Effect of Cattle Manure Biochar on the Chemical Composition of Spinach Grown at Different Water Conditions in a Calcareous Soil

Suitable soil and availability of adequate nutrient elements are necessary for successful plant production. Nutrient elements not only should be in readily available form but also their balance is important. Organic matter and soil amendments that are used in soil reclamation or for prevailing the stress conditions can influence the concentration of nutrient elements. Therefore, this research aimed to evaluate the effect of cattle manure biochar on the chemical composition of spinach (Virofly var.) grown at different water conditions of a calcareous soil by conducting a factorial greenhouse experiment arranged in a completely randomized design with three replications. Treatments consisted of four biochar levels (0, 1.25%, 2.5%, and 5% w/w) and three levels of water status (field capacity, FC (no stress), 0.70 FC, and 0.55 FC). Results indicated that water stress resulted in a significant decrease in the uptake of all studied nutrient elements and significant increase in shoot concentration of Na, K, P and N of spinach. Furthermore, application of 1.25% biochar increased Mn, Na, and K; application of 2.5% biochar increased P, Mg, Na, and K and application of 5% biochar also increased Mn, N, P, Mg, and Na concentration in the shoot of spinach. In general, application of biochar and water conditions resulted in significant changes in chemical composition and nutrient concentration and uptake (especially for macro nutrients) of spinach shoot. Therefore, in the cases that biochar is used for mitigating the adverse effects of water stress, probable changes in chemical composition and nutrient concentration of plants should be considered, and this issue must be considered in plant nutrition and soil fertility management in arid regions. It should be noticed that the influence of biochar on the chemical composition and also soil attributes depends on the source material and preparation conditions of biochar, the type and variety of plant, and the studied soil conditions. Therefore, to obtain the wider and more accurate results, it is recommended to conduct these types of researches for other plant species by applying different sources and conditions for preparing biochar under field conditions.