Split Application under Reduced Nitrogen Rate Favors High Yield by Altering Endogenous Hormones and C/N Ratio in Sweet Potato

Xiangbei Du,Xinyue Zhang,Lingcong Kong,Min Xi

doi:10.3390/agronomy10091243

Xiangbei Du, Xinyue Zhang + Show 2 more

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https://doi.org/10.3390/agronomy10091243

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Abstract

A process for reducing the nitrogen (N) application rate while maintaining sweet potato yield urgently needs to be determined. A two-year pot experiment was conducted with three N management strategies to explore the mechanism underlying yield increase caused by a split application under a reduced N rate through an investigation of the changes in the carbon (C)-N metabolism and endogenous hormone. Results revealed that, compared with conventional basal N management, split application under a reduced N rate increased storage root yield by 22.1% through improving the storage root number and mean storage root weight by 12.3% and 10.2%, respectively. During the storage root formation period, split application under a reduced N rate decreased the soil-available N (AV-N) content and N content in storage root, inducing elevated C content, C/N ratio, auxin (IAA) content, zeatin and zeatin riboside (Z + ZR) content and reduced abscisic acid (ABA) content in storage roots, promoting storage root formation. During the storage root bulking period, split application under a reduced N rate appropriately elevated the soil AV-N content and N content in the storage root which, together with increased ABA content, which enhanced C content and C/N ratio in the storage root, resulted in an improved mean storage root weight. These results will facilitate the generation of appropriate N management strategies to improve sweet potato productivity.

Highlights

Sweet potato (Ipomoea batatas (L.) Lam) is an important staple food in tropical, subtropical and temperate regions and positioned as the seventh most important crop in the world [1]
As an important root crop, sweet potato yield is determined by the storage root number and mean storage root weight [2], which are closely related to the initial formation and development of storage root
N Contentsignificantly decreased during the storage root formation period but The soil N availability increasedThe during the storage root bulking period in the RS treatment with period that inbut the CM

Summary

Introduction

Sweet potato (Ipomoea batatas (L.) Lam) is an important staple food in tropical, subtropical and temperate regions and positioned as the seventh most important crop in the world [1]. As an important root crop, sweet potato yield is determined by the storage root number and mean storage root weight [2], which are closely related to the initial formation and development of storage root. Nitrogen (N) management is an important agronomic practice affecting the initial formation and development of storage root [3]. N fertilizer (Urea) is often excessively applied (90–200 kg ha−1 ) as basal fertilizer in sweet potato production in China, which is far beyond the amount of recommended. The mean storage root weight could be enhanced by increasing the N application due to higher leaf source strength (e.g., leaf area index, leaf area duration, net assimilation rate) during the storage root bulking period [5], increased N application tends to hinder the formation of storage roots during the storage root formation period [6].

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