Organic Fertilizer Substitution for Chemical Fertilizer Improves Yield, Medicinal Active Compounds and Amino-Acid Profiles of Dendrobium officinale with Multi-Index Comprehensive Evaluation

Abstract

Dendrobium officinale (D. officinale) is an important medicinal horticultural crop. Its wild resources are threatened by over-exploitation. Fertilization regimes that balance yield and medicinal quality are urgently required for its artificial cultivation. This study aimed to investigate the effects of reduced chemical fertilizer combined with organic fertilizer on the yield and quality of D. officinale, and screen the optimal combined fertilization pattern, so as to provide a theoretical basis for standardized fertilization in D. officinale cultivation. A bed-cultivation experiment was carried out in greenhouse. Seven treatments were set up, including no fertilizer application (CK), sole chemical fertilizer (CF), 20% organic fertilizer substitution for chemical fertilizer (T20), 40% organic fertilizer substitution for chemical fertilizer (T40), 60% organic fertilizer substitution for chemical fertilizer (T60), 80% organic fertilizer substitution for chemical fertilizer (T80), and single organic fertilizer application (OM). Plant growth traits, yield, active ingredients, protein and amino acid components of D. officinale were determined. The membership function method was adopted for comprehensive evaluation of all treatments. Fertilization significantly improved the growth traits, yield and quality of D. officinale. Compared with CK, stem length, stem diameter and yield under fertilized treatments increased significantly by 15.5%-60.3%, 34.2%-64.7% and 65%-143.2%, respectively; dendrobine, polyphenols and alcohol-soluble extract contents increased significantly by 21.2%-83.7%, 14.0%-49.1% and 10.8%-26.9%, respectively. The highest plant growth and yield were observed under sole chemical fertilizer treatment. With the increase of organic fertilizer substitution ratio, plant growth and yield decreased gradually, while medicinal active ingredients including dendrobine, polysaccharides and flavonoids showed a trend of rising first and then falling. A total of 17 amino acids were detected in all treatments. T40 and T60 treatments significantly increased total amino acids, essential amino acids, as well as contents of medicinal, umami and bitter-tasting amino acids, whereas excessive proportion of organic fertilizer led to the decline of amino acid contents. Most growth, quality and amino acid indicators showed significant or extremely significant positive correlations with each other. The comprehensive evaluation order by membership function method was T40 > T60 > CF > T20 > T80 > OM > CK, and T40 obtained the highest comprehensive evaluation value. Sole chemical fertilizer contributes to yield increase of D. officinale, while combined application with organic fertilizer improves its medicinal quality. The 40?% organic substitution scheme provides a feasible fertilization strategy for high-quality greenhouse production of this medicinal horticultural plant.