418 MANAGING ORCHARD SOILS AND FERTILIZING TREES 



factory. This system is also occasionally used in young non-bearing 

 trees on level ground (Fig. 164.) It is very questionable, however, 

 whether it pays to cultivate the tree rows in orchards on very steep 

 land. It would, no doubt, be just as satisfactory to use the sod mulch 

 plus heavy fertilization over the entire area. 



With older orchards, alternate cultivation is often used, every other 

 row being cultivated one year while the remaining rows are in sod 

 mulch. The following year the systems are reversed and the cultivated 

 rows are seeded down. By these means erosion is prevented and a part 

 of the orchard is cultivated each year. In the past this system has often 

 seemed advisable, but whether it will continue to be so in the future, 

 in view of the satisfactory responses being obtained in sod-mulch 

 orchards when heavier applications of nitrogen fertilizers per tree are 

 used, is questionable. 



(7) Clean Cultivation and Cover Crops: Unless the or* 

 chard is planted on very steep land, the system of clean culti- 

 vation plus cover crops will generally be found to be very 

 satisfactory and profitable. On level land, no other system can 

 quite equal it in many cases, unless a very large supply of 

 some cheap additional mulch is available for use, as outlined 

 previously. 



The clean cultivation and cover-crop system consists es- 

 sentially of plowing the ground early in the spring, harrowing 

 or disking it several times through the summer in order to kill 

 weeds and keep a good dust mulch on the surface, and finally 

 sowing a cover crop, which is to be plowed under later 

 (Fig. 162 a, dj e). In some of the lighter soils, disking can be 

 substituted for plowing, but even then it will generally pay to 

 plow at least once in every three or four years, in order to 

 prevent the formation of a hardpan layer just beneath the 

 depth to which the disk reaches. 



By cultivation, weeds are destroyed; the soil becomes bet- 

 ter aerated and warmer; the soil particles are broken up into 

 smaller pieces, thus presenting a greater feeding area for the 

 roots; nitrates are produced early in the spring and in large 

 quantities through increased nitrification; the water of rains 

 is quickly absorbed, and the loss of water is prevented through 



