100 CONSERVATION AND IMPROVEMENT OF SOIL 



use judgment in deciding whether to plow a field in the fall or to 

 have it protected with a cover crop. He must consider the char- 

 acter of soil, slope, insect enemies, the possibilities regarding 

 time and labor, and perhaps other special matters which bear upon 

 these points. 



Packing Loose Soil. Soils which are plowed in the spring, 

 only a short time before the planting of the crop, may be so loose 

 as to prevent the capillary rise of water to the seeds or to the roots 

 of the crop after it begins growth. To correct this difficulty 

 it is necessary to bring the surface soil in contact with the 

 soil below 'the furrow-slice. This may be done by packing 

 the soil with a plank drag or roller. If the latter is used 

 the soil should be left with a loose, broken surface to pre- 

 vent too rapid evaporation. The harrow may follow the roller, 

 unless the roller is of a type which leaves a roughened 

 surface. Packing may sometimes be accomplished by the use 

 of a common spike-tooth harrow with the teeth sloping 

 backward. 



Sandy soils or other loose soils may be greatly improved by 

 packing. (See Chapter VII.) 



GREEN MANURING 



This term applies to the growth of crops not intended as money 

 crops, but intended to be plowed under to benefit the soil. They 

 are not always turned under in their green state, but may improve 

 the soil nearly or quite as much if they die before being plowed 

 under. 



Green Manure from Cover Crops. A double purpose is very 

 often accomplished in this operation. (1) The crop, while grow- 

 ing, serves the purpose of a cover crop. (2) It may be used as 

 green manure to improve the soil. 



The other purposes of cover crops should here be mentioned: 



(a) Erosion of soil is checked or prevented; this is particularly 

 helpful on hillsides. 



(6) When grown in orchards they prevent the frequent freez- 

 ing and thawing of tree roots and thus avoid much winter injury. 



(c) If grown in late summer and fall in orchards they check 

 the growth of the trees, so that the wood may become more mature 

 before winter. 



(d) They conserve plant food and moisture which would 

 otherwise be wasted. 



