In situ 13C isotope labelling of maize to determine root carbon inputs to the soil.

Soil organic carbon (SOC) depletion mainly affects croplands, and it reduces the function of soil to control erosion, to hold water and to store carbon. Hence, arable production needs adaptation of restorative practices to increase C sequestration. Roots are key for sustainable agriculture because they are the main precursors of SOC. Increased and deeper roots are a viable option to maximize carbon input to the soil to enhance SOC. However, there is a lack of data on the extent and distribution of roots for different crop types under different management conditions. This study aimed to quantify root carbon inputs and sequestration potential of maize as well as to determine root biomass and architecture under different organic amendment applications. Maize was labelled with ¹³C-CO₂ in the field at the beginning of the growing period. Leaf, root, and soil subsamples from labelled and unlabelled plants were taken during the three weeks after labelling. The carbon distribution and turnover in the investigated pools was assessed by analysing ¹³C by Elemental Analyzer Isotope Ratio Mass Spectrometer (EA-IRMS). Furthermore, to test the effect of the organic amendments on root growth, maize was grown in an adjacent field with identical conditions with the following treatments: (i) control, (ii) biochar (iii) compost and (iv) NPK. At the end of the growing period, roots were excavated to 30 cm depth and prepared for biomass and root architecture determination. The data collected will allow us to determine carbon distribution and turnover in the investigated pools and assess total C inputs to the soil. Moreover, it will allow us to assess whether the management practices investigated can be used to enhance root C input.