Fertilisation causes

Fig. 5.4 Long-term impact of reduced nitrogen fertilisation on the yield of whole crop cereals and SRCs on a sandy soil in Germany (relative yield related to the yield of an application rate of 150 kg N ha-1). The reduction of the N application rate by 50% results in a mean relative yield loss of -10% after 15 years for rye and triticale. Non-fertilisation cause significantly higher losses. By contrast, the relative yields of poplar and willow on reduced and even non-fertilised stands do not decrease, but instead increase, although the absolute yields grow over time. One of the reasons for this phenomenon seems to be mycorrhica...

Fertilisers generally increase the biomass organic fertilisers cause a... 

Nitrogen compounds These also arise from both natural and synthetic sources. Thus ammonia is formed in the atmosphere during electrical storms, but increases in the ammonium ion concentration in rainfall over Europe in recent years are attributed to increased use of artiflcial fertilisers. Ammonium compounds in solution may increase the wettability of a metaland the action of ammonia and its compounds in causing season cracking , a type of stress-corrosion cracking of cold-worked brass, is well documented. 

The salts content of soils may be markedly altered by man s activities. The effect of cathodic protection will be discussed later in this section. Fertiliser use, particularly the heavy doses used in lawn care, introduces many chemicals into the soil. Industrial wastes, salt brines from petroleum production, thawing salts on walks and roads, weed-killing salts at the base of metal structures, and many other situations could be cited as examples of alteration of the soil solution. In tidal areas or in soils near extensive salt deposits, depletion of fresh ground-water supplies has resulted in a flow of brackish or salty sea water into these soils, causing increased corrosion. 

Normal agricultural practices generally cause an enrichment of heavy metals in soil, particularly Zn, Cu and Cd, due to the application of manure or its derivatives, compost or sludge and inorganic fertilisers and other human activities such as... 

The sequestration of carbon in soil has a considerable influence on the GHG balance of biofuels. Although the GHG balance of the production and utilisation of energy crops is approximately zero, except for some additional C02 equivalents mainly caused by the N fertilisation and the consumption of fossil energy (see Chapters 7 through 9), the storage or the release of carbon in soil may disturb this balance. 

The nitrogen content of the various crop species and their parts exhibits a wide range of variation from 0.2- 4% (Table 5.9). It depends not only on the species and on the harvest time, but also on the fertilisation rate. This is known for conventional crops (Mollers 2000) and was confirmed for energy crops too (Scholz et al. 1999, 2004a). Depending on the species, the application of e.g. 150 kg N ha-1 causes an average absolute increase in the N content by 0.1-0.3%. 

The environmental relevance of heavy metals in energy crops results from both the use of energy crop residues as fertiliser and their influence on the conversion processes. Among the heavy metals analysed in plants, those especially relevant are the ones whose accumulation in soil and crops is caused by the energy-related input and/or the input from fertilisers (BioAbfV 2002 Diing MV 2003 Diinge V 2003) and/or whose emissions are legally limited, in particular cadmium (Cd < 0.2 mg nr1), lead (Pb < 5.0 mg nr1), copper (Cu < 5.0 mg in-3) and zinc (Zn) (TA-Luft 2002). 

Reliable long-term measurements have been performed by Hellebrand et al. (2008). They measured the N20 emissions on different fertilised energy crop plots on a sandy soil over a period of 9 years and found differences not only between the various fertilisation levels, but also between the crop species. In spite of the yearly spread it can be summarised that SRCs cause less N20 than cereals and grass. So the N20 emissions rate on non-fertilised poplar and willow fields is only 17-26% of the rate on conventionally fertilised cereal fields (Fig. 5.5). 

Fig. 5.5 Crop-specific N20-N emissions with and without hotspots for different N fertilising rates according to Hellebrand et al. (2008), continuously measured for up to 9 years on sandy soil in Germany. The additional N20 emissions caused by the hotspots are not insignificant. However, the reason for these irregular increases is not yet clear...

DAM KOFOED, A. (1980). Water pollution caused by run-off of manure and fertiliser. In Nitrogen losses and surface run-off from landspreading of manures. Brogan, J C (ed) Nijhoff/Junk, The Hague, 1981 70-75. 

In contrast, conventional farming can cause mortality in fledglings, as reported for starlings, due to the use of pesticides and synthetic fertilisers, which cause unbalanced diets, but also due to the change of the habitat through, for example, the reduction of ditches and pastures (Tiainen et al. 1989). 

Although NH3 is not one of the greenhouse gases, NHs-emissions cause negative environmental effects through soil acidification and uncontrolled nitrogen re-circulation. The latter is due to ammonia losses from organic and mineral fertilisers and re-import from the atmosphere to soil by precipitation. 

Chemical fertilisers are highly reactive and can cause extreme pH fluctuations in localised... 

The fact that water is such an effective solvent can cause some problems. These include the formation of hard water and leaching of fertilisers (Figure 11.22, p. 182). Flard water can cause further problems and must in certain circumstances undergo a softening process. This is discussed in detail on p. 188. 

Pollution The modification of the environment caused by human influence. It often renders the environment harmful and unpleasant to life. Atmospheric pollution is caused by gases such as sulfur dioxide, carbon monoxide and nitrogen oxides being released into the atmosphere by a variety of industries and also by the burning of fossil fuels. Water pollution is caused by many substances, such as those found in fertilisers and in industrial effluent. 

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