Changes in the Soil–Plant–Water System Due to Biochar Amendment

The aim of this study was to do a complex examination of the soil–plant–water system and soil greenhouse gas emissions when biochar is applied to soil planted with sweet corn (<i>Zea mays</i> L. <i>var. saccharata</i>). The study covers two consecutive vegetation periods. We investigated (i) the changes in plant growth, (ii) soil water and temperature at different depths, (iii) greenhouse gas (GHG) emissions (CO₂ and N₂O) after biochar application, and (iv) the soil water, chemistry, and plant interactions. We used discrete measurements for plant growth, biomass production, and soil chemistry, while continuously monitoring the soil water content and temperature, and the state of plant health (i.e., using spectral reflectance sensors). Plant response in the control plot showed higher values of normalized difference vegetation index (NDVI; 0.3%) and lower values for photochemical reflectance index (PRI) and fraction of absorbed photosynthetically active radiation (fAPAR) by 26.8% and 2.24%, respectively, than for biochar treatments. We found significant negative correlations between fAPAR and soil water contents (SWC), and NDVI and SWC values (−0.59 < <i>r</i> < −0.30; <i>p</i> < 0.05). Soil temperature at the depth of 15 cm influenced soil CO₂ emissions to a larger extent (<i>r</i> > 0.5; <i>p</i> < 0.01) than air temperature (0.21 < <i>r</i> < 0.33) or soil water content (<i>r</i> < 0.06; <i>p</i> > 0.05). Our data showed strong connections between GHG production and soil chemical parameters of soil pH, nitrogen, potassium, or phosphate concentrations. Biochar application increased soil CO₂ emissions but reduced N₂O emissions. Our results demonstrated that biochar amendment to soils can help plant growth initially, but might not result in enhanced crop yield. The plant parameters were substantially different between the investigated years for both control and biochar amended parcels; therefore, long-term studies are essential to document the lasting effects of these treatments.