76 



TROPICAL AGRICULTURE 



CHAP. 



The action 

 of the 

 plough. 



Ridges and 

 furrows. 



The Plough is an implement used to perform the work 

 of the spade. It consists of a curved blade of iron — the 

 vioidd-board or turn furrow, terminating in a strong steel 

 extremity— the ploughshare, and so arranged that it can be 

 dragged through the earth by cattle, and guided by a man. 

 In front of the ploughshare is a strong, knife-like, cutting in- 

 strument called the coulter, which cuts the earth and thus 

 allows the free entry of the ploughshare, the mould- board 

 then turns over the slice of earth to one side, thereby 

 bur}dng the weeds and exposing the under surface of the soil 

 to the sun and air. Ploughed land is made up of alternate 

 ridges and furrows, and therefore a much larger extent of 

 soil is exposed to the atmosphere, than if it were dead 

 level. Some ploughs are made to run along the furrows 

 made by the ordinary plough, in order to break up the 

 subsoil, for it has been found that continual ploughing 

 of the land to one uniform depth causes the subsoil to be- 

 come so hardened and compact that the roots of plants can- 

 not easily penetrate it. This compact layer is called a 

 Plough pans, piougkpan, and one of the objects of the subsoil plough is to 

 break it up. 



The Cultivator or Grubber is an implement made 

 on the type of the rake. It consists of a strong frame to 

 which are attached many teeth, called tines, descending 

 obliquely downwards and forwards. Its use is to break up 

 the soil after it has been ploughed, so as to expose fresh sur- 

 faces for the atmospheric agencies to work on, and it also 

 serves to draw out the weeds that have been torn up by the 

 plough. 



The Harrow is made in various forms ; and it too is 

 simply an extension of the type of the rake. Harrows are 

 used for turning over and breaking up clods, so that the soil 

 may be pulverized and the particles exposed to the air and 

 sun. Some light harrows made of chain work are used to 

 rake the soil over seeds that have been sown, and others are 



