A dissertation submitted to the graduate division of the university of hawaii in partial fulfillment of the requirements for the degree of




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GROWTH AND YIELD RESPONSES OF Glycine max and Phaseolus


vulgaris TO MODE OF NITROGEN NUTRITION AND TEMPERATURE
CHANGES WITH ELEVATION

A DISSERTATION SUBMITTED TO THE GRADUATE DIVISION OF

THE UNIVERSITY OF HAWAII IN PARTIAL FULFILLMENT

OF THE REQUIREMENTS FOR THE DEGREE OF

DOCTOR OF PHILOSOPHY

IN AGRONOMY AND SOIL SCIENCE

DECEMBER 1988

BY


THOMAS GEORGE

Dissertation Committee:


Duane P. Bartholomew, Chairman

B. Ben Bohlool

Paul W. Singleton

James A. Silva

Francoise M. Robert

ACKNOWLEDGEMENTS
My sincere gratitude goes to Dr. Duane P. Bartholomew, Dr. B. Ben Bohlool and Dr. Paul W. Singleton for their constant guidance, constructive criticisms and spirited support during this research. I am especially appreciative of the help given by Dr. Singleton and Dr. Bartholomew in the preparation of the manuscript. I am grateful to Dr. James A. Silva and Dr. Francoise M. Robert for their helpful suggestions and advice.

I would like to acknowledge Kevin Keane, Rick Koglin, Goeff Haines, Brian Duffy and Thomas Walker for their assistance in the field, the NifTAL Project staff for their untiring help, Robert Abaidoo for his participation in a part of this research.

Lastly, my heartfelt thanks goes to Maria Luz Caces, my best friend.

This research was supported in part by the U.S. Agency for International Development grants DAN-1406-G-SS-4081-00 (Indo/US Initiative on Science and Technology) and DAN-0613-C-00-2064-00 (NifTAL Project), National Science Foundation/Ecology Program, and the International Atomic Energy Agency.



ABSTRACT

Efficient exploitation of the legume-Rhizobium symbiosis in varied environments requires an understanding of the responses of both the host and the bacteria to management and environmental variables. The objective of this research was to study the growth, development and yield responses of soybean (Glycine max L. Merrill) and common bean (Phaseolus vulgaris L.) to mode of N nutrition and temperature at sites in an elevational transect differing in mean temperatures. In the first experiment five soybean varieties and their non-nodulating isolines from four maturity groups were grown after inoculating with three Bradyrhizobium japonicum strains. The proportion of nodules formed by each B. japonicum strain was not affected significantly by temperature, soil type, or soybean genotype. Soybean grain yield and total plant N decreased with increasing elevation. At a given site, the proportion of total plant N derived from symbiotic N2 fixation was approximately constant. Between sites, the proportion of fixed N was inversely related to soil N availability. Vegetative and total crop durations were prolonged by cool temperature. Maturity of soybean was hastened by N insufficiency. In a second experiment, inoculated and uninoculated soybean and common bean were grown with either 9, 120, or 900 kg N ha-1. As a result of extended crop durations at the higher elevation, total biomass production was similar between elevations in both legumes. Grain yield of common bean was similar at the cool and warm sites; in contrast the grain yield of soybean was greatly reduced at the cool site. Yield and total plant N of both legumes increased at mineral N levels of 120 and 900 kg ha-1 compared to 9 kg N ha-1. Significant symbiotic N2 fixation limited yield and total N assimilation in soybean. Common bean utilized proportionately more mineral N than soybean throughout growth and had a higher fertilizer N use efficiency than soybean during the vegetative phase. Common bean also had a lower N requirement and N assimilation was more uniform throughout growth when compared to soybean. Maximizing N derived from fixation in common bean may require altering its N assimilation characteristics.

TABLE OF CONTENTS
ACKNOWLEDGEMENTS . . . . . . . . . . . . . . . . . . iii

ABSTRACT . . . . . . . . . . . . . . . . . . . . . . iv

LIST OF TABLES . . . . . . . . . . . . . . . . . . . vii

LIST OF FIGURES . . . . . . . . . . . . . . . . . . . xii

CHAPTER I. INTRODUCTION . . . . . . . . . . . . . . 1

CHAPTER II. NODULATION AND INTERSTRAIN COMPETITION BY



Bradyrhizobium japonicum IN SOILS ALONG AN

ELEVATIONAL TRANSECT . . . . . . . . . . 6

CHAPTER III. EFFECT OF TEMPERATURE AND MATURITY GROUP

ON PHENOLOGY OF FIELD GROWN SOYBEAN . . 28

CHAPTER IV. YIELD, SOIL N UPTAKE AND N2 FIXATION BY

SOYBEANS FROM FOUR MATURITY GROUPS GROWN

AT THREE ELEVATIONS . . . . . . . . . . 48

CHAPTER V. GROWTH RESPONSES OF FIELD GROWN SOYBEAN

AND COMMON BEAN TO TEMPERATURE AT VARYING LEVELS OF N NUTRITION . . . . . . . . . 67

CHAPTER VI. NITROGEN ASSIMILATION AND N2 FIXATION IN

SOYBEAN AND COMMON BEAN AS AFFECTED BY

ELEVATION AND MINERAL N AVAILABILITY . . 89

SUMMARY AND CONCLUSIONS . . . . . . . . . . . . . . . 109

APPENDIX . . . . . . . . . . . . . . . . . . . . . . 114

LITERATURE CITED . . . . . . . . . . . . . . . . . . 123

LIST OF TABLES


Table Page

II-1 Soil and site characteristics of three

locations in an elevational transect on

the island of Maui, Hawaii . . . . . . . . . . . 21

II-2 Proportion of nodules formed by B. japonicum

strains from five soybean varieties grown in

three soils in the field and greenhouse . . . . . 22

II-3 Proportion of nodules formed by B. japonicum

strains from five soybean varieties grown in

the field and greenhouse . . . . . . . . . . . . 23

II-4 Number and dry weight of nodules from five

soybean varieties at 45 days after planting

at three different elevations . . . . . . . . . . 24

II-5 Number and dry weight of nodules from five

soybean varieties at 45 days after planting

in three different soils in the greenhouse . . . 25

II-6 Shoot dry weight of five soybean varieties

at 45 days after planting at three different

elevations . . . . . . . . . . . . . . . . . . . 26

II-7 Shoot nitrogen content of five soybean varieties

grown at three different elevations at 45 days

after planting . . . . . . . . . . . . . . . . . 27


III-1 Mean maximum and minimum temperatures during

growth of five soybean varieties at three

elevations on the island of Maui, Hawaii . . . . 40

III-2 Days to first flower and physiological maturity

of nodulating isolines of five soybean varieties

grown at three elevations . . . . . . . . . . . . 42

III-3 Growing degree days accumulated during

vegetative growth and up to physiological

maturity for nodulating isolines of five

soybean varieties grown at three elevations . . . 43

III-4 Duration of seed-filling of nodulating isolines

of five soybean varieties at three elevations . . 44

III-5 Rate of seed dry matter accumulation of

nodulating isolines of five soybean varieties

grown at three elevations . . . . . . . . . . . . 45

III-6 Mean days to first flower and physiological

maturity for nodulating and non-nodulating

isolines of five soybean varieties grown at

two elevations . . . . . . . . . . . . . . . . . 46

III-7 Mean grain and shoot nitrogen concentrations of

nodulating and non-nodulating isolines and grain

yield of non-nodulating isolines of five soybean

varieties grown at three elevations . . . . . . . 47

IV-1 Characteristics of three sites in an elevational

transect on the island of Maui, Hawaii . . . . . 59
IV-2 Grain and stover yields of five nodulating

soybean varieties grown at three different

elevations . . . . . . . . . . . . . . . . . . . 60

IV-3 Total nitrogen assimilation by five nodulating

soybean varieties grown at three different

elevations . . . . . . . . . . . . . . . . . . . 61

IV-4 Symbiotically fixed nitrogen by five soybean

varieties grown at three different elevations . . 62

IV-5 Average rate of nitrogen assimilation by five

soybean varieties grown at three different

elevations . . . . . . . . . . . . . . . . . . . 63

IV-6 Percent of total nitrogen derived from symbiotic

fixation by five soybean varieties grown at

three elevations . . . . . . . . . . . . . . . . 64

IV-7 Comparison of estimated amounts of mineralized N

and actual soil nitrogen uptake by five soybean

varieties at three elevations . . . . . . . . . . 65

IV-8 Nitrogen uptake by Clark non nodulating plants

grown in three soils in the greenhouse at a mean

soil temperature of 27 C . . . . . . . . . . . . 66

V-1 Environmental characteristics at two sites in an

elevational transect on the island of Maui,

Hawaii . . . . . . . . . . . . . . . . . . . . . 81

V-2 Days to first flower and physiological maturity

of inoculated soybean and common bean grown at

two elevations with three levels of N . . . . . . 82

V-3 Grain yield of soybean and common bean as

affected by elevation and N application . . . . . 83

V-4 Effect of elevation by legume species interaction

on harvest index and whole plant tissue N

concentration at physiological maturity . . . . . 84

V-5 Main effects of elevation, legume species and N

level on dry weights at different growth stages . 85

V-6 Main effects of elevation, legume species and

N levels on mean crop growth rate during

different growth phases . . . . . . . . . . . . . 86

V-7 Effect of elevation by legume species

interaction on leaf characteristics at different

growth stages . . . . . . . . . . . . . . . . . . 87

V-8 Effect of elevation and legume species on unit

leaf rate during different growth phases . . . . 88

VI-1 Elevation by legume by N level interaction on

N assimilation at physiological maturity . . . . 103

VI-2 Effect of elevation, N level and growth stage

on N2 fixation by soybean at different growth

stages . . . . . . . . . . . . . . . . . . . . . 104

VI-3 Effect of elevation, N application and legume

species on the rate of N assimilation during

crop cycle . . . . . . . . . . . . . . . . . . . 105

VI-4 Relative N assimilation during different growth

phases of soybean and common bean grown at two

elevations . . . . . . . . . . . . . . . . . . . 106

VI-5 Effect of legume and N levels on fertilizer N

use efficiency during the crop cycle . . . . . . 107

VI-6 Effect of legume and N levels on KCl-extractable

soil N during the crop cycle . . . . . . . . . . 108

A-1 Effect of elevation and N level on nodule dry

weight at end bloom . . . . . . . . . . . . . . 114

A-2 Days to flowering and physiological maturity

of the non-nodulating isoline of Clark soybean

grown at two elevations with three levels

of mineral N . . . . . . . . . . . . . . . . . . 115

A-3 Effect of N level on harvest index of legumes

grown at two elevations. . . . . . . . . . . . . 116

A-4 Grain yield of the non-nodulating isoline of

Clark soybean grown at two elevations with three

levels of mineral N . . . . . . . . . . . . . . 117

A-5 Total N assimilation by the non-nodulating

isoline of Clark soybean grown at two elevations

with three levels of mineral N . . . . . . . . . 118

A-6 Effect of N level on the leaf area and leaf weight

of legumes at different growth stages . . . . . 119

A-7 Effect of N level on the unit leaf rate of

legumes at different growth stages . . . . . . . 120

A-8 Fertilizer use efficiency of legumes grown at two

elevations with three N levels . . . . . . . . . 121

A-9 KCl-extractable soil N after harvest of legumes

grown at two elevations with three N levels . . 122

LIST OF FIGURES

Figures Page

1 Weekly mean temperatures and daylengths during the

growth of five soybean varieties at three elevations

on the island of Maui, Hawaii . . . . . . . . . . . 41

Chapter 1

INTRODUCTION

Legumes respond to the environment in the same way other plants do, but what makes them physiologically distinct from other plants is their ability to harbor nitrogen-fixing rhizobia in a symbiotic relationship. The establishment of the legume-Rhizobium symbiosis starts with the infection of the legume host by compatible rhizobia, resulting in the formation of nodules.

Both symbiotic N2 fixation and mineral N assimilation contributes to the N requirement of legumes. The symbiosis is functional when the legume is stressed for nitrogen and, to some degree, compensates for decreased mineral N availability. However, mineral nitrogen suppresses symbiotic N2 fixation (Allos and Bartholomew, 1959; Chen and Phillips, 1977; Dart and Wildon, 1970; Oghoghorie and Pate, 1971). While N2 fixation is readily replaced by mineral N, evidence presented by Gibson and Pagan (1977), Manhart and Wong (1980), and Streeter (1985) do not show any direct inhibitory effect of mineral N on N2 fixation.

The general consensus regarding the N nutrition of legumes is that legumes require N from both symbiotic and mineral N sources for maximum yield (Bhangoo and Albritton, 1976; Harper, 1974). However, there are indications that legumes relying on mineral N produce yields similar to or greater than symbiotic plants (Kato et al. 1984; Ryle et al. 1978; Silsbury, 1977). Schweitzer and Harper (1985) found that increasing light interception by a soybean canopy using reflectors increased nitrate reductase activity in nitrate-supplied plants more than it increased nodule activity in inoculated plants, and the nitrate-supplied plants consequently produced greater dry weight. Also, Tanaka (1986) showed that if photosynthetic activity decreased, N2 fixation decreases more than mineral N absorption. Accordingly, Mahon and Child (1979) argued that it is difficult to increase N2 fixation and the productivity of legumes simultaneously. Salsac et al., (1984) also concluded that plants entirely or partly dependent on mineral N had yields higher than symbiotic plants. The assimilation of mineral nitrogen does not involve the maintenance of specialized structures like root nodules as in the symbiotic plant, so it is a more energy efficient source of N. Finke et al. (1982) concluded that dependence of the plant solely on N2 fixation is an energy expensive process.

If there is sufficient N in the soil to meet the plant's requirement, and if assimilation from the soil is not limited by other factor(s), then symbiotically fixed N will not be a major source of N for the plant. Any factor which limits the availability, uptake or assimilation of soil N should favor N2 fixation. Low temperature is one factor which reduces the rate of soil N mineralization (Stanford et al., 1973; Cassmann and Munns, 1980), and uptake of available soil nitrogen (McDuff and Hopper, 1986; Tolley and Raper, 1985). Low temperature, therefore, may favor N2 fixation over mineral N assimilation unless it decreases nitrogenase activity to the same degree that soil N assimilation is decreased.

Nitrogen nutrition presumably can range from complete dependence on mineral N to complete dependence on symbiotic N2 fixation. Plants dependent on N2 fixation or mineral N may respond differently to the environment because of the differences in their root morphology, N assimilation process, and N nutritional level. In the case of the symbiotic plant, the response may be further complicated by specific interactions between the legume host and the rhizobial microsymbiont. The interaction between the legume host and the rhizobial microsymbiont is specific, and the compatibility of the host with any one of the competing rhizobial strains may determine whether or not a productive symbiosis will be established. Thus, any attempt to correlate legume response to environment requires careful consideration of the mode of N nutrition and the N requirement of the plant.

Developing a holistic approach to legume productivity research requires the evaluation of the legume rhizobium system from soil, plant, and microbial perspectives in the field. Such an approach would render the results more relevant to productivity research and improve the degree of predictability of outcomes in varied environments.

Considering the complexity of environmental factors in agricultural ecosystems, the delineation of effects of single factors is often difficult. Although management variables may be made optimum and thus, eliminated as sources of variation, the effects of environmental variables such as temperature, photoperiod and irradiance are often confounded.

Temperature has direct and indirect effects on biological or biochemical processes and in legumes, these responses are readily modified by photoperiod (Salisbury, 1981). The field evaluation of temperature effects is simplified when the confounding effects of irradiance and photoperiod are minimal. Sites in an elevational transect may permit this kind of evaluation if changes in irradiance with elevation are small.

Two experiments were conducted to study the effects of mode of N nutrition, temperature and other elevation-associated variables on the ecophysiological response of soybean and common bean. The approach taken was to study host-Rhizobium-environment interactions and plant genotype-temperature-mode of nitrogen nutrition interactions in soybeans adapted to a wide range of latitudes, and use the data thus obtained as the basis for a second experiment to evaluate the growth and yield responses of soybean and common bean to temperature under a range of mineral N availability conditions.

The Objectives of the experiments were:

1. Determine the effects of elevation-associated site characteristics (temperature, soil type) and soybean genotype on the competition pattern of Bradyrhizobium japonicum strains.

2. Determine the effects of temperature and mode of N nutrition on the phenology of a range of soybean maturity groups under similar photoperiodic regimes.

3. Assess the effects of site characteristics and soybean genotype on the contribution of N2 fixation to plant N.

4. Evaluate the growth responses of soybean and common bean to cool and warm environments at varying levels of soil N availability.

5. Evaluate the responses of soybean and common bean to mineral N application and contrast the N assimilation patterns of the two legumes.



Chapter 2

NODULATION AND INTERSTRAIN COMPETITION BY Bradyrhizobium



japonicum IN SOILS ALONG AN ELEVATIONAL TRANSECT

Abstract

A better understanding of the ecology of Bradyrhizobium japonicum in relation to its host and its environment may aid in making appropriate management decisions for soybean production in a wide range of conditions. Success of one or more of the competing rhizobial strains in forming nodules and establishing an effective symbiosis is influenced by host genotype, soil type and temperature. The effects of temperature and soil type on interstrain competition, nodulation and nitrogen assimilation in five soybean varieties belonging to maturity groups 00, IV, VI, and VIII were investigated at three sites devoid of soybean rhizobia along an elevational transect in Hawaii. The soils are classified as Humoxic Tropohumult (clayey, ferritic, isohyperthermic), Humoxic Tropohumult (clayey, oxidic, isothermic) and Entic Dystrandept (medial over loamyskeletal, isomesic) at elevations of 320, 660 and 1050 m, respectively. Sites were amended with Ca(OH)2 to a pH between 5.5 and 6.0. Nutrients, except nitrogen, were provided in non limiting amounts. Seeds were inoculated with equal numbers of Bradyrhizobium japonicum strains USDA 110, USDA 136b (CB 1809) and USDA 138. The mean soil/air temperatures during the experiment were 25/24, 24/22 and 22/18 C at the respective elevations. A greenhouse pot experiment was also conducted using the same soils and inoculum under a fixed temperature regime. Plant tops and nodules were sampled at 45 days after seeding. Nodule occupancy was determined by immunofluorescence. Competition patterns of the three strains were unaffected by soil type or soil temperature. Strain USDA 110 was the best competitor, occupying on the average (5 cultivars) 81 and 64% of the nodules in the field and greenhouse experiments, respectively. Strain USDA 138 was the least successful in the field. Its nodule occupancy under greenhouse conditions, however, was significantly greater than in the field. Nodule occupancy was also related to soybean maturity group. Strain USDA 110 formed 61, 71, 88, 88, and 98% of the nodules in the field on Clay (00), Clark (IV), D68 0099 (VI), N77 4262 (VI), and Hardee (VIII), respectively. Strain USDA 136b formed very few nodules on Hardee, an Rj2 soybean variety incompatible with that strain; its nodule occupancy on all other cultivars in the field averaged about 30% (including nodules containing more than one strain). Both nodule number and weight were significantly reduced as elevation increased. Nodule number increased with increasing maturity group within a site, but nodule weight did not. Shoot dry weight and nitrogen assimilation decreased drastically with increased elevation. Nitrogen assimilation decreased from 246 mg N per plant at 320 m elevation to 26 mg N per plant at 1050 m. While soil type and temperature had no effect on strain competition, temperature had a profound influence on nodule parameters and plant growth.



Introduction

The establishment of an effective and efficient symbiosis between rhizobia and the host legume is basic to viable legume production without mineral N fertilization. The symbiosis is modified by various environmental factors. An understanding of the effects of environmental factors on the symbiosis is therefore, essential for selecting adapted cultivars and management practices that will enhance symbiotic nitrogen fixation and yield.



Bradyrhizobium japonicum strains differ considerably in competitive ability, nodulation and nitrogen fixation (Abel and Erdman, 1964; Caldwell, 1969; Johnson and Means, 1964). The competition and nodulation characteristics of the strains have been shown to be influenced by the host genotype (Caldwell and Vest, 1968; Materon and Vincent, 1980).

Soil type may also influence the competition between strains for nodule sites. Dominance of different B. japonicum strains in soybean nodules from different soils have been reported (Damirgi et al., 1967; Ham et al., 1971; Johnson and Means, 1963; Keyser et al., 1984). Soil type greatly influenced the distribution of strains, with distinctly different populations of rhizobia in soybean nodules from six different soils (Damirgi et al., 1967). According to Ham et al. (1971), the presence of individual strains in soybean nodules was related to two or more of the soil properties, the most important of which was soil pH. Kosslak and Bohlool (1985) have reported that in soils devoid of native B. japonicum, the pattern of competition between two introduced strains remained the same regardless of soil type or soil amendments.

The recovery of specific rhizobial strains in the nodules, and nodulation and N2 fixation are also related to temperature. Caldwell and Weber (1970) found that the dominance of different serogroups in soybean nodules was altered by planting dates, and Weber and Miller (1972) concluded that the effect was due to differences in soil temperature. Low soil temperatures have also been shown to adversely affect both nodulation and nitrogen fixation (Lindeman and Ham, 1979; Waughman, 1977).

To understand the ecology of rhizobia in relation to the host and its environment, experiments were conducted along an elevational transect located on the island of Maui, Hawaii (part of the Maui Soil, Climate and Land Use Network: Mauinet), which provided a field laboratory of varied edaphic and climatic (primarily temperature) conditions. The purpose of the investigation reported here was to study B. japonicum strain competition, nodulation and early nitrogen assimilation on selected genotypes of soybean in field environments that differ in soil type, and soil and air temperatures. Other soil variables were assumed to be controlled by equalizing pH, and applying nutrients other than N at maximum levels.


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