Archive image from page 12 of Decomposition of green manures at. Decomposition of green manures at different stages of growth .. decompositionofg00mart Year: 1921 Decomposition of Green Manures 145 Effect of stage of growth of green manure on rate of humus formation It would appear in general, from the curves shown in figures 28 and 29 that the greater the succulency of the manure when incorporated with the soil, the larger is the amount of humus formed. The first marked exception to this generalization, however, appears in figure 27, showing the results of allowing the material to decompose
Archive image from page 12 of Decomposition of green manures at. Decomposition of green manures at different stages of growth .. decompositionofg00mart Year: 1921 Decomposition of Green Manures 145 Effect of stage of growth of green manure on rate of humus formation It would appear in general, from the curves shown in figures 28 and 29 that the greater the succulency of the manure when incorporated with the soil, the larger is the amount of humus formed. The first marked exception to this generalization, however, appears in figure 27, showing the results of allowing the material to decompose for twelve months. Here, in every instance, the most succulent crop resulted in the least amount of humus. This is in exact opposition to the results shown in figures 28 and 29, when the manure was allowed to decompose Fig. 26. ST.\GES of .\nd decrease in humus production The A-B part of the figure represents the period of humus formation, during which humus is formed and no end products are developed. B-C indicates the stage in which there is a humic-decomposition process at work and end products are formed as rapidly as the humus is produced from the crude organic material. C-D represents the stage in which the humic-decomposition process is in the ascendancy and more end products are produced than there is humus formed. for four and five months, respectively. The data given in table I from which the curves in figure 2 7 were obtained, show that more dry matter was added to each soil as the maturity of the manure increased; but the rate of increase of this dry matter added was, in general, less than the rate of increase of the humus formed. It would seem that in the breaking down of the crude organic material of the soil into its end products, there occur a period of humus formation and a period of himius decomposition, involving three distinct steps which are illustrated in figure- 26. With this understanding of the process, the results shown in figure 27 may
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