^12 Journal of Agricultural Research voi. xii, No. 8 



The low initial percentage of humus in the basins is partly due to the 

 fact that 5 or 6 inches of the surface soil were removed in making the 

 basins, owing to sloping ground. 



The percentage of humus in the manured basins in 191 6 was about the 

 same as in 191 5, while in the alfalfa basins it was less. The decrease in 

 the humus content in the manured soil furrow-irrigated and surface- 

 cultivated is very appreciable, indicating that this system did not con- 

 serve the humus as well as the basin system. 



The grove in which this experiment was conducted was deteriorating 

 along with other groves in the neighborhood when the basins were in- 

 stalled. The whole grove was in better condition in October, 191 6, but 

 there was no apparent difference in the appearance of or the amount of 

 fruit on the trees basined as compared with trees not basined. The 

 mulch-basin system in experiments conducted by this office has always 

 produced a quicker response on trees on clay loam soil than on trees on 

 sandy loam or light sandy loam soil. 



The deterioration of the grove above mentioned was evidently due to 

 bad soil conditions, which quite likely affected the bacterial flora in such 

 a way as to make it less efficient in converting the alfalfa into humus. 



In most cases presented above the percentage increase in humus during 

 a period of from 9 to 1 7 months was greater in the basins on the clay loam 

 soil than in those on the sandy loam soil, with both manure and alfalfa 

 as the mulch. On the whole, the manured basins gained slightly more 

 in humus content on both types of soil than the alfalfa-mulched basins. 

 No correction has been made for the amount of humus added with the 

 manure. This material contained about 5 per cent of humus when ap- 

 plied, part of which undoubtedly found its way into the surface soil when 

 the basins were irrigated. The percentage increase of humus in the 

 manured basins therefore does not necessarily indicate that the manure 

 had been humified to a greater extent than alfalfa. Data to be presented 

 in another paper would indicate that the increase is likely due to the 

 humus added with the manure. 



In all cases where lime was added to manure in basins the increase in 

 humus was somewhat less than when manure alone was used. In most 

 cases the addition of lime to alfalfa in basins produced slightly more 

 humus than when alfalfa was added alone. Frear and Hess (j) found 

 that field plots receiving manure and lime contained less active humus 

 than unmanured plots. 



The amount of alfalfa or manure necessary to form a unit amount of 

 humus can not be stated with exactness from the data available. In 

 Experiments I and II the average increase in humus in the basins in 

 1 91 6 over the average amount present in 191 5 would indicate that i part 

 of humus was formed from about 10 to 12 parts of alfalfa, and i part of 

 humus from about 26 parts of manure. These calculations agree fairly 



