Abstract
Abstract The influence of P, K, and S on symbiotic fixation of N 2 in alfalfa nodules under field conditions is not well documented, even though through this mechanism shoot yield may be limited. The objective of this experiment was to study the effect of P, K, and S fertilization on alfalfa shoot yield, nodule numbers, and N 2 ‐fixation as estimated by acetylene reduction by taking core samples (80 mm diam) at two sampling times at two locations (a silt loam and a loamy sand soil). Potassium fertilization increased shoot weight per plant, nodule number per core, and N 2 ‐fixation rate at both locations more than the other nutrients studied. Shoot weight per plant increased 166% on the silt loam soil and 178% on the sandy soil with the addition of 448 kg K ha −1 . Phosphorus fertilization also increased shoot weight at both sites but less than did K fertilization. Addition of P and S increased nodule numbers on the sandy soil but not on the silt loam soil. Nitrogen‐fixation rate was increased by 2.8 fold with the addition of 224 kg K ha −1 on the sandy soil and 1.7 fold on the silt loam soil. Increased N 2 ‐fixation resulted from K fertilization only when P was added to the silt loam soil. Phosphorus addition increased nodule numbers and N 2 ‐fixation only on the sandy soil. The presence of a K ✕ S interaction for N 2 ‐fixation but not for shoot weight or nodule number per core indicates that some differences in fertility response exist between N 2 ‐fixation and other variables, even though all tend to be positively correlated. Sulfur fertilization had no effect on shoot weight but increased nodule numbers in alfalfa grown on sandy soil.
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Claims 12
Claim · model-written summary
Potassium fertilization increased alfalfa shoot weight, nodule number and nitrogen fixation at both locations more than other nutrients.
- Taxon
- Alfalfa
Medicago sativat0 - Treatment
- Potassium fertilizatione0
- Outcome
- shoot weight per plant, nodule number per core, and N 2 ‐fixation ratee0
- Direction
- increasede0
- Comparator
- other nutrients studiede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Potassium fertilization increased shoot weight per plant, nodule number per core, and N 2 ‐fixation rate at both locations more than the other nutrients studied.”
t0“Alfalfa”
Claim · model-written summary
With 448 kg K ha −1, shoot weight increased 166% on silt loam.
- Taxon
- AlfalfaMedicago sativat0
- Treatment
- 448 kg K ha −1e0
- Outcome
- Shoot weight per plante0
- Direction
- increasede0
- Value
- 166%e0
- Setting
- silt loam soile0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Shoot weight per plant increased 166% on the silt loam soil and 178% on the sandy soil with the addition of 448 kg K ha −1”
t0“Alfalfa”
Claim · model-written summary
With 448 kg K ha −1, shoot weight increased 178% on sandy soil.
- Taxon
- AlfalfaMedicago sativat0
- Treatment
- 448 kg K ha −1e0
- Outcome
- Shoot weight per plante0
- Direction
- increasede0
- Value
- 178%e0
- Setting
- sandy soile0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Shoot weight per plant increased 166% on the silt loam soil and 178% on the sandy soil with the addition of 448 kg K ha −1”
t0“Alfalfa”
Claim · model-written summary
Phosphorus increased shoot weight at both sites less than potassium did.
- Taxon
- AlfalfaMedicago sativat0
- Treatment
- Phosphorus fertilizatione0
- Outcome
- shoot weighte0
- Direction
- increasede0
- Comparator
- K fertilizatione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Phosphorus fertilization also increased shoot weight at both sites but less than did K fertilization.”
t0“Alfalfa”
Claim · model-written summary
P and S increased nodule numbers on sandy soil but not on silt loam.
- Taxon
- AlfalfaMedicago sativat0
- Treatment
- P and Se0
- Outcome
- nodule numberse0
- Direction
- increasede0
- Setting
- sandy soile0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Addition of P and S increased nodule numbers on the sandy soil but not on the silt loam soil.”
t0“Alfalfa”
Claim · model-written summary
Adding 224 kg K ha −1 increased nitrogen fixation 2.8 fold on sandy soil.
- Taxon
- AlfalfaMedicago sativat0
- Treatment
- 224 kg K ha −1e0
- Outcome
- Nitrogen‐fixation ratee0
- Direction
- increasede0
- Value
- 2.8 folde0
- Setting
- sandy soile0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Nitrogen‐fixation rate was increased by 2.8 fold with the addition of 224 kg K ha −1 on the sandy soil and 1.7 fold on the silt loam soil.”
t0“Alfalfa”
Claim · model-written summary
Adding 224 kg K ha −1 increased nitrogen fixation 1.7 fold on silt loam.
- Taxon
- AlfalfaMedicago sativat0
- Treatment
- 224 kg K ha −1e0
- Outcome
- Nitrogen‐fixation ratee0
- Direction
- increasede0
- Value
- 1.7 folde0
- Setting
- silt loam soile0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Nitrogen‐fixation rate was increased by 2.8 fold with the addition of 224 kg K ha −1 on the sandy soil and 1.7 fold on the silt loam soil.”
t0“Alfalfa”
Claim · model-written summary
Potassium increased nitrogen fixation on silt loam only with added phosphorus.
- Taxon
- AlfalfaMedicago sativat0
- Treatment
- K fertilizatione0
- Outcome
- N 2 ‐fixatione0
- Direction
- Increasede0
- Qualifier
- only when P was addede0
- Setting
- silt loam soile0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Increased N 2 ‐fixation resulted from K fertilization only when P was added to the silt loam soil.”
t0“Alfalfa”
Claim · model-written summary
Phosphorus increased nodule numbers and nitrogen fixation only on sandy soil.
- Taxon
- AlfalfaMedicago sativat0
- Treatment
- Phosphorus additione0
- Outcome
- nodule numbers and N 2 ‐fixatione0
- Direction
- increasede0
- Setting
- sandy soile0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Phosphorus addition increased nodule numbers and N 2 ‐fixation only on the sandy soil.”
t0“Alfalfa”
Claim · model-written summary
K and S interacted for nitrogen fixation.
- Taxon
- AlfalfaMedicago sativat0
- Treatment
- K ✕ Se0
- Outcome
- N 2 ‐fixatione0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The presence of a K ✕ S interaction for N 2 ‐fixation but not for shoot weight or nodule number per core”
t0“Alfalfa”
Claim · model-written summary
Sulfur had no effect on shoot weight.
- Taxon
- alfalfaMedicago sativae0
- Treatment
- Sulfur fertilizatione0
- Outcome
- shoot weighte0
- Direction
- no effecte0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Sulfur fertilization had no effect on shoot weight but increased nodule numbers in alfalfa grown on sandy soil.”
Claim · model-written summary
Sulfur increased nodule numbers on sandy soil.
- Taxon
- alfalfaMedicago sativae0
- Treatment
- Sulfur fertilizatione0
- Outcome
- nodule numberse0
- Direction
- increasede0
- Setting
- sandy soile0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Sulfur fertilization had no effect on shoot weight but increased nodule numbers in alfalfa grown on sandy soil.”
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