I03 



er recognizes also, as every farmer recognizes it, that too much 

 nitrogen in the soil is inimical to the production of a large crop of 

 fruit. 



I know a market gardener who used animal manure year after 

 year. He finally reached a point where he could produce the crops 

 that were formerly produced. He has been forced to learn that 

 a large amount of nitrogen tends to force large growth rather than 

 to encourage seed production, and when there is too much nitro- 

 gen in the soil it effects the wood and the fruit buds are not set as 

 they should be. 



If we use alfalfa or vetch or crimson clover as cover crops, 

 we are apt to reach a point when the cover crops are likely to do 

 more harm than good, because of the excessive wood growth, 

 which is a disadvantage in the case of fruit. For this reason: the 

 fruit grower will often resort to the use of cover crops for the 

 special purpose of stopping the further development of tissue in 

 the tree in late summer, and when he has that purpose in mind he 

 will prefer to use barley or oats perhaps, rather than crimson clover, 

 vetch, etc. In this particular case he wants to get out of the soil as 

 large an amount of nitrogen as he can to prevent the soil from mak- 

 ing that nitrogen and the trees from getting it, so as ripen and 

 mature earlier in the season. 



C. J. Tyson. Dr. Lipman, will you allow a question? In the 

 case of cover crops of cowpeas, are the nitrates available to the 

 tree and tree roots in the same season in which the growth has taken 

 place, or is it necessary for the plants to decay? 



Dr. Lipman. It may to some extent. This question happens 

 to bear on investigations that I have been making for several years 

 on the influence of what we call "associated" growth of legumes 

 and non-legumes. 



To answer your question directly, I should say that there is a 

 gain even in the same season, but it will depend on other factors. 

 In the case of cowpeas and soy beans grown with corn, in our ex- 

 perience the yield of corn was decreased rather than increased, be- 

 cause it happened that the season was exceptionally dry and mois- 

 ture was the limiting factor. Before the trees could be stopped 

 from lack of nitrogen they were stopped by lack of moisture in the 

 soil. The corn had enough nitrogen but did not have enough mois- 

 ture. I think that Hedrick has come to that conclusion that trees 

 can benefit from legume cover crops. 



So much for the advantages of growing cover crops. As to the 

 disadvantages, I have already referred to one. That is the excess- 

 ive forcing of wood growth. The soil is itself inclined to be de- 

 ficient in phosphoric acid and potash unless provisions were made 

 for using enough fertilizer during the season when the cover crop 

 is being produced. 



As to moisture, I think I have already referred to that and 

 need not say anything more about it. We might pass on to the ques- 

 tion, what could the farmer do to utilize cover crops in a practical 



