Measured and modeled nitrogen balances in lowland rice-pasture rotations in temperate South America

A - Papers appearing in refereed journals

Castillo, J., Kirk, G. J. D., Rivero, M. J., Fabini, G., Terra, J. A., Ayala, W., Roel, A., Irisarri, P. and Haefele, S. M. 2023. Measured and modeled nitrogen balances in lowland rice-pasture rotations in temperate South America. Frontiers in Sustainable Food Systems. 7, p. 1103118. https://doi.org/10.3389/fsufs.2023.1103118

AuthorsCastillo, J., Kirk, G. J. D., Rivero, M. J., Fabini, G., Terra, J. A., Ayala, W., Roel, A., Irisarri, P. and Haefele, S. M.
Abstract

Rotational rice systems, involving pastures, other crops and/or livestock, are common in temperate South America, exemplified by the rice-pasture-livestock system of Uruguay which combines very high rice yields with tight nitrogen (N) balances. The generally good nutrient use efficiency in these systems provides a template for nutrient management in other mixed farming systems, if the underlying processes can be sufficiently well quantified and understood. Here, we studied N balances in rice–non-rice rotations in a long-term experiment in Uruguay, with the aim of parameterizing and testing the DNDC model of N dynamics for such systems for use in future work. The experiment includes three rotations: continuous rice (RI-CONT), rice-soybean (RI-SOY) and rice-pasture (RI-PAST). We considered 9 years of data on N balances (NBAL), defined as all N inputs minus all N outputs; N surplus (NSURP), defined as all N inputs minus only N outputs in food products; and N use efficiency (NUE), defined as the fraction of N inputs removed in food products. We parameterized DNDC against measured yield and input and output data, with missing data on N losses inferred from the N balance and compared with literature values. The model performance was assessed using standard indices of mean error, agreement and efficiency. The model simulated crop yields and rice cumulative N uptake very well, and soil N reasonably well. The values of NBAL were +45 and−20 kg N ha−1 yr−1 in RI-CONT and RI-SOY, respectively, and close to zero in RI-PAST (−6 kg N ha−1 yr−1). Values of NSURP decreased in the order RI-CONT >> RI-SOY > RI-PAST (+115, +25 and +13 kg N ha−1 yr−1, respectively). Values of NUE (84, 54, and 48% for RI-SOY, RI-PAST, and RI-CONT, respectively) decreased as NBAL increased. The sensitivity of DNDC's predictions to the agronomic characteristics of the different crops, rotations and water regimes agreed with expectations. We conclude that the DNDC model as parameterized here is suitable for exploring how to optimize N management in these systems.

KeywordsNitrogen use efficiency; DNDC model; Nitrogen budgets; Nutrient balances; Long-term experiment
Year of Publication2023
JournalFrontiers in Sustainable Food Systems
Journal citation7, p. 1103118
Digital Object Identifier (DOI)https://doi.org/10.3389/fsufs.2023.1103118
Web address (URL)https://www.frontiersin.org/articles/10.3389/fsufs.2023.1103118/full
Open accessPublished as ‘gold’ (paid) open access
FunderBiotechnology and Biological Sciences Research Council
Natural Environment Research Council
Funder project or codeS2N - Soil to Nutrition - Work package 2 (WP2) - Adaptive management systems for improved efficiency and nutritional quality
S2N - Soil to Nutrition - Work package 1 (WP1) - Optimising nutrient flows and pools in the soil-plant-biota system
AgZero+
Publisher's version
Output statusPublished
Publication dates
Online03 Apr 2023
Publication process dates
Accepted13 Mar 2023
PublisherFrontiers Media SA
ISSN2571-581X

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