Nutrient removal and balance

Phosphate

Typical removal in cereal grain is 7.8 kg P₂O₅/t. Phosphate content of straw is very much lower than potash. Removal of straw thus has little effect upon phosphate offtake.

Typical removal standards

		Metric kg/t of grain		Imperial units/t of grain
		P2O5	K2O	P2O5	K2O
Cereals	- Grain only	7.8	5.6	15.6	11.2
	- Grain & Straw Winter wheat/barley	8.4	10.4	16.8	11.2
	Spring wheat/barley	8.6	11.8	17.2	23.6
	Oats	8.8	17.3	17.6	34.6

Recommendations

The recommendations below are calculated to achieve full yield and maintain, improve or reduce soil P and K according to the soil Index. The approach firstly identifies the amount of nutrient removed by the cereal crop grown (the 'maintenance' amount) and then makes additions to this if necessary (soil fertility adjustment), according to the current soil Index level.

Phosphate

Maintenance requirement (replacement of P removed)		Metric kg/P2O5/ha	Imperial units/P2O5/acre
Grain only - All cereals		yield t/ha x 7.8	yield t/acre x 15.6
Grain + Straw
	Winter wheat/barley	yield t/ha x 8.4	yield t/acre x 16.8
	Spring wheat/barley	yield t/ha x 8.6	yield t/acre x 17.2
	Oats	yield t/ha x 8.8	yield t/acre x 17.6

 

Soil fertility adjustment - additional phosphate requirement at soil Index 0 or 1
	Metric			Imperial
P Index	0	1	2	0	1	2
mg/l	0-9	10-15	16-25	0-9	10-15	16-25
	kg/P2O5/ha			units/P2O5/acre
Phosphate requirement	+60	+30	0	+50	+25	0

Potash

Maintenance requirement (replacement of K removed)		Metric kg/K2O/ha	Imperial units/K2O/acre
Grain only - All cereals		yield t/ha x 5.6	yield t/acre x 11.2
Grain + Straw
	Winter wheat/barley	yield t/ha x 10.4	yield t/acre x 20.8
	Spring wheat/barley	yield t/ha x 11.8	yield t/acre x 23.6
	Oats	yield t/ha x 17.3	yield t/acre x 34.6

 

Soil fertility adjustment - additional potash requirement at soil Index 0 or 1
	Metric			Imperial
K Index	0	1	2-	0	1	2-
mg/litre	0-60	61-120	121-180	0-60	61-120	121-180
	kg/K2O/ha			units/K2O/acre
Adjustment	+60	+30	0	+50	+25	0