Answer: You are right in that runoff could possibly affect the wetland areas. You may want to consult with a landscape architect or other trained professional with experience in drainage plans and grading to make sure that the existing swales and drainage patterns and flood control methods are optimized to prevent this.
Since you live on a large property, perhaps you will not need to have a picture perfect lawn. If this is the case, then you may be able to tolerate a few weeds and imperfections in order to greatly reduce the fertilizer and chemical inputs. A lawn that is grown lean, meaning not overly supplied with nutrients, tends to be healthier and less subject to pests and diseases. It also grows a bit slower thus reducing the mowing needs somewhat.
In many cases a soil analysis will show that lawns are routinely overfertilized, so make sure to run some basic soil tests and find out what nutrients are (or are not) lacking in the soil, as well as check the pH. Your county extension (344-1234) should be able to help you with the tests and interpreting the results with an eye on minimum fertilizer and chemical use. They should also be able to suggest which specific varieties of lawn grasses do best in your area with minimal inputs.
In my experience, routine mowing at the prescribed heights is often one of the most effective things you can do to maintain a self-sustaining lawn. In spring, this usually means mowing more than once a week, in summer if the lawn is not watered, you may not need to mow for quite some time. Make sure to leave the clippings in place as these are an ongoing supply of nitrogen for the grass. A mid to late fall fertilization schedule rather than a spring schedule is also very helpful in building a healthy lawn without causing excessive spring growth.
You might also consider minimizing the lawn area to what is truly needed for recreation or other purposes, and using ground covers or mass plantings of natives that would require less maintenance and would be able to colonize and grow essentially on their own. You might be able to do this in such a way that you would encourage and accommodate an even wider variety of wildlife and safe yourself a lot of landscaping maintenance work at the same time. Your county extension, area park naturalists and local clubs such as the Audubon Society might be able to help you in determining a plan.
Enjoy your new home!
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