Epsilon Archive for Student Projects

Abstract

The objective of this thesis is to explore opportunities to enhance the phosphorus use efficiency
of inorganic fertilizers in crop production, with techniques available today and in the
future. Phosphorus is a finite resource of declining quality; therefore a phosphorus use efficiency
in crop production of only 15-30 % is unacceptable. The main reason for low efficiency
is the retention by Ca and Mg in calcareous soils and Fe and Al in non-calcareous
soils. Due to the low mobility of phosphorus, plant uptake is mainly dependent on root growth
rather than diffusion. Therefore, measurements need to be taken that benefit contact between
root and fertilizer, before fertilizer phosphorus becomes unavailable to the plant. Among the
most common fertilizers no consistent difference in efficiency exists although the initial reaction
pH of the fertilizer may have an impact on the efficiency. Dressing should be done every
year 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 be
further improved on some soils by increasing the granular size to limit contact between fertilizer
and soil, thereby minimizing retention and keeping phosphorus in solution. On other soils
it might be of advantage to use a smaller granular size that places phosphorus fertilizers in a
continuous 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 phosphorus
in soil solution must be synchronized with plant demand. To feed a growing world population
at a reasonable environmental as well as monetary expense, further steps need to be taken to
increase the efficiency to an acceptable level.