Movement of Soil Nitrate Through a Pembroke Soil as Affected by Tillage Method and Time of Nitrogen Application

Of all the plant nutrients, nitrogen has been subjected to the most extensive study. The amount of inorganic nitrogen in the soil is small while the quantity needed annually by crops is comparatively large. Of the macronutrients usually applied in commercial fertilizers, nitrogen seems to have the quickest and most pronounced effect on plant growth. In applying the nitrogen fertilizer for crop use, one must be concerned with placement, form, and availability, and with keeping the fertilizer where it is placed throughout the critical part of the growing season. The nitrogen supply molded by non-leguminous plants is of extreme importance and its availability is complicated by the fact that nitrogen in soils is easily converted into forms which are more or less mobile and available. The time of application of nitrogen fertilizer can significantly affect its availability. It commonly is applied in either the spring or fall in row crop culture. Under our climatic conditions, nitrogen applied in the fall tends to be lost by denitrification and leaching over the winter period, and the practice is not economical. There are also disadvantages associated with spring application of nitrogen. Application is needed at a time when the farmer is extremely busy and where the soil may be too wet to support the application equipment. No-tillage farming, which is relatively new, apparently increases the rate of nitrogen movement through the soil profile. No-tillage results in a mulch of dead plant material on the surface. The mulch tends to keep more moisture in the soil. This extra moisture can be beneficial to the crop but it also permits the nitrogen to move more rapidly through the soil. The present student was initiated to study the effects of tillage practice and time of nitrogen application on the movement of nitrate through a Pembroke silt loam soil. This soil is typical of the well-drained limestone soils found in Southern Kentucky