Available Nitrogen in Paddy Soils Depth: Influence on Rice Root Morphology and Plant Nutrition
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ORIGINAL PAPER
Available Nitrogen in Paddy Soils Depth: Influence on Rice Root Morphology and Plant Nutrition Gerson Laerson Drescher 1 & Leandro Souza da Silva 1 & Qamar Sarfaraz 2 & Trenton L. Roberts 3 & Fernando Teixeira Nicoloso 4 & Raíssa Schwalbert 4 & Anderson Cesar Ramos Marques 1 Received: 2 October 2019 / Accepted: 27 January 2020 # Sociedad Chilena de la Ciencia del Suelo 2020
Abstract Nitrogen (N) is a key nutrient for rice (Oryza sativa L.) and its availability in soil profile can influence the plant root morphology and total nutrient uptake. This study evaluated if N from deeper soil layers would increase rice root growth, N uptake and influence plant nutritional status. Flooded rice was grown in undisturbed soil samples from three locations with 15N-labeled ammonium sulfate application at different depths (0, 10, 20, 30, and 45 cm). At rice heading, chlorophyll content and photosynthesis rate were measured at flag leaves and rice biomass production, root morphology, and total N and 15N uptake were evaluated. Higher biomass and N uptake were observed with N application at near soil surface layers. The majority of rice N uptake was derived from soil, which was more evident when N fertilizer was injected at 45 cm deep (on average 74%). The highest root growth was observed at the near surface layers with constant decrease in depth, up to 60 cm. Roots from deeper layers exhibited smaller diameter, as they were mainly highly branched roots. The N application at 30 and 45 cm depths provided N later in the season, resulting in plants with lower total biomass but with higher N content in aboveground biomass, with higher chlorophyll content, photosynthesis rate, and carboxylation efficiency by Rubisco. The N available below 20 cm contributes to plant nutrition and root growth, hence soils with available N in depth likely cause plants to function more optimally in photosynthates supply. Keywords
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N . Lowland soils . N recovery . Oryza sativa L. . Photosynthesis . Soil fertility
1 Introduction Nitrogen (N) is one of the most limiting nutrients for rice crop production. Plant growth requires a large amount of N, and symptoms of an insufficient N supply to plants include lower chlorophyll content, photosynthesis activity, biomass production, and root growth, premature leaf senescence, and a decrease in grain yield and quality (Fageria and Baligar 2005).
* Gerson Laerson Drescher [email protected] 1
Department of Soil Science, Federal University of Santa Maria, Santa Maria, RS 97105-900, Brazil
2
Department of Soil and Environmental Sciences, University of The Poonch Rawalakot, Rawalakot, AJK 12350, Pakistan
3
Department of Crop, Soil, and Environmental Sciences, University of Arkansas, Fayetteville, AR 72701, USA
4
Department of Biology, Federal University of Santa Maria, Santa Maria, RS 97105-900, Brazil
Thus, the ability of a soil supply N is a key component of rice plant nutrition, optimal fertilizer-N management, and preventing potential environmental risks due to N losses associated wi
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