Sentence:  Seed should be sown thinly and evenly to enable seedlings to be <WSD>pricked</WSD> out without disturbing those that have just emerged. If there is space, seedlings should be <WSD>pricked</WSD> out individually, either into small pots or module trays. 
Meaning of the word marked with <WSD> tags:  "Usually in the form" '''prick out''': to plant (seeds or seedlings) in holes made in soil at regular intervals.