WEEDS 109 



The pH or acidity of the soil should be determined in the 

 spring, and if it is more acid than a pH of 6, ground lime- 

 stone should be mixed with the top 8 inches, or if possible the 

 top foot, at the rate of 50 pounds per 1,000 square feet, or 

 more if the soil is very acid. An application, 50 pounds per 

 1,000 square feet, of phosphate in the form of bonemeal may 

 be mixed with the soil at the same time. The remainder of 

 the summer the area may be kept free of weeds. About 

 August first manure or other humus-bearing material should 

 be spaded into the soil so that it has a six inch covering. 

 (Most of its weed seeds will exhaust their food supply before 

 they can reach the surface.) The manure is valuable at this 

 time because humus is difficult to add later and the stimu- 

 lation it gives the grass helps to control the weeds. 



In late summer or early fall apply 30 pounds per 1,000 

 square feet of complete fertilizer and one week later sow the 

 seed. The photograph (Plate VI) shows the influence of 

 fertilizer on new grass. See Chapters 21, 22, and 23 for 

 further information about soil improvement and the appli- 

 cation of fertilizers. Daily watering with a very gentle 

 sprinkle will be necessary unless rains are favorable, until 

 the grass is well started. Not all species of grass germinate 

 at the same time, for example, Kentucky bluegrass may re- 

 quire two weeks or more. If it gets a top of two inches or 

 more it will need no winter attention. 



The grass should make an early rapid growth in the 

 spring. It should be cut frequently to a length of one and 

 a half inches. If it is thick and standing nearly two inches 

 high weeds will be shaded and weakened in their early seed- 

 ling stages when they should be pulled to prevent their going 

 to seed. Many of them will not have enough food stored in 

 the seed to feed the seedling until it can carry on photo- 

 synthesis. Most annual weeds soon disappear under such 

 conditions. 



Crabgrass, the worst annual weed in the lawn, makes 



