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soil profile cm

Catalogue: GRDC Updates
Figure 1: Effects of (a) application of an additional 40-60 kg P/ha to soils prior to planting, relative to normal starter P applications alone; and (b) placing that additional P deeper in the soil profile (15-20cm), compared to surface (5-7cm) bands... half of the soil P removed by cropping comes from below the top 10cm and about 90% of that removed P comes from forms/pools of P not measured in the Colwell (bicarbonate P) soil test; and (ii) when luxury rates of P are applied annually , >95% of the residual P stays in the top 10cm of the profile and the depletion of the subsoils continued unchanged... , we used a bioassay to assess how much of the P in the various pools was actually available for plant uptake, and how well this correlated with what the Colwell test predicted...
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