SUB-SOILII^G, TRENCH PLOWIJTG, TILLAGE. 61 



ter weather and frosts. The autumn tillage, however, 

 as well as that at other seasons, should conform with the 

 requirements of the cropping which is to follow. 



Keeping the soil covered, — Land is not cleaned and 

 tilled with the object of being left bare. Let, therefore, 

 the stubble cleaning and autnmn tillage be done early 

 enough to admit of a catch-crop, if not a regular winter 

 crop being sown. The Eothamsted experiments have 

 clearly demonstrated the desirableness of this course. 

 When there is no vegetation, or even when there is veg- 

 etation, during excessive drainage, nitric acid is lost in 

 large quantity through the drains. The remedy for this 

 is to sow the newly-cleaned stubbles with clover, mustard, 

 rape, winter rye, or, in mild climates, to plant cab- 

 bages. The catch-crop will pay well for growing, and 

 the land will be clean after its removal m spring. It will 

 then require comparatively little labor to prepare the 

 soil for the summer crop ; whereas, when all the clean- 

 ing remains to be done at that period, it is so laborious 

 and difficult that it is seldom well done, while the proper 

 season for sowing is often lost through the work not be- 

 ing accomplished in time. Nor must it be forgotten that 

 keeping the soil covered is not everything ; for, as Sir 

 J. B. Lawes points out, the power of vegetation to utilize 

 the nitric acid in the soil is much diminished if there be 

 a deficiency of available mineral constituents. This de- 

 ficiency is to be prevented or made good by stubble clean- 

 ing, autumn plowing, and exposure of the soil ; and fer- 

 tility is to be retained by concurrent good management 

 in cropping. 



Water-furrowing. — It is of the utmost importance in 

 the cultivation of stiff soils, whether they be under- 

 drained or not, that the field be laid up m lands or ridges 

 before winter, and that the intervening furrows be well 



