Hi Antonio,
Regarding the disappearing seeds, here in Murcia I had the same problem. I thought it were ants, but after observing closely I found out it was a small species of mouse (a very tiny one!) and one particular species of bird (blackbird).
I read that the mice can smell where you planted the seeds as the area smells different then compared to the surrounding areas, I guess because of the seed and your hand. I solved this by laying some dead weeds on top to disperse the smell. Also against the birds we cut small pieces of shade net (the white type of net the greenhouses use here) and lay it on top of the area where I planted seeds, with 4 small rocks in each corner. This also helps against most snails for the first 2 weeks. After that the plant should be big enough.
This solved the problem for me for species that prefer direct planting like pumpkins and melons etc. Some other vegetables that are not so sensitive, like beans, I first raise in pots and then transplant as it is easier.
I also have bad soil here and made beds in order to improve things a bit. I mix the bad soil, with compost from my compost pile, fermented animal manure and old straw from my chickens. All mixed together it makes nice beds for the vegetables and they are happy.
Hope this helps
Cheers,
John
