Effects of Nitrogen Level and Soil Moisture on Sweet Potato Root Distribution and Soil Chemical Properties
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ORIGINAL PAPER
Effects of Nitrogen Level and Soil Moisture on Sweet Potato Root Distribution and Soil Chemical Properties Siping Li 1,2 & Lei Zhao 2 & Shuhai Zhang 2 & Qing Liu 2 & Huan Li 1,2 Received: 18 September 2020 / Accepted: 10 November 2020 # Sociedad Chilena de la Ciencia del Suelo 2020
Abstract A culture pot experiment with sweet potato was conducted to investigate the influence of nitrogen (N) variation on fibrous root growth and storage root differentiation under two levels of soil moisture. Sweet potato plants were supplied with low N (N0, no supplemental N), medium N (N75, 75 mg kg−1), or high N (N150, 150 mg kg−1) under normal water supply (field capacity 75%) or drought (field capacity 50%) conditions. The results indicated that during storage root formation, sweet potato root biomass and storage root differentiation were greater in N75. But high N application inhibited storage root differentiation, root biomass, and morphological traits decreased sharply under drought conditions. Under normal water supply, medium N application promoted a uniform distribution of roots in the 0–30-cm soil layer, whereas excessive N application resulted in roots being distributed mainly on the surface of the soil. Water stress increased deep root growth under the N0, significantly decreased deep root growth under the N150. Under drought stress, the N75 improved the plasticity of the root system and increased Fv/Fm, qP, ETR, and PIABS, which alleviated the effect of drought stress on root growth and maintained the functioning of photosystem II. However, high N affected the pH and EC in the soil layer and was not conducive to root development. All of these results indicate an association between variation in N application and the architectural attributes of sweet potato root. This information has great importance for complete N evaluation to improve root plasticity and drought resistance in sweet potato. Keywords Sweet potato . Nitrogen . Root distribution . Drought resistance
1 Introduction Sweet potato [Ipomoea batatas (L.) Lam.] is an important root crop grown in developing countries and ranks as the seventh major food crop produced annually worldwide (Motsa et al. 2015). It has a high and stable yield, is an important food reserve crop throughout the world, and is the first choice for improving peoples’ dietary nutrition (Mukhopadhyay et al. 2011; Mohanraj and Sivasankar 2014). Drought is a crucial abiotic stress factor that limits plant growth and development. Sweet potatoes are mainly grown as a rain-fed crop in the barren hilly areas in China, in which the
* Huan Li [email protected] 1
Key Laboratory of Degraded and Unused Land Consolidation Engineering, Ministry of Natural Resources, Xi’an 710075, China
2
College of Resources and Environmental Sciences, Qingdao Agricultural University, Qingdao 266109, China
sweet potato production is seriously affected by the less rainfall during the growth period (Ma et al. 2012). Although sweet potato is more drought tolerant than other food crops (Nair 2000), i
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