Drainage- Waters at Rothamsted. 
18. The drainage-waters from plots manured with ammonium- 
salts are richest in nitrates shortly after their application. With 
400 lbs. of ammonium-salts per acre applied in March, the April 
drainage-waters have averaged 6'7 lbs. of nitrogen (=42"81bs. 
nitrate of sodium) per inch of drainage. 
19. With -an equivalent amount of nitrogen applied at the 
same time as nitrate of sodium, the April drainage-waters have 
contained 1 1*8 lbs. of nitrogen (= 75"6 lbs. nitrate of sodium) 
per inch of drainage. 
20. In summer the drainage-waters from plots receiving 
200-400 lbs. ammonium-salts contain little or no nitrates if 
phosphates and potash have been supplied ; but with an excess 
of ammonia, or a deficiency of ash-constituents, the nitrates 
produced are imperfectly assimilated by the crop, and appear 
in the drainage-water. 
21. In winter time the drainage-waters from all the plots tend 
to approximate in composition. 
Quantity of Nitrogen Lost per Acre by Drainage, 
22. Taking the average of two seasons of excessive drainage, 
but for which we have analyses of every running from the drain- 
pipes in the Experimental Wheat-field, it was estimated that 
Irom 15 to 17 lbs. of nitrogen were lost per acre per annum by 
drainage from plots which had received no nitrogenous manure 
for many years. Nearly the whole of this loss occurred during 
the period of the year when there was either no crop on the 
ground, or but little growth. 
23. With 44, 88, and 132 lbs. nitrogen applied as ammonium- 
salts in the spring, the estimated loss by drainage was 22, 28, 
and 42 lbs. of nitrogen per acre per annum. With 88 lbs. of 
nitrogen applied as ammonium-salts, without or with different 
mineral manures, the loss ranged from 28 lbs. with the most 
liberal mineral manure, to 50 lbs. without any mineral manure 
for many years. The loss was the greater, the greater the 
deficiency of available potash and phosphoric acid in the soil. 
With nitrate of sodium, spring sown, the loss was greater than 
with ammonium-salts ; but it was greater still with ammonium- 
salts, autumn sown. 
24. Reckoned over thirty years, with much better average 
seasons, the estimated loss by drainage was from 10 to 12 lbs. 
of nitrogen per acre per annum, without any nitrogenous 
manure. With 43, 86, and 129 lbs. nitrogen applied as ammo- 
nium-salts, in most years autumn sown, the estimate<l loss was 
19, 31, and 42"4 lbs. ; and with 86 lbs. nitrogen applied, with- 
out, or with dilferent mineral manures, the estimated loss ranged 
