Abstract
Plastic film mulching and nitrogen (N) fertilization are two important field management practices used to increase crop yields in rain-fed agriculture in arid and semi-arid areas. These two practices, however, can have opposing effects on soil organic carbon (SOC) stock and turnover. To clarify and analyze the combined effects of these practices, we conducted a 7-year continuous maize cultivation experiment with four treatments: (1) no plastic film mulching without N fertilization (Control), (2) plastic film mulching without N fertilization (PFM), (3) N fertilization without plastic film mulching (N), and (4) plastic film mulching with N fertilization (PFM + N). The 13C natural abundance of in the light and heavy fractions of organic carbon (LFOC and HFOC) was used to differentiate “old” (>7 years) and “new” (<7 years) C in the soil after C3 to C4 vegetation change. PFM increased soil temperature and moisture content over 7 years and led to a 150 % and 108 % increase in the above-ground and root biomass of maize, respectively. Hot and wet conditions under PFM accelerated the decomposition of both labile C (i.e., LFOC) and persistent C (i.e., HFOC), as measured by CO2 efflux from the soil. PFM decreased the LFOC and HFOC pools due to the fast decomposition of “old” C and inadequate stabilization of “new” C. Furthermore, PFM accelerated HFOC decomposition to a greater extent than that of LFOC. The Q10 values of SOC decomposition remained similar both in the presence and absence of PFM. Nitrogen fertilization increased the aboveground and root biomass of maize by 54 % and 40 %, respectively. In the control soil, microorganisms decomposed organic N owing to limited availability of mineral N and in the absence of any from replenishment by fertilizer N. Thus, the increase in LFOC content under N fertilization, was primarily attributed to the reduced decomposition of “old” C. The use of N fertilization produced a similar HFOC content as that of the control soil, while also accelerating the decomposition of “old” C and promoting the stabilization of “new” C, resulting in a faster turnover rate. Consequently, the impact of N fertilization on SOC turnover was negligible owing to the contrasting effects on LFOC and HFOC. The application of N fertilization resulted in a reduction of the Q10 value as compared to control. The combination of PFM and N fertilization accelerated the decomposition of HFOC and SOC, while having absent effect on SOC, labile C and persistent C contents. This indicates that 7 years weren’t long enough to trigger a response to the combination of PFM and N fertilization from SOC and HFOC contents. In summary, PFM led to a decline in the SOC content by accelerating the decomposition of both LFOC and HFOC. Conversely, N fertilization maintained SOC content by inhibiting LFOC decomposition and enhancing HFOC decomposition.
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Claims 20
Claim · model-written summary
Plastic film mulching increased soil temperature and moisture over seven years.
- Treatment
- PFMe0
- Outcome
- soil temperature and moisture contente0
- Direction
- increasede0
- Qualifier
- over 7 yearse0
Not reportedTaxonComparator
Verbatim
e0“PFM increased soil temperature and moisture content over 7 years”
Claim · model-written summary
Mulching increased maize above-ground biomass by 150%.
Zea maysNot reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“PFM increased soil temperature and moisture content over 7 years and led to a 150 % and 108 % increase in the above-ground and root biomass of maize, respectively.”
Claim · model-written summary
Mulching increased maize root biomass by 108%.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“PFM increased soil temperature and moisture content over 7 years and led to a 150 % and 108 % increase in the above-ground and root biomass of maize, respectively.”
Claim · model-written summary
Hot wet conditions under mulching accelerated decomposition of labile and persistent carbon.
- Outcome
- decomposition of both labile C (i.e., LFOC) and persistent C (i.e., HFOC)e0
- Direction
- acceleratede0
- Qualifier
- Hot and wet conditionse0
Not reportedTaxon
Verbatim
e0“Hot and wet conditions under PFM accelerated the decomposition of both labile C (i.e., LFOC) and persistent C (i.e., HFOC), as measured by CO2 efflux from the soil.”
Claim · model-written summary
Mulching decreased light and heavy organic carbon pools through old-carbon decomposition and inadequate new-carbon stabilization.
- Treatment
- PFMe0
- Outcome
- LFOC and HFOC poolse0
- Direction
- decreasede0
- Qualifier
- fast decomposition of “old” C and inadequate stabilization of “new” Ce0
Not reportedTaxon
Verbatim
e0“PFM decreased the LFOC and HFOC pools due to the fast decomposition of “old” C and inadequate stabilization of “new” C.”
Claim · model-written summary
Mulching accelerated heavy-carbon decomposition more than light-carbon decomposition.
Not reportedTaxon
Verbatim
e0“PFM accelerated HFOC decomposition to a greater extent than that of LFOC.”
Claim · model-written summary
SOC decomposition Q10 remained similar with and without mulching.
- Treatment
- presencee0
- Outcome
- Q10 values of SOC decompositione0
- Direction
- remained similare0
- Comparator
- absence of PFMe0
Not reportedTaxon
Verbatim
e0“The Q10 values of SOC decomposition remained similar both in the presence and absence of PFM.”
Claim · model-written summary
Nitrogen fertilization increased maize aboveground biomass by 54%.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Nitrogen fertilization increased the aboveground and root biomass of maize by 54 % and 40 %, respectively.”
Claim · model-written summary
Nitrogen fertilization increased maize root biomass by 40%.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Nitrogen fertilization increased the aboveground and root biomass of maize by 54 % and 40 %, respectively.”
Claim · model-written summary
Control-soil microorganisms decomposed organic nitrogen because mineral nitrogen was limited and unreplenished.
Not reportedDirection
Verbatim
e0“In the control soil, microorganisms decomposed organic N owing to limited availability of mineral N and in the absence of any from replenishment by fertilizer N.”
Claim · model-written summary
Nitrogen fertilization increased light-carbon content primarily by reducing old-carbon decomposition.
- Treatment
- N fertilizatione0
- Outcome
- LFOC contente0
- Direction
- increasee0
- Qualifier
- reduced decomposition of “old” Ce0
Not reportedTaxon
Verbatim
e0“the increase in LFOC content under N fertilization, was primarily attributed to the reduced decomposition of “old” C.”
Claim · model-written summary
Nitrogen fertilization maintained heavy-carbon content similar to control.
Not reportedTaxon
Verbatim
e0“The use of N fertilization produced a similar HFOC content as that of the control soil”
Claim · model-written summary
Nitrogen fertilization accelerated old-carbon decomposition and new-carbon stabilization, yielding faster heavy-carbon turnover.
- Treatment
- N fertilizatione0
- Outcome
- turnover ratee0
- Direction
- fastere0
- Qualifier
- accelerating the decomposition of “old” C and promoting the stabilization of “new” Ce0
Not reportedTaxon
Verbatim
e0“The use of N fertilization produced a similar HFOC content as that of the control soil, while also accelerating the decomposition of “old” C and promoting the stabilization of “new” C, resulting in a faster turnover rate.”
Claim · model-written summary
Nitrogen had negligible impact on SOC turnover because light and heavy carbon effects contrasted.
- Treatment
- N fertilizatione0
- Outcome
- SOC turnovere0
- Direction
- negligiblee0
- Qualifier
- contrasting effects on LFOC and HFOCe0
Not reportedTaxon
Verbatim
e0“the impact of N fertilization on SOC turnover was negligible owing to the contrasting effects on LFOC and HFOC.”
Claim · model-written summary
Nitrogen fertilization reduced Q10 relative to control.
Not reportedTaxon
Verbatim
e0“The application of N fertilization resulted in a reduction of the Q10 value as compared to control.”
Claim · model-written summary
Combined mulching and nitrogen accelerated heavy-carbon and SOC decomposition.
- Treatment
- combination of PFM and N fertilizatione0
- Outcome
- decomposition of HFOC and SOCe0
- Direction
- acceleratede0
Not reportedTaxonComparator
Verbatim
e0“The combination of PFM and N fertilization accelerated the decomposition of HFOC and SOC”
Claim · model-written summary
Combined mulching and nitrogen had no effect on SOC, labile-carbon and persistent-carbon contents.
- Treatment
- combination of PFM and N fertilizatione0
- Outcome
- SOC, labile C and persistent C contentse0
- Direction
- absent effecte0
Not reportedTaxonComparator
Verbatim
e0“The combination of PFM and N fertilization accelerated the decomposition of HFOC and SOC, while having absent effect on SOC, labile C and persistent C contents.”
Claim · model-written summary
Seven years was insufficient to trigger SOC and heavy-carbon content responses to combined management.
Not reportedTaxonDirection
Verbatim
e0“7 years weren’t long enough to trigger a response to the combination of PFM and N fertilization from SOC and HFOC contents.”
Claim · model-written summary
Mulching decreased SOC content by accelerating light and heavy carbon decomposition.
- Treatment
- PFMe0
- Outcome
- SOC contente0
- Direction
- declinee0
- Qualifier
- accelerating the decomposition of both LFOC and HFOCe0
Not reportedTaxon
Verbatim
e0“PFM led to a decline in the SOC content by accelerating the decomposition of both LFOC and HFOC.”
Claim · model-written summary
Nitrogen maintained SOC content by inhibiting light-carbon decomposition and enhancing heavy-carbon decomposition.
- Treatment
- N fertilizatione0
- Outcome
- SOC contente0
- Direction
- maintainede0
- Qualifier
- inhibiting LFOC decomposition and enhancing HFOC decompositione0
Not reportedTaxon
Verbatim
e0“N fertilization maintained SOC content by inhibiting LFOC decomposition and enhancing HFOC decomposition.”
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