VI.] ROLLING AND HOEING in 



down ; (2) cooler at the surface than is a piece of adjoin- 

 ing land which has been kept loosely covered with soil. 

 Too much stress cannot be laid on the importance of 

 consolidating the soil round the roots of plants, 

 especially in their earlier stages of growth ; although 

 gardeners are accustomed to tread over their beds 

 before sowing small seeds like onions, they often allow 

 the soil of flower-beds to become altogether loose and 

 porous down to considerable depth, simply by doing 

 too much trenching and deep digging. 



As soon as the plant has been established the chief 

 work of the farmer or gardener consists in maintaining 

 a loose surface of the soil for the remainder of the season. 

 Not only are the various processes which liberate plant 

 food from the reserves in the soil promoted by a constant 

 stirring of the surface, but above all things the stock of 

 water in the soil is conserved for the uses of the plant 

 alone. A loose surface tilth soon dries itself, but as it 

 possesses no close connection with the layer below there 

 is no continuous water film from the water-bearing layers 

 to the surface at which loss is suffered by evaporation. 

 The water is lifted by surface tension as far as the soil 

 is consolidated, i.e. up to the roots of the plant, but it 

 cannot get into the layer which is actually exposed to 

 the drying wind and sun, because this layer is only lying 

 loosely on the water-holding soil with large gaps 

 between. The loose, friable layer of soil acts as a screen 

 on the soil below, protecting it from evaporation : it is in 

 fact a soil mulch, and serves just the same purpose as a 

 layer of farmyard manure, or straw, or grass clippings 

 — any of the materials which a gardener usually calls a 

 mulch. By keeping it constantly renewed, the soil 

 mulch may be completely effective in preserving all the 

 water originally present in the soil until the only loss of 

 water to the soil is that which the crop takes and utilises. 



