Abstract
Abstract Long‐term irrigated alfalfa ( Medicago sativa L.) field experiments at two locations in Colorado [Keith clay loam (Aridic Argiustolls) and Ravola loam (Typic Torrifluvents)] were established to (i) determine the magnitude and frequency of P and K fertilization required to maintain initial soil tests, and (ii) evaluate the residual value of soil and fertilizer P and K. Ten P and K treatments (3 annual, 1 triennial, and 1 initial application) were used. Alfalfa yield, P and K uptake, NaHCO 3 ‐extractable P, and NH 4 C 2 H 3 O 2 ‐exchangeable K were measured over 6 production years. Soil test P declined in both soils to levels where significant yield responses to fertilizer P were expected, but none were observed. Organic P mineralization and/or an extensive mycorrhizal association were suggested as contributing factors to P availability. Generally, application of 50 kg P ha −1 maintained initial NaHCO 3 ‐P at both locations, while soil P declined below the initial level for all other P rates. Phosphorus uptake was significantly increased by P fertilization on the Keith soil, due to lower NaHCO 3 ‐P level, but not on the Ravola soil. Soil test K remained at high levels in both soils and no yield responses to fertilizer K were observed. Application of 380 and 5 kg K ha −1 were calculated to maintain initial NH 4 C 2 H 3 O 2 ‐K in the Keith and Ravola soils, respectively. The low maintenance requirement of the Ravola soil was due apparently to a high nonexchangeable K release rate which buffered exchangeable K near 100 mg kg −1 . Potassium uptake was significantly increased by K fertilization in the Ravola soil, due to a lower exchangeable K level, but not in the Keith soil. The results indicate very large P and K reserves exist in both soils and unless improved forage quality influences the economic benefit from P and K fertilizer application, fertilization of these soils would not be recommended.
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Claims 16
Claim · model-written summary
Soil test P declined in both soils in the alfalfa experiments.
- Taxon
- alfalfa
Medicago sativae0 - Outcome
- Soil test Pe1
- Direction
- declinede1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“alfalfa ( Medicago sativa L.)”
e1“Soil test P declined in both soils”
Claim · model-written summary
Despite declining soil test P, no significant yield response to fertilizer P was observed in alfalfa although one was expected.
- Taxon
- alfalfaMedicago sativae0
- Treatment
- fertilizer Pe1
- Outcome
- yield responsese1
- Direction
- none were observede1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“alfalfa ( Medicago sativa L.)”
e1“significant yield responses to fertilizer P were expected, but none were observed”
Claim · model-written summary
Organic P mineralization and/or an extensive mycorrhizal association were suggested as contributing to P availability.
- Taxon
- alfalfaMedicago sativae0
- Interactor
- mycorrhizal associatione1symbiont
- Outcome
- P availabilitye1
- Qualifier
- Organic P mineralization and/or an extensive mycorrhizal associatione1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“alfalfa ( Medicago sativa L.)”
e1“Organic P mineralization and/or an extensive mycorrhizal association were suggested as contributing factors to P availability”
Claim · model-written summary
Application of 50 kg P per ha maintained the initial NaHCO3-extractable P at both locations.
- Taxon
- alfalfaMedicago sativae0
- Treatment
- application of 50 kg P ha −1e1
- Outcome
- initial NaHCO 3e1
- Direction
- maintainede1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“alfalfa ( Medicago sativa L.)”
e1“Generally, application of 50 kg P ha −1 maintained initial NaHCO 3”
Claim · model-written summary
Soil P declined below the initial level for all P rates other than 50 kg P per ha.
- Taxon
- alfalfaMedicago sativae0
- Treatment
- all other P ratese1
- Outcome
- soil Pe1
- Direction
- declinede1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“alfalfa ( Medicago sativa L.)”
e1“soil P declined below the initial level for all other P rates”
Claim · model-written summary
Phosphorus uptake by alfalfa was significantly increased by P fertilization on the Keith soil.
- Taxon
- alfalfaMedicago sativae0
- Treatment
- P fertilizatione1
- Outcome
- Phosphorus uptakee1
- Direction
- increasede1
- Setting
- Keith soile1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“alfalfa ( Medicago sativa L.)”
e1“Phosphorus uptake was significantly increased by P fertilization on the Keith soil”
Claim · model-written summary
Phosphorus uptake by alfalfa was not increased by P fertilization on the Ravola soil.
- Taxon
- alfalfaMedicago sativae0
- Treatment
- P fertilizatione1
- Outcome
- Phosphorus uptakee1
- Direction
- no_changeinferrede2
- Setting
- Ravola soile2
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“alfalfa ( Medicago sativa L.)”
e1“Phosphorus uptake was significantly increased by P fertilization on the Keith soil”
e2“but not on the Ravola soil”
Claim · model-written summary
Soil test K remained at high levels in both soils.
- Taxon
- alfalfaMedicago sativae0
- Outcome
- Soil test Ke1
- Direction
- remained at high levelse1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“alfalfa ( Medicago sativa L.)”
e1“Soil test K remained at high levels in both soils”
Claim · model-written summary
No yield responses of alfalfa to fertilizer K were observed.
- Taxon
- alfalfaMedicago sativae0
- Treatment
- fertilizer Ke1
- Outcome
- yield responsese1
- Direction
- no yield responsese1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“alfalfa ( Medicago sativa L.)”
e1“no yield responses to fertilizer K were observed”
Claim · model-written summary
Application of 380 kg K per ha was calculated to maintain initial exchangeable K in the Keith soil.
- Taxon
- alfalfaMedicago sativae0
- Outcome
- maintain initial NH 4 C 2 H 3 O 2e1
- Value
- 380e1
- Setting
- Keithe2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“alfalfa ( Medicago sativa L.)”
e1“Application of 380 and 5 kg K ha −1 were calculated to maintain initial NH 4 C 2 H 3 O 2”
e2“in the Keith and Ravola soils, respectively”
Claim · model-written summary
Application of 5 kg K per ha was calculated to maintain initial exchangeable K in the Ravola soil.
- Taxon
- alfalfaMedicago sativae0
- Outcome
- maintain initial NH 4 C 2 H 3 O 2e1
- Value
- 5 kg K ha −1e1
- Setting
- Ravolae2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“alfalfa ( Medicago sativa L.)”
e1“Application of 380 and 5 kg K ha −1 were calculated to maintain initial NH 4 C 2 H 3 O 2”
e2“in the Keith and Ravola soils, respectively”
Claim · model-written summary
The low K maintenance requirement of the Ravola soil was apparently due to a high nonexchangeable K release rate that buffered exchangeable K near 100 mg per kg.
- Taxon
- alfalfaMedicago sativae0
- Compound
- nonexchangeable Ke1
- Outcome
- low maintenance requiremente1
- Setting
- Ravola soile1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“alfalfa ( Medicago sativa L.)”
e1“The low maintenance requirement of the Ravola soil was due apparently to a high nonexchangeable K release rate which buffered exchangeable K near 100 mg kg −1”
Claim · model-written summary
Potassium uptake by alfalfa was significantly increased by K fertilization in the Ravola soil.
- Taxon
- alfalfaMedicago sativae0
- Treatment
- K fertilizatione1
- Outcome
- Potassium uptakee1
- Direction
- increasede1
- Setting
- Ravola soile1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“alfalfa ( Medicago sativa L.)”
e1“Potassium uptake was significantly increased by K fertilization in the Ravola soil”
Claim · model-written summary
Potassium uptake by alfalfa was not increased by K fertilization in the Keith soil.
- Taxon
- alfalfaMedicago sativae0
- Treatment
- K fertilizatione1
- Outcome
- Potassium uptakee1
- Direction
- no_changeinferrede2
- Setting
- Keith soile2
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“alfalfa ( Medicago sativa L.)”
e1“Potassium uptake was significantly increased by K fertilization in the Ravola soil”
e2“but not in the Keith soil”
Claim · model-written summary
Very large P and K reserves exist in both soils.
- Taxon
- alfalfaMedicago sativae0
- Outcome
- P and K reservese1
- Direction
- very largee1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“alfalfa ( Medicago sativa L.)”
e1“very large P and K reserves exist in both soils”
Claim · model-written summary
Unless improved forage quality changes the economic benefit, P and K fertilization of these soils is not recommended.
- Taxon
- alfalfaMedicago sativae0
- Outcome
- fertilization of these soils would not be recommendede1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“alfalfa ( Medicago sativa L.)”
e1“fertilization of these soils would not be recommended”
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See all 184 papers →Claims are grouped by organism, treatment and what was measured or targeted. A paper counts as positive when any of its claims in the group is positive.