FERTILIZER TESTS ON PASTURES 5 



Plan and Method of Experimentation 



The Worcester County experiments were conducted on duplicated plots 1 rod 

 square, laid out in the checkerboard fashion. The experimental field was not 

 fenced, and dairy stock grazed the plots at will along with the rest of the pasture. 

 Grass samples for determining growth response were obtained by hand clipping 

 of areas protected from grazing by means of a wire cage designed by the writer. 

 (Figure 1.) This cage was 2 ft. x 1.5 ft. x 9 in. and was made by covering a frame 

 built of angle iron with 2-inch mesh chicken wire. Each time a clipping was made 

 the cage was removed to a fresh, grazed spot within the plot. In this way, the 

 condition of continuous grazing of the clipped area was approached. With the 

 exception of 1930 when a dry August prevented normal late growth of grass, 

 three cuttings were taken from each sampled plot. 



The Amherst pasture plots were handled in a manner somewhat different from 

 that just described. The dimensions of the original plots on this field were 10 ft. x 

 10 ft. Later these were subdivided into plots 5 ft. x 10 ft., one of which received 

 minerals, and the other minerals plus sodium nitrate. The cows were excluded 

 from the experimental field from the beginning of the growing season until about 

 the first week of June, when the plots were sampled by the quadrat method. The 

 cows were then allowed to graze the plots down to the customary' level. Then 

 they were excluded and the grass allowed to make sufficient growth for a second 

 cutting, after which the plots were grazed for the rest of the pasture season. 

 In this way normal pasture conditions were simulated, but not so well as in the 

 Worcester County experiments. 



The treatments were as follows: 



Key Pounds per Acre 



Materia! Letter 



Worcester Amherst 



Finely ground limestone L 2400 1740* 



Superphosphate (16% P.,0.5) P 480 435 



Muriate of potash (48-50% K,,0) K 160 108 



Chilean nitrate of soda (15.5-16% N) N 160 193.5 



*Amherst Experiment: 2L = .3480 .3L = 10S7o 



2P = 1740 8P = 5220 



2K= 216 3K= 432 



The Worcester experiments received all materials but the nitrate in the fall 

 of 1929; the nitrate was applied in the spring of 1930, 1931, and 1932. The Amherst 

 experiment received the non-nitrogenous materials in the spring of 1924 and 1929, 

 and the nitrate in the spring of 1929, 1930, 1931, and 1932. 



Weather Conditions 



The mean annual precipitation at Amherst, Massachusetts, was 43.49 inches 

 for the period 1889-1928. For the same period the mean total precipitation for 

 the normal pasture season, which includes May, June, July, August, and Septem- 

 ber, was 19.53 inches. This varied from 3.5 inches to 4.3 inches per month. For 

 the typical, well-drained, upland pasture soil of Massachusetts a minimum of 

 about 3 inches of rain a month is required for good growth of grasses and clovers. 

 If the total falls below 2 inches for any one month, a drouthy condition restrictive 

 of growth usually results. This occurred in the late summer of 1930. If the 



