Långsiktig förändring av fosforhalt och skördenivåer för jordar med höga P-AL-tal
The field trial Exploatering av höga P-AL-tal (Exploiting P in heavily P dressed soils) started in 1982-1983 and included seventeen study sites placed across Sweden. Each site included three treatments, one unfertilized control (A), one aiming at replenishment of harvest removal, i.e. fertilized wi...
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| Formato: | First cycle, G2E |
| Lenguaje: | sueco sueco |
| Publicado: |
2014
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| Materias: | |
| Acceso en línea: | https://stud.epsilon.slu.se/7430/ |
| Sumario: | The field trial Exploatering av höga P-AL-tal (Exploiting P in heavily P dressed soils) started in 1982-1983 and included seventeen study sites placed across Sweden.
Each site included three treatments, one unfertilized control (A), one aiming at replenishment of harvest removal, i.e. fertilized with 15 kg P ha-1 year-1 (B) and one over-fertilized (C) with 30 kg P ha-1 year-1. In this thesis data from the five longestrunning study sites are analysed based on four hypotheses. The hypotheses stated
that in soils with high P-AL values and a pH over 6.0 P-AL will not decrease over time in the control (A) or in the replenishment treatment (B), that P-AL and P-HCl
in the top soil will increase at all sites for the over-fertilized treatment (C) and that yields will not decrease as long as the P-AL is above 12 mg P 100 g-1 soil.
My conclusions from the analysis of data from the selected sites are as follows:
- A pH above 6.0 cannot guarantee a stable P-AL value in an unfertilized
but phosphorus-rich soil.
- The P-AL of unfertilized soils decreased faster at lower soil pH than at
higher pH.
- In the replenishment treatment (B) the rate of P-AL decrease seems to fall
at a pH of 6.5. However, the influence of the soil type cannot be ignored.
- P-AL and P-HCl did not increase in all over-fertilized treatments. A higher
pH-value seems to be connected with an increase in P-AL. The soil type
seems to have impact, since one site with clay soil has an increase in P-AL
but one site with sand soil has a decrease at the same average pH value.
- The yields seem to be stable with a P-AL above 12 mg P 100 g-1 soil but
this should be seen more as a rule of thumb than as an absolute threshold. |
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