Nutrient removal after hay or grain harvesting


Whether this year’s winter crop is coming off as fodder now or grain in the coming weeks and months, significant levels of nutrients will be removed from the paddock.


The good news is, growers and their advisers have the opportunity at harvest to find out exactly how much nitrogen, phosphorus, potassium, sulphur, zinc and copper is coming off these paddocks.

While soil testing is an integral part of farm management, plant tissue testing, including grain testing, provides great insights too. This data can be used to assist in formulating the 2019 fertiliser budget.

Nothing comes for free and these nutrients will come at a cost to replace.

However, in some instances, the nutrients may be in abundance in the soil, above a point where additional yield will not occur if more is supplied. In this situation, growers can legitimately ‘mine’ these nutrients, without the need to replace all that has been removed in crop.

If soil test values are within the critical range where maximum yield is achievable, then a nutrient replacement strategy can be adopted.

If soil test values are below the critical range where maximum yield is achievable, then a maintenance nutrient replacement strategy plus a capital nutrient application needs to be made to bring soil fertility up.

Comparing nutrient removal in fodder and grain

The table below was collated based on plant tissue analysis of fodder cut from this year’s wheat and canola and grain test results from six years of trials conducted in the Riverine Plains.

It provides an insight into the nutrient removal of wheat and canola on a per tonne basis, and the associated cost of the nutrients removed at current fertiliser prices.

While this does give an indication of the likely removal, it is always better to arrange your own testing. The values will change with different crop types, soils and growing seasons.

Both fodder and grain can be tested through the Nutrient Advantage® laboratory, as a grain sample or a tissue sample.

Nutrient concentrations, Riverine Plains, Victoria


N (kg/t)

P (kg/t)

K (kg/t)

S (kg/t)

Zn (g/t)

Cu (g/t)

Canola grain
(6% moisture)

32.9 - 35.3

4.3 - 5.4

6.5 - 7.7

4 - 4.1

43.5 - 44.8

2.7 - 3

Canola hay/silage at 50% flower
(0% moisture)







Wheat grain
(12% moisture)

15.5 - 20.8

2.1 - 2.28

3.1 - 3.4

1.33 - 1.53

18 - 31

2.6 - 3.1

Wheat hay/silage at early flower
(0% moisture)

18 - 23

1.8 - 2.1

20 - 27

1.9 - 2

17 - 21

3.9 - 5

Cost of nutrient removed per tonne








Canola grain
(6% moisture)







Canola hay/silage at 50% flower
(0% moisture)







Wheat grain
(12% moisture)







Wheat hay/silage at early flower
(0% moisture)







Source: Incitec Pivot Fertilisers, 2018. Hay/silage data from 2018, grain data from 2013-2018. Mid-range numbers used to determine costs. Based on indicative fertiliser prices of urea for nitrogen at $600/t, DAP for phosphorus at $750/t, Muriate of Potash for potassium at $550/t, GranAm for sulphur at $400/t, zinc sulphate monohydrate for zinc at $2,300/t and copper granules for copper at $4,600/t.

Based on these figures, the total cost of replacement nutrients from canola cut for hay or silage is $14/t more than for canola harvested for grain.

With wheat, the value of nutrients removed from a fodder cut is also higher than for grain, with fodder adding up to a total of $58.95/t while the grain crop was $33.64/t.

The main difference in nutrient removal between fodder or grain is in the potassium.

Potassium accumulates in the leaves and stems of plants in higher concentrations than in grain, so fodder removes more potassium per tonne of commodity.

The soil profiles on the Riverine Plains are generally rich in potassium and potassium responses are limited, so mining of potassium would be an acceptable strategy in this case.

However, in other districts and also where there is windrow burning, lighter sandy soil types or paddocks with a history of fodder conservation, there may be a need for potassium replacement. Soil testing will show whether potassium reserves are within the critical range or above.

A further consideration after fodder conservation is the greater rate of acidification it can cause compared with grain harvesting, due to the higher cation removal (mainly from potassium).

While approximately 9 kg/t of lime is required to balance the acidifying effects of harvesting wheat as grain, around 30-40 kg/t of lime is required to balance the acidifying effects of harvesting wheat as hay.

Grain or tissue testing is easy through the Nutrient Advantage laboratory. Collect 400 grams of harvested grain from the header or the same weight of hay, place it in a sample bag and send it to the laboratory for analysis.

It’s a quick and reliable way to analyse nutrient removal from this year’s winter crops.

If you would like to discuss nutrient budgeting and planning for nutrient replacement with me, you can call on 0412 565 176 or email