Abstract
Abstract Pure maize ( Zea mays L.) cultivation is associated with excessive nitrogen (N) fertilization and high nitrate leaching risk. We assumed that maize intercropped with climbing beans ( Phaseolus vulgaris L.) can reduce N fertilizer demand if the beans use biological nitrogen fixation (BNF) at reduced fertilization, thereby balancing yields across N fertilization levels. We further assumed that beans can reduce nitrate leaching through uptake of excess mineral N and increase the subsequent crop yield through additional crop residues. These hypotheses were tested in two experiments between 2019 and 2022 at two sites in Germany. In Experiment 1, intercropping and pure maize were tested with three N fertilization levels. Traits included yield, nitrate leaching, and subsequent crop yield. In Experiment 2, intercropping was additionally tested with rhizobia inoculation, and pure maize with full fertilization served as a reference. Traits included nodulation and BNF of bean as well as yield. Nodulation, BNF, and yield variables differed among the two sites. At the site with nodulation and BNF, intercropping yields were comparable across N fertilization levels, and the grain yield of the subsequent crop was significantly higher (+15% to +20%) after intercropping compared with pure maize at reduced N fertilization. Nitrate leaching was significantly lower (−40% to −48%) after reduced N fertilization compared with full fertilization, but did not differ significantly between intercropping and pure maize. Inoculation could neither induce nor enhance nodulation. Without N fertilization and with nodulation, BNF of beans reached 25 kg/ha. We recommend intercropping with reduced N fertilization on fields where rhizobia naturally occur.
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Claims 9
Claim · model-written summary
Nodulation, BNF and yield differed between the two sites.
Verbatim
e0“Nodulation, BNF, and yield variables differed among the two sites”
t0“Maize–bean”
Claim · model-written summary
At the site with nodulation and BNF, intercropping yield was comparable across N levels.
- Outcome
- intercropping yieldse0
- Direction
- comparablee0
- Comparator
- N fertilization levelse0
- Setting
- site with nodulation and BNFe0
Zea maysOrganisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“At the site with nodulation and BNF, intercropping yields were comparable across N fertilization levels”
t0“Maize–bean”
Claim · model-written summary
Subsequent crop grain yield was 15–20% higher following intercropping than pure maize under reduced N.
- Treatment
- intercroppinge0
- Outcome
- grain yield of the subsequent crope0
- Direction
- highere0
- Value
- +15% to +20%e0
- Comparator
- pure maizee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the grain yield of the subsequent crop was significantly higher (+15% to +20%) after intercropping compared with pure maize at reduced N fertilization”
t0“Maize”
Claim · model-written summary
Reduced N fertilization lowered nitrate leaching by 40–48% compared with full N.
- Treatment
- reduced N fertilizatione0
- Outcome
- Nitrate leachinge0
- Direction
- lowere0
- Value
- −40% to −48%e0
- Comparator
- full fertilizatione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Nitrate leaching was significantly lower (−40% to −48%) after reduced N fertilization compared with full fertilization”
t0“Maize”
Claim · model-written summary
Nitrate leaching did not significantly differ between intercropping and pure maize.
- Treatment
- intercroppinge0
- Outcome
- Nitrate leachinge0
- Direction
- did not differ significantlye0
- Comparator
- pure maizee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Nitrate leaching was significantly lower (−40% to −48%) after reduced N fertilization compared with full fertilization, but did not differ significantly between intercropping and pure maize”
t0“Maize”
Claim · model-written summary
Rhizobia inoculation did not induce nodulation of beans.
Not reportedComparator
Verbatim
e0“Inoculation could neither induce nor enhance nodulation”
t0“bean”
Claim · model-written summary
Rhizobia inoculation did not enhance bean nodulation.
Not reportedComparator
Verbatim
e0“Inoculation could neither induce nor enhance nodulation”
t0“bean”
Claim · model-written summary
Without N fertilization and with nodulation, bean BNF reached 25 kg/ha.
Verbatim
e0“Without N fertilization and with nodulation, BNF of beans reached 25 kg/ha”
Claim · model-written summary
The authors recommend intercropping with reduced N where rhizobia naturally occur.
- Interactor
- rhizobiae0symbiont
- Outcome
- intercropping with reduced N fertilizatione0
- Qualifier
- fields where rhizobia naturally occure0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“We recommend intercropping with reduced N fertilization on fields where rhizobia naturally occur”
t0“Maize–bean”
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