178 THE NURSERY-MANUAL 



Nurserymen now often grow a cover-crop between trees to 

 supply the needed humus, the various annual leguminous crops 

 (as crimson clover) being preferred, although rye and buck- 

 wheat are good. In regions where they mature, cowpeas are 

 sown. On account of the scarcity and cost of labor, nurseries 

 are likely not to be kept so clean as formerly throughout the 

 season, and the weeds may add useful fiber to the land; yet 

 weeds are not to be recommended for this purpose. 



For the resting period or rotation between nursery crops, 

 longer-lived crops may be used. Kains suggests sweet clover 

 as specially valuable (M. G. Kains, "Plant Propagation, Green- 

 house and Nursery Practice," 1916), " because this plant burrows 

 deeply and opens up the soil well besides adding considerable 

 humus, both by its decaying roots and its tops, when these are 

 turned under. Perhaps it would reduce the resting period to 

 two or three years, as against three to five or even more under 

 common practice." Usually the nursery lands are rested in 

 red clover or other meadow crop ; and if they can be pastured 

 before treed again, the result is supposed to be better. 



Although the chemical analyses of nursery trees show com- 

 paratively small amounts of the more important plant-foods, 

 nursery lands need fertilizing. Nitrogen is needed in com- 

 paratively large amounts. It chiefly conduces to strong 

 growth. It is also augmented by the addition of humus and 

 the improvement of the physical condition of the soil. When 

 nursery stock is making a poor growth, the grower should 

 first see that the tillage of the soil is as thorough and perfect 

 as possible, to supply additional plant-food and to preserve 

 the soil moisture. He may then add nitrogen in the form of 

 chemicals. The application should be made in spring or early 

 summer. He should then be sure that insect or fungous at- 

 tacks are averted. If the land was originally in fit condition 

 for trees, and adapted to them, these suggestions should afford 

 relief. More attention is being given to the complete fertiliz- 



