Plant propagation 60 plant layering 59 plant harvesting 58 Sociology 33 Extension 19 metabolism 19 Genetics 18 Marketing management 18 Crop improvement 16 Economics 15 Currency 14 Prices-- Production economics 14 Trade Union 14 Wage Act 14 Cytology 13 photosynthesis 13 Engineering 12 Expenditure 12 Income tax 12 Operations Research-- Information management-- Executive management 12 Plant Breeding 12 Public debt 12 Taxation 12 morphology 12 Plant cell 11 Social stratification 11 personal saving 11 Computer programming 10 Finance 10 Graph theory-- Mathematics 10