494 WHY LAND BECOMES CLOVER-SICK. 



wheat, oats) usually grown, must be raised. But of the leguminous 

 crops we have the choice of beans, peas, vetches, and clover — of root 

 crops, turnips, carrots, beets, and potatoes — while of grasses, there is a 

 great variety. Instead, therefore, of a constant repetition of the turnip 

 every four years, theory says — make the carrot or the potatoe take its 

 place now and then, and instead of perpetual clover, let tares or beans, 

 or peas, occasionally succeed to your crops of corn. The land loves a 

 change of crop, because it is better prepared with that food which the 

 new crop will relish, than with such as the plant it has long fed before 

 continues to require. 



It is for this reason that new species of crop, or new varieties, when 

 first introduced, succeed remarkably for a time, and give great and en- 

 couraging returns. But they are continued too long — till the soil has 

 been exhausted in some degree of those substances in which the new 

 crops delighted. They cease in consequence to yield as before, and fall 

 into undeserved disrepute. Give them a proper place in a long rotation, 

 and they will not disappoint you. 



. It is constant variety of crops, which, with rich manuring, makes our 

 market gardens so productive — and it is the possibility of growing in the 

 fields many diflferent crops in succession, that gives the fertiUty of a gar- 

 den to parts of Italy, Flanders, and China.* 



§ 5. Why land becomes tired of clover {clover-sick). 



What I have said of the general principle might be supposed to 

 explain fully why crops fail at one time and succeed at another — why 

 the soil will nourish one plant well, while it is unable adequately to sus- 

 tain another. But a brief reference to the case of the clover plant will 

 enable us to see how modes of culture, apparently skilful and generous, 

 may yet be of such a kind as to lead, sooner or later, to the inevitable 

 failure of a particular crop. 



It is known that upon many well cultivated famis the lands become 

 now and then tired or sick of clover, and this crop failing, the wheat 

 which succeeds it in a great measure fails also. It may be said that the 

 soil in such a case is in want of something, and so it is, — but how does 

 this deficiency of supply arise ? The land is skilfully managed and 

 has been well manured, and the failure of the clover crop is, therefore, a 

 matter of surprise. 



If farm-yard manure be copiously applied previous to the root crop, 

 the land has received a certain more or less abundant return of all those 

 substances which the last rotation of crops had carried off from it, — and 

 which the new rotation will require .or food. When the clover comes 

 round, therefore, a supply of proper food is ready for it, as well as for 

 the wheat which is to follow. 



But if ihe turnip crop be raised by means of bones only, the lime 



* A method of superseding in some measure the necessity of a rotation of crops is de- 

 scribed by Mr. James Wilson as long practised in Shetland, in the neighbourhood of Ler- 

 wick. " It is known that bear has been grown in the same patch for perhaps 100 years suc- 

 cessively, and this they managed by scarifying other parts of the ground (the out field por- 

 tion), and renovating the arable patch by spreading it over the surface." This was varying 

 the soil instead of the crop. A five years' rotation, however, is now getting into favour, and 

 the average produce, after liming, is found to be increased by it four-fold. In this district 

 much herring refuse is employed as a manure, and the improved land lets at aOs. an acre. 

 —Wilson's Voyage round the Coast of Scotland, II., p. 268. 



