26 OKCHAED GEEEN-MANURE CROPS IN CALIFORNIA. 



In Table II the weight of the green material produced per acre is 

 presented, together with the weight of the same when dry. The 

 green material was weighed at the time of cutting, and for estimates 

 of the yield of dry matter was weighed again in thirty days. During 

 this period the various crops had become nearly dry, but undoubt- 

 edly the moisture content, even at this time, would vary to some 

 extent, although not nearly so much as in the green state. 



That the yield of green material as shown by its weight may be 

 misleading without proper correction for the moisture it contains is 

 shown in Table II in the case of the two lots of black-purple vetch. The 

 first lot was quite succulent at the time of cutting, and consequently 

 was very heavy in the green state, while the other was a little older and 

 less succulent, and so was much lighter. The latter did not show the 

 heavy loss in drying that the former did, however, and thus the dif- 

 ference in the amount of organic matter of the two is not nearly so 

 great as the difference in the weights of the green matter would indi- 

 cate. In this connection it should also be noted that varying yields 

 are often due to a difference in the stands rather than to differences 

 in the growth of the crop. In the comparative data presented in 

 the tables this has been reduced to a minimum by selecting for this 

 purpose crops with as nearly uniform stands as possible. 



From all data available it seems clear that of the commonly grown 

 green-manure crops, vetch, peas, bur clover, and fenugreek, the 

 vetch returns the most organic matter to the soil and the peas the 

 least. The light yield of peas is not due to a lack of stem growth, 

 which on the contrary is always good, but to the generally poorer 

 stand and more open habit of growth. Bur clover, while weighing 

 heavy green, is very succulent when young, and when compared with 

 an equal weight of green vetch represents much less organic matter. 

 Fenugreek yields well, but not so much as vetch. 



In securing the yield of green manure per acre, as presented in 

 Table I, the plants growing on a plat 6 by 20 feet were cut and 

 weighed green and the yield per acre computed from these weights. 

 In Table II a plat 10 by 10 feet square of each crop was cut and 

 weighed green and the yield per acre thus calculated. The same 

 was weighed again in thirty days, as shown in the table, giving the 

 yields of the dry matter. In Table III the weights shown were 

 taken from crops being grown by orchardists during the winter of 

 1908-9 at the places mentioned in the table and are representative 

 of these crops as grown under actual orchard conditions. To obtain 

 the results the plants growing on a space between four trees were cut 

 and the yield per acre calculated from such weights. 



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