Agricultural Research in New Hampshire 31 



Run-off, Erosion, and Methods of Control 



In addition to seven run-off plots, two additional field areas have been 

 leased in the township of Strafford, New Hampshire, for the purpose of 

 discovering a suitable rotation for commercial potato farmers. The two 

 areas represented are located on Paxton fine sandy loam, but they have 

 been cropped differently so that the topsoil of each of the areas may be 

 considered as being in a different stage of erosion. 



Nonerodible— This condition of Paxton fine sandy loam is represent- 

 ed by run-off plots. This area had been in sod for about fifteen years 

 and had been top-dressed with hen manure occasionally so that the per 

 cent of organic matter and degree of aggregation were high when the 

 piece was plowed in the fall of 1939. 



Slightly Erodible.— Th\s condition was found in a field which had 

 been in sod for a number of years until 1938, when it was plowed and 

 cropped to potatoes for two years. In the spring of 1940 it was sown 

 to a grass mixture. 



Erodible.— This condition was evidenced by a field of Paxton fine 

 sandy loam which had been cropped to potatoes continuously for twelve 

 years. 



Each of the two new fields was about three-fourths of an acre in 

 extent, and these were laid out into 20 ft. x 20 ft. plots. The slightly 

 erodible field was laid out on the contour, but this was not done on 

 the erodible field because it would have cut down on the number of rota- 

 tions which could have been used. 



The extreme drought of the past summer prevented the seedings 

 from becoming established. However, the fields were resown in the 

 fall and seem to be well established. 



Only two storms caused soil loss during, the year 1941, and- the 

 greatest amount of soil loss for any one plot was 0.022 ton per acre or 

 about one pound per plot. One soil loss occurred from a thunder storm 

 on July 12, when 1.36 inches of rain fell. The five-minute intensity of 

 this storm was 4.80 inches per hour and the thirty-minute intensity was 

 2.20. Practically all the soil came from the narrow space between the 

 last contoured row and the edge of the plot because the water did not 

 break over the contoured rows. The second soil loss was measured as 

 a result of a rainfall of 0.98 inch on December 23 and 24, which melted 

 a previous four-inch snowfall. The surface one inch of soil was thawed 

 during the storm and the small amount of soil lost was removed from 

 this thin layer. 



Run-off occurred as a direct result of seven storms during the year 

 and, in addition, occurred on fourteen days as a result of thaws which 

 melted the snow on the plots. Only one of the seven run-offs from rain 

 occurred during the summer months. Four occurred in the winter and 

 spring, and the remaining two occurred in the fall. All fourteen of the 

 thaws occurred during the winter and spring. 



The crop year 1941 was unusually dry, and all the Northeast suf- 

 fered from a drought. 



The rate at which the soil froze during the winter was again meas- 

 ured for both the grass and cultivated conditions. The trend of the 



