Perennial grain crops are expected to sequester soil carbon (C) and improve soil health due to their large and extensive root systems. To examine the rate of initial soil C accumulation in a perennial grain crop, we compared soil under perennial intermediate wheatgrass (IWG) with that under annual winter wheat 4 years after the crops were first planted. In addition, we tested the effect of three nitrogen (N) sources on C pools: Low available N (Low N (Organic N); 90 kg N ha−1 poultry litter), moderately available N (Mid N; 90 kg N ha−1 urea) and high available N (High N; 135 kg N ha−1 urea). We measured aboveground C (grain + straw), and coarse and fine root C to a depth of 1 m. Particulate organic matter (POM-C), fractionated by size, was used to indicate labile and more stabilized soil C pools. At harvest, IWG had 1.9 times more straw C and up to 15 times more root C compared with wheat. There were no differences in the size of the large (6 mm–250 µm) or medium (250–53 µm) POM-C fractions between wheat and IWG (P > 0.05) in surface horizons (0–10 cm). Large POM-C under IWG ranged from 3.6 ± 0.3 to 4.0 ± 0.7 g C kg soil−1 across the three N rates, similar to wheat under which large POM-C ranged from 3.6 ± 1.4 to 4.7 ± 0.7 g C kg soil−1. Averaged across N level, medium POM-C was 11.1 ± 0.8 and 11.3 ± 0.7 g C kg soil−1 for IWG and wheat, respectively. Despite IWG's greater above and belowground biomass (to 70 cm), POM-C fractions in IWG and wheat were similar. Post-hoc power analysis revealed that in order to detect differences in the labile C pool at 0–10 cm with an acceptable power (~80%) a 15% difference would be required between wheat and IWG. This demonstrates that on sandy soils with low cation exchange capacity, perennial IWG will need to be in place for longer than 4 years in order to detect an accumulated soil C difference > 15%.

The pyrolysis conversion of vegetable residues into energy and biochar, and its incorporation in agricultural soil, reduces CO2 emission and provides a longterm soil carbon sequestration. Moreover, biochar application in soil seems to increase nutrient stocks in the rooting layer, improving crop yield. Compared with the numerous studies assessing the positive effect of biochar on yield, however, little research has been published elucidating the mechanisms responsible for the reported benefits. Few studies cited soil moisture as the key factor, attributing the increased yield to the higher soil water availability.

The aim of this study was to investigate the effect of biochar on the physical and hydraulic properties of a bare Padana Plain (Cadriano, Bologna) agricultural soil. A preliminary plot experiment in 2009 explored the influence of 10 and 30 kg ha–1 of biochar on soil moisture, without effects from plants. Results of the first experiment suggested using higher biochar rates in a similar experimental scheme. During the second experiment, 30 and 60 t ha–1 doses were investigated. Soil water content, bulk density, electrical conductivity and soil water retention were measured. The comparison between treated soils and the control indicates that the biochar rate is directly correlated to electrical conductibility and inversely correlated with bulk density. The effect on the density of soil can be very positive in case of heavy soils. The dark colour of the char increased the surface temperature with respect to the control, while no differences were detected at 7·5 cm depth. No influences were found on other soil characteristics, including soil pH, moisture and water retention.

In this review, we discuss the potential for mycorrhizal fungi to act as a source or sink for carbon (C) under elevated CO2 and nitrogen deposition. Mycorrhizal tissue has been estimated to comprise a significant fraction of soil organic matter and below-ground biomass in a range of systems. The current body of literature indicates that in many systems exposed to elevated CO2, mycorrhizal fungi might sequester increased amounts of C in living, dead and residual hyphal biomass in the soil. Through this process, the fungi might serve as a negative feedback on the rise in atmospheric CO2 levels caused by fossil fuel burning and deforestation. By contrast, a few preliminary studies suggest that N deposition might increase turnover rates of fungal tissue and negate CO2 effects on hyphal biomass. If these latter responses are consistent among ecosystems, C storage in hyphae might decline in habitats surrounding agricultural and urban areas. When N additions occur without CO2 enrichment, effects on mycorrhizal growth are inconsistent. We note that analyses of hyphal decomposition under elevated CO2 and N additions are extremely sparse but are critical in our understanding of the impact of global change on the cycling of mycorrhizal C. Finally, shifts in the community composition of arbuscular and ectomycorrhizal fungi with increasing CO2 or N availability are frequently documented. Since mycorrhizal groups vary in growth rate and tissue quality, these changes in species assemblages could produce unforeseeable impacts on the productivity, survivorship, or decomposition of mycorrhizal biomass.