lettuce and mustard seeds grow better in regular garden soil
sand and potting soil
This depends on the species of plant. Some plants require different nutrients than others. Your best bet would be to plant in regular soil, and then after some research you can till the soil with the required nutrients.
Some plants grow better in certain types of potting soil
You're better off with potting mix because soil from outside has weed seeds and pathogens in it.
potting soil, but is better to mix 70% potting soil and 30% top soil with horse manure
No, not for most plants. Sand doesn't have the nutrients most plants need, which is why potting soil is needed.
No offence, but Mustard is rubbish. Ketchup is sooooo much better
Potting soil is better because of all the extra nutrients put in. It seems odd to say so, but if you are talking about indoor plants, potting soil may be better. You may bring all kinds of critters inside with natural soil, unless you take steps to eradicate them (by baking the soil-- you won't like this option).
I found a web page that describes how to choose potting soil that could describe it better than I ever could. Here it is: http://homeideas.howstuffworks.com/soil-and-fertilizer/how-to-choose-potting-soils.htm
Usually your plants will need fertilizer in the water everytime they are watered, use a weaker strength if you perform this at each watering. Answer. Fertiliser and potting soil are two different things. Potting soil contains fertiliser that is helpful to the plants wellbeing, potting soil is a mixture for planting in.
Green beans grow better in soil.
Violets grow better than sunflowers