Optimizing nitrogen management for microsprinkler irrigated citrus in central Arizona

Persistent Link:
http://hdl.handle.net/10150/284169
Title:
Optimizing nitrogen management for microsprinkler irrigated citrus in central Arizona
Author:
Weinert, Tom L.
Issue Date:
2000
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
A High N fertilizers citrus rates may contribute to a rise in the appearance of groundwater NO₃ around groves in central Arizona. Nitrogen fertilizer recommendations need to be reevaluated for citrus due to recent changes in fertilizers, irrigation technology, and increasing groundwater NO₃. Studies were initiated to optimize fertilizer N management for microsprinkler-irrigated citrus. Navel oranges were planted in Jan. 1997 with varying N rates and frequency of liquid urea NH₄-NO₃ or granular controlled-release fertilizers (CRFs) in order to determine tree response, N partitioning, N balance, and residual soil N. Trees grew slowly in 1997 with no more than 6% of the fertilizer N taken up by trees, while < 94% of fertilizer N remained in the top 0.9 m of soil. Leaf N was higher in fertilized plots than in controls as trees grew rapidly in 1998 with < 25% of the fertilizer N taken up by the trees. The soil contained low NO₃ concentrations, suggesting most of the fertilizer N was leached. Nitrogen is not needed during the first season after planting and rates of 68 to 136 g N tree⁻¹ applied in monthly intervals during the second season maintain adequate tree growth and N reserves. Application of CRFs resulted in little tree response during the two year study. Soil inorganic N was highest in the surface 0.6 m in 1997. In 1998, ammonium sulfate treatments resulted in higher NO₃ leaching than plots that received CRFs. Eight-year old 'Redblush' grapefruit trees were treated with two N rates and three fertigation frequencies in a factorial arrangement. There no differences in trunk diameter, or fruit quality on trees between 1996 and 1998. Leaf N content was > 18 mg kg⁻¹ in all plots in 1996. Leaf N declined in Aug. 1997 and control plots had lower leaf N than the other treatments. Yields tended to be the greatest at high N rates with monthly fertigation. Soil N levels were proportional to fertilizer N inputs. In 1998, the high N treatment at weekly and monthly frequencies increased leaf N compared to the other treatments. Results suggest that N rates of 272 to 408 g tree⁻¹ year⁻¹ at weekly or monthly frequencies may be optimal for desert-grown mature grapefruit.
Type:
text; Dissertation-Reproduction (electronic)
Keywords:
Agriculture, Agronomy.; Agriculture, Soil Science.
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Graduate College; Soil, Water and Environmental Science
Degree Grantor:
University of Arizona
Advisor:
Thompson, Thomas L.

Full metadata record

DC FieldValue Language
dc.language.isoen_USen_US
dc.titleOptimizing nitrogen management for microsprinkler irrigated citrus in central Arizonaen_US
dc.creatorWeinert, Tom L.en_US
dc.contributor.authorWeinert, Tom L.en_US
dc.date.issued2000en_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractA High N fertilizers citrus rates may contribute to a rise in the appearance of groundwater NO₃ around groves in central Arizona. Nitrogen fertilizer recommendations need to be reevaluated for citrus due to recent changes in fertilizers, irrigation technology, and increasing groundwater NO₃. Studies were initiated to optimize fertilizer N management for microsprinkler-irrigated citrus. Navel oranges were planted in Jan. 1997 with varying N rates and frequency of liquid urea NH₄-NO₃ or granular controlled-release fertilizers (CRFs) in order to determine tree response, N partitioning, N balance, and residual soil N. Trees grew slowly in 1997 with no more than 6% of the fertilizer N taken up by trees, while < 94% of fertilizer N remained in the top 0.9 m of soil. Leaf N was higher in fertilized plots than in controls as trees grew rapidly in 1998 with < 25% of the fertilizer N taken up by the trees. The soil contained low NO₃ concentrations, suggesting most of the fertilizer N was leached. Nitrogen is not needed during the first season after planting and rates of 68 to 136 g N tree⁻¹ applied in monthly intervals during the second season maintain adequate tree growth and N reserves. Application of CRFs resulted in little tree response during the two year study. Soil inorganic N was highest in the surface 0.6 m in 1997. In 1998, ammonium sulfate treatments resulted in higher NO₃ leaching than plots that received CRFs. Eight-year old 'Redblush' grapefruit trees were treated with two N rates and three fertigation frequencies in a factorial arrangement. There no differences in trunk diameter, or fruit quality on trees between 1996 and 1998. Leaf N content was > 18 mg kg⁻¹ in all plots in 1996. Leaf N declined in Aug. 1997 and control plots had lower leaf N than the other treatments. Yields tended to be the greatest at high N rates with monthly fertigation. Soil N levels were proportional to fertilizer N inputs. In 1998, the high N treatment at weekly and monthly frequencies increased leaf N compared to the other treatments. Results suggest that N rates of 272 to 408 g tree⁻¹ year⁻¹ at weekly or monthly frequencies may be optimal for desert-grown mature grapefruit.en_US
dc.typetexten_US
dc.typeDissertation-Reproduction (electronic)en_US
dc.subjectAgriculture, Agronomy.en_US
dc.subjectAgriculture, Soil Science.en_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.disciplineSoil, Water and Environmental Scienceen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorThompson, Thomas L.en_US
dc.identifier.proquest9972118en_US
dc.identifier.bibrecord.b40640619en_US
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