Organic geochemical studies of soils from the Rothamsted Classical Experiments—II, Soils from the Hoosfield Spring Barley Experiment treated with different quantities of manure

Total lipid extracts (TLEs) were obtained from soil samples taken in the years 1882, 1913, 1946, 1965 and 1995 from three treatments of the Hoosfield Spring Barley Experiment at Rothamsted Experimental Station, Harpenden, Hertfordshire, U.K. The extracts were fractionated and molecular analyses performed using gas chromatography (GC) and gas chromatography-mass spectrometry (GC/MS). In addition to the soil samples (contemporary and archived), the two primary organic inputs, barley and farmyard manure (FYM), were studied so that the composition and diagenetic behaviour of extractable lipids from the two inputs could be assessed. The major aliphatic soil lipids exhibited variable dominance with respect to the expression of barley and FYM derived lipids. Wax esters were of low abundance and too strongly affected by degradation and transesterification processes to identify a dominant input whilst the composition of soil n-alkanols was largely determined by FYM with a minor pedogenic input. n-Alkanoic acids increased in overall abundance in soils with a continual FYM input and showed appreciable degradation in soils receiving no manure. C32 ββ hopanoic acid was detected in two plots and appeared to degrade at a rate similar to 5β-stanols with the most likely source of this compound being the FYM. Measurements of absolute concentrations of 5β-stanols, biomarkers characteristic of manuring, revealed that a manuring signal persisted for >120 years within the soil which had been intensively cultivated annually and had received no manure since 1871. The persistence of a manure signal in soils has important implications for archaeological studies of agricultural practices based on 5β-stanols.