The target Index is based on critical soil phosphate levels to achieve 95 per cent of maximum crop yield for all crops. However, these values can vary between soils and crops.
Project FV 380, led by Nathan Morris of NIAB TAG, tests the levels of P required in vining pea crops and provides guidance for economically efficient production.
By targeting the dose of P, the risk of undesirable P losses to watercourses should be reduced, thereby meeting the requirements of the Water Framework Directive.
First-year results show that critical Olsen P values vary from site to site, probably due to variation in soil type. Crop vigour was reduced at or below index one (<15mg/kg) and there were clear yield differences between different soil Olsen P levels.
Crop maturity was affected by the Olsen P value. Tenderometer Readings were TR 129 at index one, whereas they were TR 116 at index two and TR 112 at index three (26-45mg/kg). For the two trial sites, vining pea yields were reduced by 0.3 tonnes per hectare or more and were more variable at measured Olsen P below the lower half of index two (16-25mg/kg).
Results from year two reflect year one and suggest clear effects on crop yield to soil Olsen P levels. The greater yield responses at index three or above at all sites are likely to have been influenced by soil structure, air temperature and rain.
Horticultural Development Company
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