Abundance of ~(13)C and ~(15)N in emmer, spelt and naked barley grown on differently manured soils: Towards a method for identifying past manuring practice

摘要

The shortage of plant-available nutrients probably constrained prehistoric cereal cropping but there is very little direct evidence relating to the history of ancient manuring. It has been shown that the long-term addition of animal manure elevates the δ~(15)N value of soil and of modern crops grown on the soil. We have examined the δ~(15)N and δ~(13)C values of soil and of the grain and straw fractions of three ancient cereal types grown in unmanured, PK amended and cattle manured plots of the Askov long-term field experiment. Manure increased biomass yields and the δ~(15)N values of soil and of grain and straw fractions of the ancient cereal types; differences in δ~(15)N between unmanured and PK treatments were insignificant. The offset in straw and grain δ~(15)N due to manure averaged 7.9 and 8.8 %, respectively, while the soil offset was 1.9 %. The soil and biomass δ~(13)C values were not affected by nutrient amendments. Grain weights differed among cereal types but increased in the order: unmanured, PK, and animal manure. The grain and straw total-N concentration was generally not affected by manure addition. Our study suggests that long-term application of manure to permanently cultivated sites would have provided a substantial positive effect on cereals grown in early agriculture and will have left a significant N isotopic imprint on soil, grains and straw. We suggest that the use of animal manure can be identified by the ~(15)N abundance in remains of ancient cereals (e.g. charred grains) from archaeological sites and by growing test plants on freshly exposed palaeosols.