The search terms or keywords you use to search are what determine the results you get. Here's a good exercise to help you generate keywords:

1. Express your topic in a topic sentence or question: What is the effect of fertilizer utilization on groundwater?

2. Generate keyword search terms by identifying the main ideas or concepts within that topic sentence: "What is the effect of fertilizer utilization on groundwater?" = Effect, fertilizer, groundwater

3. Expand your search terms by brainstorming related terms or synonyms that describe your main ideas:

• Effect - influence, consequence
• fertilizer - manure

• utilization - use, application

• ground water - aquifer 

You can create complex search strategies by combining keywords using the linking words AND, OR and NOT. For example, if your search terms are fertilizer and groundwater:

AND Narrows and focuses the search results. The search fertilizer and groundwater will bring only results where both the terms fertilizer and groundwater are present.

OR Broadens the search results. Using or will bring results where the term fertilizer is present, or results where groundwater is present, or results where both terms are present. Or is useful if you have more than one way to refer to a concept -- Example: (groundwater or aquifer).

NOT Excludes anything where the term after the NOT is present.

The use of quotation marks around a group of words indicates a specific phrase such as "organic fertilizer"