Abstract
Isatis indigotica is a commercial medicinal crop that is widely cultivated with high water and nutrient application, in the arid areas of northwest China. Rational irrigation and nitrogen application are key factors for successful crop management. The objective of this study was to determine the effect of water and nitrogen coupling on the photosynthetic characteristics, yield, and quality of Isatis indigotica produced in northwestern China. Field trials were conducted for 2 consecutive years at an irrigation test station. Data on photosynthetic parameters, yield, and quality were collected from individual Isatis indigotica for each treatment during 2018–2019. The application of nitrogen significantly increased photosynthetic rates and yield under the same irrigation conditions. However, the yields were reduced in the excess water treatments (W3N1 and W3N2) and in the excess nitrogen treatments (W1N3, W2N3, and W3N3) in contrast to the optimum W2N2 treatment. Moreover, the quality indicators of the W2N2 treatment decreased compared with CK, which was due to water stress and more photoassimilates being available to the roots, but the effective quality index value could be effectively improved by greatly increasing the yield.
Highlights
Isatis indigotica is a commercial medicinal crop that is widely cultivated with high water and nutrient application, in the arid areas of northwest China
Water and nitrogen coupling treatment had a significant effect on the photosynthetic characteristics (Fig. 1)
The net photosynthetic rates of the treatments were in the following order: CK, W1N1, W1N3, W3N1, W3N3, W2N1, W1N2, W3N2, W2N3, and W2N2
Summary
Isatis indigotica is a commercial medicinal crop that is widely cultivated with high water and nutrient application, in the arid areas of northwest China. The objective of this study was to determine the effect of water and nitrogen coupling on the photosynthetic characteristics, yield, and quality of Isatis indigotica produced in northwestern China. The major focus of research is determining ways to improve water use efficiency and to reduce nitrogen application. An increasing number of studies have focused on the effects of coupled water and nitrogen application on crops. The yield and water use efficiency of Isatis indigotica were not high due to flood irrigation. Scholars have studied the effect of water on the yield and quality of Isatis indigotica from the aspects of water-saving irrigation s ystems[9] and water s tress[10]. The aim of this research was to study the effect of water and nitrogen coupling on the photosynthesis, yield, and quality of Isatis indigotica. Treatment Low water, low nitrogen Low water, medium nitrogen Low water, high nitrogen Medium water, low nitrogen Medium water, medium nitrogen Medium water, high nitrogen High water, low nitrogen High water, medium nitrogen High water, high nitrogen Control treatment
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