Pipai, Rachel, McNeill, Ann, Unkovich, Murray, Banabas, Murom, and Nelson, Paul N. (2023) Biological nitrogen fixation by legume cover plants in oil palm plantations: calibration of the ureide technique and effects of plantation age and soil nitrate. Plant and Soil. (In Press)

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Abstract

Background and Aims. To sustainably manage N in oil palm systems quantities of N fixed by cover legumes need to be understood. Current values are scarce, based on shoot N measures and do not include litter which releases nitrate as it decomposes. We aimed to quantify N2 fixed by legumes under oil palm systems in PNG and to determine if soil nitrate influenced dependence on N2 fixation (Ndfa).

Methods. The ureide technique for estimating tropical legume Ndfa was calibrated for Calapogonium mucunoides and Pueraria phaseoloides using 15N isotope dilution, and then used to assess Ndfa for legume cover under oil palms (2 to 25 years old) in Papua New Guinea. Amounts of fixed N in aboveground legume biomass (shoot plus litter) were calculated incorporating % groundcover. Soil nitrate under the legume litter was also measured.

Results. Legume Ndfa was highly negatively correlated with soil nitrate concentration but independent of palm age. Legume groundcover, shoot and litter dry matter, and quantity of fixed N were greater under oil palms less than 5 years old, decreasing under older plantations where solely C. caeruleum was present. DM and N content of litter were similar to shoots for legumes in plantations less than 6 years old.

Conclusion. The calibrated ureide technique can be used, together with estimates of annual legume N accumulation, to quantify N input from legume groundcover during the life cycle of oil palm plantations and other tropical ecosystems, in order to support more sustainable management of N.

Item ID:	79383
Item Type:	Article (Research - C1)
ISSN:	1573-5036
Keywords:	Calapogonium, Pueraria, Mucuna, Standing biomass, Litter, Nodulation, sustainable agriculture
Copyright Information:	This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.
Funders:	ACIAR
Projects and Grants:	ACIAR John Alwright Fellowship, ACIAR SMCN-2009-013
Date Deposited:	24 Jul 2023 01:21
FoR Codes:	30 AGRICULTURAL, VETERINARY AND FOOD SCIENCES > 3004 Crop and pasture production > 300407 Crop and pasture nutrition @ 40% 41 ENVIRONMENTAL SCIENCES > 4106 Soil sciences > 410603 Soil biology @ 20% 31 BIOLOGICAL SCIENCES > 3108 Plant biology > 310899 Plant biology not elsewhere classified @ 40%
SEO Codes:	26 PLANT PRODUCTION AND PLANT PRIMARY PRODUCTS > 2606 Industrial crops > 260699 Industrial crops not elsewhere classified @ 50% 26 PLANT PRODUCTION AND PLANT PRIMARY PRODUCTS > 2601 Environmentally sustainable plant production > 260199 Environmentally sustainable plant production not elsewhere classified @ 50%
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