Responsive crop nutrition application in cereals

Can changing when to apply nutrients in response to the health of the plant result in a healthier wheat crop than conventional applications? This is one of the questions being tested at Strategic Cereal Farm Scotland. 

Nutrient application timings and plant health

  • Start: October 2020                          
  • End: Harvest 2021

Objective

To baseline the effect of adjusting nutrition in response to tissue testing as well as baselining the relationship between plant health and brix readings

Should I test plant health to time nutrient applications?

We have an extensive nutrient management research programme for arable crops, including work to improve and optimise nutrient applications that are both environmentally and economically sustainable.

Timing nutrient applications correctly is as important as applying the right amount. Crop demand varies throughout the season and is greatest when a crop is growing quickly, therefore results from standard laboratory tissue testing may be quickly outdated.

Rapid development of leaves and roots during the early stages of plant growth is crucial to reach the optimum yield at harvest, and an adequate supply of all nutrients must be available during this time. Excess application of nutrients, or application at the wrong time, can reduce crop quality and cause problems such as lodging of cereals or increases in foliar pathogens.

Many growers are moving away from regimented fungicide applications to assessing a crop before application as part of an effective IPM strategy. The aim of this trial is to see if amending nutrient applications in response to testing the plant, results in a healthier crop than when conventional nutrient applications are made.

How are we assessing nutrient application timings?

This tramline trial is in Tank Wilsons March (13.5 ha) with a sandy silt loam soil. The crop is Skyscraper winter wheat.

The treatments are designed to be representative of the industry as well as the farm standard as a control.

Standard agronomy (Tramline 1)
  • Using SAC Techincal Notes without fungicide to compare how nutrition alone affects plant health
Farm standard (Tramline 2)
  • Led by the farm’s agronomist to see how adjusting nutrients affects crop health in comparision to farm standard
Nutrient adjusted (Tramline 3)
  • Regular brix assessments are taken at the same time of day to use the tissue’s sugar as an indication of photosynthetic rate and therefore give an impression of crop health.
  • When the brix reading falls below 10, a bulk tissue sample is sent for rapid analysis and within a week the trial steering group decide the inputs as a product of the results.

In addition to the soil health, plant health and biodiversity baselining assessments taking place at the Strategic Cereal Farm Scotland, the following assessments are completed at each sampling point:

  • Growth stage
  • NDVI
  • GAI
  • Above-ground fresh and dry biomass
  • Tissue sampled for full nutrient analysis
  • Brix meter
  • Plant pH
  • Sap nutrient assessments

At harvest, the farm will collect combine yield data for SRUC to analyse.

The Farm Economics team will calculate the economic cost of production of the crop in each trial field. Using Farmbench, they will produce costs per hectare and per tonne. The calculations will use:

  • Seed, fertiliser and crop protection
  • Farm labour, machinery and equipment
  • The regional average for property, energy and administration

What results has the project delivered?

Testing physiological measures

During early stages of crop development, several test were compared to optimise sampling procedure and value of each output. At GS13-21 and GS14-23, plants in each tramline were tested using:

  • Leaf greeness (chlorophyoll estimate) using a SPAD meter 
  • Brix units using a refractometer 

As expected, there was no significant differences between the untreated (no fungicide), standard agronomy (full inputs) and adjusted nutrient and crop protection (managed or tailored approach) tramlines at this early stage. This comparison provided a useful baseline for subsequent crop assessment.

Plant development

An estimate of crop ground cover and GAI was undertaken at GS30 (21 April) from replicate samples in each tramline. 

The difference between tramlines was not significant. 

Plant counts were similar across each tramline unti GS32-17, where tramline 3 had a slighly higher plant count but fewer tillers. This was reflected in the ear count at GS71-75 with an average of 42.6 ears (average of 10 quadrat counts) in Tramline 3 compared to 44.2 and 43.1 in Tramlines 1 and 2, respectively. 

Images of crop biomass (low red to green high) generated in Climate Fieldview on 1 July (left) and 2 August 2021 (right) are shown below. Tramline 1 (untreated) and Tramline 3 (managed inputs) are visible in red.

Laboratory Sap analysis

 Graphs below show output from commercial sap testing, including pH and sixteen nutrients. At GS23 (top image) there was low (red) manganese, and good (green) and excess (blue) other nutrients across each tramline. By contrast, at GS33 there was low (red) calcium in each crop tramline, and low magesium in tramline 2. Overall, tramline 3 was closest to an optimal nutrient balance. 

Brix readings

The mean Brix values for the replicated zones taken from each tramline from GS21 in mid-March towards ear emergence in mid-June are shown on the right (Tramline 1 (T1); Tramline 2 (T2); Tramline 3 (T3)).

Overall there was no significant seasonal difference in Brix values between tramlines (P = 0.893). However, between tillering (mid-April) to stem extension (early-May), Brix values were just significantly greater (P = 0.05) in tailored agronomy (21.3) compared to untreated (17.9) and standard agronomy (19.4).

Cost of production

Using FarmBench data (below) for Tank Wilsons March, it was possible to estimate several efficiencies for each tramline.

Preliminary results suggest that overall wheat grain yield was low in this field, and that the standard agronomy tramline resulted in a higher yield compared to the untreated and tailored (adjusted) agronomy tramlines. 

In terms of efficiency measures: (1) as yield per cost of nutrient input, or N offtake or estimated grain N use efficiency (NUE), the standard agronomy tramline was substantially higher than the untreated and tailored (adjusted) agronomy tramlines, (2) when using crop protection costs only, the tailored agronomy had most yield-to-cost benefit, and (3) for overall input costs, yield-to-cost benefit was comparable among each tramline.   

Action points for farmers and agronomists

  • As this project refines protocols and quantifies cost-benefits towards a tailored agronomy approach, all farms will be invited to check and compare crop assessment methods that are most appropriate and timely for their fields and cropping system.
  • At this stage, several lab and field tests for monitoring crop health are being evaluated for productivity and efficiency value.
  • Measurement of Brix units and established approaches such as SPAD (leaf cholorophyll) readings has potential to report on crop health, which in the longer term could become part of remote sensing for crop nutrient and health status.

Useful resources 

Nutrient Management Guide (RB209)

Wheat growth guide

Barley growth guide

Our Strategic Farms are an opportunity to see how to use our research on a commercial farm. Find out more about our Strategic Cereal Farm Scotland programme

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