http://des.nh.gov/organization/divisions/water/wetlands/cspa/categories/faq.htm#faq9

Can I use fertilizer or pesticides within the protected shoreland? 

No fertilizer, except limestone, can be used within 25 feet of the reference line. Beyond 25 feet, slow or controlled release fertilizer may be used. Always check with local town ordinances as several towns have restrictions that are more stringent than the SWQPA.

Pesticide use is prohibited within 25 feet of the reference line per Administrative Rules Pes 1001.01 (NH Dept. of Agriculture) and may only be applied by a licensed applicator with a permit from the NH Agricultural Department.

What is slow or controlled release fertilizer?

Slow or controlled release fertilizer means fertilizer that is guaranteed, as indicated on the package label, to contain not more than 2 percent phosphorous and a nitrogen component that is at least 50 percent slow release nitrogen