Contributions of Nutrients in Biochar to Increase Spinach Production: A Pot Experiment

Studies have shown that biochar amendment could increase soil nutrient availability and crop production, but the contributions of nutrients including nitrogen (N), phosphorus (P), and potassium (K) in the biochar to plant production need to be tested. A pot experiment was conducted to identify the effects of maize straw-based biochar (BC) amendment on spinach fresh yield and dry biomass production, compared with non-biochar non-fertilization control (CT) and non-biochar chemical fertilization (NBF, equivalent amounts of N, P, and K). After 50-day growth, fresh leaf yield was increased by 63.7% or 38.0% under BC or NBF than under CT, and by 18.7% under BC than under NBF. Meanwhile, both leaf dry biomass and total plant (leaves + roots) biomass were similar between BC and NBF, but significantly higher under BC (47.5% in total) and NBF (56.2% in total) than under CT. In addition, root dry biomass was similar between BC and CT, but significantly higher under NBF than under BC or CT. These results indicated that about 60% of the contributions to yield/biomass increase might be from nutrients in the biochar. On the one hand, plant N and K uptake was highest, but P uptake was lowest, under BC than under CT and NBF. On the other hand, significantly higher soil available N ranked as CT ≈ BC > NBF, soil available P as CT ≈ BC ≈ NBF, and soil available K as BC ≈ NBF > CT. In conclusion, our results demonstrated that nutrients in the biochar could contribute to plant growth significantly.