1. Why do we need to sterilize the growing media ? 2. Why do we need to follow the proper placing of soil media in the
seedbox ?

1. When microbiological media has been made, it still has to be sterilized because of microbial contamination from air, glassware, hands, etc. Within a few hours there will be thousands of bacteria reproducing in the media so it has to be sterilized quickly before the microbes start using the nutrients up.

2.)Clear existing crops and weeds. ...

Spread rotted compost or manure over the surface of the bed (not shown);

Dig the soil to the depth of a spade, turning the soil to bury any weed seedlings, and breaking up any large clods as you progress. ...

Rake roughly level;

Tread over the bed using 'pigeon steps'.

Explanation: