90 EGYPTIAN AGRICULTURE. 



of the open soil, and its heating and cooling, cause the soil 

 clods to crumble away, more especially when the air is very 

 moist and the soil has been cultivated when in a proper 

 state. A long exposure to the atmosphere has the further 

 advantage of checking the growth or killing off injurious 

 insects and fungi. In reviewing the various tillage opera- 

 tions, it is rather difficult to settle the real function of, 

 for example, the native plough : its action is something 

 between that of a plough and a cultivator. Similarly the 

 zahaffa combines some of the functions of the harrow and 

 the roller. The tillage operations which it is proposed to 

 consider are ploughing, subsoiling, ridging, cultivating, 

 zahaffing, levelling, fassing, and weeding. 



It is most convenient to define ploughing as the opera- 

 tion of turning over the soil. The turning over is often far 

 from being complete, but at any rate ploughing turns over 

 more soil than any other tillage operation. The objects 

 of ploughing are : firstly, to change the position of the soil 

 so that the next crop may have a layer of fresh soil to 

 feed on, and so that the rich surface layer may be turned 

 down to the plant roots, and the exhausted lower part of 

 the soil may be brought to the surface to recover under the 

 action of another set of weathering agents. Secondly, to 

 mix the soil so that the plants will obtain a regular supply 

 of food in every direction in which their roots may travel. 

 Thirdly, to loosen and free the soil, to destroy its packing 

 and make it friable. Lastly, to kill the weeds which are 

 ever ready to rob the plant of food and space. Land should 

 be ploughed when it is neither too wet nor too dry, in fact 

 it is best ploughed when it offers least resistance to the 



