Effect of cropping pattern on agronomic characteristics, yield and quality of radix isatidis

Radix isatidis (Isatis indigotica Fort.), a biennial cruciferous plant, is an important traditional Chinese medicine plant that is extensively cultivated across China. Its main producing area is in the central region of Hexi Corridor in Qilian Mountaint. In 2012, Minle County in Ganshu Province was named the "hometown" of radix isatidis in China. However, standardized cultivation technique has been the main problem affecting the yield and quality of radix isatidis. Cropping pattern has been critical for yield and quality of Chinese medicinal plants. In order to explore the best cropping pattern for radix isatidis in irrigated oasis in Hexi Corridor, we designed a two-factor randomized block field experiment. One factor was the cultivation model (consisting of ridge plowing and flat breaking) and the other was film mulching (no film cover, white film cover and black film cover). The experiment included six cropping patterns-flat breaking without film mulching, flat breaking with white film mulching, flat breaking with black film mulching, ridge plow without film mulching, ridge plow with white film mulching, and ridge plow with black film mulching. The agronomic characteristics of root, yield and content of epigoitrin in radix isatidis under different treatments were determined every month for period from sowing to harvest. Results showed that under different cultivation methods, main root length, root diameter and root dry weight of individual plant tracked S-shaped curve across the growth stages that was best fitted by logarithmic growth equation. The differences in root yield under various cultivation methods were significant. While ridge plow with black film mulching had the highest yield (4 514.45 kg·hm^-2), ridge plow with white film mulching had the lowest yield (3 116.378 kg·hm^-2). Different treatments had significantly effects on epigoitrin content in radix isatidis. While ridge plow with white film mulching had the highest epigoitrin content (2.61 g·kg^-1), ridge plow without film mulching had the lowest epigoitrin content (1.37 g·kg^-1). Ridge plow with black film mulching cultivation method should be widely used in radix isatidis cultivation in the irrigated oasis in Hexi Corridor.