Losses from fertilizers

The agricultural emissions of NHj, NjO and NO must be considered in context the processes which lead to net loss from the soil and vegetation are natural and form a part of the land-atmosphere cycling of this vital nutrient. The current agricultural processes, however, create conditions in which the small natural background fluxes, in the range of a few ngNm s are dwarfed by losses from fertilized land. 

The primary use of a-picoline (2) is as a precursor of 2-vinylpyridine (23). It is also used in a variety of agrochemicals and pharmaceuticals, such as nitrapyrin [1929-82-4] (60) to prevent loss of ammonia from fertilizers picloram [1918-02-1] (61), a herbicide and amproHum [121 -25-5] (62), a coccidiostat. 

How much does Nitrogen Fertilizer Contribute to Nitrate Leaching when Winter Wheat is Growiii We saw earlier that direct nitrate losses from nitrogen fertilizer given to winter wheat are often relatively small. We saw too that... 

The interest in gaseous losses of nitrogen from soil is now extensive and includes the well established community of soil scientists concerned with losses of fertilizer-applied nitrogen by nitrification and denitrification. More recently, interest in ammonia losses from plants and soil has been stimulated by the very large emissions from intensive cattle production in the Netherlands and their... 

Phytoestrogens were first associated with adverse effects on mammalian development and fertility from observations of animals consuming phytoestrogen-rich plants. Ewes feeding on Australian clover developed abnormal plasma concentrations of endogenous hormones with subsequent loss of fertility (Bennett etal.,l 946 Moersch et al., 1967 Obst and Seamark, 1975). 

In addition to a complete water balance, EPIC estimates plant biomass production, fertilizer use, wind and water erosion, loss of nitrogen and phosphorus from the soil, and the effect of nutrient loss from the soil on plant growth. 

Most information on ammonia losses is coming from fertilizer experiments. In calculating N-balances, losses of N can be considered as caused by volatilization of ammonia or by denitrification. 

Cai GX, Zhu ZL, Trevitt ACF, Freney JR, Simpson JR. 1986. Nitrogen loss from ammonium bicarbonate and urea fertilizers applied to flooded rice. Fertiliser Research 10 203-215. 

Eutrophication. Thus far N has been discussed in terms of its prominence as an acidic anion (i.e., as N03 ). As in terrestrial ecosystems, inorganic forms of N also act as nutrients in aquatic systems, and a possible consequence of chronic N loss from watersheds is the fertilization of lakes and streams. Establishing a link between N deposition and the eutrophication of aquatic systems depends on a determination that the productivity of the system is limited by N availability and that N deposition is a major source of N to the system. In many cases the supply of N from deposition is minor when compared to other anthropogenic sources, such as pollution from either point or nonpoint sources. 

The researchers stress that the net effect of all of these processes, except uptake by regrowing vegetation, is insufficient to prevent or delay losses from relatively fertile sites and thus such sites have the potential for very high nitrate losses fulluwing disturbance. 

Citrus trees are a long-term investment, and growers cannot afford crop damage or yield loss from weed competition, cultural operations, or misapplication of chemicals. The most critical time to control weeds in trees is from planting to early establishment, which spans from 3 to 6 years depending upon soil fertility. 

Biomass development (Jordan 1985) and regeneration capacity (Uhl 1987) are not always clearly associated with differences in soil fertility, but they are certainly related to rates and patterns of nutrient cycling (Vitousek and Sanford 1986, Medina and Cuevas 1989, Tiessen et al. 1994b). On poor soils, nutrients may cycle without substantial losses from the system (Baillie 1989, Burnham 1989). In such dystrophic systems, organic matter and particularly the forest litter mat may play an essential role in conserving nutrients for sustaining forest produaion (Stark and Jordan 1978). 

Kilmer, V.J., 1974. Nutrient losses from grasslands through leaching and runoff. In D.A. Mays (Editor). Forage Fertilization. The American Society of Agronomy, Madison, WI, pp. 341—360. 

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