Fertiliser application

In hospitals, chemical analysis is widely used to assist in the diagnosis of illness and in monitoring the condition of patients. In farming, the nature and level of fertiliser application is based upon information obtained by analysis of the soil to determine its content of the essential plant nutrients, nitrogen, phosphorus and potassium, and of the trace elements which are necessary for healthy plant growth. 

Lindenthal, T., Spiegel, H. and Freyer, B. (2000) Effects of long-term p-fertiliser application with different p-types and p-rates on p-balances, soil p-contents and yields. Proceedings of the 13th International IFOAM Scientific Conference, Basel, Switzerland, p. 23. 

Nitrous oxide emissions are generally induced by fertiliser application. Emission strength varies with soil type, temperature and moisture and is substantially crop specific. There is a considerable difference between woody species and cereals. While the Intergovernmental Panel on Climate Change (IPCC) general N20 emission value is set to 1.25% of the nitrogen applied an average of 0.8 to 1.0% could be found from sandy soils. 

In the pedosphere, the main outputs of sulfur are represented by river runoff and biogenic H2S, and inputs by dead organic matter, precipitation, dry deposition and fertiliser application. Friend (1973) assumes that the pedosphere is in dynamic equilibrium and retains a constant sulfur concentration. This is partially supported by experiments cited by Eriksson (1963) where, under SO2 exposure, soils rich in sulfate evolved H2S while those poor in sulfate gained sulfate. Removal of sulfur from the pedosphere by river run-off was estimated by Friend (1973) to be 89 Tg S y" based on differences between total run-off and the volcanic and rock weathering inputs to rivers. Friend also estimated that biogenic H2S released from the pedosphere was in the order of 58 Tg S y, assuming that sulfur inputs and removals from the pedosphere are balanced. The plant-soil cycle probably represents a net transfer of atmospheric sulfur (uptake by live plants) to the pedosphere (plant decay) although some H2S is released back to the atmosphere in the latter process. 

Eriksson s (1963) estimation for fertiliser application in 1960 (10 Tg S y" ) was increased by Friend (1973) to 26 Tg S y" on the basis of increased use of fertiliser nutrients. This estimation assumed that the sulfate content of fertilisers remained constant. However, until recently there was a trend towards greater use of high-nitrogen fertilisers such as urea and ammonium nitrate rather than (NH4)2S04. In fact, the use of these fertilisers has created sulfur deficiencies in some soils. 

Do an investigation into the variability of soil P between different locations, soil types or different parts of a field. The ultimate objective might be to adapt fertiliser applications to specific sites or to select sites for further experimentation. 

Macronutrients include N, K, PO3 and lime and are usually applied to the soil as natural or artificial fertilisers. The effects of additional fertilisers on medicinal plant productivity is generally beneficial, but scientific results have often revealed contradictory results and each plant must be investigated separately to determine the optimum level and frequency of fertiliser application. 

Figure 6.1 Main aerial application techniques used for applying pesticides and fertilisers. Application volumes are typical of those used in Australia...

Very little free ammonia is normally found in the soil, although it might be expected as a result of nitrogen fixation or fertiliser application. This is because of rapid oxidation by soil bacteria to... 

Before fertiliser addition, the commonest inorganic soil phosphate is usually apatite, although some of the other salts listed in Table 12.8 may also be present. The concentration of these salts may increase quickly after fertiliser application, but it is variable and depends on many factors, particularly soil pH. In alkaline soils, calcium salts tend to predominate, but under acid conditions with pH < 6, which are favoured by weathering, the proportion of iron and aluminium salts is increased. Complicated and sensitive equilibria exist, as indicated in Figure 12.5. 

Consideration of sulphur in animal nutrition is important in areas of intensive livestock production where sulphur in soils is not replaced regularly by fertiliser application. 

The mineral content of pasture is very variable, depending upon the species, stage of growth, soil type, cultivation conditions and fertiliser application an indication of the normal range in content of some essential elements is given in Table 18.2. 

Abstract This chapter explains the importance of feeding crops and ensuring that soil fertility is maintained. It discusses the main elements required by crops, both major and trace. It explains why liming is so important for crop nutrition. It deals with the calculations and sources of information needed to accurately decide on fertiliser application rates, and cost them. It describes the materials used on-farm as fertilisers and explains the differences between straights, compounds and blends, as well as dealing with liquids and solid fertilisers. There is a section on the use of oiganic manures and slurries and how to make best use of them. Finally, the chapter deals with the effect of fertilisers on the environment, during both their manufacture and application. 

Excess nitrogen, potassium and sodium also leads to higher levels of impurities in the sugar. This makes the sugar more difficult and expensive to extract in the factory. This is now one of the measured factors determining price so it is important that growers tailor their fertiliser applications to the crop requirements and take into account the nutrient contribution from any organic fertiliser applied in the form of slurry or manure. 

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