Nitrogen fixation in tropical cropping systems [Elektronisk resurs] / K.E. Giller.

• Part I Introduction -- 1 Tropical Environments: Climates, Soils and Cropping Systems -- Tropical Climates -- The major climatic zones -- Tropical Soils -- Soils with low activity clays -- Soils with high activity clays -- Chemical characteristics of leached soils -- Tropical Cropping Systems -- Shifting cultivation -- Fallow systems -- Permanent farming -- Conclusions -- 2 N2-fixing Organisms in the Tropics -- Prokaryote Classification -- N2-fixing Species in Tropical Cropping Systems -- Bacteria that Fix N2 with Legume Host Plants -- Common elements of the symbiosis -- Variations on the theme -- Nodulation in the Leguminosae -- Classification of rhizobia -- Actinomycetes that Fix N2: Frankia–Plant Symbioses -- Infection of host plants by Frankia strains -- Classification and identification of Frankia strains -- Cyanobacteria -- The Azolla–cyanobacterial symbiosis -- Free-living and Endosymbiotic Bacteria -- Conclusions -- 3 The Process of N2-fixation -- What Is N2-fixation? -- Nitrogenase structure -- Mechanism of N2-reduction -- Acetylene reduction by nitrogenase -- Alternative nitrogenases -- Hydrogen -- Oxygen Sensitivity of Nitrogenase -- Assimilation of Biologically Fixed N -- Assimilation of ammonium ions into glutamate -- Further metabolism of fixed N -- Detoxification of ammonia -- Energy Costs of N2-fixation -- Regulation of N2-fixation -- Inhibition by fixed N in free-living N2-fixing organisms -- Regulation of nodulation and N2-fixation in symbioses with plants -- Conclusions -- 4 Assessment of the Role of N2-fixation -- Direct Methods -- Rates of activity -- Integrated measurements -- Indirect Methods -- Rates of activity -- Integrated measurements -- Conclusions -- 5 Cycling of Fixed N in Tropical Cropping Systems -- Legume-based Cropping Systems -- Factors Governing Amounts of N2 Fixed and Contributions to the Cropping System -- Inputs from N2-fixation in Simultaneous Systems -- N transfer in legume/cereal intercrops or mixed legume/grass swards -- Mechanisms for underground ‘transfer’ of N -- Legumes in Crop Rotations -- Crop yield responses and N fertilizer equivalency -- 15N measurements of residual effects -- N contributed below ground in roots and nodules -- N Release from Legume Residues -- Managing organic residues for N release and maintenance of soil fertility -- Legumes as feed and fodder -- Conclusions -- Part II Tropical Crops and Cropping Systems -- 6 Cereal Crops and Grasses: Free-living, Root-associated and Endophytic N2-fixing Bacteria -- N2-fixation in the Rhizosphere -- Associations between N2-fixing bacteria and roots of grasses -- Root carbon as an energy source for N2-fixation -- Endophytic N2-fixing Bacteria in Cereals and Grasses -- Amounts of N2 Fixed with Cereals and Grasses -- Proof of N2-fixation using 15N2 -- Estimates using the acetylene reduction assay -- N balance studies -- 15N isotope dilution experiments -- Responses to Inoculation with Heterotrophic N2-fixing Bacteria -- N2-fixation by Free-living Bacteria in Soil -- Genetic Engineering of Cereals to Fix N2 -- Introducing nitrogenase into cereal crops -- Nodulating cereals -- Conclusions -- 7 Cyanobacteria and Azolla as Green Manure for Wetland Rice -- Cyanobacteria -- Natural distribution -- Amounts of N2 fixed by cyanobacteria in rice production -- Inoculation with cyanobacteria -- Manipulation of indigenous populations of cyanobacteria -- Azolla as a Green Manure -- Production of ‘inoculum’ -- Constraints to the growth of azolla -- Amounts of N2 fixed -- Recovery of fixed N by rice -- Yield responses to azolla incorporation -- Other uses of azolla -- Conclusions -- 8 Grain Legumes for Food, Fodder and Soil Fertility -- Tropical Grain Legumes -- Arachis -- Cajanus -- Cicer -- Glycine -- Phaseolus -- Vigna -- Minor grain legumes -- Amounts of N2 Fixed -- Characters required for an effective symbiosis -- Comparative ability of grain legumes to fix N2 -- Need for Inoculation -- The soybean story -- ‘Promiscuous’ grain legumes -- Phaseolus – a special case? -- Potential for strain selection for grain legumes -- Breeding Grain Legumes for Enhanced N2-fixation -- Breeding for enhanced N2-fixation in P. vulgaris -- Breeding for enhanced N2-fixation in soybean -- Selection criteria -- Intercrops of Grain Legumes and Cereals -- Effects of intercropping on N2-fixation -- Net N benefits and residual effects of grain legumes -- Conclusions -- 9 Legumes as Green Manures and Cover Crops -- The Main Green Manure and Cover Crop Legumes -- Canavalia -- Crotalaria -- Mucuna -- Green manures for cool climates -- Legumes as Cover Crops and Green Manures in Upland Soils -- N2-fixation in legume green manures -- Managing legume green manures -- Managing the mulch -- Effects on growth of subsequent crops -- Farmers’ experimentation and use of cover crops in upland soils -- Legume Green Manures in Lowland Rice Production -- N accumulation and N2-fixation in legume green manures in rice systems -- Release of N and recovery by the rice crop -- Legumes as nitrate catch crops -- Current use and problems of green manures -- Conclusions -- 10 Forage Legumes in Pastures and Leys -- Tropical Pastures -- Distribution of tropical savannah -- Types of grazing systems -- Approaches to improvement of pastures and rangeland -- Tropical Pasture Legumes -- Legume evaluation -- Some important legumes for pasture improvement -- Requirements for inoculation -- Legume establishment and maintenance -- Ley Farming -- Fodder banks -- Pastures in rotation with arable crops -- Inputs to the N Cycle from N2-fixation -- How much N2 do the legumes fix? -- Cycling of the fixed N -- Factors regulating availability of N in pasture soils -- Other benefits and problems of pasture legumes -- Current Use of Pasture Legumes in the Tropics -- Conclusions -- 11 Plantation Crops: Understorey Legumes and Shade Trees -- Cover Crops in Plantations -- The crop cycle -- Legume cover crops -- Benefits and management of legume covers -- Contributions from N2-fixation -- Additional benefits of legume cover crops -- Legume Trees for Shade -- Leguminous shade trees -- Conclusions -- 12 Agroforestry: N2-fixing Trees in Integrated Agriculture -- N2-fixing Trees -- Nodulated legume trees for agroforestry -- Non-nodulating legume trees for agroforestry -- Actinorhizal trees for agroforestry -- Requirements for inoculation -- How Much N2 Can Trees Fix? -- Uses of N2-fixing Trees in Agroforestry -- Fuelwood and timber -- Trees as food and forage producers -- Inclusion of trees to promote soil fertility -- Legume Trees in Agroforestry Systems -- Trees in fields of the arid zones -- Alley cropping -- Barrier fences -- Improved fallows -- Fodder banks, woodlots and cut-and-carry for mulch -- N2-fixing trees for reclamation of degraded land -- Conclusions -- Part III Optimizing N2-fixation -- 13 Environmental Constraints to N2-fixation -- Physical Constraints -- Temperature -- Drought -- Saline and sodic soils -- Waterlogging -- Chemical Constraints -- Toxicities -- Nutrient deficiencies -- Diagnosis and correction of nutrient problems -- Pollution -- Biological Factors -- Multiple Stresses -- Conclusions -- 14 Approaches to Enhancing N2-fixation -- Inoculation with Rhizobia -- Assessing the need for inoculation -- Inoculum technology -- Some inoculation success stories -- Selection of Rhizobium Strains -- Screening of strains in Leonard jars -- Competitive ability of rhizobial strains -- Screening for adaptation to stress -- Strain selection in soil -- Other roles for rhizobia? -- Manipulating the bacterium -- Construction of new rhizobial strains -- Improvement of Legumes for N2-fixation -- Breeding legumes for increased N2-fixation -- Finding New Niches for Legumes in Tropical Cropping Systems -- Multi-purpose food legumes -- Multi-purpose fodder legumes -- Multi-purpose legumes for soil fertility replenishment -- Conclusions -- 15 Future Impacts of N2-fixation in Tropical Agriculture -- The Role of N2-fixation in Tropical Agriculture -- Direct contributions to crop production -- N2-fixation in animal production -- N2-fixation in the maintenance of soil fertility -- Impact of Research into N2-fixation -- Holistic or ecological approaches? -- Development, testing and extension of promising technologies -- New models for agricultural research and development? -- Conclusions. 

• The second edition of this book, first published in 1991 and intended for students and researchers, contains revised and updated material on the theory and practice of nitrogen fixation in tropical cropping systems. There are 15 chapters in 3 parts. Part I, Introduction, contains 5 chapters on tropical environments (climate, soils and cropping systems), nitrogen fixing organisms, the process of nitrogen fixation, assessment of the role of nitrogen fixation, and cycling of nitrogen in tropical cropping systems. Part II, Tropical crops and cropping systems, comprises 7 chapters on freeliving, root-associated and endophytic nitrogen fixing bacteria of cereal crops and grasses, cyanobacteria and Azolla as green manure for wetland rice, grain legumes, legumes as green manures and cover crops, forage legumes, understorey legumes and shade trees in plantation crops, and nitrogen fixing trees in agroforestry. Part III, optimizing nitrogen fixation, includes 3 chapters on environmental constraints, approaches to enhancement, and future impacts on nitrogen fixation in tropical agriculture. A list of common names and subject index are included. 

Ämnesord

Legumes  -- Tropics (LCSH)

Nitrogen-fixing plants  -- Tropics (LCSH)

Nitrogen  -- Fixation (LCSH)

Klassifikation

SB297.4.L44 (LCC)

633.3/0913 (DDC)

Qdddd (kssb/8 (machine generated))