Nitrogen fertilizer excessive applications

Typically, phosphorus is added in various forms to a watershed (Figure 9.1). These include fertilizers, nonhazardous wastes (animal manures and biosolids), and nutrient-enriched waters. Historically, organic wastes such as animal manures were applied to agronomic crops and pastures on the basis of the nitrogen availability, which has resulted in excessive application of phosphorus. As a result, many uplands used for land application of wastes have accumulated phosphorus in excess amounts. A major portion of the phosphorus added to uplands is retained within the soil. However, as upland soils become saturated or overloaded with phosphorus, a significant portion of the stored phosphorus can be released and transported with water during runoff events. 

To eliminate the disadvantage of using excessive amounts of inert polymers as carriers, in addition to the drawbacks of using soluble nitrogen fertilizers, the principle of dual application of a controlled-release herbicide-fertilizer combination has been... 

Uses. Since 1947, 70 to 85% of the annual USA production of nitric acid has gone into the production of NH4 nitrate fertilizer, initially in the form of solid prills currently, increasing amounts have been supplied mixed with excess ammonia and/or urea as aqueous nitrogen solution for direct application to the soil. Some 15% is used in explsj (nitrates nitro compds), and about 10% is consumed by the chemical industry. As the red fuming acid or as nitrogen tetroxide, nitric acid is used extensively as the oxidizer in proplnts for rocketry. It is estimated that current USA capacity for nitric acid is in excess of 10 million tons (Refs 30, 34, 36 37)... 

Chemical fertilizers are used in most parts of the world, although less so in developing countries because of the high cost. The nitrogen content in chemical fertilizers is known, and application rates can be determined accurately, These may vary depending on the cropping system used. Nutrients are more immediately available for plant uptake in chemical fertilizers than in manure however, they may be more easily leached into groundwater if used in excess. Slow-release fertilizers reduce this loss,... 

Nitrogen is a key element of many biogeochemical processes and can be both a nutrient limiting the productivity of terrestrial and aquatic ecosystems and a pollutant, which excessive accumulation in biogeochemical food chains leads to many environmental problems. The main anthropogenic sources of nitrogen pollution are related to fertilizer application, waste production and emission of gaseous species. 

JACOBSON Yes. We did that for the soybean experiment by applying fertilizer according to information that we obtained about what one should do for soybeans in this particular soil. The amount of sulfur that one applies in fertilizer is far in excess of sulfur deposited in an equivalent land area in a single rain event. However, rain events occur repeatedly over the course of a growing season and supply sulfur to the soil as well as directly to the foliage in a very dilute form. By comparing these two very different situations, one can develop an opinion that the sulfur or nitrogen in rain is totally irrelevant as far as plant nutrition is concerned to one where it is possible that it has some importance because of the different mode and pattern of application. 

The soil macronutrients, nitrogen (N), phosphorus (P), and potassium (K), are essential for crop growth, and the use of commercial N, P, and K fertilizers has contributed greatly to the increased yield of agricultural crops. However, excessive fertilizer applications can lead to environmental contamination, primarily of surface and ground waters.Ideally, fertilizer application should be adjusted to match the requirements for optimum crop production at each within-held location, because there can be high spatial variability in the N, P, and K levels found within helds. ° ° ... 

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