Evaluation of late nitrogen applications to achieve yield potential and increased protein content in wheat

In the southeastern Australian high rainfall cropping zone, growers have the opportunity to apply nitrogen later in crop growth because of the higher probability of followup rains. This project established eight field experiments to help growers refine N source, rate and time for this region.


01 Jul 2013

Project Description

This project aims to contribute to the knowledge gaps identified by the HRZ RCSN in the program logic for the very high priority issue of nitrogen management. The research question is – Can we achieve optimum yield (measured at 10.5 -11% protein) and still increase the grain protein (to 12%) of wheat produced in the HRZ? Specific to the project is – What impact will delaying the timing of nitrogen applications after GS32 have on wheat yield and protein and is there an advantage of using solid or liquid fertiliser?

Trial sites will be established in wheat crops to evaluate the impact of late (post GS32) nitrogen application rates, products and timings on yields and grain quality. The treatments are outlined under “Detailed Methodology”.
Grain yield and protein quality data will be collected.

Project objectives, updates and trial results will be extended through farming systems and GRDC networks via a range of mediums and activities, including field days and trial results presentations.

Growers and agronomists have to make a number of key tactical decisions, each season, in respect of their overall nitrogen management. These decisions include such things as:
• Application rates, based on seasonal conditions and their effect on yield potential
• The price of nitrogen fertiliser and how this will impact on the potential $ return/ha
• The timing of applications and the ability to get nitrogen into the crop with sufficient rainfall or moisture, especially when applied later in the season.

In the current season with good soil moisture in both medium and high rainfall areas and a positive outlook for the spring from the majority of climate models, these issues have been identified as a high priority issue by the GRDC HRZ RCSN.

The low protein levels of wheat from last season would suggest that the optimum nitrogen requirements were not being met and therefore limited yield potential. The above average yields of this past season combined with low protein grain leads us to assume that the soil nitrogen supply will also be low. This has been confirmed by the results of deep soil nitrogen availability from tests both prior to sowing and those taken over recent months. Given the dry summer and little mineralisation of nitrogen and now a wet winter it is likely that protein levels of wheat could again be low. Another factor contributing to lower available nitrogen inputs into the system is the lack of nitrogen fixing break crops. The consequence of eroded nitrogen levels in the soil is that nitrogen fertiliser input requirements will be significantly higher than most growers have been used to applying, to achieve yield potential and grain quality (protein and screening). The timing of nitrogen applications is also important to ensure that the supply of nitrogen matches that of the crop demand.

The need for additional nitrogen fertiliser inputs this season to achieve yield potential at accepted receival standards for protein content is not clearly understood and/or under-estimated by the majority of agronomists and growers. The type of nitrogen fertiliser applied, whether as a liquid or in the solid form, has not been researched when applied after GS32, as in many seasons the conditions are not suitable for further yield gains and grain protein enhancement.

These trials will provide objective data to assist farmers make decisions on late nitrogen applications from GS32 (second node detectable) through to GS70 (grain watery ripe) comparing solid urea with two forms of liquid nitrogen. This will demonstrate strategies growers can utilise in the future to achieve increased grain yields, whilst maintaining acceptable grain protein, in seasons where crops have adequate soil water.

Additional Resources

Late N Project ProposalSize: 0.08 MB