36 



directly from the air, and for this reason they are called 

 green manure crops. In citrus groves a number of legumes 

 are used such as cowpeas, velvet-beans, lablab beans, 

 canavalia, etc. The practice is to plant a crop between 

 the trees at the beginning of the rainy season, and stop 

 all cultivation as long as the rains last, except keeping 

 the vines from climbing up the trees. In this way the 

 soil is greatly benefited by the large amount of humus 

 and the fertilizer bill is greatly reduced, because it is 

 necessary to apply only potash and phosphorous, and 

 these ingredients are cheap compared to the nitrogen 

 which is in this case supplied by the cover crops. 



INFLUENCE OF FERTILIZERS ON THE TREES 



In sandy soils there is no question about fertilizers 

 being needed, because experience has shown very thor- 

 ourghly that a citrus tree will not make satisfactory 

 growth without it. Those who start groves on heavier 

 soils such as clay and clay loam often do so because 

 they figure that they will not have to use fertilizers. 

 This is unfortunately a mistake, and the sooner a 

 planter realizes the fact the better it is for him. It is 

 undeniable that citrus trees often grow faster on such 

 soils without fertilizer than on lighter soils with fertil- 

 izer, but too frequently the loss is very great from gum- 

 ming. On light soil a tree will begin to bear when three 

 years old if properly .fertilized, but on many of the 

 heavier soils trees 5 to 6 years -old do not even bloom. 

 Such soils do respond 'to fertilizers however, and a med- 

 ium heavy soil if well drained can be handled very 

 satisfactorily and usually cheaper than a light sandy 

 soil. The thing to remember is that virgin soil containing 



