The California studies revealed that crop characteristics influence the 

 use of defoliants. Crops that are open and erect usually permit adequate 

 penetration and greater net gains. Those that are thick and matted may- 

 require two or more applications, the first to treat outside growth and 

 expose the lower, protected growth and the subsequent to treat this lower 

 growth. Enough time must elapse between treating and harvesting to permit 

 the plant to dry adequately, but not enough time for shattering or regrowth. 



In the Southeast, use of chemicals on crimson clover reduced threshing 

 and cleaning losses and reduced seed moisture, and thereby significantly 

 increased harvested yields in 2 of 4years.In sericea lespedeza, harvested 

 yields were 3 to 1 percent higher and moisture content of seed was sig- 

 nificantly lower in each of 4 years. In evaluating these results, the scientists 

 concluded that the gains were not large enough (even though they were 

 statistically significant) to justify chemical defoliation as a general prac- 

 tice. 



The use of chemical defoliants on clover and alfalfa seed crops 

 has been extensively investigated in England by the National Institute of 

 Agricultural Botany. Dinitro -ortho -cresol, sulphuric acid, pentachloro- 

 phenol, and sodium monochloroacetate are some of the chemicals used by 

 the English investigators. Because these chemicals act only by contact, 

 high spraying pressure is needed. Maximum effect is usually seen within 

 a week of application; 3 to 5 days should elapse between application and 

 combining. The chemicals arrest crop and seed development. It is there- 

 fore important not to spray too early otherwise a high proportion of im- 

 mature seed will be harvested. Viability of mature seed is not impaired. 

 When dinitro -ortho -cresol or other poisonous chemicals are used, no part 

 of the crop can be fed after threshing, and stock has to be kept out of the 

 treated fields for some time after harvest. 



RESEARCH FOLLOWUPS 



Using a suction seed reclaimer, harvesting early, and employing other 

 techniques may cut in half the losses normally sustained during seed 

 harvest. But if losses are to be further reduced, better combines will have 

 to be designed and better ways of operating them will have to be worked out. 

 The study of these twin necessities forms a large part of the research 

 planned by ARS and State experiment stations during ensuing years. 

 Specific items to be investigated include an experimental wind reel and 

 multiple threshing cylinders, which, it is hoped, will increase harvesting 

 and threshing efficiency. 



Mowing subclover 3 weeks earlier than usual gave such encouraging 

 results that time -of -harvest studies for this crop are being continued. 

 Concomitants include determining the best type mower and cutter assem- 

 blies to use. Specific items to be investigated include chrome and conven- 

 tional steel sickle blades and their relative merits under adverse field 

 conditions. 



The use of moisture meters to determine degrees of maturity appears 

 to be better than relying on judgment or stage of growth, if the necessary 

 calibrations can be accurately established through additional research. 



10 



