156 Food from the Soil 



up the field, and let it alone to recover itself; in other 

 words, he allowed it to lie fallow. 



And what goes on in a fallow field ? Generally 

 speaking it is, or was, both ploughed and harrowed 

 repeatedly, so that the soil might be exposed as much 

 as possible to the action of the air and rain, by which 

 the mineral matter would be dissolved ready for the 

 next crop. Then in the winter the soil would be yet 

 further broken up by the freezing of the moisture in 

 its pores, which would separate grain from grain, 

 reducing it to powder in a way that no plough or 

 harrow yet invented can do. The crumbling of the 

 soil would make it yet more easily dissolved by water, 

 as well as more easy for roots to penetrate ; nor must 

 it by any means be forgotten that while the land lay 

 idle the worms were busy, turning it over, also, grain 

 by grain, and enriching it as already described. And 

 though the farmer did not sow it, seeds were sown by 

 the wind, and a crop of weeds was certain to spring 

 up, whose half-decayed leaves the worms would drag 

 into their burrows. The whole wild crop, too, would 

 be ploughed in, and, with the roots of the farmer's last 

 crop, would be gradually decayed. The soil when 

 damp would absorb ammonia from the air, and 

 ammonia would also be brought down by rain and 

 snow, and converted into nitric acid, which would 

 combine with some of the minerals already mentioned; 

 and in this way, as well as by the decay of the organic 

 matter left in, or added to, the soil, a fresh supply of 

 nitrates would be prepared. 



