XII.] USE OF FARMYARD MANURE 239 



long period in the soil before becoming available for the 

 plant. In consequence, dung is a lasting manure, which 

 accumulates in the soil to build up what a farmer calls 

 "high condition" — the state of affairs which prevails 

 when the reserves of manure in the soil are steadily and 

 continuously passing into the available condition in 

 sufficient amount for the needs of the crop, so that 

 there is no necessity for freshly applied active manure — 

 a mode of nutrition which results in healthy growth and 

 good quality. But however marked the farmer's prefer- 

 ence is for such lasting manures, the delay in realising 

 the capital they represent means a certain amount of 

 loss ; besides which, some of the constituents of farm- 

 yard manure are so slowly acting as to be hardly 

 recoverable during the lifetime of the tenant. 



An examination of the records at Rothamsted shows 

 that when farmyard manure was put on at the rate of 

 14 tons per acre every year for the wheat crop, at the 

 end of fifty years only 26 per cent, of the nitrogen applied 

 had been recovered in the crop, and less than 20 per cent, 

 remained stored up in the soil ; more than half had 

 been wasted either by bacterial processes giving rise to 

 nitrogen gas in the soil, or by the washing out of nitrates 

 into the drains. This, of course, is a very extreme case, 

 both because wheat is a plant taking a comparatively 

 small amount of nitrogen out of the soil, and also 

 because the land had become so laden with farmyard 

 manure, that all the processes of bacterial decay and 

 destruction of the nitrogenous compounds had been 

 increased far beyond the normal. On the mangold plot, 

 about 32 per cent, of the nitrogen in the dung has been 

 recovered when the dung had been put on year by year, 

 but when the manure was only put on once in four years, 

 about three-quarters of the total nitrogen applied was 

 recovered in the four crops grown with that manure and 



