192 Physics of the Soil. 



ally be a little deeper in the middle of the space between 

 rows, than close to the hills, because of less danger of root 

 pruning. 



224. Best Time to Cultivate Corn and Potatoes. The best 

 time to till land for corn, potatoes and similar crops, where 

 intertillage is practiced, is before the ground is planted 

 and just as the crop is coming up. When the ground is 

 plowed two or three weeks before the crop is to be planted 

 there is opportunity to develop the nitrates, to kill one 

 or two crops of weeds, and to store in the upper five feet 

 of soil the largest reserve of soil moisture from the spring 

 rains. Besides these advantages there is no period in 

 the growth of the crop when the ground can be stirred so 

 rapidly and so cheaply. Before planting "the disk or 

 spring-tooth harrow may be used and afterward the dif- 

 ferent weights of spike-tooth harrows, which enable a 

 larger area of ground to be covered in a day by a man 

 and team. The harrowing of corn and potatoes should 

 be continued until the plants are well out of the ground 

 and if care is taken to do the work during the hot por- 

 tion of the day, when from slight wilting the plants do 

 not break off readily, there need be but little serious in- 

 jury to them. 



The different types of mulch producing tools are dis- 

 cussed in Chapter XL 



225. Harrowing and Rolling Small Grain After It Is Up. 

 It sometimes happens in humid climates, when drying 

 weather follows a wet period, that a crust forms on the 

 surface of fields sowed to the small grains, which may 

 be injurious to the plants by preventing sufficient aera- 

 tion and increasing the loss of moisture. In such cases 

 the difficulties may be partly corrected by using either the 

 roller or the light harrow with teeth sloping backward. 



If the grain is large, and especially if the surface of 

 the field has been left narrowly ridged and somewhat 

 lumpy, thp nan of the rnllor wlicn Hie surface soil ?*.<? fJnj 



