DENITRIFICATION LOSSES IN CROPPED SOILS

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Mar 21, 1997 - (NO3-) is chemically reduced to gaseous nitrous oxide (N20) and molecular N2. ... temperature (24 ±2°C), denitrification rates were five to 50 times higher .... pressure buildup inside the chamber may inhibit further diffusion of gases out of the soil ...... 1.0. Log(l+den. rate in g N20-N/ha/d) Ambient incubation.
DENITRIFICATION LOSSES IN CROPPED SOILS WITH SUBSURFACE DRIP IRRIGATION by Uriel Figueroa-Viramontes

Dissertation Submitted to the Faculty of the

DEPARTMENT OF SOIL, WATER AND ENVIRONMENTAL SCIENCE In Partial Fulfillment of the Requirements For the Degree of

DOCTOR OF PHILOSOPHY In the Graduate College THE UNIVERSITY OF ARIZONA

1999

2 THE UNIVERSITY OF ARIZONA GRADUATE COLLEGE As members of the Final Examination Committee, we certify that we have read the dissertation prepared byUriel Figueroa-Viramontes entitled Denitrification losses in cropped soils with subsurface drip irrigation.

and recommend that it be accepted as fulfilling the dissertation requirement for the Degree of Doctor of Philosophy

)/S/9

Date

Date

/— Date Date

Steven P. McLaughlin

Final approval and acceptance of this dissertation is contingent upon the candidate's submission of the final copy of the dissertation to the Graduate College. I hereby certify that I have read this dissertation prepared under my direction and recommend that it be accepted as fulfilling the dissertation requirement.

Dissertation Director D

ornas L. Thompson

Date

3

STATEMENT BY AUTHOR This dissertation has been submitted in partial fulfillment of requirements for an advanced degree at The University of Arizona and is deposited in the University Library to be made available to borrowers under rules of the Library.

Brief quotations from this dissertation are allowable without special permission, provided that accurate acknowledgment of source is made. Requests for permission for extended quotation or reproduction of this manuscript in whole or in part may be granted by the head of the major department or the Dean of the Graduate College when in his or her judgement the proposed use of the material is in the interests of scholarship. In all other instances, however, permission must be obtained from the author. Signed:

4 ACKNOWLEDGMENTS Thanks to Dr. Thomas L. Thompson, my advisor and dissertation director, for his guidance to complete my degree. I really appreciate his way of teaching how to do the field work by example. Thanks to Dr. Janick F. Artiola, Dr, David M. Hendricks, Dr. James W. O'Leary, and Dr. Steven P. McLaughlin for participating as members of my Committee. I appreciate the suggestions to the manuscript. I also learned a lot from their courses. Thanks to all the staff and students in the Soil Fertility Laboratory during the four years that I spent here. Special thanks to Scott A. White for his help in many things in the field and in the lab. Thanks the staff in the main office of the SWES Department for their help. Thanks to CONACYT and INIFAP in México for the scholarship that supported my academic and living expenses.

5 DEDICATION

To my wife Koris, my daughter Mariel, and my son Alejandro. To the memory of my Parents.

6 TABLE OF CONTENTS Page LIST OF ILLUSTRATIONS LIST OF TABLES ABSTRACT 1. INTRODUCTION

8 10 12 14

2. REVIEW OF LITERATURE the Process of Denitrification Methods to Evaluate Denitrifi cation in Soils ' 5N-Isotope Techniques Acetylene Inhibition Denitrifying Enzyme Activity (DEA) Main Factors Controlling Denitrification in Soils Organic Carbon Inorganic Nitrogen Oxygen and Soil Aeration Temperature Denitrification Rate in Different Irrigation Methods

17 17 19 19 20 22 23 23 25 27 28 29

3. MATERIALS AND METHODS Cauliflower Experiments Sweet Corn Experiment Evaluation of Denitrifi cation and Related Measurements Field Sampling and Core Incubation GC System Description Calculation of Denitrification Rate Cores with Nitrogen and Carbon Amendments Denitrifying Enzyme Activity Total and Soluble Organic Carbon Statistical Analysis

32 33 38 41 41 42 46 48 49 50 51

4. RESULTS AND DISCUSSION Cauliflower 1996-97 Denitrification Rate Yield Nitrogen Balance

52 52 52 59 60



7

TABLE OF CONTENTS Continued Page Cauliflower 1997-98 Denitrificati on Rate Carbon and Nitrogen Amendments Organic Carbon Denitrifying Enzyme Activity Yield Nitrogen Balance

62 63 70 74 75 77 77

Sweet corn 1997

81 81 88 89 91 93

Denitrification Rate

Organic Carbon Denitrifying Enzyme Activity Yield Nitrogen Balance 5. CONCLUSIONS

96

APPENDIX

98

REFERENCES

123

8 LIST OF ILLUSTRATIONS Figure

Page Oxidative electron transport in bacterial respiration showing the aerobic and the denitrification pathways

18

Maximum and minimum temperatures and precipitation during the 199697 cauliflower growing season

35

Maximum and minimum temperatures and precipitation during the 199697 cauliflower growing season

36

Maximum and minimum temperatures and precipitation during the 1997 sweet corn growing season

39

Diagram of the two Porapak columns and the two positions of 4-port valve inside the GC oven

45

4-1

Denitrification rates during the 1996-97 cauliflower growing season

54

4-2

Relationship between WFPS and denitrification rate in cores taken 24 hr after fertilization. Cauliflower 1996-97

56

Relationship between nitrate and denitrification rate in cores taken 24 hr after fertilization. Cauliflower 1996-97

57

Denitrification losses of N in control and fertilized plots. Cauliflower 1996-97

61

Denitrification rate evaluated at ambient and room temperature. Cauliflower 1997-98

65

Relationship between WFPS and denitrification rate in cores taken 24 hr after fertilization. Cauliflower 1997-98

67

Regression analysis of denitrification rate evaluated at ambient versus room temperature. Cauliflower 1997-98

69

2-1

3-1 3-2 3-3 3-4

4-3

4-4

4-5

4-6

4-7

4-8

Relationship between nitrate and denitrification rate in cores taken 24 hr after fertilization. Cauliflower 1997-98

71

9 LIST OF ILLUSTRATIONS Continued

Page

Figure Denitrification rate in soil cores amended with N and C. Cauliflower 1997-98

72

Denitrifying enzyme activity at the beginning and end of the 1997-98 cauliflower season

76

Denitrification losses of N in control and fertilized plots. Cauliflower 1997-98

80

4-12

Denitrification rates during the 1997 sweet corn season

83

4-13

Relationship between WFPS and denitrification rate in cores taken 24 hr after fertilization for sweet corn, 1997

85

Relationship between nitrate and denitrification rate in cores taken 24 hr after fertilization for sweet corn, 1997

87

Denitrifying enzyme activity at the beginning and end of the 1997 sweet corn season

90

Residual ammonium and nitrate at the end of the 1997 sweet corn season

92

Cumulative denitrification N losses during the 1997 sweet corn season

95

4-9

4-10

4-11

4-14

4-15

4-16

4-17

10 LIST OF TABLES Page

Tables 2-1

Reduction reactions involved in denitrification

17

3-1

Target and average SWT, water applied, and rainfall in the 1996-98 cauliflower growing seasons

33

3-2

Schedule of N fertilizer applications for Cauliflower

34

3-3

Particle size distribution, bulk density, organic C, and N for the Casa Grande soil, 0-30 cm of depth

37

Target and average SWT, water applied, and rainfall in the 1997 sweet corn growing season

40

3-5

Schedule of N fertilizer applications according to crop growth stage

40

3-6

Particle size distribution, bulk density, organic C, and N for the Gila soil

41

Sampling dates for the evaluation of denitrification and extreme temperatures during the soil incubation in cauliflower 1996-97 and 1997-98 seasons

43

Sampling dates for the evaluation of denitrification and extreme temperatures during the soil incubation in sweet corn 1997

44

3-9

Concentration of N and C in solutions applied to soil cores

49

4-1

Distribution and coefficients of variation in the different sampling dates in cauliflower 1996-97

53

Total biomass, marketable yield , and head diameter in cauliflower 1996-97

59

4-3

Nitrogen balance and unaccounted for N in cauliflower 1996-97

60

4-4

Frequency distribution, coefficients ofvariation, and statistical significance in the cauliflower 1997-98 experiment

64

3-4

3-7

3-8

4-2

11 LIST OF TABLES Continued Page

Tables Concentrations of total (TOC) and soluble (SOC) organic carbon. Cauliflower 1997-98

74

4-6

Marketable yield and above ground biomass. Cauliflower 1997-98

78

4-7

Nitrogen balance and unaccounted for N. Cauliflower 1997-98

78

4-8

Frequency distribution, coefficients ofvariation, and statistical significance in the sweet corn experiment, 1997

82

Concentrations of total (TOC) and soluble (SOC) organic carbon. Sweet corn 1997

89

4-10

Total biomass, marketable yield, and plant height in sweet corn, 1997

93

4-11

Nitrogen balance and unaccounted N for sweet corn, 1997

94

A-1

Corrected tensiometer readings. Cauliflower 1996-97

99

A-2

Corrected tensiometer readings. Cauliflower 1997-98

99

A-3

Corrected tensiometer readings. Sweet corn 1997

A-4

Meter readings and calculation of water applied. Cauliflower 1996-97 . . . . 101

A-5

Meter readings and calculation of water applied. Cauliflower 1997-98

101

A-6

Meter readings and calculation of water applied. Sweet corn 1997

102

A-7

Denitrification rate and related data. Cauliflower 1996-97

103

A-8

Denitrification rate and related data. Cauliflower 1997-98

107

A-9

Denitrification rate and related data. Sweet corn 1997

115

A-10

Cumulative N lost by denitrification. Cauliflower 1996-97

120

A-11

Cumulative N lost by denitrification. Cauliflower 1997-98

121

4-5

4-9

A-12

Cumulative N lost by denitrification. Sweet corn 1997

100

122

12 ABSTRACT

Denitrification is a microbial process of anaerobic respiration in which nitrate (NO 3-) is chemically reduced to gaseous nitrous oxide (N2 0) and molecular N2. Fertilizer N can be lost to the atmosphere through this process. Subsurface drip irrigation may create favorable conditions for denitrification, such as high moisture and NO 3- content. The objectives of this research were to: 1) determine the denitrification rate in drip-. irrigated cauliflower and sweet corn crops; 2) evaluate the effect of soil water tension on the denitrification rate, and; 3) estimate an N balance under subsurface drip irrigation, including denitrification losses. Two field experiments with subsurface drip-irrigated cauliflower were conducted during the 1996-98 winter growing seasons at the Maricopa Agricultural Center, in Maricopa, AZ. An additional study with subsurface drip-irrigated sweet corn was conducted at the Campus Agricultural Center in Tucson, AZ. All the experiments were complete factorial designs with two soil water tension levels (low, high), two levels of N fertilizer (zero, adequate), and three replications. The denitrification rates evaluated at ambient temperature were

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