Returns for different nutrient strategies

If you put no fertilizer on over these grain crops, you produced 17.6 t of grain, if you used 9:40 produced 25.4 t of grain; 18:80 produced 29.3 t of grain. The gross margin for the same period was $1770 if no fertilizer was used – but the 9:40 strategy is $3645 - $125 per year added return over spending around $60 per hectare on fertilizers ($18.50 for P and $40 for N) – that is a 3:1 return on investment over 15 years including two ducks.

a) Average Grain Yield (t/ha) b) Mean Profit $/ha/y
N	0	9	18		36	Mean	N	0	9	18	36
0	1.18	1.46	1.50		1.52	1.41	0	118	202	196	159
20	1.25	1.69	1.75		1.75	1.61	20	120	244	246	160
40	1.36	1.69	1.81		1.79	1.66	40	141	229	243	199
80	1.30	1.81	1.95		1.81	1.72	80	89	235	254	170
160	1.35	1.71	1.81		1.78	1.66	160	25	141	145	101
Mean	1.29	1.67	1.76	1.73

Year to year variations: 9 or 18 kg P was always best, around 80 better earlier, now 20-40 is best.

Year	Crop	$/ha	N	P
1998	Barley	952	160	36
1997	Chickpea	504	20	18
1998	Canola	534	80	9
1999	Wheat	250	20	9
2000	Barley	573	80	18
2001	Lentil	286	0	9
2003	Wheat	668	20	9
2004	Barley	48	20	18
2005	Lentil	267	160	9
2007	Wheat	329	20	9
2008	Barley	116	20	9
2009	Chickpea	1	40	0
2010	Canola	1319	40	18