Abstract
Decades of heavy phosphorus (P) fertilization of vegetable crops in the Salinas Valley of California has increased soil test P (STP) levels, with bicarbonate-extractable P (P bc ) values >50 mg·kg –1 now common. To evaluate the response of lettuce ( Lactuca sativa L.) to P fertilization in fields with elevated STP levels, 12 trials were conducted in commercial fields during 2002–03. Initial P bc at the trial sites varied from 53 to 171 mg·kg –1 . In each trial, four replicate plots receiving the growers' P application were compared with paired plots in which no P was applied. Leaf P was monitored at midseason and at harvest. At harvest, mean whole and marketable plant mass and percent of marketable plants were recorded. A significant increase in lettuce yield with P fertilization was achieved at only one trial site, a spring planting with 54 mg·kg –1 P bc ; at all other sites, including three with P bc <60 mg·kg –1 , P application resulted in no significant yield increase. Phosphorus application resulted in only a marginal increase in plant P uptake; in the nonresponsive fields leaf P concentration of nonfertilized plots was in excess of established sufficiency levels. In a laboratory study, the correlation of P bc to bioavailable P (P ba ) was evaluated using 30 representative Salinas Valley soils; P bc varied among these soils from 15 to 177 mg·kg –1 . P ba was estimated by P adsorption on an anion resin membrane during a 16 hour incubation. The effect of temperature on P bioavailability in six of these soils was estimated by conducting the P ba incubation at 5, 15, and 25 °C. P ba was highly correlated with P bc ( r = 0.89), and increased about 40% across soils with each 10 °C increase in soil temperature. Therefore, P bc was determined to be an accurate reflection of bioavailable P in these soils, although the addition of a temperature correction factor in setting threshold values is desirable.
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Claims 8
Claim · model-written summary
P fertilization gave a significant increase in lettuce yield at only one trial site, a spring planting.
- Taxon
- lettuce
Lactuca sativae0 - Treatment
- P fertilizatione1
- Outcome
- lettuce yielde1
- Direction
- significant increasee1
- Qualifier
- at only one trial sitee1
- Comparator
- paired plots in which no P was appliede7
- Setting
- spring plantinge1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“To evaluate the response of lettuce ( Lactuca sativa L.) to P fertilization in fields with elevated STP levels, 12 trials were conducted in commercial fields”
e1“A significant increase in lettuce yield with P fertilization was achieved at only one trial site, a spring planting”
e7“paired plots in which no P was applied”
Claim · model-written summary
P application gave no significant lettuce yield increase at the other trial sites, including three with low P bc.
- Taxon
- lettuceLactuca sativae0
- Treatment
- P applicatione2
- Outcome
- yielde2
- Direction
- no significant yield increasee2
- Comparator
- paired plots in which no P was appliede7
- Setting
- commercial fieldse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“To evaluate the response of lettuce ( Lactuca sativa L.) to P fertilization in fields with elevated STP levels, 12 trials were conducted in commercial fields”
e2“P application resulted in no significant yield increase”
e7“paired plots in which no P was applied”
Claim · model-written summary
Phosphorus application gave only a marginal increase in lettuce plant P uptake.
- Taxon
- lettuceLactuca sativae0
- Treatment
- Phosphorus applicatione3
- Outcome
- plant P uptakee3
- Direction
- marginal increasee3
- Comparator
- paired plots in which no P was appliede7
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“To evaluate the response of lettuce ( Lactuca sativa L.) to P fertilization in fields with elevated STP levels, 12 trials were conducted in commercial fields”
e3“Phosphorus application resulted in only a marginal increase in plant P uptake”
e7“paired plots in which no P was applied”
Claim · model-written summary
In nonresponsive fields, leaf P concentration of nonfertilized lettuce plots was above established sufficiency levels.
- Taxon
- lettuceLactuca sativae0
- Organ / stage
- leafe4
- Outcome
- leaf P concentratione4
- Qualifier
- in excess of established sufficiency levelse4
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“To evaluate the response of lettuce ( Lactuca sativa L.) to P fertilization in fields with elevated STP levels, 12 trials were conducted in commercial fields”
e4“in the nonresponsive fields leaf P concentration of nonfertilized plots was in excess of established sufficiency levels”
Claim · model-written summary
Bicarbonate-extractable P (P bc) was highly correlated with bioavailable P (P ba) across 30 Salinas Valley soils (r = 0.89).
- Taxon
- lettuceLactuca sativae0
- Outcome
- P bae5
- Direction
- highly correlatede5
- Value
- r = 0.89e5
- Comparator
- P bce5
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“To evaluate the response of lettuce ( Lactuca sativa L.) to P fertilization in fields with elevated STP levels, 12 trials were conducted in commercial fields”
e5“P ba was highly correlated with P bc ( r = 0.89), and increased about 40% across soils with each 10 °C increase in soil temperature”
Claim · model-written summary
Bioavailable P (P ba) increased about 40% with each 10 °C increase in soil temperature.
- Taxon
- lettuceLactuca sativae0
- Treatment
- soil temperaturee5
- Outcome
- P bae5
- Direction
- increasede5
- Value
- about 40%e5
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“To evaluate the response of lettuce ( Lactuca sativa L.) to P fertilization in fields with elevated STP levels, 12 trials were conducted in commercial fields”
e5“P ba was highly correlated with P bc ( r = 0.89), and increased about 40% across soils with each 10 °C increase in soil temperature”
Claim · model-written summary
P bc was an accurate reflection of bioavailable P in the studied soils.
- Taxon
- lettuceLactuca sativae0
- Outcome
- accurate reflection of bioavailable Pe6
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“To evaluate the response of lettuce ( Lactuca sativa L.) to P fertilization in fields with elevated STP levels, 12 trials were conducted in commercial fields”
e6“P bc was determined to be an accurate reflection of bioavailable P in these soils, although the addition of a temperature correction factor in setting threshold values is desirable”
Claim · model-written summary
A temperature correction factor should be added when setting P bc threshold values.
- Taxon
- lettuceLactuca sativae0
- Outcome
- addition of a temperature correction factor in setting threshold valuese6
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“To evaluate the response of lettuce ( Lactuca sativa L.) to P fertilization in fields with elevated STP levels, 12 trials were conducted in commercial fields”
e6“P bc was determined to be an accurate reflection of bioavailable P in these soils, although the addition of a temperature correction factor in setting threshold values is desirable”
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