agricultural machinery and equipment 45 agricultural engineering 42 agriculture 38 landscape gardening 27 landscape forming 25 green areas 23 forestry 18 more ... soil science 16 landscape architecture 15 history 13 forests 13 parks 13 soils 10 horticulture 10 environment protection 9 ecology 8 ornamental plants 8 gardening 8 green roofs 8 soil erosion 7 permanently sustainable development 7 city planning 7 environmental pollution 7 ecosystems 6 forest managment 6 public open spaces 6 environment 6 animal husbandry 5 domestic gardens 5 woody plants 5 less ...