Alkaline hydrolyzable nitrogen and properties that dictate its distribution in paddy soil profiles |
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| Authors: | Gerson Laerson DRESCHER Leandro Souza DA SILVA Qamar SARFARAZ Gustavo DAL MOLIN Laura Brondani MARZARI Augusto Ferreira LOPES Cesar CELLA Daniela Basso FACCO and Rodrigo Knevitz HAMMERSCHMITT |
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| Institution: | 1Department of Soil Science, Federal University of Santa Maria, Santa Maria 97105-900 (Brazil);
2Federal University of Santa Maria, Campus Cachoeira do Sul, Cachoeira do Sul 96506-310 (Brazil) |
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| Abstract: | Nitrogen (N) is a key nutrient for rice production, and its bioavailability in paddy soils is strongly coupled to soil organic matter (SOM) cycling. A better understanding of potentially available N forms in soil, such as alkaline hydrolyzable N (AH-N), and their depth distribution will support the development of best management practices to improve the N use efficiency of rice while minimizing adverse environmental effects. Fifteen rice (Oryza sativa L.) fields from Southern Brazil were selected, and stratified soil samples were taken to a depth of 60 cm before crop establishment. Selected soil physical and chemical properties were analyzed to evaluate their relationships with AH-N contents in the soil profile. The AH-N contents below 20 cm varied extensively (increased, reduced, or constant) compared with that above 20 cm. Although clay and clay + silt contents were highly correlated to AH-N for some soils, the major property dictating AH-N distribution by depth was total N (TN), as the correlation between TN and AH-N was mainly by direct effect. The proportion of TN recovered as AH-N across sites and depths presented high amplitude, and thus AH-N was not a constant N pool across depths, indicating that AH-N can be affected by soil management practices even when TN showed no major changes. The distinct distribution of AH-N across soil sampling sites and depths indicates that depths greater than 20 cm should be considered when calibrating the AH-N index for N fertilizer recommendations for flooded rice in Southern Brazil. |
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| Keywords: | fertilizer recommendation nitrogen availability nutrient management practices organo-mineral interaction Oryza sativa L soil analysis soil organic matter |
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