Growth and development of pepper are affected by humic substances derived from composted sludge

Summary

A greenhouse experiment evaluated how humic substances extracted from composted sewage sludge (HSS) influenced pepper growth and development compared to leonardite-derived humic substances and controls. HSS significantly enhanced early-stage plant growth metrics (dry matter up to 560%, leaf area up to 1397%) and accelerated flowering and ripening by 12–14 days, with increased photosynthetic activity, though effects on final fruit yield were minimal. The growth-promoting mechanisms appear unrelated to nutrient uptake differences, suggesting the active components may be linked to the humic substances' chemical structure.

Regional applicability

The greenhouse trial methodology and pepper cultivar (Capsicum annuum) are relevant to protected horticultural production in temperate regions including the United Kingdom. Practical application would depend on local availability of composted sludge-derived humic substances and validation under UK growing conditions; the findings suggest potential value for accelerating vegetative development in pepper cultivation but require field-based confirmation of yield impacts.

Key measures

Plant dry-matter production, plant height, leaf area, net photosynthesis rate, stomatal conductance, days to flowering and ripening, chlorophyll concentration, leaf nutrient concentrations, total fruit yield, number of fruits per plant, fruit size, humic substance chemical composition (nitrogen, aliphatic and aromatic carbon content)

Outcomes reported

The study measured effects of humic substances extracted from composted sewage sludge on pepper plant growth, phenological development, photosynthetic activity, and yield compared to leonardite-derived humic substances and control treatments. Key metrics included dry-matter production, plant height, leaf area, net photosynthesis, stomatal conductance, flowering time, and fruit yield.

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