Updating nitrogen and sulphur fertiliser recommendations for spring barley

S.L. Kendall, T.F.J. Fitters, P. Berry, SP Hoad, IJ Bingham

Research output: Book/Report/Policy BriefCommissioned report

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Abstract

This project aimed to improve nitrogen (N) and sulphur (S) fertiliser management guidelines for modern spring barley varieties. The work was conducted to help farmers achieve grain N% targets and high (economically optimal) yields more reliably. Specific objectives were to:
1) Review data to understand how soil N supply, applied N and yield potential affect grain N%
2) Quantify the effect of timing of soil applied N and S fertiliser on grain N%
3) Quantify the effect of rate of soil applied N fertiliser on grain N%
4) Produce N and S fertiliser guidelines for achieving grain N% targets with maximum yield
5) Transfer guidelines to farmers and agronomists
Eleven N-response experiments resulted in an average optimum N rate (Nopt) of 118 kg N/ha, with an average yield of 7.4 t/ha and an average grain N% of 1.63%. Analysis of new experimental data and a UK review dataset confirmed that the crop N demand increased with yield, with an additional 20 kg N/ha for each additional tonne, equating to an additional fertiliser requirement of 33 kg N/ha per tonne. On average, the current RB209 recommendations over-estimated N requirement by over 40 kg N/ha, with an average error of +/- 48 kg N/ha. Two options are proposed that deal with this inaccuracy (both give similar N recommendations at expected yields of 7–8 t/ha):
i) Change the expected yield value from which N rate is adjusted from 5.5 t/ha to 7.5 t/ha.
ii) Adopt a method to calculate fertiliser N requirement based on crop N demand and fertiliser recovery.
Across the new experimental data and UK review dataset, reducing grain N% by 0.1% required a reduction in N rate of 29 kg N/ha, thus confirming the current RB209 recommendation of a reduction of 30 kg N/ha. The average grain N% at the Nopt was 1.72% and 67% of crops achieved a grain N% of <1.8% at the Nopt. A cost-benefit analysis indicated reducing the N rate recommended for optimum yield by 30 kg N/ha would maximise the reliability of achieving a grain N% of less than 1.8%. However, if historic grain N% data for the field indicates that grain N% is consistently below 1.8% with fertiliser rates optimised for yield then it may not be necessary to reduce the N rate.

Eleven N-timing experiments clearly indicated that all the N should be applied between the time of drilling and GS30, with at least 40 kg N/ha in the seedbed. However, to minimise the risk of nitrate leaching, no more than 40 kg N/ha should be applied in the seedbed, if the crop is sown before March, grown on a light-sand soil or if there is a likelihood of substantial rainfall soon after drilling.
The results indicated that there was no requirement to alter current recommendations for S fertiliser, with applications of 25–50 kg SO3/ha, where a risk of S deficiency is identified.
Original languageEnglish
PublisherAHDB
Number of pages183
Volume635
Publication statusPrint publication - May 2021

Keywords

  • Spring Barley
  • Nitrogen
  • Sulphur
  • Fertiliser
  • Recommendations
  • Yield
  • Grain Quality
  • Malting
  • N Use
  • Efficiency
  • AHDB
  • MAGB

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