Soil Fertilizer

1 soil

1.1 acidification
1.2 accumulation of toxic elements

1.2.1 cadmium
1.2.2 fluoride
1.2.3 radioactive elements
1.2.4 other metals


1.3 trace mineral depletion
1.4 changes in soil biology

soil
acidification

nitrogen-containing fertilizers can cause soil acidification when added. may lead decreases in nutrient availability may offset liming.

accumulation of toxic elements
cadmium

the concentration of cadmium in phosphorus-containing fertilizers varies considerably , can problematic. example, mono-ammonium phosphate fertilizer may have cadmium content of low 0.14 mg/kg or high 50.9 mg/kg. because phosphate rock used in manufacture can contain as 188 mg/kg cadmium (examples deposits on nauru , christmas islands). continuous use of high-cadmium fertilizer can contaminate soil (as shown in new zealand) , plants. limits cadmium content of phosphate fertilizers has been considered european commission. producers of phosphorus-containing fertilizers select phosphate rock based on cadmium content.

fluoride

phosphate rocks contain high levels of fluoride. consequently, widespread use of phosphate fertilizers has increased soil fluoride concentrations. has been found food contamination fertilizer of little concern plants accumulate little fluoride soil; of greater concern possibility of fluoride toxicity livestock ingest contaminated soils. of possible concern effects of fluoride on soil microorganisms.

radioactive elements

the radioactive content of fertilizers varies considerably , depends both on concentrations in parent mineral , on fertilizer production process. uranium-238 concentrations can range 7 100 pci/g in phosphate rock , 1 67 pci/g in phosphate fertilizers. high annual rates of phosphorus fertilizer used, can result in uranium-238 concentrations in soils , drainage waters several times greater present. however, impact of these increases on risk human health radinuclide contamination of foods small (less 0.05 msv/y).

other metals

steel industry wastes, recycled fertilizers high levels of zinc (essential plant growth), wastes can include following toxic metals: lead arsenic, cadmium, chromium, , nickel. common toxic elements in type of fertilizer mercury, lead, , arsenic. these potentially harmful impurities can removed; however, increases cost. highly pure fertilizers available , perhaps best known highly water-soluble fertilizers containing blue dyes used around households, such miracle-gro. these highly water-soluble fertilizers used in plant nursery business , available in larger packages @ less cost retail quantities. there inexpensive retail granular garden fertilizers made high purity ingredients.

trace mineral depletion

attention has been addressed decreasing concentrations of elements such iron, zinc, copper , magnesium in many foods on last 50–60 years. intensive farming practices, including use of synthetic fertilizers suggested reasons these declines , organic farming suggested solution. although improved crop yields resulting npk fertilizers known dilute concentrations of other nutrients in plants, of measured decline can attributed use of progressively higher-yielding crop varieties produce foods lower mineral concentrations less productive ancestors. is, therefore, unlikely organic farming or reduced use of fertilizers solve problem; foods high nutrient density posited achieved using older, lower-yielding varieties or development of new high-yield, nutrient-dense varieties.

fertilizers are, in fact, more solve trace mineral deficiency problems cause them: in western australia deficiencies of zinc, copper, manganese, iron , molybdenum identified limiting growth of broad-acre crops , pastures in 1940s , 1950s. soils in western australia old, highly weathered , deficient in many of major nutrients , trace elements. since time these trace elements routinely added fertilizers used in agriculture in state. many other soils around world deficient in zinc, leading deficiency in both plants , humans, , zinc fertilizers used solve problem.

changes in soil biology

high levels of fertilizer may cause breakdown of symbiotic relationships between plant roots , mycorrhizal fungi.