As the dust settles on the 2024 harvest, farmers across the region are diving into their yield data, evaluating how drought and frosty conditions impacted their crops. With this valuable information in hand, it’s the perfect time to assess the nutrient removal caused by grain or hay production and make informed decisions for the upcoming fertiliser program.
To help with this process, we’re sharing key takeaways from Sean Mason of Agronomy Solutions, who recently offered expert advice on nutrient management following a dry season.
Nutrient Removal: Hay vs. Grain
When crops are cut for hay instead of harvested for grain, the removal of nutrients from the paddock can differ. Understanding these differences is crucial for planning fertiliser budgets for the upcoming season. Here’s how major nutrients compare: These are based off averages and will vary across paddocks depending on soil type nutrient stats and 2024 applications.
– Nitrogen (N): Nutrient removal for hay is roughly equivalent to grain, with about 20 kilograms of nitrogen removed per tonne.
– Phosphorus (P): Hay removal is slightly lower, with about 1.5–2.5 kilograms of phosphorus per tonne (can be lower). Phosphorus is mobile within the plant, concentrating in the grain during harvest, which potentially reduces its removal in hay on a total plant weight basis.
– Potassium (K): This is where the major difference lies. With hay, the entire plant is removed, leading to about 20-30 kilograms of potassium per tonne being taken from the paddock—significantly more than grain, which typically removes around 6–7 kilograms per tonne.
– Sulphur (S): Like nitrogen, sulphur removal is comparable between hay and grain. Farmers can expect 1.5–2 kilograms of sulphur per tonne of hay.
These figures underline the importance of considering the whole plant removal when budgeting for inputs next season. While hay cutting doesn’t remove dramatically higher amounts of nitrogen or sulphur, the higher potassium removal is noteworthy.
Potassium: A Hidden Concern?
Potassium may not always be top of mind for growers in the Mallee, but Sean highlighted it as a “sleeper issue” worth monitoring. Critical potassium levels vary depending on soil type and texture:
– In sandy soils, potassium levels at or below 50–60 milligrams per kilogram are often considered critical.
– In heavier textured loams, higher levels—up to 100–150 milligrams per kilogram—may be necessary for optimal crop performance.
Soil testing remains the best way to gauge potassium levels. Keep in mind that potassium movement is influenced by soil characteristics:
So in heavier soils with high cation exchange capacity (CEC), potassium is less mobile and remains closer to the surface. In sandy soils with lower CEC, potassium can leach more easily through the profile, especially after significant rainfall. This would suggest, similar to nitrogen that sampling beyond 0-10cm would be worthwhile to gauge K levels.
Farmers cutting hay on a regular basis should pay close attention to potassium levels, especially in high-production zones where historical nutrient removal may already have depleted subsoil reserves.
Input Planning for 2025
Given the nutrient removal figures are likely to be on the low side for hay and grain in 2024, it is likely less inputs will be required in optimising input efficiency next season:
- Soil Testing: Start the season with comprehensive soil tests to understand nutrient availability, particularly nitrogen, phosphorous and sulphur levels. Following poor crop yields, savings are likely to be achieved but it’s important to know where.
- Variable Rate Technology (VRT): Even if you haven’t set up zoning for fertiliser inputs in the past, consider zoning paddocks based on nutrient needs this coming season. This approach allows targeted fertiliser application, reducing costs while ensuring nutrients are applied where they’re most needed.
- Monitor Seasonal Conditions: Some nutrients can move down the profile with heavy summer rainfall particularly in lighter soils. Sampling nutrients down the soil profile can help determine where nutrients are concentrated.
By understanding the unique nutrient dynamics of grain and hay removal, farmers can make informed decisions to balance soil health and maximise productivity. Nutrient budgeting isn’t just about replacing what’s removed; it’s about planning for a system that supports sustainable and efficient production in the long term.
If you’re planning for next season and would like to delve deeper into soil health or input strategies, reach out to your local agronomist or join upcoming discussions in the Zoning and Variable Rate Fertiliser Project, supported by the SA Drought Resilience Adoption and Innovation Hub.
Check out the Facebook Live event held with Sean Mason 14th of November 2024 here
