Decomposition of Sweet Clover as a Green Manure 131 



was covered v/ith only a thin layer of soil. At the end of ten days the 

 plants were thinned, leaving twelve in each pot. 



The pots were divided into three groups as regarded time of harvest. 

 At each period, four of the pots limed with hydrate, four of those limed 

 with carbonate, and four of the check pots, were harvested. From six 

 of these pots the roots and the tops were removed and a sample of the 

 soil was taken. The plants from the remaining six pots were chopped 

 up and incorporated with the soil, pending later examination for rate of 

 decay. Before the plant material was added a sample of the soil was 

 taken. The pots in which the plants were turned under were kept at a 

 moisture content of 30 per cent, in order that conditions might be 

 favorable for decomposition. The pots from which the plants were 

 removed were kept under similar conditions, so that they might serve 

 as checks on any measurements made later regarding the rate of decay 

 of the material turned under. 



According to the above procedure, the thirty-six pots were harvested, 

 in groups of twelve, on July 21, August 17, and September 15. These 

 dates represented periods of growth of sixty-two, eighty-nine, and one 

 hundred and eighteen days, or approximately two, three, and four months, 

 respectively. At each time of harvest a photograph was taken of repre- 

 sentative pots in order to give an idea of the amount of growth and the 

 differences noticeable according to the different treatments of the soil. 

 These photographs are shown in figures 9, 10, and 11. A foot rule is 

 shown in each pot. 



It is seen that at the end of the first period the plants had reached a 

 height of from eight to twelve inches. Differences due to lime are not 

 noticeable. At the end of three months a height of from fifteen to twenty 

 inches had been attained and many lateral branches had been sent out. 

 During the final period the height increased from five to eight inches 

 more. This period was especially characterized, as the figure indicates, 

 by a development of dense foliage. In both the second and the third 

 period the effect of lime is evident. 



In taking up the plants at the different periods, some observations 

 were made regarding root development and nodule formation. During 

 the first two periods slender taproots were developed, many attaining 

 a length of four or five feet. During the final period the roots grew 

 somewhat in length, but the most noticeable development was a thickening 

 and branching a few inches below the root crown. At the first harvest 

 it was noticed that practically all the roots bore nodules, the roots in 

 the limed pots being more plentifully supplied. This is in accordance 

 with what has previously been observed regarding the influence of lime 

 on nodule formation. In no case, even at the end of the final period, 



243 



