TRUCK FAKmNQ. 589 



cnltiiral benefactor, Sir John Bennet Lawes, assisted by Dr. Gilbe;t, 

 carried ou with the utmost care for forty years, near Sothamsted, Eng- 

 land, at his own expense, substantiate the fact that manures buried iu 

 clay soils become very slowly decomposed, and that such soils hold large 

 quantities of plant-food locked up in unavailable form. 



Xumber two of the twenty-nine experimental wheat plots has received 

 during forty successive years an annual application of 14 long tons of 

 fresh barn yard manure, or, since the first season of 1843-44:, an aggre- 

 gate of &2'i.2 tons of 2,000 pouhds, while plot Xo. 3 has remained con- 

 tinuously unmanured. Xow, Sir John having kindly sent me a pamphlet 

 containing the experiments up to the fortieth season inclusive, I tiud 

 the last crop of the plot manured annually with 14 tons barn-yard man- 

 ure to have been 3i^ bushels, against 35^ bushels, the average yield of 

 the first recorded sixteen years. In other words, after having been 

 manured with G27i tons barn-yard manure in the aggregate for forty 

 years, the soil produced only one-eighth of a bushel more the last sea- 

 son than the average of sixteen years first recorded. 



The result on the continuously unmanured plot is still more astonish- 

 ing. The yield the fortieth season was 13J bushels and the weight 

 of clean grain Gl^ i^ounds per bushel. The average yield of sixteen 

 years (1852 to 1867) was 14J bushels ; of the sixteen years (1808 to 1883) 

 it was llf bushels, and the average of the thirty-two years 13J bushels; 

 with the weight of clean grain, 57f pounds per bushel. In other words, 

 the plot, without the least manure of any kind, produced the fortieth 

 season only 1 bushel less than the average of the first sixteen, 2| more 

 than the average of the second sixteen, and three-fourths of a bushel 

 more than the average of the preceding thirty-two years ; and the weight 

 of the clean grain j^er bushel the last season was 3 J pounds greater 

 than the average of the preceding thirty-two years. 



These remarkable results are attributable to the fact that the Roth- 

 amsted experimental wheat-field is a heavy loam with a subsoil of yel- 

 lowish red clay, a rich, retentive soil with an abundance of plant-food 

 for the demand of many more such cro])S, becoming available very 

 slowly notwithstanding the superior tillage practiced at the Eotham- 

 sted experimental station. 



The average removal of nitrogen in the wheat crops of the unmanured 

 plot per acre per annum for thirty-two years was, by analysis, ascer- 

 tained to have been 20.7 pounds. In 1881 six samples of the soil were 

 analyzed three times, 9 inches deep, from each of nineteen plots. The 

 first 9 inches of the continuously unmanured plot alone contained 2,404 

 pounds of nitrogen in the 2,552,202 pounds of dry mold. Without 

 taking into consideration the actual gain of nitrogen by the ammonia 

 and nitric acid in dews and rains, nor the probably heavier loss in 

 drainage, we have, after the removal of the thirty eighth crop, still 

 enough left in the upper 9 inches of soil alone for one hundred and six- 

 teen more. 



The explanation of the results of the plot manured annually with 

 14 tons barn-yard manure, lies in the fact that the fresh manure was 

 turned under deeply, probably with a four-horse plow, as customary in 

 England, where neither air nor water could find ready access to pro- 

 mote decomposition and render it available for crops, thus leaving to 

 the clay its full power of suspending decay. 



Had the manure been applied upon the surface, or harrowed into the 

 top soil, or had the soil been of a more sandy character, the results 

 would have undoubtedly been different. 



Having learned that the method of deeply plowing under their 



