11B. The Effect of Fertilizer Treatments upon the Quantity and Quality of Pasture Vegetation: II. Nitrogen Treatments¹

Abstract

A permanent pasture is a floral expression of a soil subjected to a long-continued grazing practice. By the application of fertilizers or by a change in grazing practices the flora may, in a very few years, be radically changed both in species represented and in chemical composition. Experiments showing the effect of fertilizers on pastures are not abundant but are of sufficient number, at least, to be quie suggestive of the values of the several nutrient elements.The influence of nitrogen on plants is positive and of easy observation. It promotes vegetative growth, increasing the amount of stem and leaf, essential preliminaries to complete plant development. A lack of nitrogen results in a stunting of general growth and in the production of a relatively high proportion of seeds to the total weight of the plant. Upon analysis the plant, however, shows no marked deficiency of nitrogen (1).3 Apparently, phosphorus, potassium, calcium, and other mineral nutrients are taken only in the amounts that can be used as determined by the supply of available nitrogen present.One would expect the usual growth phenomena to occur in a pasture treated with the different nitrogenous fertilizer materials. However, the longest continued experiment on the treatment of a pasture will scarcely support this expectation.At Cockle Park, in northeast England, in 1897, there was begun a pasture experiment that has continued to this time (2) in which sheep were grazed. This experiment was duplicated many times elsewhere in England, but for shorter periods of time. To one plat was applied 784 pounds of superphosphate per acre the first and fourth years in the first nine years of the experiment at Cockle Park and Sevington and the first year in three years at Yeldham. On another plat the same quantity of superphosphate was applied and in addition in the first, third, fourth, and seventh years, 84 pounds of sulfate of ammonia per acre at Cockle Park and 97 pounds at Sevington were applied. At Yeldham there were applied roo pounds of sulfate of ammonia the first and second years and 2oo pounds the third year.The outcome of the treatment is given in Tabler, and shows a loss of 27 pounds of mutton at Cockle Park for the application of 336 pounds of sulfate of ammonia. Similarly, at Sevington the loss was 124 pounds of mutton for the use of 398 pounds ofthe nitrogen carrier. At Y eldham in three years 400 pounds of sulfate of ammonia accounts for a gain of 24 pounds as compared with the use of superphosphate alone.