• NUlogic models are available for wheat and lupins. These model outputs can help to evaluate the season’s fertiliser strategy (especially nitrogen, sulfur and trace elements). Understanding this performance can assist with fine tuning next season’s strategy.
• Confirming grain nutrient concentrations can improve nutrient budgets.
This harvest, why not take advantage of CSBP’s analytical tools to review this season’s performance and be more informed about fertiliser use efficiencies. Grain sampling now can help optimise returns on fertilisers next season.
Grain sampling is easy. Collecting about 50 heads from a site is sufficient for analysis. These can be sent to the lab using the standard NUlogic plant testing kit. Header grain samples or stored grain from silos can also be submitted for the purpose of calculating paddock based nutrient budgets and assessing retained seed for 2022; NUlogic has calibrated standards for wheat and lupins.
Grain analysis can be used to:
• review this season’s fertiliser strategy in terms of nutrient deficiencies (for nitrogen, sulfur and trace elements), and
• plan for next season by developing nutrient budgets (nutrient application rates balanced against crop removal rates) if yields are known.
Nutrient budgets indicate starting points or carry-over of nutrients for next season. Nutrients can accumulate (surplus), deplete (deficit) or be in balance.
The nutrient trend over time is important, especially if paddocks have not been soil tested for some years. Nutrient trends can show if the inputs and outputs are balanced and if all the nutrient losses are accounted for. If the soil nutrient bank is being run down but there are no yield penalties yet, the trend data can show when to anticipate deficiencies and to increase nutrient rates accordingly.
Grain analysis can also be a handy tool to assist with troubleshooting problem areas in crops, and can tell you whether poor performance was caused by nutritional deficiencies, or other causes such as frost. Average nutrient removal rates exist, but they are just that: averages. Most grain nutrient concentrations vary significantly (by more than 50%). Only grain testing can confirm nutrient removal rates. What might seem like minor differences can actually be quite substantial. For example, compare a grain P concentration of 0.19% and 0.43%. Assuming a grain moisture percent of 11, this equates to a P removal rate of 1.7 kg/t versus 3.9 kg/t. In a high yielding situation, P removal could be higher than what has been applied, without even accounting for other losses to applied fertiliser P.
Be mindful that grain removal does not account for all nutrient losses and therefore maintenance rates need to be above removal rates. Nutrients are lost through leaching, adsorption, volatilisation, denitrification, stubble burning or hay cutting. Burning wheat stubble can cause 80% of the N and S in the straw to be lost and 40 and 60% of the P and K in the straw to be lost respectively (IPNI and Agriculture Victoria). Bare soil increases the risk of nutrient losses due to erosion. Cutting frosted wheat or barley hay will also lead to 0.5-7.0 kg K/t and 0.2-0.3 kg P/t removal. Considering all nutrient imports and exports with comprehensive nutrient budgeting helps with sustainable, balanced, and profitable nutrient applications.
If you missed the opportunity to plant sample during the season or want to find out how much nutrition you are exporting from your paddocks, contact your local CSBP area manager.