Efficient use of nitrogen on crop land in the Northeast /

Abstract

Bulletin 792 com grain yields with optimum soil regimes for water and fertilizer have been between 200 and 240 bu/ acre (12 to 15 tons/ha). These yields are only occasionally reached. For example, yields in research plots in Maryland, New York, and Pennsylvania have rarely exceeded the 200 bu/acre level. Among the nearly 2,000 entries in corn growing contests in Pennsylvania from 1968 to 1978, the 200 bu/acre level has been broken only twenty times, and the maximum yield reported was 239 bu/acre (15 tons/ha). A much more common maximum yield, and therefore yield goal, is about 180 bu/acre (11 to 12 tons/ha) in Pennsylvania and Maryland and 150 bu/acre (10 tons/ha) in New York and New England. It would be wasteful to attempt to fertilize corn for crop yields exceeding these yield goals, using present day production practices and genetic plant material. Crop yield goals for other common field crops in the Northeast are listed below: Yield Goal Crop Common Units Metric Units Corn silage 20 tons/acre 45 tons/ha Soybeans 40 bu/acre 2.7 tons/ha Millet 3 tons/acre 6.8 tons/ha Sudangrass 3 tons/acre 6.8 tons/ha Sorghum 5 tons/acre 1 1 .3 tons/ha Alfalfa 5.5 tons/acre 12.5 tons/ha Clover 3 tons/acre 6.8 tons/ha Crop Wheat Barley Oats Rye Yield Gool Common Units Metric Units 60 bu/acre 4.1 tons/ha 75 bu/acre 5.1 tons/ha 80 bu/acre 2.9 tons/ha 30 bu/acre 2.0 tons/ha Moisture and temperature are the principal limitations to yields on fertile, well-managed soils of the Northeast. A recent study for the feasibility of irrigation of corn in Pennsylvania (Kibler et al. 1977) concluded that supplemental irrigation would increase yields in one year out of two. In the sandy soils of the Maryland peninsula, water deficits limit maximum yields to 100 bu/acre (6.3 tons/ha). Cool temperatures, short growing season, and poorly drained soils limit maximum yields in many areas of the region to about 80 bu/acre (5 tons/ha). In most areas of the region, the maximum yield goals are rarely met, and most farmers, due to limitations in soil, climate and management, attain yields lower than the maximum. Thus, when the average good farmer uses yield goals in N management, crops will be produced more efficiently and fertilization will cause less pollution if yield goals are realistic for the soil and climatic zone. Fertilization to Meet Crop Production Goals Nitrogen Fert-ilizat-ion of Corn in the Amount' Ideally, the amount of fertilizer N applied to a corn crop is based on knowledge of plant needs, the amount of N that can be expected to be supplied by the soil, and a knowledge of fertilizer N efficiency under local conditions. Stanford (1973) expressed this in a formula N, = (Np-NJ/E, where Nf = N fertilizer to apply, Np = plant N uptake, Ns = N supplied by the soil, and E is efficiency of fertilizer N (i.e., the fraction of N fertilizer that becomes part of Np).

Snap Bean Plant Responses to Nitrogen Fertilization1

“…rate of uptake of N in relationship to rate of assimilation of nitrate N within the plants at a short time period prior to sampling the plant parts. The total N in the plants shows the accumulation of total N within the plants since planting (Barker, 1980;Peck, 1981 ). However, precipitation may leach some N substances from the plants (Tukey, 1970).…”

“…There were very few or no visible nodules on the roots of plants grown with soil N plus fertilizer N at 12 g m-2 • During 1978 and 1979 the total N in cabbage plants grown without fertilizer N, and after similar cover crops and similar precipitation patterns during the growing season, averaged 14 g m-2 • The dry weight averaged 480 g m-2 at midseason or about the same length of time from planting as snap bean plants at the pod stage (Peck, 1981 ). At the pod stage, total N in the snap bean plants grown with residual soil N but without fertilizer N was 15.7 g m-2 and dry weight was 629 g m-2 • Since soil N tests are affected by environmental factors, uptake of N by the plants is a better indicator of N availability within the rooting zone (Barker, 1980).…”

“…milis] plants as well as the pod set and development (Paterson et al, 1966). Soil and fertilizer management must be designed to furnish a continuous supply of available Nand adequate plant growth factors for producing high yield and quality while withstanding unpredictable plant stress conditions in order to obtain economical, profitable, and reliable production of snap bean pods throughout the processing season (Barker, 1980).…”

Efficiency of Nitrogen Fertilizer Use by Shade Tobacco Improved by Timed Applications1

“…Fertilization schemes to improve the N use efficiency of shade-grown tobacco and involving timed applications of inorganic N sources have been previously suggested (2,7,16). Growers have resisted such methods, maintaining that the use of natural organics improves leaf quality despite evidence to the contrary (I , 5,8,12,13,16,24).…”