From 1968 Broadbalk was divided into 10 sections. Grain and straw from selected sections and plots were collected and stored in the Sample Archive. They were analysed for nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), sodium (Na) and sulphur (S). Data is presented as % nutrient in wheat grain and straw and is the response to different fertiliser treatments and cropping. Nitrogen is available all years and other nutrients for selected years, and for varying sections (see Table of Contents for summary and downloadable file for detail).
Nitrogen (N) 1968-1995: nitrogen content was determined by Kjeldahl digest, the digest was then analysed colorimetrically using a Technicon segmented flow analyser. If nitrate-N was expected to be high in the sample, the salicylic acid modification was used (Bremner, 1965).
1996 onwards: nitrogen content is determined by combustion analyser, based on the Dumas method. Originally a Heraeus Combustion analyser, currently a LECO combustion system is used.
Phosphorus (P), Potassium (K), Calcium (Ca), Magnesium (Mg), Sodium (Na) and Sulphur (S) 1968-late 1980s: dry ashing techniques, as described by Piper (1942) were used to produce an acid extract. The extracts were analysed for P colorimetrically on a Technicon Auto Analyser, or later equivalents (Alpkem continuous flow system / Skalar SanPlus segmented flow system), using the modified Murphy & Riley (1962) molybdenum blue method developed from Fogg & Wilkinson (1958). K, Ca, Mg and Na were determined using automated atomic absorption methods. The SP90 atomic absorption flame photometer was used to analyse Ca, Mg and Na; K was analysed by the EEL flame photometer until 1973, K was then analysed with Ca, Mg and Na by the SP90. S was not routinely measured until 1996.
1980s onwards: since the late 1980s the open tube nitric-perchloric digestion (Zarcinas, et al, 1987) has been used to produce an acid extract. P, K, Ca, Mg and Na have been determined by ICP-OES (Inductively coupled plasma optical emission Spectrometer) since 1982, and S since 1996.
Blank (control) values: Data for sodium is presented after the analysis blanks (controls) have been subtracted from the raw data. Sodium blank values tend to be relatively large, and can be greater than the raw data. If subtracting the blank resulted in a negative value, this is shown as zero. Thus the sodium data should be treated with some caution. Blank (control) readings for the other nutrients are very small, relative to the treatment values, and have not been subtracted.
This dataset is available under a Creative Commons Attribution Licence (4.0).
YOU MUST CITE AS: Sarah Perryman, Wendy Wilmer (2021). Dataset: Broadbalk Crop Nutrient Content, Wheat 1968-2017 Electronic Rothamsted Archive, Rothamsted Research 10.23637/rbk1-BKNUTRW-01
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N is available every year whereas P, K, Ca, Mg, Na and S for some years only. S only from 1996, N only 1976-1985. Not all sections were analysed, Section 1 and 1st wheat every year, and some other sections in other years. Straw not always available in same years that grain measured.
This dataset is derived from measurements made by the Analytical Chemistry Unit, Rothamsted Research, Harpenden.
The Analytical Chemistry Unit follows the Joint Code of Practice (JCoPR) and participates in European Quality Assurance programmes. All performance is strictly monitored using certified external standards alongside in-house standard materials. Standards and check samples are monitored and recorded.
With thanks to Andy Macdonald, Paul Poulton, Steve Freeman, Ruth Skilton and Wendy Gregory for help with compiling this information.
For analytical techniques see following references;
Bremner, J. M. (1965). Total nitrogen. In Methods of Soil Analysis. Part 2 (Ed. C. A. Black), pp. 1149-1178. Madison. American Society of Agronomy. Fogg, D.N. and Wilkinson, N.T. (1958). The colorimetric determination of phosphorus. Analyst, London, 83:406-414. Piper, C.S. (1942) Soil and plant analysis. The University of Adelaide, Adelaide, Australia. Zarcinas, B.A., Cartwright, B., Spouncer, L.R., 1987. Nitric acid digestion and multi-element analysis of plant material by inductively coupled plasma spectrometry. Communications in Soil Science and Plant Analysis 18, 131–146.
Nutrient data for other crops on Broadbalk is available as separate datasets, see Related Documents.
For further information and assistance, please contact the e-RA curators, Sarah Perryman and Margaret Glendining using the e-RA email address: email@example.com