Biosolids and the need for Potash

Nutrient uptake

Typical uptake for cereal crops

Arable

For arable crops the typical uptake pattern of major nutrients is shown in the graph. Relatively small amounts of nutrient are required during the establishment period, but such supplies are vital to the development potential of the crop. Daily uptake increases dramatically during vegetative growth and restriction of nutrient supply at this stage can critically affect final yield and product quality such as grain sample, tuber size and numbers, sugar content etc. Peak uptake for potash is around flowering time for most combinable crops and at the end of the growing season for root crops. Peak uptake for nitrogen and phosphate coincides with the end of season.

Typical potash uptake and removal for high yielding crops

Plants must be able to take up nutrients when required at the rate to match potential growth. The total supply must provide for peak uptake rather than just the quantity removed at harvest. These can be very different especially for potash.

Grass and forage crops

With grazing, the livestock are continuously re-cycling nutrients back to the soil via dung and urine so replenishment needs are low. However hay and silage are similar to the arable situation - but more so!

Grassland conservation removes the whole crop, possibly several times a season, thus both uptake and removals of potash can be very large.