12 



Timing of herbicide treatment in relation to seeding 



Glyphosate applied in early May and followed by a mid to late-May 

 seeding resulted in highest seedling densities and alfalfa yields in 

 1979 (Tables 8 and 9). Treatment just prior to seeding in late May was 

 much less suitable. In all seedings made from 1977 to 1980 treatment 

 early in May with seeding delayed 2-3 weeks resulted in higher yields 

 of alfalfa the first harvest than did treatment later in May with the 

 same seeding date (Table 9) . First harvest yields of seedings made in 

 1979 were lower than those in 1977 due to a virtual lack of rainfall 

 from early June through July. The best alfalfa ground cover ratings 

 were obtained with the combination of early treatment and mid-to late- 

 May seeding (Table 10). By the second year, however, there was little 

 difference among treatment date/seeding date combinations in alfalfa 

 yield. These results are in agreement with previous research results, 

 which indicate that there is an advantage to delayed seeding following 

 glyphosate application (3,10,18). 



Table 8. Effects of glyphosate application and seeding dates on alfalfa 

 seedling density at four locations. 



Glyphosate Seeding Alfalfa seedling density by location 



applications date Madbury Lee Pittsfield Northwood 



Fall Early May 



Fall Mid- late May 



Early May Early May 



Early May Mid- late May 



Mid- late May Mid- late May 



Means followed by the same letter within a column do not differ at the 

 5% level. 



Seedling counts were made one month after seeding and are averaged over 

 glyphosate rates of 1.3, 2.0, and 2.7 lbs/acre, except at Madbury, which 

 received only 2.0 lbs/acre. 



