Plant propagation 62 plant layering 60 plant harvesting 59 Genetics 51 Management 49 Sociology 47 Computer science 43 Computer 28 Engineering 28 Economics 25 Extension 24 metabolism 24 Marketing management 22 Operating systems 22 Plant cell 22 Mathematics 21 Operations research 20 Calculus 19 computer architecture 19 Biochemistry 18 morphology 17 Crop improvement 16 Cytology 16 Plant physiology 16 Cell Division 15 Financial management 15 Currency 14 Metabolism 14 Morphology 14 Prices-- Production economics 14