Effects of fertilization on growth physiology, yield and medicinal quality of Schizonepeta tenuifolia Briq.

To clarify a suitable fertilization mode for optimized yield and medicinal quality of Schizonepeta tenuifolia Briq., a single-factor random block design field experiment with three replications was conducted. The seven treatments in the experiment included three levels of organic manure (chicken compost manure 5 250 kg·hm^-2, 10 500 kg·hm^-2 and 15 750 kg·hm^-2, respectively), three levels of chemical fertilizers (with the same ratios and quantities of nitrogen, phosphorus and potassium as the three manure treatments, respectively), and the control treatment without any fertilization. Leaf photosynthetic pigments and soluble protein, total flavonoid contents in different above-ground parts during different periods, and total dry-matter yield of S. tenuifolia after harvest were determined. The results showed that under the experimental conditions, both total dry-matter yield and photosynthetic pigment contents of S. tenuifolia under manure and chemical fertilizer treatments were significantly higher than those of the control (P < 0.05). Significant differences in dry-matter yield and photosynthetic pigment contents existed among different levels of manure and chemical fertilizer─ high level > medium level > low level. The differences between manure and chemical fertilizer with the same quantities of available nutrients were insignificant. Organic manure enhanced the accumulation of total flavonoids in stems, leaves and spikes of S. tenuifolia. The contents of total flavonoids varied in the order of low level > medium level > high level of manure treatments. Chemical fertilizer decreased the accumulation of total flavonoids in stems, leaves and spikes. Total dry-matter yield, total flavonoid contents of plants under high organic manure treatment were significantly higher than those of the other treatments and CK. Based on the results, it was concluded that chemical fertilizers with nitrogen, phosphorus and potassium increased yields and decreased both the total flavonoid content and medicinal quality of S. tenuifolia. Suitable quantities of organic manure increased both the dry-matter yield and total flavonoid contents in stems, leaves and spikes of S. tenuifolia. Hence organic manure was a better alternative to chemical fertilizers in the production of S. tenuifolia. The recommended amount of chicken compost manure for S. tenuifolia production in Hebei Province was 15 750 kg·hm^-2.