Stable Nitrogen isotope composition of common wheat in intercropping with Persian clover (Tuscany, Italy)

Intercropping is the simultaneous growth of two or more crops in the same space for a significant part of their life cycle (Willey, 1979). In this context, samples from one farm experiments in the growing season 2015/2016 and 2016/2017, embedded in the cropping systems of one arable farm in the surrounding of Pisa, central-western part of Italy, were collected for analysis. The treatments were: PCW, a temporary intercropping system of wheat and persian clover, sown in paired rows; CONTROLSTRIP, unfertilized wheat as a sole crop, sown in paired rows.

The samples were collected from a farm located in Valtriano, around 20 km from Pisa (43°36’N 10°29’E). The temporary intercropping system comprises common wheat (Triticum aestivum L., cv. Bolero) and persian clover (Trifolium resupinatum L., cv. Laser). Sampling of above-ground plant biomass was done by hands in March 2016 and 2017. For each treatment, above-ground plant biomass was collected several plots which includes three subplots with dimension of 0.25m2 in 2016 and 0.075 m2 in 2017. The samples collected, only for the green part of the plant, were dried at 60°C for 48 h. Then, coarse grinding of the plant fibres (about 1 mm in diameter) was carried out, followed by further cryogenic grinding.