what is the essential to do in a tropical country to grow vegetables
i try many time seeedling tomato, chinese cabbage,parsley,escarole etc....they don't growth and juste disapear, how to prevent that
It could be birds, rodents, insect pests, or plant disease. I suspect it may be a soil-borne disease, called "damping off". I'm in Thailand and it is very common.
You should start your seeds in a sterilized planting medium and then plant them out in the garden when they have grown a little and will have more resistance. Or use a soil that you have pre-treated with a biological fungicide like Trichoderma harzianum.
Check with this Univ of Philippines department for recommendations of a local product. https://biotech.uplb.edu.ph/products/biofertilizers
And I just found this source: http://bswm.da.gov.ph/Products/LaboratoryProducts
Here's an article that has other tips: