Abstract
Previous research indicates a correlation between leaf area index (LAI) and yield of full-season soybean [Glycine max (L.) Merrill], which is a single crop planted early in the season. Leaf area index values of at least 3.5–4.0 in the reproductive stages are required for maximum potential yield. It is unknown how yields of double-crop soybean, which is planted late into harvested small grain fields, respond to changes in leaf area index. We hypothesized that double-crop soybean would be more sensitive to defoliation than full-season soybean. This study used linear and linear plateau models to describe the yield response of full-season and double-crop soybean to reductions in leaf area index through manual defoliation, and evaluated the yield response of double-crop soybean to reductions in leaf area index through natural insect defoliation. From 15 manual defoliation experiments over 3 yr, significant linear decreases in yield occurred in both full-season and double-crop soybean when leaf area index values were below 3.5–4.0 by developmental stages R4 to R5, whereas yields usually reached a plateau at higher leaf area index levels. Average yield loss was 769 ± 319 kg ha−1 for each unit decrease in leaf area index below the plateau; average maximum yield was 3,484 ± 735 kg ha−1. From eight field experiments over 2 yr, insect defoliators had no effect on double-crop soybean yield; leaf area index levels were above 4.0 by the developmental stage when leaf area index estimates were taken (R3 to R6). Therefore, double-crop soybean that maintains leaf area index values above the 3.5–4.0 critical level by mid-reproductive developmental stages can tolerate defoliating pests.
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Claims 6
Claim · model-written summary
Manual defoliation caused significant linear yield decreases in full-season and double-crop soybean when leaf area index was below 3.5–4.0 at R4 to R5, relative to higher leaf area index.
- Taxon
- soybean
Glycine maxe1 - Treatment
- manual defoliatione0
- Outcome
- yielde1
- Direction
- decreasese1
- Comparator
- higher leaf area index levelse2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“From 15 manual defoliation experiments over 3 yr”
e1“significant linear decreases in yield occurred in both full-season and double-crop soybean when leaf area index values were below 3.5–4.0 by developmental stages R4 to R5”
e2“whereas yields usually reached a plateau at higher leaf area index levels”
Claim · model-written summary
Yields of soybean usually reached a plateau at higher leaf area index levels.
- Taxon
- soybeanGlycine maxe1
- Outcome
- yieldse2
- Direction
- reached a plateaue2
- Comparator
- higher leaf area index levelse2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“significant linear decreases in yield occurred in both full-season and double-crop soybean when leaf area index values were below 3.5–4.0 by developmental stages R4 to R5”
e2“whereas yields usually reached a plateau at higher leaf area index levels”
Claim · model-written summary
Average yield loss was 769 ± 319 kg ha−1 for each unit decrease in leaf area index below the plateau.
- Taxon
- soybeanGlycine maxe1
- Outcome
- yield losse3
- Direction
- decreasee3
- Value
- 769 ± 319 kg ha−1e3
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“significant linear decreases in yield occurred in both full-season and double-crop soybean when leaf area index values were below 3.5–4.0 by developmental stages R4 to R5”
e3“Average yield loss was 769 ± 319 kg ha−1 for each unit decrease in leaf area index below the plateau”
Claim · model-written summary
Average maximum soybean yield was 3,484 ± 735 kg ha−1.
- Taxon
- soybeanGlycine maxe1
- Outcome
- maximum yielde4
- Value
- 3,484 ± 735 kg ha−1e4
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“significant linear decreases in yield occurred in both full-season and double-crop soybean when leaf area index values were below 3.5–4.0 by developmental stages R4 to R5”
e4“average maximum yield was 3,484 ± 735 kg ha−1”
Claim · model-written summary
Insect defoliators had no effect on double-crop soybean yield in field experiments.
- Taxon
- double-crop soybeane5
- Treatment
- insect defoliatorse5
- Interactor
- insect defoliatorse5pest
- Outcome
- yielde5
- Direction
- had no effecte5
Not reportedComparator
Verbatim
e5“From eight field experiments over 2 yr, insect defoliators had no effect on double-crop soybean yield”
Claim · model-written summary
Double-crop soybean that keeps leaf area index above the 3.5–4.0 critical level can tolerate defoliating pests.
Verbatim
e6“double-crop soybean that maintains leaf area index values above the 3.5–4.0 critical level by mid-reproductive developmental stages can tolerate defoliating pests”
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pruning · yield · Glycine max (soybean)Positive and negative results
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