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

Ágota Horel,Eszter Tóth

doi:10.3390/w13091216

Abstract

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 (Zea mays L. var. saccharata). 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 < r < −0.30; p < 0.05). Soil temperature at the depth of 15 cm influenced soil CO2 emissions to a larger extent (r > 0.5; p < 0.01) than air temperature (0.21 < r < 0.33) or soil water content (r < 0.06; p > 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.

Highlights

Due to the long-term cultivation of agricultural soils, changes in their quality is inevitable
Crop yield showed significantly lower values for the biochar treatments compared to the control during the first year of the study, which diminished for the second year (Figure 2b)
When examining the root dry mass of the plants, we found that biochar treatment improved root growth especially at the first year of the study; these differences reduced by the end of the second year (Figure 2c)

Summary

Introduction

Due to the long-term cultivation of agricultural soils, changes in their quality is inevitable. Biochar use in soils gained interest in recent years as a possible tool to mitigate climate change effects, reduce greenhouse gas (GHG) emissions [1,2], and to improve crop yield [3,4,5]. Many studies investigated how biochar will affect soil moisture dynamics, especially in soils with low water holding capacities. Biochar use can cause increased yield production of maize or other crops, which might result from the improved soil conditions of soil moisture [4,14], reduced bulk density [15], or specific soil chemical and biological parameters [13,16]. Biochar amendment alone cannot guarantee increased maize production [17]; continuous plant response measurements to soil amendments might provide us with a better understanding of the influencing factors derived from the changing environmental conditions

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Discussion

Conclusion