RESIDUES LEFT 1^' LECTM I NOIS CIJops -jo:; 



spectively— /.e?., of the crops c-oiniiiL; in the srcmul aii.l thin I 

 yccirs after the growtli of the h\miininoiis crop. 



The results show lliat wlicrc the inamirin^ i-, wiili miiicials 

 only the effect of tlie leguminous crop is very marked hoth in 

 the roots and in the barley, /.<'., that the nitrogen introdnc.-.l ])y 

 the growth of clover is operative, not only in the wiii-ai whicli 

 follows it, but also in the roots and the barley which follow tli.- 

 wheat; in fact, in all the crops of the rotation until the ch.v.r 

 comes round again. The root crop is increased by -J.") per cent., 

 and the barley crop by' nearly .")() per cent., the magnitude (.f 

 the increase being due to the fact that the leguminous crop 

 represents the only source of nitrogen on this plot. AVhen, 

 however, the manure put on to the Swedes contains nitrogen, the 

 effect of the nitrogen stored up in the soil by the clover cro}) 

 two seasons before is masked by the fresh nitrogen introduced, 

 and produces no increase of crop. It, however, becomes 

 manifest in the succeeding barley crop, which is 19 per cent, 

 greater on the portion cropped with leguminous plants than on 

 the fallowed portion, so that we can say the value of a c-Iovcr 

 crojD is felt for three years after its growth in all the crops of 

 the rotation, even under the ordinary conditions of fanning when 

 a manure introducing large quantities of nitrogen is use<l once 

 dm-ing the rotation. Of course it must be remembered that thr 

 above mean results are for the four last courses after ten 

 rotations had been completed, and that as the l)enetit is 

 doubtless somewhat cumulative from one rotation to the 

 next, the results represent not so nmch the value of a single 

 clover crop as of its constant introduction into the rtdation 

 in.stead of taking a bare fallow. On the otluM- hand, if wc 

 compare the effects of the single crops, we find that tin- (r«)p.>, 

 of beans, just as they show little effect in the succeeding wlirat 

 crops, so also they cause but a small benefit to the roots and 

 barley coming later still. The continuous enrichnimt ot" thr 

 land shown in the above table has therefc^re been duf in the 

 main to the five occasions on which clover has been taken during 

 the thirteen complete courses covere<l by the table. 



