المساعد الشخصي الرقمي

مشاهدة النسخة كاملة : اهميه المادة العضويه للمتخصصين



mloshm
09-05-2007, 03:17 PM
http://www.2shared.com/file/1890659/6cfae4dc/The_importance_of_organic.html (http://www.2shared.com/file/1890659/6cfae4dc/The_importance_of_organic.html)?
محتويات الكتابContents

Acknowledgements viii
Preface ix
List of acronyms xi
Introduction 1
Organic matter decomposition and the soil food web 5

Soil organic matter 5
The soil food web 5
Decomposition process 7
Non-humic substances: significance and function 8
Compounds and function of humus 8

Natural factors influencing the amount of organic matter 11

Temperature 11
Soil moisture and water saturation 12
Soil texture 12
Topography 13
Salinity and acidity 13
Vegetation and biomass production 13

Practices that influence the amount of organic matter 15

Human interventions that influence soil organic matter 15

Practices that decrease soil organic matter 15

Decrease in biomass production 15

Replacement of perennial vegetation 15
Replacement of mixed vegetation with monoculture of crops and
pastures 16
High harvest index 16
Use of bare fallow 17

Decrease in organic matter supply 17

Burning of natural vegetation and crop residues 17
Overgrazing 17
Removal of crop residues 17

Increased decomposition rates 18

Tillage practices 18
Drainage 19
Fertilizer and pesticide use 19
Practices that increase soil organic matter Increased biomass production 20
Increased water availability for plants: water harvesting and irrigation 20
Balanced fertilization 21
Cover crops 21
Improved vegetative stands 22

iv

Agroforestry and alley cropping 23
Reforestation and afforestation 26
Regeneration of natural vegetation 27

Increased organic matter supply 27

Protection from fire 27
Crop residue management 27
Utilizing forage by grazing rather than by harvesting 28
Integrated pest management 28
Applying animal manure or other carbon-rich wastes 28
Compost 29
Mulch or permanent soil cover 29

Decreased decomposition rates 30

Reduced or zero tillage 30

Creating drought-resistant soil 35

Effect of soil organic matter on soil properties 35
Inefficient use of rainwater 35
Increased soil moisture 35
Reduced soil erosion and improved water quality 38

Key factors in sustained food production 41

Increased plant productivity 41
Increased fertilizer efficiency 41
Reduced waterlogging 42
Increased yields 42
Reduced herbicide and pesticide use 44
Increased biodiversity 45
Resilience 46

The role of conservation agriculture in organic matter
deposition and carbon sequestration 47

Principles of conservation agriculture 47
Organic matter deposition 47
Increased carbon sequestration 48

Conclusions 51
Bibliography 53
Annexes

Soil organisms 61
Effects of organic matter on soil properties

زهير عمر
09-01-2008, 01:41 PM
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