Abstract
Arizona is ranked third in the nation in fresh vegetable production, however, overfertilization and overirrigation have been common practices used to maintain adequate yields and crop quality. Concern for groundwater contamination, water availability and costs have made it necessary to increase water and nitrogen (N) use efficiency. The objectives of this research were: 1. optimize water and N inputs applied through a subsurface trickle irrigation system to leaf lettuce, spinach and collards. 2. evaluate water and N effects on midrib nitrate (NO₃-N) concentration as a tool for monitoring plant N status throughout the growing season. A field experiment was conducted during fall-winter 1992-93 at the University of Arizona Maricopa Agricultural Center, Maricopa, AZ. A factorial design with three target soil water potentials and four N levels was used to determine response surfaces for yield, net return, and water and N use efficiency. Tensiometers were used as an aid to schedule irrigations, and midrib NO₃-N concentrations at critical growth stages were used to monitor N status. Spinach and collard midrib N03-N concentrations showed a high response to N rates throughout the growing season. Leaf lettuce midrib NO₃-N was responsive to treatments at the beginning and end of its growing season. Some yield and efficiency parameters were significantly affected by the irrigation treatments with an effect generally negative. Nitrogen had tremendous influence on them, perhaps due to the wet seasonal conditions which may have promoted nitrate leaching and denitrification. For leaf lettuce, maximum fresh weight was estimated to be 60861 kg ha⁻¹ at -4.3 kPa soil water potential and 367 kg N ha⁻¹. Maximum net return was estimated to be $18,089 ha⁻¹ when average soil water potential was -6.0 kPa and applied N was 355 kg N ha⁻¹. Estimated maximum nitrogen use efficiency (NUE) was 0.8 at -10.3 kPa soil water potential, and 2 kg N ha⁻¹. It was not possible to determine a maximum value for applied water use efficiency (A WUE). For spinach, maximum yield was estimated to be 33948 kg ha⁻¹ at -8.0 kPa soil water potential and 400 kg N ha⁻¹. Estimated net return was $18,573 ha⁻¹ when soil water potential and applied N rate were -8.2 kPa and 398 kg N ha⁻¹ respectively. For NUE, the estimated maximum was 0.7 at -11.2 kPa and -42 kg N ha⁻¹. It was not possible to determine a maximum for A WUE. For collards, 49466 kg ha-1 was the estimated maximum yield when soil water potential was -9.0 kPa and applied N was 396 kg N ha⁻¹. Maximum net return was estimated to be $15,561 ha⁻¹ at -9.3 kPa and 394 kg N ha⁻¹. It was not possible to determine maximums for A WUE or NUE. The relationship between midrib NO₃-N concentrations and chlorophyll meter readings was poor, and prediction of plant NO₃-N status was not as reliable as expected.
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Claims 17
Claim · model-written summary
Spinach and collard midrib NO3-N concentrations responded strongly to N rates throughout the growing season.
Not reportedDirection
Verbatim
e1“Spinach and collard midrib N03-N concentrations showed a high response to N rates throughout the growing season”
Claim · model-written summary
Leaf lettuce midrib NO3-N was responsive to treatments at the beginning and end of its growing season.
Not reportedDirection
Verbatim
e1“Leaf lettuce midrib NO₃-N was responsive to treatments at the beginning and end of its growing season”
Claim · model-written summary
Irrigation treatments significantly affected some yield and efficiency parameters, with an effect generally negative.
- Taxon
- leafy winter vegetablest0
- Treatment
- irrigation treatmentse1
- Outcome
- yield and efficiency parameterse1
- Direction
- generally negativee1
Not reportedComparator
Verbatim
t0“leafy winter vegetables”
e1“Some yield and efficiency parameters were significantly affected by the irrigation treatments with an effect generally negative”
Claim · model-written summary
Nitrogen had a tremendous influence on yield and efficiency parameters.
Not reportedDirection
Verbatim
t0“leafy winter vegetables”
e1“Nitrogen had tremendous influence on them”
e2“Some yield and efficiency parameters were significantly affected by the irrigation treatments”
Claim · model-written summary
For leaf lettuce, maximum fresh weight was estimated at 60861 kg ha⁻¹ at -4.3 kPa soil water potential and 367 kg N ha⁻¹.
Verbatim
e0“For leaf lettuce”
e1“For leaf lettuce, maximum fresh weight was estimated to be 60861 kg ha⁻¹ at -4.3 kPa soil water potential and 367 kg N ha⁻¹”
Claim · model-written summary
For leaf lettuce, maximum net return was estimated at $18,089 ha⁻¹ when average soil water potential was -6.0 kPa and applied N was 355 kg N ha⁻¹.
Verbatim
e0“For leaf lettuce”
e1“Maximum net return was estimated to be $18,089 ha⁻¹ when average soil water potential was -6.0 kPa and applied N was 355 kg N ha⁻¹”
Claim · model-written summary
For leaf lettuce, estimated maximum nitrogen use efficiency was 0.8 at -10.3 kPa soil water potential and 2 kg N ha⁻¹.
Verbatim
e0“For leaf lettuce”
e1“Estimated maximum nitrogen use efficiency (NUE) was 0.8 at -10.3 kPa soil water potential, and 2 kg N ha⁻¹”
Claim · model-written summary
For leaf lettuce, a maximum applied water use efficiency could not be determined.
Verbatim
e0“For leaf lettuce”
e1“It was not possible to determine a maximum value for applied water use efficiency (A WUE)”
Claim · model-written summary
For spinach, estimated maximum yield was 33948 kg ha⁻¹ at -8.0 kPa soil water potential and 400 kg N ha⁻¹.
- Taxon
- spinach
Spinacia oleraceae1 - Outcome
- maximum yielde1
- Value
- 33948 kg ha⁻¹e1
- Qualifier
- -8.0 kPa soil water potentiale1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“For spinach, maximum yield was estimated to be 33948 kg ha⁻¹ at -8.0 kPa soil water potential and 400 kg N ha⁻¹”
Claim · model-written summary
For spinach, estimated net return was $18,573 ha⁻¹ when soil water potential and applied N rate were -8.2 kPa and 398 kg N ha⁻¹.
- Taxon
- spinachSpinacia oleraceae0
- Outcome
- net returne1
- Value
- $18,573 ha⁻¹e1
- Qualifier
- soil water potential and applied N rate were -8.2 kPae1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“For spinach”
e1“Estimated net return was $18,573 ha⁻¹ when soil water potential and applied N rate were -8.2 kPa and 398 kg N ha⁻¹ respectively”
Claim · model-written summary
For spinach, estimated maximum nitrogen use efficiency was 0.7 at -11.2 kPa and -42 kg N ha⁻¹.
- Taxon
- spinachSpinacia oleraceae0
- Outcome
- NUEe1
- Value
- 0.7e1
- Qualifier
- -11.2 kPae1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“For spinach”
e1“For NUE, the estimated maximum was 0.7 at -11.2 kPa and -42 kg N ha⁻¹”
Claim · model-written summary
For spinach, a maximum applied water use efficiency could not be determined.
- Taxon
- spinachSpinacia oleraceae0
- Outcome
- maximum for A WUEe1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“For spinach”
e1“It was not possible to determine a maximum for A WUE”
Claim · model-written summary
For collards, estimated maximum yield was 49466 kg ha-1 when soil water potential was -9.0 kPa and applied N was 396 kg N ha⁻¹.
- Taxon
- collards
Brassica oleracea var. viridise1 - Outcome
- maximum yielde1
- Value
- 49466 kg ha-1e1
- Qualifier
- soil water potential was -9.0 kPae1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“For collards, 49466 kg ha-1 was the estimated maximum yield when soil water potential was -9.0 kPa and applied N was 396 kg N ha⁻¹”
Claim · model-written summary
For collards, estimated maximum net return was $15,561 ha⁻¹ at -9.3 kPa and 394 kg N ha⁻¹.
- Taxon
- collardsBrassica oleracea var. viridise0
- Outcome
- net returne1
- Value
- $15,561 ha⁻¹e1
- Qualifier
- -9.3 kPae1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“For collards”
e1“Maximum net return was estimated to be $15,561 ha⁻¹ at -9.3 kPa and 394 kg N ha⁻¹”
Claim · model-written summary
For collards, a maximum applied water use efficiency or nitrogen use efficiency could not be determined.
- Taxon
- collardsBrassica oleracea var. viridise0
- Outcome
- maximums for A WUE or NUEe1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“For collards”
e1“It was not possible to determine maximums for A WUE or NUE”
Claim · model-written summary
The relationship between midrib NO₃-N concentrations and chlorophyll meter readings was poor.
- Taxon
- leafy winter vegetablest0
- Outcome
- relationship between midrib NO₃-N concentrations and chlorophyll meter readingse1
- Comparator
- chlorophyll meter readingse1
Not reportedDirection
Verbatim
t0“leafy winter vegetables”
e1“The relationship between midrib NO₃-N concentrations and chlorophyll meter readings was poor”
Claim · model-written summary
Prediction of plant NO₃-N status from chlorophyll meter readings was not as reliable as expected.
Verbatim
t0“leafy winter vegetables”
e1“prediction of plant NO₃-N status was not as reliable as expected”