Improved tomato development by biochar soil amendment and foliar application of potassium under different available soil water contents

Abstract

The use of carbonaceous materials such as biochar has been considered an innovative solution in agriculture, especially to mitigate dry events caused by climate change. Biochar can improve water holding capacity, physical and chemical properties of soil, and increase the productivity of agricultural systems. However, underlying physiological mechanisms remain poorly understood. Mineral supplementation with potassium nitrate (KNO3) via foliar application is another promising strategy in agricultural management under irrigation deficit. Thus, we investigated the combined effects of biochar and foliar application of KNO3 on growth, yield, and physiology of tomato plants under different irrigation regimes. Results did not indicate a synergistic effect of biochar and foliar application of KNO3. Biochar application alleviated tomato plant stress under deficit irrigation, with plants showing better functioning of photosynthetic apparatus, higher yield, and better fruit quality, as well as increased water use efficiency. Coffee husk biochar (K-rich feedstock) fully met the tomato plant’s demand for K and partially met the demand for some other elements (P, Mg, Fe, Zn, Mn, and Cu). Although positive effects of KNO3 application was verified for some physiological and fruit quality components, overall, foliar application of KNO3 did not improve tomato yield. It is concluded that biochar soil amendment can be a promising practice to increase yield and quality of tomato fruits under deficit irrigation. Therefore, biochar-based fertilizer can be an alternative K source that also provides stable carbon to soil and helps to mitigate stress caused by prolonged drought.