60 RESULTS WITH BARLEY 



The crops yielded by every plot in these fine seasons are 

 seen to be much above the average, but the return per unit of 

 sulphate of ammonia supplied is by no means increased to the 

 extent we observed in the wheat experiments. The ordinary 

 produce in the barley field is, in proportion to the ammonia 

 supplied, so much better than that yielded in the case of wheat, 

 that much less margin is left for the increase due to a special 

 season. Nevertheless, we find that the return for one cwt. of 

 sulphate of ammonia, employed with superphosphate, is now 

 1 4' i bushels. The return where alkalies were also applied is 

 distinctly less. On this point we have to recollect that four out 

 of the five seasons selected fall in the early years of the 

 experiment when the alkali salts produced no beneficial result, 

 and indeed in some years distinctly diminished the crop. In 

 1858 the quantity of alkali salts supplied in the manure was 

 diminished in consequence of the ill effect observed ; it was 

 still many years before any beneficial effect was perceived from 

 their use on plot 4A. 



2 Experiments at Woburn. The continuous cultiva- 

 tion of barley with various manures has been carried on in the 

 same field, and with precisely similar manures, as those em- 

 ployed in the wheat experiments already described. The 

 superphosphate and alkali salts are applied to the land before 

 sowing the seed. The ammonia salts are put on as a top 

 dressing after the corn is up, usually about the middle of May. 



The produce of barley on the plots receiving ammonia salts 

 during the first ten years, and the second ten years of the ex- 

 periment, will be found in Table XV. (p. 61). The produce 

 yielded by the ammonia salts has shown a considerable falling off 

 in the later years of the experiment ; this special falling off on the 

 ammonia plots is attributed by Dr. Voelcker to the exhaustion 

 of the lime contained in the soil. This exhaustion of lime in 

 the soil would at first have the effect of retarding the nitrifi- 

 cation of the ammonia, and, when the exhaustion became com- 

 plete, would altogether prevent its utilisation by the crop. This 

 subject has been already discussed on page 27. In consequence 

 of this deterioration in the effect of the ammonia salts, we shall 

 take the average produce of the first sixteen years as the basis 



