A 4-year comparison of pasture mixtures, including those with deep-rooting Festulolium, on herbage and soil and root properties in 50 cm cores, plus associated botanical species surveys

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This dataset was collected between 2014 and 2018 to investigate how different grass and clover varieties affect soil and herbage properties at a field scale. In particular, to determine whether Festulolium with a deep root architecture could increase carbon storage in grassland subsoils. Fields sown with Festulolium (cv. Prior, and later cv. BX511), perennial ryegrass (Lolium perenne cv. Abermagic), both either alone or sown with white clover (Trifolium repens cv. Aberherald), or permanent pasture were studied. Data were collected on 6 occasions: in Sept 2014, May and Sept 2015, May 2016, Oct 2017 and Sept 2018. On the first four sample dates, the same 7 fields were sampled, and 5 replicate samples were taken from each. On the last two sample dates, only 3 of the fields were sampled, again with 5 replicate samples taken. Data includes: Soil, root and herbage carbon and nitrogen contents (percentage and stable isotope); herbage yield; botanical survey of species present and percentage cover; root mass; soil bulk density; count of macroinvertebrates present; clay depth.
The experiment took place on the North Wyke Farm Platform (NWFP), a UK National Capability in SW England. The NWFP is split into a number of self-contained farms (‘farmlets’) that are managed according to different operation philosophies or practices. At the time of the experiment, there were three farmlets on the NWFP with different pasture management strategies. Permanent pasture (PP), a perennial ryegrass monoculture (HS) which was sown with a high sugar Lolium perenne cv. AberMagic, and a white clover/perennial ryegrass mix (WC) with the same ryegrass variety as the HS pasture. The exception were the fields known as Longlands North (WC farmlet) and Longlands East (HS farmlet), where the perennial ryegrass was replaced with Festulolium. The PP and HS pastures received N fertilizer at a standard rate, but the WC pastures did not due to the inclusion of a legume. Fields within a farmlet are cut for silage and grazed by cattle and sheep, with livestock grazing or consuming silage only from one farmlet. The Longlands North, Longlands East and Longlands South (PP farmlet) are treated as a ‘trio’, that typically undergo very similar timings in agricultural management, such as grazing by the same species at the same time, as far as is feasible.
The NWFP is highly instrumented and monitored, and core NWFP datasets are open and include in-situ water flow and chemistry taken at 15-minute intervals; 15-minute Met measurements; 15-minute soil moisture measurements; 30-minute GHG emissions; soils, crop and botanical field survey data; livestock and crop performance data; and farm operational activities, and contextual information is also available. See https://nwfp.rothamsted.ac.uk/ and https://doi.org/10.23637/rothamsted.98y1x

Sample locations

Five sample locations per field were sampled on each sample date, and the same locations were not revisited on subsequent sampling dates. How sample locations were selected varied by sample date. In Sept 2014 and May 2015, a virtual 25 m grid of sampling points was placed over the fields, and 5 locations per field selected randomly in advance from those points. On all other sampling dates, the 25 m grid was not used, and 5 sampling locations per field were selected randomly and in advance. The exceptions were the Longlands North and Longlands East fields between Sept 2014 and May 2016. These fields had been sown with Festulolium, but cover was very patchy. As the original study wanted to see how this species affected soil and herbage properties, in these fields patches of Festulolium were identified and 5 of them used as the sampling locations. All sampling points are recorded on British National Grid.

Sample collection and analysis

At each location, a 25 x 25 cm quadrat (total area 625 cm2) was placed on the ground, avoiding livestock dung and large weeds such as docks and thistles. A botanical assessment noted species present and their percentage cover. The herbage was then cut to ground level, fresh weight measured, dried at 80 oC for 48 h, and weighed again. Dry herbage samples were coarse ground using a Retsch cutting mill, and then finely ground using a ball mill.
At centre of each cut quadrat and on the same day that the botanic survey was completed, a 50 cm deep, 7 cm diameter, soil core was taken using a deep soil sampling rig. The cylinder was removed from the ground using a lifting jack and the core was removed from the cylinder using a trailer winch. The sample was cut into 5 x 10 cm lengths in the field, and each 10 cm core section weighed fresh. A small sub sample (~10 g) of each core section was dried at 105 oC for 48 hours to assess dry matter content, sieved and finely ground, and retained for analysis. The remainder of each core section was washed over a 1 mm sieve to extract the non-soil components. Roots were dried at 80 oC for 48 h, weighed, and ground in a ball mill. Macro invertebrates were counted and discarded. Stones were weighed and volume determined by displacement of water in a measuring cylinder.
Soil, roots and herbage were assessed for carbon (C) and nitrogen (N) content (percentage and isotope abundance, ‰). Analysis is via combustion in a Carlo Erba NA1500 Elemental Analyser and element mass determination in a PDZ Europa Stable Isotope Mass Spectrometer. Stable isotope nitrogen measurements referenced to IAEA-N1 ammonium sulphate which is 0.4 per mil delta 15N versus air and contains 21.2% nitrogen. Stable isotope carbon measurements referenced to IAEA-CH6 sucrose which is -10.4 per mil delta 13C versus PDB and contains 42.1% carbon. The system was calibrated with flour of known elemental and isotopic composition, and blanks and analytical quality control standards relevant to the sample type were run with each batch of samples. Samples falling below the limit of quantification or above the working calibration range were reanalysed with a different quantity of material, until results fell within the working calibration range.

Important notes:

At the time of the Oct 2017 sampling (2017-10-16), the Longlands North and Longlands East fields had not long been resown (sowing dates 2017-09-26 and 2017-10-04 respectively). Seedlings were still only 3 – 4 cm, so roots at depth were not from Festulolium cv. BX511. Furthermore, soil had been inverted during the reseeding process so roots from the surface had been incorporated into the lower soil.
Fields were often being grazed by livestock at the time of, or shortly before, the sampling dates (see the Land_use column of Locations.csv). While obvious livestock manure was avoided, there may be some contamination of the herbage or of the 0-10 cm soils. This concern was particularly noted during the Sept 2018 sampling.

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