Effects of Biochar on Biointensive Horticultural Crops and Its Economic Viability in the Mediterranean Climate

Abstract

The effects of biochar on different horticultural crops (lettuce, tomato, sweet pepper, and radish) were evaluated in the Mediterranean climate. Biochar was produced by pyrolysis of Pinus pinaster wood chips at 550 °C and used at 1 (B1) and 2 (B2) kg/m2 application rates on six 3.5 m2 plots in each treatment, with two control plots (B0). No fertilizer was used. Treatment B1 led to a significant increase (p < 0.01) of 35.4%, 98.1%, 28.4%, and 35.2% in the mean fresh weight of radishes, lettuce, tomatoes, and sweet peppers, respectively. Treatment B2 resulted in an improvement of 70.7% in radishes, 126.1% in lettuce, 38.4% in tomatoes, and 95.0% in sweet peppers (p < 0.01). Significant differences between treatments B1 and B2 were observed in the radish, tomato, and sweet pepper crops but not in lettuce. The profitability of biochar application to these crops was studied by considering a biochar price of 800 EUR/t and applying a CO2 fixation subsidy, assuming the updated February 2022 price (90 EUR/t). In lettuce, tomato, and sweet pepper crops, the investment payback period was approximately one year. Application of biochar generated economic benefit either from the first harvest or in the second year. In radish, this period was longer than two years; however, an increase in the annual frequency of cultivation should be studied to optimize the benefit. The dose that provided the greatest benefit was B1 (for all crops, except for sweet pepper). Biochar considerably improved fruit and vegetable yield under the Mediterranean climate; however, further studies are needed to assess the effects of biochar on soil properties and yield to estimate long-term environmental and economic benefits.