Abstract
Citrus production in the southwestern U.S. is highly dependent on inputs of irrigation and N fertilizer to achieve optimum fruit yield and quality. Microsprinkler irrigation may allow for substantial increase in efficiency of N and water application. However, best management practices have not yet been developed for microsprinkler use, particularly on newly established citrus trees. Experiments were conducted during 1997–98 in central Arizona to evaluate the effects of various N rates and fertigation frequencies on growth and N partitioning in young `Newhall' navel oranges planted in Apr. 1997. Two experiments were conducted, each with factorial combinations of N rate and fertigation frequency. In one experiment, non-labeled N fertilizer was used and in the other 15 N-labeled N fertilizer. Trunk diameter, leaf N, and 15 N partitioning in the trees were measured. During 1997, neither trunk diameter or leaf N were affected by N rate or fertigation frequency. No more than 6% of the N applied was taken up by the trees, and about 50% of the fertilizer N taken up was found in the leaves. Trees grew much more rapidly in 1998. Leaf N in fertilized plots was significantly higher than in control plots, but leaf N in all trees remained above the critical level of 2.5%. Despite rapid tree growth during 1998, no more than 25% of the fertilizer N applied was taken up by the trees. About 60% of the fertilizer N taken up was found in the leaves. Results suggest that N applications are not needed during the first growing season after planting for microsprinkler-irrigated citrus trees in the Southwest. Only modest rates (68 to 136 g/tree) will be needed during the second season to maintain adequate tree reserves.
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Claims 11
Claim · model-written summary
In 1997, N rate and fertigation frequency did not affect trunk diameter.
- Taxon
- Navel Orange Trees
Citrus sinensist0 - Treatment
- N rate or fertigation frequencye0
- Outcome
- trunk diametere0
- Direction
- neithere0
- Qualifier
- During 1997e0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“During 1997, neither trunk diameter or leaf N were affected by N rate or fertigation frequency.”
t0“Navel Orange Trees”
Claim · model-written summary
In 1997, N rate and fertigation frequency did not affect leaf N.
- Taxon
- Navel Orange TreesCitrus sinensist0
- Treatment
- N rate or fertigation frequencye0
- Outcome
- leaf Ne0
- Direction
- neithere0
- Qualifier
- During 1997e0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“During 1997, neither trunk diameter or leaf N were affected by N rate or fertigation frequency.”
t0“Navel Orange Trees”
Claim · model-written summary
Trees took up no more than 6% of applied N in 1997.
- Taxon
- Navel Orange TreesCitrus sinensist0
- Outcome
- N applied was taken up by the treese0
- Direction
- No more thane0
- Value
- 6%e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“No more than 6% of the N applied was taken up by the trees”
t0“Navel Orange Trees”
Claim · model-written summary
About 50% of fertilizer N uptake was in leaves in 1997.
- Taxon
- Navel Orange TreesCitrus sinensist0
- Organ / stage
- leavese0
- Outcome
- fertilizer N taken up was found in the leavese0
- Value
- 50%e0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“about 50% of the fertilizer N taken up was found in the leaves.”
t0“Navel Orange Trees”
Claim · model-written summary
Trees grew much more rapidly in 1998.
- Taxon
- Navel Orange TreesCitrus sinensist0
- Outcome
- Trees grewe0
- Direction
- much more rapidlye0
- Qualifier
- 1998e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Trees grew much more rapidly in 1998.”
t0“Navel Orange Trees”
Claim · model-written summary
Leaf N was significantly higher in fertilized plots than controls in 1998.
- Taxon
- Navel Orange TreesCitrus sinensist0
- Treatment
- fertilized plotse0
- Outcome
- Leaf Ne0
- Direction
- highere0
- Comparator
- control plotse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Leaf N in fertilized plots was significantly higher than in control plots”
t0“Navel Orange Trees”
Claim · model-written summary
All trees retained leaf N above the 2.5% critical level in 1998.
- Taxon
- Navel Orange TreesCitrus sinensist0
- Outcome
- leaf Ne0
- Direction
- abovee0
- Value
- 2.5%e0
- Qualifier
- critical levele0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“leaf N in all trees remained above the critical level of 2.5%.”
t0“Navel Orange Trees”
Claim · model-written summary
No more than 25% of fertilizer N was taken up in 1998.
- Taxon
- Navel Orange TreesCitrus sinensist0
- Outcome
- fertilizer N applied was taken up by the treese0
- Direction
- no more thane0
- Value
- 25%e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“no more than 25% of the fertilizer N applied was taken up by the trees.”
t0“Navel Orange Trees”
Claim · model-written summary
About 60% of fertilizer N uptake was in leaves in 1998.
- Taxon
- Navel Orange TreesCitrus sinensist0
- Organ / stage
- leavese0
- Outcome
- fertilizer N taken up was found in the leavese0
- Value
- 60%e0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“About 60% of the fertilizer N taken up was found in the leaves.”
t0“Navel Orange Trees”
Claim · model-written summary
The authors recommend no N application in the first growing season.
- Outcome
- N applications are not needed during the first growing season after plantinge0
- Qualifier
- microsprinkler-irrigatede0
- Setting
- Southweste0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“N applications are not needed during the first growing season after planting for microsprinkler-irrigated citrus trees in the Southwest.”
Claim · model-written summary
The authors recommend modest N rates of 68 to 136 g/tree in the second season.
- Taxon
- Navel Orange TreesCitrus sinensist0
- Outcome
- modest ratese0
- Value
- 68 to 136 g/treee0
- Qualifier
- during the second season to maintain adequate tree reservese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Only modest rates (68 to 136 g/tree) will be needed during the second season to maintain adequate tree reserves.”
t0“Navel Orange Trees”
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