Möjligheter till ökat utnyttjande av fosfor genom grödan med mineralgödselmedel
The objective of this thesis is to explore opportunities to enhance the phosphorus use efficiencyof inorganic fertilizers in crop production, with techniques available today and in thefuture. Phosphorus is a finite resource of declining quality; therefore a phosphorus use efficiencyin crop production of only 15-30 % is unacceptable. The main reason for low efficiencyis the retention by Ca and Mg in calcareous soils and Fe and Al in non-calcareoussoils. Due to the low mobility of phosphorus, plant uptake is mainly dependent on root growthrather than diffusion. Therefore, measurements need to be taken that benefit contact betweenroot and fertilizer, before fertilizer phosphorus becomes unavailable to the plant. Among themost common fertilizers no consistent difference in efficiency exists although the initial reactionpH of the fertilizer may have an impact on the efficiency. Dressing should be done everyyear in spring and root uptake is enhanced by placing the fertilizer in bands under the seed,about 10 cm from the surface. It is possible to make complimentary dressing by foliar application.Further enhancements may be accomplished by using liquid fertilizer. Efficiency may befurther improved on some soils by increasing the granular size to limit contact between fertilizerand soil, thereby minimizing retention and keeping phosphorus in solution. On other soilsit might be of advantage to use a smaller granular size that places phosphorus fertilizers in acontinuous band to improve root proliferation. Enhanced efficiency phosphorus fertilizers(EEF:s) may further increase plant utilization by slow release or cation adsorption. However,more research needs to be done on the subject. For maximum efficiency, fertilizer phosphorusin soil solution must be synchronized with plant demand. To feed a growing world populationat a reasonable environmental as well as monetary expense, further steps need to be taken toincrease the efficiency to an acceptable level.