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Title: Pathways of soil organic matter formation from above and belowground inputs in a Sorghum bicolor bioenergy crop
Abstract

When aboveground materials are harvested for fuel production, such as withSorghum bicolor, the sustainability of annual bioenergy feedstocks is influenced by the ability of root inputs to contribute to the formation and persistence of soil organic matter (SOM), and to soil fertility through nutrient recycling. Using13C and15N labeling, we traced sorghum root and leaf litter‐derived C and N for 19 months in the field as they were mineralized or formedSOM. Our in situ litter incubation experiment confirms that sorghum roots and leaves significantly differ in their inherent chemical recalcitrance. This resulted in different contributions to C and N storage and recycling. Overall root residues had higher biochemical recalcitrance which led to more C retention in soil (27%) than leaf residues (19%). However, sorghum root residues resulted in higher particulate organic matter (POM) and lower mineral associated organic matter (MAOM), deemed to be the most persistent fraction in soil, than leaf residues. Additionally, the overall higher root‐derived C retention in soil led to higher N retention, reducing the immediate recycling of fertility from root as compared to leaf decomposition. Our study, conducted in a highly aggregated clay‐loam soil, emphasized the important role of aggregates in newSOMformation, particularly the efficient formation ofMAOMin microaggregate structures occluded within macroaggregates. Given the known role of roots in promoting aggregation, efficient formation ofMAOMwithin aggregates can be a major mechanism to increase persistentSOMstorage belowground when aboveground residues are removed. We conclude that promoting root inputs inS. bicolorbioenergy production systems through plant breeding efforts may be an effective means to counterbalance the aboveground residue removal. However, management strategies need to consider the quantity of inputs involved and may need to supportSOMstorage and fertility with additional organic matter additions.

 
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PAR ID:
10461696
Author(s) / Creator(s):
 ;  
Publisher / Repository:
Wiley-Blackwell
Date Published:
Journal Name:
GCB Bioenergy
Volume:
11
Issue:
8
ISSN:
1757-1693
Page Range / eLocation ID:
p. 971-987
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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