Evaluation of Biochar and Compost Mixes as Substitutes to a Commercial Propagation Mix

Abstract

The effects of biochar (BC) on seed propagation depend on the type of BC, BC incorporation rate, base substrate, and plant seed species. Limited research tested BC-compost mixes for seed propagation. High percentages (70% or 80%, by volume) of BC with vermicompost (VC) or chicken manure compost (CM) were evaluated to substitute a commercial propagation mix (control) in three experiments. Seeds, including basil, coleus, edamame, marigold, okra, petunia, radish, salvia, tomato, vinca, and zinnia in Experiments 1 and 2 had similar or higher emergence percentages (EPs) and emergence indexes (EIs) in both BC:VC mixes, while celosia, cowpea, corn, and pumpkin had lower EPs or EIs in either 8BC:2VC or 7BC:3VC mixes compared to the control. Seedling fresh weights in both BC:VC mixes were similar to the control except for vinca, pumpkin, marigold, and salvia. The BC:VC mixes had no negative effects on plant dry weights at 7 weeks after transplanting. In Experiment 3, BC:CM mixes suppressed the seed germination or seedling growth of coleus, corn, cowpea, marigold, petunia, pumpkin, radish, salvia, vinca, watermelon, and zinnia due to high pH and CM's high electrical conductivity. Therefore, 7BC:3VC and 8BC:2VC can be used as seed propagation mix, while 7BC:3CM and 8BC:2CM are not recommended. Appl. Sci. 2019, 9, 4394 2 of 11 production adds extra value to the bioenergy process [19]. Research has shown the potential of BC to be used in seed propagation substrate for agricultural production [20]. It was shown that coconut shell BC (5%, 10%, 20%, or 40%, by volume) could be mixed with an adapted cornell seed germination mix and did not affect final germination percentages [21]. Additionally, the rate of BC incorporation, base substrate, and the plant species all have effects on the final seed germination and seedling growth. Prasad et al. [22] showed tomato (Solanum lycopersicum) seed germination and plant growth were higher in peat mixes with 10% woodchips BC than those in mixes with 50% BC. Similarly, Margenot et al.[23] evaluated the softwood BC substitution for peat in a 70:30 (v/v) peat:perlite mixture on marigold (Tagetes erecta) seed germination and seedling growth. They concluded that mixes with high BC substitution rate (50%, 60%, or 70%, by vol) had lower germinations than the mixes with low BC rates (0, 10%, 20%, 30%, or 40%, by vol) with all substrate pHs adjusted to 5.8. Compared to the 70:30 (v/v) peat:perlite mixture, mixes with 10% or 70% BC led to lower plant height while mixes with 20%, 30%, 40%, 50%, or 60% BC had no effect. Fan et al. [24] also pointed out that the lower germination rate and plant height of water spinach (Ipomoea aquatica Forsk) were found in substrates with more wheat straw BC, and that the seed germination rate and plant height in substrates with 16% (by volume) BC with 0.8 g L −1 super absorbent polymer were higher than the substrates without super absorbent polymer, indicating that both the BC incorporation rate and base substrate affect seed germination and seedling establishment....

Biochar reduces containerized pepper blight caused by Phytophthora capsici

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