Effect of nitrogen application rate under organic and conventional systems on rice (Oryza sativa l.) growth, grain yield, soil properties, and greenhouse gas emissions

Authors: LI, X - Texas A&M University; JIANG, J - Texas A&M University; GUOA, J - Texas A&M University; McClung, Anna; CHEN, K - University Of Connecticut; VELARCA, M - Texas A&M University; Torbert, Henry - Allen; DOU, FUGEN - Texas A&M University

Submitted to: Journal of Plant Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/5/2022
Publication Date: 3/15/2023
Citation: Li, X., Jiang, J., Guoa, J., Mcclung, A.M., Chen, K., Velarca, M.V., Torbert III, H.A., Dou, F. 2023. Effect of nitrogen application rate under organic and conventional systems on rice (Oryza sativa l.) growth, grain yield, soil properties, and greenhouse gas emissions. Journal of Plant Nutrition. 46:167-1649. https://doi.org/10.1080/01904167.2022.2093746.
DOI: https://doi.org/10.1080/01904167.2022.2093746

Interpretive Summary: The use of appropriate nitrogen (N) rates is important to optimize organic rice yield potential while minimizing environmental impact and input costs. A greenhouse experiment was conducted to identify the optimal N rate for rice (Oryza sativa L.) managed organically as compared to a conventional system and to determine its effects on soil properties, rice yield components, yield and greenhouse gas emissions. A study was conducted using six N rates (0, 50, 100, 150, 200 and 250 kg ha-1) and two cropping systems (organic system and conventional system). Results indicated that the optimal N rate was 200 kg/ha for organic rice and 250 kg/ ha or higher for conventional rice to approach yield potential. The CO2 and CH4 emission fluxes peaked at the reproductive stage, whereas N2O emission flux peaked at the vegetative stage of rice. Global warming potential increased with increasing N rate but GHG emission per unit of rice yield was not affected by N rate in both systems.

Technical Abstract: The use of appropriate nitrogen (N) rates is important to optimize organic rice yield potential while minimizing environmental impact and input costs. A greenhouse experiment was conducted to identify the optimal N rate for rice (Oryza sativa L.) managed organically as compared to a conventional system and to determine its effects on soil properties, rice yield components, yield and greenhouse gas emissions. Using a high-yielding hybrid rice (XP753), six N rates (0, 50, 100, 150, 200 and 250 kg ha-1) and two cropping systems [organic system receiving an organic certified soil amendment, Nature Safe (13-0-0); conventional system receiving a urea (46-0-0) fertilizer] were arranged in a randomized complete block design with four replicates. Plant dry biomass, panicle number, and grain yield of conventional rice linearly increased with increasing N rate from 0 to 250 kg ha-1, whereas those of organic rice increased significantly with increasing N rate until 200 kg ha-1. Conventional rice had a significantly taller plant, whereas organic rice had a significantly greater tiller number. At the optimal N rate, the panicle number and grain yield of organic rice were 77.3% and 92.7% of those of conventional rice, respectively. CO2 and CH4 emissions peaked at the reproductive stage, whereas N2O emission peaked at the vegetative stage. Global warming potential (GWP) increased with increasing N rate and peaked at 200 kg N ha-1 and 250 kg N ha-1, respectively, in the organic and conventional system; however, greenhouse gas intensity, a measure of GHG emission per unit of rice yield, was not affected by N rate in both systems. Of the measured soil parameters, total microbial biomass was significantly correlated to plant growth, yield, and GWP. Our study indicated that the optimal N rate was 200 kg ha-1 for organic rice and 250 kg ha-1 or higher for conventional rice to approach yield potential.