Grain & Hay: Understanding Nutrient Removal and Replacement

Author: Lee Menhenett, IPF Technical Agronomist

ABC Radio Victorian Country Hour reported on Thursday, 6 November 2025 that 105,000 hectares of the Victorian wheat crop had been cut for hay. That is twice as much as 2024, with similar amounts of hay cut in South Australia as 2024. Sam Atkinson from Digital Agriculture Services explained that by using satellite imagery and AI, changes in crop production can be measured.

Cutting winter crops for hay provides growers with an alternative option to manage droughted or frosted crops, or to help manage weed burdens. As the nutrient profile of hay differs from that of grain, gaining an understanding of removal values is important when implementing a replacement strategy. Total nutrient removal is the concentration of nutrient in the commodity exported multiplied by the yield.

Yields vary based on crop type, soil type, district, nutrient limitations and moisture. So too do nutrient concentrations. Figure 1 shows the grain phosphorus (P) concentration and removal in a canola trial (Figure 1). The site had a Colwell P of 41mg/kg and PBI 55. Yield was maximised (3t/ha) at 16kg P/ha rate.

_{Figure 1 – Phosphorus grain concentration and offtake in Dookie Canola Trial 2013. Source – IPL 2014.}

Higher yielding crops tend to cause a dilution effect on plant or grain nutrient concentrations, however total nutrient offtake is often on the higher side.

Norton (2009) analysed wheat grain samples from National Variety Trials (NVT) across south-eastern Australia in 2008 and 2009. He reported that mean P concentration ranged from 2.3 – 3.6kg P/t grain (corrected to 12% moisture). Norton (2014) also reported mean canola P concentrations from 54 NVT sites across southern Australia ranged from 4.5 – 7.1 kg P/t grain (corrected to 8% moisture).

Table 1 summarises the range of nutrient removal for wheat and canola from Norton’s assessment. There is a wide variation in grain concentration of nutrients which highlight the flaws in using average removal numbers. For example, there is a 20% variation from the maximum wheat P value compared to the mean and for canola the variation is a huge 48%. The table also highlights the variation of grain nutrient removal between the two different crops.

_{Table 1 – Summary of nutrient removal for wheat and canola grain.}

		Wheat		Canola
Nutrient		range	mean	range	mean
Nitrogen	kg/t	19 – 27.5	23	30 – 46.8	40
Phosphorus	kg/t	2.6 – 3.6	2.9	4.5 – 7.1	3.4
Potassium	kg/t	3.7 – 4.4	4	5.6 – 6.8	6.7
Sulphur	kg/t	1.3 – 1.7	1.5	2.8 – 4.4	3.8
Copper	g/t	3.0 – 4.9	4.2	2.2 – 3.12	2.8
Zinc	g/t	16.4 – 25.3	20.4	23.5 – 40.8	34.9
Boron	g/t	1.1 – 4.0	1.9	9.8 – 11.9	11.8
Moisture Correction		12%		8%

_{Source – Summary of data from Norton (2009) and Norton (2014).}

IPF has accumulated data on grain and hay nutrient analysis, including yield, from a variety of different crops across different regions. The data provided in Table 2 provides an insight into how large the variation of nutrient concentrations and removal can be, both within a specific crop and between different commodity types. Some observations include: 

• large removal of potassium in hay crops compared to grain
• vetch hay has high boron levels compared to other crop types
• nitrogen kg/t values in hay (except vetch) are lower compared to grain crops, although removal/ha is comparable
• phosphorus kg/t values in hay are lower compared to grain crops with removal/ha slightly less
• barley grain phosphorus values/t are less than wheat, however removal/ha range is similar
• canola grain phosphorus, potassium, sulphur and zinc kg/t values and removal/ha are higher than all other crops
• canola sulphur kg/t values (and removal kg/ha) are lower than typical budgeting values.

_{Table 2 – Nutrient removal per tonne and per hectare for various grain and hay crops.}

					Nutrient removal
Commodity	Yield Range t/ha		Nutrient		kg/t       or         g/t	kg/ha     or     g/ha
Vetch Hay 4 samples	Vetch Hay		Nitrogen		19 – 31	44 – 184
			Phosphorus		1.1 – 2.2	3 – 14
			Potassium		12.1 – 19.8	28 – 119
			Sulphur		1.3 – 1.9	3 – 12
			Copper		3.2 – 4.5	7 – 28
			Zinc		13.9 – 15.3	32 – 92
			Boron		26.1 – 32	74 – 162
Oaten Hay 6 samples	3.5 – 11.0		Nitrogen		9 – 10.8	48 – 119
			Phosphorus		0.9 – 1.4	3 – 16
			Potassium		9 – 15.3	32 – 168
			Sulphur		0.6 – 0.9	2 – 10
			Copper		2.2 – 2.6	8 – 29
			Zinc		4.7 – 10.8	22 – 99
			Boron		5.5 – 10.8	45 – 69
Wheat Hay 3 samples	4.0 – 9.3		Nitrogen		7.5 – 14.1	48 – 70
			Phosphorus		0.9 – 1.4	3 – 9
			Potassium		15.3 – 22.9	68 – 142
			Sulphur		0.7 – 1.2	4 – 7
			Copper		2.3 – 3.6	10 – 28
			Zinc		3 – 22.9	28 –78
			Boron		4.6 – 21	43 – 71
Wheat Grain 14 samples	1.5 – 8.0		Nitrogen		15 – 27	41 – 173
			Phosphorus		2.1 – 4	6 – 13
			Potassium		3.1 – 5.3	6 – 23
			Sulphur		1.2 – 1.9	3 – 9
			Copper		2 – 6.3	7 – 26
			Zinc		6.2 – 35	37 – 161
			Boron		1.1 – 4.3	3 – 16
Barley Grain 9 samples	2.4 – 5.2		Nitrogen		13 – 18.9	45 – 98
			Phosphorus		2 – 3.2	5 – 15
			Potassium		3.8 –4.9	11 – 26
			Sulphur		0.9 – 1.3	2 – 5
			Copper		1.8 – 5.6	8 – 27
			Zinc		13 – 21	41 – 109
			Boron		0.9 – 5.7	4 – 30
Canola Grain 2 samples	3.1 – 3.3		Nitrogen		33 – 33.9	106 – 109
			Phosphorus		4.9 – 6.7	15 – 22
			Potassium		6.5 – 7.6	21 – 24
			Sulphur		2.8 – 4	9 – 13
			Copper		2.5 – 2.9	8 – 9
			Zinc		29 – 44.8	96 – 140
			Boron		11 – 15.3	36 – 48

_{Source – IPF 2025.}

Summary

Using generic crop removal values can provide some guidance, however, to really nail down actual paddock or zone numbers, individual grain or hay samples should be taken and sent to the Nutrient Advantage Laboratory for analysis. Recording yield in these areas and multiplying by the nutrient value will allow for more accurate nutrient replacement values to be determined.  

In addition to nutrients being exported from farming systems, they can also be lost through other processes such as erosion, leaching, gaseous losses or soil complexing reactions, depending on the nutrient.

Strategies on nutrient replacement are aligned to either mine, maintain or capital applications, which need to be based on soil testing for major nutrients and preferably in conjunction with leaf tissue analysis for trace elements.  Long–term soil test records are more valuable than single–year samples, as they show nutrient trends over time, which identifies nutrient trends. Longer term data allows calibration against the nutrient replacement strategy adopted.

Further Information

For more information, contact IPF Technical Agronomist Lee Menhenett on 0412565176 or via email: lee.menhenett@incitecpivot.com.au

References

ABC Radio “Victorian Country Hour”, Thursday 6^th November 2025.

Norton R (2009) Grain Nutrient Concentrations – report on a survey from 70NVT wheat sites. International Plant Nutrition Institute, Australia and New Zealand.

Norton R (2014) Canola seed nutrient concentrations for southern Australia. ARAB XVIII Conference Proceedings