Biochar Type and Ratio as a Peat Additive/Partial Peat Replacement in Growing Media for Cabbage Seedling Production

Abstract

Biochar has been proposed mainly as a soil amendment, positively affecting plant growth/yield, and to a lesser degree for growing media. In this study, four commercial grade biochars (A-forest wood; B-husks and paper fiber; C-bamboo and D-fresh wood screening), mostly wood-based materials, were selected. Initial mixtures of peat (P) with different Biochar type and ratios (0-5-10-15-20%) were selected for cabbage seedling production. Biochar material had high K content and pH ≥ 8.64 which resulted in increased pH of the growing media. Biochar A and C at 20% reduced cabbage seed emergence. Biochar A, B and D maintained or improved plant growth at low ratio (i.e., 5–10%) while all Biochars increased N, K and P content in leaves. Biochars A and D were further examined at 7.5% and 15% with the addition of two doses of minerals (1-fold and 1.5-fold). Biochar A and D, initially stimulated seed emergence when compared to the control. High dose of fertilizer favored plant growth in Biochar A at 7.5% and Biochar D at 15%. Leaf stomatal conductance was decreased at Biochar A+Fert at 7.5% and Chlorophyll b content was decreased at Biochar A+Fert at 15%. The presence of Biochar A increased the antioxidant activity (as assayed by 2,2-diphenyl-1-picrylhydrazyl-DPPH). Lipid peroxidation was higher in plants grown with fertilized peat and Biochar A at 15%, activating antioxidant enzymatic metabolisms. Potassium, phosphorous and copper accumulation and magnesium deficiency in cabbage leaves were related to the Biochar presence. Wooden biochar of beech, spruce and pine species (Biochar A) at 7.5% and fertilized biochar of fruit trees and hedges (Biochar D) were more promising for peat replacement for cabbage seedling production.

Plant Nutrient Availability and pH of Biochars and Their Fractions, with the Possible Use as a Component in a Growing Media

“…This is primarily due to the excessive level of K, which is a feature of most but not all biochars. Additionally, in our resent study, K, P and Cu accumulation and Mg deficiency in cabbage leaves were related to the biochar presence and feedstock [10]. In that study, the biochar's feedstock, rate and the addition of fertilizers could affect the cabbage seedling performance.…”

“…Biochar is an organic carbon-rich solid by-product, which is gaining great interest in research for its utilization under the environmental and agricultural management [1][2][3]. Therefore, in addition to the common use as soil amendment material, biochar is being explored in terms of use for soil remediation [4][5][6][7], water filtration [8] and soilless substrates [9,10]. Recently there has been great interest in the use of biochar as a bioresource and growing media material [11][12][13][14].…”

“…Biochar has unique chemical properties. It can reduce leaching of nutrients, including nitrate [28] and P; act as a bio stimulant, especially affecting the roots and suppressing root disease [10,29,30]; reduce greenhouse gases (GHG) from growing media when ebb and flood irrigation is practiced, as anoxic conditions occur for short periods; and sequester C at the end of life of growing media, when it ultimately ends in soil [17]. At present, the costs of biochars are prohibitive.…”

“…Numerous papers have evaluated biochar's positive effects on plant growth [10,11,36], but very few, such as the studies from Bedussi et al [32], Kaudal et al [20] and Mendez et al [37], have characterized the biochar used in the growing media. Recently, some studies have been conducted to look at the effect of biochar particle size on physical properties of growing media [27,38].…”

Biochar Type, Ratio, and Nutrient Levels in Growing Media Affects Seedling Production and Plant Performance

“…Fewer studies investigated the impacts of biochar on different plant growth characteristics that affect yield, such as seed germination and the architecture of shoots or roots [1,30,31]. A few papers have applied low rates of biochar at 1-15% to peat [1,16,32,33] and have found a positive response, not only on fresh and dry weight, but also morphological and physiological changes [28,29,34]. We also know from previous publications that all biochars do not behave in a similar way ("not all biochars are made equal") and crop response depends on crop species.…”