DOI: 10.23637/rpg5-pgfactors-01
title: Dataset: Park Grass factors for yield and nutrient conversions pre- and post- 1960

description: This dataset contains the factors for comparing yields of the first cut of herbage cut green since 1960 with the yields of hay up until 1959 and for comparing nutrient concentrations in green crop and hay and nutrient uptake by the green crop and offtake in hay.

In 1960 the method of estimating the yield of the first crop of herbage changed. Until 1959 the herbage on each plot/sub-plot was cut with a tractor mounted mower (previously horse-drawn and originally by scythe) and made into hay. The cut herbage was tedded (turned) at least once and when dry the whole plot/sub-plot was raked up and weighed. Samples were taken for archiving and to measure % moisture content and thus calculate the yields of hay. Since 1960, 2 or 4 strips (1.01 m wide; 1.5 m wide since 2021) have been cut from each plot/sub-plot with a flail-type forage harvester. This has been raked up (or collected by the machine since 2021), weighed and samples taken for archiving and to measure % moisture content to calculate the yields of the green crop. Once the green crop has been weighed and sampled the remainder is spread back on the cut strips, the rest of the plot/sub-plot is cut and it is all made into hay. Thus, most of the herbage is made into hay, continuing previous practice and the return of seed etc. But, since 1960 it has been the yield of green crop that is reported, NOT hay.

There can be very considerable losses of dry matter and nutrients during hay making (Zamudio et al. 2024). Seed will be shed, and small pieces of leaf material may be broken when the drying hay is turned and not picked up when the hay is raked up (or baled) for weighing and sampling. The losses are likely to be proportionately greater on lower yielding sub-plots with a short sward. Nutrients may also be lost during the hay-making process as seed and leaf material is likely to contain higher concentrations of NPK etc. Also, if there is rain during the hay-making period nutrients may be leached out of the drying herbage. In 1959, and again in 1992 - 1994, yields of hay and green crop were compared on a very limited number of sub-plots. The 1959 samples were not analysed and in 1992 and 1993 not all the samples were analysed for P, K, Mg and Na. However, although the data is limited and variable, particularly so for some nutrients, we can derive factors so that green crop yields, nutrient concentrations and uptakes since 1960 can be compared with hay yields, nutrient concentrations and offtakes up until 1959. With very few exceptions the second crop of herbage has been cut, weighed, sampled and carted green, although the machinery will have changed. 

The yield and nutrient data were graphed and the most suitable trendlines fitted. The data, illustrative figures and the factors are provided in the dataset.
description: <b>Excel file</b> ParkGrass-ForagevHayFactors-data-01.xlsx, that provides the data in a readily readable tabular format, containing separate sheets:
- <b>Factors table</b> Summary table containing all the conversion factor equations for yields and nutrients. Use these factors (Equations) to convert the hay yields pre-1960 to equate to the forage yields from 1960 to present. as obtained from the data and charts in this dataset, see other sheets.
- <b>Data</b> The yield and nutrient data used to calculate the conversion factors.
yields The yields chart and conversion factor
- <b>N</b> The nitrogen uptake/offtake chart and conversion factor
- <b>%N</b> The % nitrogen uptake/offtake chart and conversion factor
- <b>P</b> The phosphorous uptake/offtake chart and conversion factor
- <b>%P</b> The % phosphorous uptake/offtake chart and conversion factor
- <b>K</b> The potassium uptake/offtake chart and conversion factor
- <b>%K</b> The % potassium uptake/offtake chart and conversion factor
- <b>Ca</b> The calcium uptake/offtake chart and conversion factor
- <b>%Ca</b> The % calcium uptake/offtake chart and conversion factor
- <b>Mg</b> The magnesium uptake/offtake chart and conversion factor
- <b>%Mg</b> The % magnesium uptake/offtake chart and conversion factor
- <b>Na</b> The sodium uptake/offtake chart and conversion factor
- <b>%Na</b> The % sodium uptake/offtake chart and conversion factor
- <b>data for charts</b>for charts The source data used in the charts (same as that in Data sheet)
- <b>Note</b> Information about the change in harvest techniques that prompted these conversion factors.
description: This dataset is from measurements led by Andy Gregory, Andy Macdonald Paul Poulton, and previous scientists, and latterly analysed by the Analytical Chemistry Unit, Rothamsted Research, Harpenden, see list of contributors. The data have been calculated by Suzanne Clark and collated into this FAIR dataset by Sarah Perryman, checked by Margaret Glendining. 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.