Paola Rossi Pisa

The effects of biochar on the physical properties of bare soil

The pyrolysis conversion of vegetable residues into energy and biochar, and its incorporation in agricultural soil, reduces CO 2 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.

Sugarbeet seed’s yield and quality as affected by irrigation

Irrigation to the sugar-beet seed crop is a common practice since many years in Emilia Romagna region, even though information on the most suitable ways to irrigate is very limited. The aim of this three-year long experimentation was to evaluate the influence of timing and number of irrigation treatments on seed yield and quality. Treatments at the onset, at full, and at the end of flowering, wit all their possible combinations were compared among themselves and with the non-irrigated control. During the second and third years the water content of the soil was monitored weekly, starting from just before the first treatment to harvest. These measurements indicate that the upper layers (0-20 cm), which are more subjected to evapotranspiration, are more affected by irrigations than the deeper layers (20-40). The effectiveness of irrigation treatments on seed yield was tightly dependent in the distribution of precipitations. The treatments applied in full or late flowering, both separately or together, determined significant increases in yield and in the percentage of seed balls with a diameter higher than 4.0 mm, whereas those at the beginning of flowering did not produced any improvements. No significant effects of the different treatments on 1000-seed weight and germinability were observed, except for a slightly negative influence of irrigations applied at the end of flowering.When all the traits were considered, an overall moderate correlation was detected between seed yield and quality.