Abstract
Root growth responds to local differences in N-form and concentration. This is known for artificial systems and assumed to be valid in soil. The purpose of this study is to challenge this assumption for soil mesocosms locally supplied with urea with and without nitrification inhibitor. Soil column experiments with Vicia faba (‘Fuego’) and Hordeum vulgare (‘Marthe’) were performed to investigate soil solution chemistry and root growth response of these two species with contrasting root architectures to the different N-supply simultaneously. Root growth was analysed over time and separately for the fertiliser layer and the areas above and below with X-ray CT (via region growing) and WinRHIZO. Additionally, NO3− and NH4+ in soil and soil solution were analysed. In Vicia faba, no pronounced differences were observed, although CT analysis indicated different root soil exploration for high NH4+. In Hordeum vulgare, high NO3− inhibited lateral root growth while high NH4+ stimulated the formation of first order laterals. The growth response to locally distributed N-forms in soil is species specific and less pronounced than in artificial systems. The combination of soil solution studies and non-invasive imaging of root growth can substantially improve the mechanistic understanding of root responses to different N-forms in soil.
Highlights
Root system architecture (RSA) is an important property that can be influenced by the availability of nutrients and their concentration and distribution in the growth medium[1,2,3,4,5]
Urea is rapidly hydrolysed to N H4+ which is subsequently adsorbed to clay particles and organic matter or further oxidised to N O3− if the relevant microorganisms are present and active
Experiment 1 revealed NH4+ formation by hydrolysis of urea and the subsequent depletion of NH4+ by nitrification. Both treatments were characterised by the same hydrolysis velocity, as the applied inhibitor selectively influenced nitrification
Summary
Root system architecture (RSA) is an important property that can be influenced by the availability of nutrients and their concentration and distribution in the growth medium[1,2,3,4,5] This is a well-known phenomenon for phosphorus[6,7,8], and of high interest for nitrogen (N), not least due to the agricultural application of fertilisers with different N-species composition. The goal is to enhance the understanding of temporal and spatial dynamics of root response in situ, in the soil to different N forms For this purpose we used two different plant species with contrasting RSA, a real soil substrate (i.e. including sorption capacity, soil organic matter and microbial N turnover) as growth medium and commercial urea fertiliser granules with and without a nitrification inhibitor (NI) in order to create treatments varying in N O3− and N H4+ concentrations. X-ray CT is currently one of the best non-invasive imaging techniques for visualising and quantifying plant roots in soil in-situ over time[50]
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
