Improvement of tomato growth by biochar and potassium foliar application under contrasting irrigation regimes

Abstract

Employment of carbonaceous materials such as biochar has been considered an innovative solution in agriculture, especially with the goal of mitigating extreme weather events caused by climate change. Biochar can improve soil water-holding capacity, its physical and chemical properties, as well as increase agricultural systems productivity. Nevertheless, underlying physiological mechanisms remain poorly understood. Mineral supplementation with potassium nitrate (KNO3) via foliar application is another promising strategy in agricultural management under an irrigation deficit. Thus, combined effects of adding biochar and KNO3 foliar application under different irrigation regimes were investigated over tomato growth, yield, and physiology. Results did not indicate a synergistic effect regarding biochar with KNO3 foliar application. Biochar application itself alleviated tomato plant stress under water deficit, with plants showing better functioning of photosynthetic apparatus, improved yields and fruit quality, as well as increased water use efficiency. Coffee husk biochar (K-rich feedstock) met tomato plant demand for K and partially met the demand for some other elements (P, Mg, Fe, Zn, Mn, and Cu). Although positive KNO3 effect was verified for some physiological and fruit quality components, overall, KNO3 foliar application did not improve tomato yield. It is concluded that biochar amendment can be a promising practice to increase productivity and quality of tomato fruits under deficit irrigation regimes. Furthermore, biochar may be a sustainable biofertilizer and alternative K source, in addition to supplying stable carbon to soil and mitigating the stress caused by prolonged droughts.