Chitosan modifies the substrate and influences growth of chili seedlings

Abstract

ABSTRACT The addition of chitosan to soil has been shown to promote plant development, although its actions on the soil and the plants remain unclear. Chili (Capsicum annum L.) seedlings were grown in a greenhouse (20–33°C, 65%–70% RH) on a substrate (topsoil, rice husk charcoal, and coconut coir) at a ratio of 2:1:1 (v/v) amended with 0%, 1%, or 10% (w/w) chitosan powder. Shoot and root dry weights of chili seedlings grown in a substrate containing 1% chitosan exhibited a 2.5-fold and 1.6-fold increase compared to those in 0% and 10% chitosan treatments, respectively. Leaf chlorophyll content was 2.7-fold higher at 20 days after transplanting. Chitosan at 1% improved the cation exchange capacity (CEC), substrate organic matter, and plant essential nutrient absorption (P, K, Ca, Mg, Mn, Cu, and Zn). In contrast, the substrate added with 10% chitosan had a negative effect on chili seedlings, possibly due to an excess of total available nitrogen (1.54% or 1.6 times higher) and organic matter (30% or 1.6 times higher). Seedlings exhibited leaf chlorosis, poor root development, and fewer essential nutrients in tissues than the control and 1% chitosan treatments. Use of 1% chitosan appears to promote chili growth by improving substrate characteristics.