NITRATES IX DK'AINACK WATKIJS -u 



from month to month in ])oth tlic (.-oiicvnt ration ..ftli.' <iiaiMa<:<' 

 water and the loss of nitrat(\ Tlic (•(•nccntratioii is at it> 

 lowest in February, a tinu^ of ycai- when tlic s(.il is still at a 

 very low temperature and lias Immmi thorouLihly washed |.\ 

 the winter's rains. In April the cdnccntration has iiurrasiMl 

 but little, and this combined with a smaller jiercolatioii 

 resuhs in the minimum loss of nitrates t'nr the veai- in 

 this month. The rise in concentration is still slow until 

 July, when there is a considerable juiiip, the concent rat inn 

 reaching its maximum in Septemltcr. The niaximnm lo>- 

 of nitrates comes as soon after this [)oinL as the rain 

 fall is abundant enough to wash through the soil; on the 

 average the greatest annual loss of nitrates takes place in 

 November, from which time onwards both concentration 

 and total loss diminish. All these results refer to soil 

 which is kept bare and uncropped, \\here in consequence 

 the percolation is at a maximum, and where also there 

 are no growing crops to take up the nitrates as they are 

 produced. The effects to be seen under more ordinary condi- 

 tions can be followed in the analyses of the drainage water> 

 from the Broadbalk wheat field, under each phjt of which runs 

 a tile drain at a depth of from 2 feet to 2 feet 6 inches. The>e 

 <lrains all debouch into a cross trench at the bottom of the field, 

 and a record is kept of the occasions upon which there is an\ 

 flow from the drains. Determinations of the nitrates contained 

 in the waters are also made, but as it is im]iossil)le to with 

 draw an ahquot sample of the whole How of the drain. an<l a- 

 also during any particular running the concentration is ah\ay> 

 changing, the earlier discharge being sometimes .stronger and 

 sometimes weaker than the later, it is impossil)le to make any 

 exact account of the quantity of nitrogen removed by each 

 drain. By coml)ining, however, the results obtained over the 

 whole period of the determinations, an aj)proximate i<lea of the 

 concentration of the discharge will be ol)taiiie(l. ()th"r cnn 

 siderations lead one to .suppose that the (lischar<:e fmni the 

 drains does not represent, either in ((uantity or concentration. 



