Abstract
Soil conservation measures such as establishing grass barriers or cover crops effectively control erosion but also provoke competition, which reduces yields of companion crops. We used 13C and 15N natural abundance profiles to identify the causes of competition of soil conservation measures on a field with 59% slope in Northwest Vietnam three years after establishment. Treatments were maize under farmer’s practice (T1, control), maize with Guinea grass barriers (T2), maize under minimum tillage (MT) with Pinto peanuts as cover crop (T3), and maize under MT and relay cropped with Adzuki beans (T4). A pretest using data from zero-N plots revealed that abundance of water and limited nitrogen availability induced low grain N concentrations, enriched leaf δ13C, and reduced maize grain yield. Similar low N leaf concentrations and elevated δ13C values were observed in maize growing close to frequently pruned grass barriers under positive water balance conditions, indicating that yield decline in these rows can be attributed mainly to N competition. Enriched δ15N values of maize from rows next to barriers indicated reliance on soil N rather than on 15N-depleted fertiliser N. Vigorous cover crop growth under MT resulted in maize yield decline due to N competition while relay-cropped legumes did not trigger inter-species competition having a similar maize yield, leaf N concentration, δ13C, and δ15N as the control.
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Claims 10
Claim · model-written summary
Abundance of water and limited nitrogen availability were associated with low grain N concentrations in maize.
- Treatment
- abundance of water and limited nitrogen availabilitye1
- Outcome
- grain N concentrationse1
- Direction
- lowe1
Zea maysOrganisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Identifying resource competition in maize-based soil conservation systems using13C and15N isotopic discrimination”
e1“A pretest using data from zero-N plots revealed that abundance of water and limited nitrogen availability induced low grain N concentrations, enriched leaf δ13C, and reduced maize grain yield”
Claim · model-written summary
Abundance of water and limited nitrogen availability were associated with enriched leaf δ13C in maize.
- Treatment
- abundance of water and limited nitrogen availabilitye1
- Outcome
- leaf δ13Ce1
- Direction
- enrichede1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Identifying resource competition in maize-based soil conservation systems using13C and15N isotopic discrimination”
e1“A pretest using data from zero-N plots revealed that abundance of water and limited nitrogen availability induced low grain N concentrations, enriched leaf δ13C, and reduced maize grain yield”
Claim · model-written summary
Abundance of water and limited nitrogen availability were associated with reduced maize grain yield.
- Treatment
- abundance of water and limited nitrogen availabilitye1
- Outcome
- maize grain yielde1
- Direction
- reducede1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Identifying resource competition in maize-based soil conservation systems using13C and15N isotopic discrimination”
e1“A pretest using data from zero-N plots revealed that abundance of water and limited nitrogen availability induced low grain N concentrations, enriched leaf δ13C, and reduced maize grain yield”
Claim · model-written summary
Maize near frequently pruned grass barriers had low leaf N concentrations under positive water balance.
- Treatment
- frequently pruned grass barrierse2
- Outcome
- N leaf concentrationse2
- Direction
- lowe2
- Qualifier
- under positive water balance conditionse2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Identifying resource competition in maize-based soil conservation systems using13C and15N isotopic discrimination”
e2“Similar low N leaf concentrations and elevated δ13C values were observed in maize growing close to frequently pruned grass barriers under positive water balance conditions”
Claim · model-written summary
Maize near frequently pruned grass barriers had elevated leaf δ13C values.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Identifying resource competition in maize-based soil conservation systems using13C and15N isotopic discrimination”
e2“Similar low N leaf concentrations and elevated δ13C values were observed in maize growing close to frequently pruned grass barriers under positive water balance conditions”
Claim · model-written summary
Yield decline in grass-barrier rows is attributed mainly to nitrogen competition.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Identifying resource competition in maize-based soil conservation systems using13C and15N isotopic discrimination”
e3“indicating that yield decline in these rows can be attributed mainly to N competition”
Claim · model-written summary
Maize from rows next to grass barriers had enriched δ15N values, indicating reliance on soil N.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Identifying resource competition in maize-based soil conservation systems using13C and15N isotopic discrimination”
e4“Enriched δ15N values of maize from rows next to barriers indicated reliance on soil N rather than on 15N-depleted fertiliser N”
Claim · model-written summary
Vigorous cover crop growth under minimum tillage resulted in maize yield decline due to N competition.
- Treatment
- Vigorous cover crop growth under MTe5
- Outcome
- maize yielde5
- Direction
- declinee5
- Qualifier
- due to N competitione5
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Identifying resource competition in maize-based soil conservation systems using13C and15N isotopic discrimination”
e5“Vigorous cover crop growth under MT resulted in maize yield decline due to N competition”
Claim · model-written summary
Relay-cropped legumes under minimum tillage gave a maize yield similar to the control.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Identifying resource competition in maize-based soil conservation systems using13C and15N isotopic discrimination”
e6“while relay-cropped legumes did not trigger inter-species competition having a similar maize yield, leaf N concentration, δ13C, and δ15N as the control”
Claim · model-written summary
Relay-cropped legumes gave leaf N concentration, δ13C and δ15N similar to the control in maize.
- Treatment
- relay-cropped legumese6
- Outcome
- leaf N concentration, δ13C, and δ15Ne6
- Direction
- similare6
- Comparator
- the controle6
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Identifying resource competition in maize-based soil conservation systems using13C and15N isotopic discrimination”
e6“while relay-cropped legumes did not trigger inter-species competition having a similar maize yield, leaf N concentration, δ13C, and δ15N as the control”
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