Intertillage of crops and formation of nitrates in soil

Attention is called to the desirability of conducting experiments on fairly heavy soil of the North Eastern States to ascertain whether stirring with a cultivator under such conditions increases the formation of nitrates; investigations in the Middle West having indicated that stirring does not increase such action. Experiments during two years on a silty clay loam soil at Ithaca, N.Y. to ascertain the effect of cultivating, scraping, and mulching with straw, respectively, on the nitrate content of unplanted soil and on the yields of corn are recorded. Nitrates were highest during both years in the cultivated plats, next in the scraped, and lowest in the mulched. Determinations of moisture in these plats indicated that the higher nitrate content of the cultivated plats was not due to moisture; as that constituent was practically the same in the cultivated and scraped soil. The mulched plats had the highest moisture content. Yields of corn were greater on the mulched than on the scraped plats; but this could not be attributed to the larger supply of nitrate nitrogen as the mulched plats also yielded more than the scraped altho the nitrates were much lower on the mulched plats. This is an illustration of the fact that the productivity of a soil is not always proportional to its facility for nitrate production. The evidence here presented is in favor of the assumption that the nitrate content of the cultivated plats is higher than that of the scraped plats because of the aeration production by stirring with the cultivator. Cylinders of soil taken from the field without disturbing the soil structure nitrified only slightly on standing at a moisture content and temperature favorable to the formation of nitrates, while similar soil that had been aerated gave a larger increase in nitrates. Under similar conditions a cylinder of soil from a more compact part of the field nitrified less than did one from a less compact section.