Elemental concentrations and growth characteristics of wild-type and cultivated varieties of pasture species

The objective of the experiment that generated this dataset was to determine how pasture species (grasses, legumes and forbs) differ in their macro- and micronutrients concentrations and growth traits. Cultivated and wild-type varieties of species were grown as it was hypothesised that breeding of cultivated varieties that respond well to inorganic NPK fertilizers may have resulted in plants that have fewer traits that enable them to acquire other macro- and micronutrients from soil.
Data includes:
• Plant yield
• Macro- and micronutrient concentrations (and some potentially toxic elements): Al, As, Ca, Cd, Co, Cr, Cu, Fe, I, K, Mg, Mn, Mo, Na, Mi, P, Pb, S, Se, Ti, and Zn. Note that nitrogen was not measured.
• Plant traits: leaf mass, root mass, aboveground dry weight, leaf area.
• Growing medium total and extractable element concentrations, plus pH and cation exchange capacity.

Plant species and soil/growing medium
Species grown and the varieties used are identified in the table below.

Latin name Common name Commercial Wild
Grasses
Alopecurus geniculatus* Marsh foxtail WildA
Alopecurus pratensis* Meadow foxtail ZuberskaB
Anthoxanthum odoratum* Sweet vernal grass CommercialB WildA
Dactylis glomerata* Cocksfoot SpartaB WildA
Festuca arundinacea Tall fescue DebussyB
Festulolium loliaceum Festulolium AberNicheB
Holcus lanatus Yorkshire fog WildB
Lolium perenne* Perennial ryegrass NiftyB WildA
Phleum pratense Timothy PromesseB
Poa trivialis Rough meadow grass DasasB
Legumes
Lotus corniculatus* Birdsfoot trefoil LeoB WildB
Medicago lupulina* Yellow trefoil (Black medick) VirgoB WildA
Melilotus officinalis* Sweet Clover (Ribbed meliot) CommercialB WildA
Trifolium dubium Lesser trefoil WildC
Trifolium hybridum Alsike clover DawnB
Trifolium pratense* Red clover MerulaB & AltaswedeB EssexB
Forbs
Achillea millefolium* Yarrow CommercialB WildB
Centaurea nigra Black knapweed WildB
Cichorium intybus Chicory Puna IIB
Plantago lanceolate* Ribwort plantain EnduranceB WildB
Sanguisorba minor* Salad burnet CommercialB WildB

A,B,C Supplier: A = Herbiseed (Reading, UK), B = Cotswold Seeds (Moreton-in-Marsh, UK), C = John Chambers Wildflowers (Arkedale, UK).
* Species that have both a wild and cultivated version. Note that Alopecurus geniculatus and Alopecurus pratensis are considered to be analogous.

The plants were grown in a growing medium (“Rothamsted prescription soil”, Petersfield Growing Mediums, Leicester, UK), which contained 80% sterilised loam, 15% 2EW sand and 5% lime free grit (5mm). The growing medium was assessed for its nutrient status (Growing_medium_characterisation.csv) by analysing both the total and extractable concentrations of macro- and micronutrients in the soil, as well as soil pH, and methods are given below. Due to the amount of growing medium used and the difficulty in homogenising it, a total of 15 replicates were analysed for total nutrient concentrations. For financial reasons, only 5 were analysed for extractable nutrient concentrations. No additional fertilizer was added to the growing medium and no plants appeared to suffer from any signs of nutrient deficiency during the experiment.
Plant growth
The plants were grown in 4.5 L pots (21 cm max diameter, 18.3 cm height). Seeds were broadcast-sown and thinned to 10 evenly spaced plants per pot after germination. Plants were kept well-watered with deionised water and weeded to remove any weeds. The plants were grown at Rothamsted Research (Harpenden, UK), in an area that was outdoors but roofed to protect from rainfall. The area was surrounded by netting to prevent herbivory.
Plants were sown on 25/4/18 and on the 29/6/18 (65 days later), plants were cut to 2 cm above the soil surface, but no analysis was done of this herbage. On 12/9/18 (a further 75 days later), plants were sampled for growth traits, data can be found in Plant_data.csv. Five fully expanded, healthy leaves were sampled per pot (for the legumes, a ‘leaf’ constituted a set of three leaflets). The fresh weight of the leaves was recorded (column Leaf_fresh_wt), and the leaf area (column Leaf_area) measured using a WinDias leaf area meter (Delta-T devices). The leaves were dried at 80 oC for 24 hours to record dry weight (column Leaf_dry_wt). The remaining vegetative material (excluding inflorescences) was cut to 2 cm above the soil surface. A subsample was dried at 40 oC for 48 hours, finely milled, and analysed for iodine content. The remainder was dried at 80 oC, finely milled, and the total macro- and micronutrient concentrations determined. The column AGDWT gives the aboveground dry weight per pot excluding Leaf_dry_wt and excluding inflorescence (mass of inflorescence not recorded), and includes the mass of both the subsamples dried at 40 oC and 80 oC. Roots were washed free of soil by hand and oven-dried at 80 oC for 24 hours. Calculated values of leaf dry matter content (column LDMC) as Leaf_dry_wt / Leaf_fresh_wt, specific leaf area (column SLA), calculated as Leaf_area / Leaf_dry_wt, and root weight ratio (column RWR), calculated as Root_dry_wt / (Leaf_dry_wt + AGDWT + Root_dry_wt), are given in Plant_data.csv.
Element concentration analysis methods
Available P was assessed by Olsen P extraction (Olsen et al. 1954), and available K and Mg by ammonium nitrate extraction (Standing Committee of Analysts (DoE) 1979) by NRM (Berkshire, UK). Soil pH was measured in water (1:2.5 soil:water), and Mehlich III extractable Cu, Zn, Fe, S, Co and Mn were analysed by ICP-OES (Mehlich 1984, NRM, Berkshire, UK). Total macro- and micronutrient concentrations were determined via aqua regia digest for soil (McGrath and Cunliffe 1985), and nitric perchloric digestion for plant material (Zarcinas et al. 1987), followed by ICP-MS (NexION 300X Inductively Coupled Plasma – Mass Spectrometer, Perkin Elmer) or ICP-OES (Optima 7300 DV Inductively Coupled Plasma – Optical Emission Spectrometer, Perkin Elmer) analysis. Herbage total I was analysed using a 25% tetramethylammonium hydroxide (TMAH) extraction for 4 hours with analysis by ICP-MS by NUVetNA (University of Nottingham, UK). Results are corrected for the dry matter of soil or herbage analysed and corrected for blanks.

References
McGrath SP, Cunliffe CH (1985) A simplified method for the extraction of the metals Fe, Zn, Cu, Ni, Cd, Pb, Cr, Co and Mn from soils and sewage sludges. J Sci Food Agric 36: 794-798. doi: https://doi.org/10.1002/jsfa.2740360906.
Mehlich A (1984) Mehlich 3 soil test extractant: A modification of Mehlich 2 extractant. Commun Soil Sci Plant Anal 15: 1409-1416. doi: 10.1080/00103628409367568.
Olsen S, Cole C, Watanabe F, Dean L (1954) Estimation of available phosphorus in soils by extraction with sodium bicarbonate. USDA Circular Nr 939, US Gov Print Office, Washington, DC.
Standing Committee of Analysts (DoE) (1979) The Analysis of Agricultural Materials. MAFF Technical Bulletin RB427, Second Edition, HMSO, London, UK.
Zarcinas BA, Cartwright B, Spouncer LR (1987) Nitric acid digestion and multi‐element analysis of plant material by inductively coupled plasma spectrometry. Commun Soil Sci Plant Anal 18: 131-146. doi: 10.1080/00103628709367806.