Close Sartfield is one of the Trust's larger reserves and is part of the Ballaugh Curragh, the Island's premier wetland. The reserve derives its name from the fact that it was an enclosure or close rented over a long period by the owners of Sartfield farm in the neighbouring parish of Jurby whose home fields were often very dry in summer so that meadow hay from the damp Curragh fields was valued as a fodder supplement.

Close Sartfield is excellent for birdwatching. A variety of small birds depend on the many invertebrates that thrive amongst the rich flora and in the soft wet ground. These in turn are sought out by birds of prey as well as animals including stoats. Breeding species within the reserve include lesser redpoll, grasshopper wabler, reed bunting, sedge warbler, whitethroat, curlew and probably water rail. Hen harriers are seen frequently throughout the year and the hide is well sited to observe their evening return to a mid-winter roost. Visitors to the hide may be lucky enough to see a peregrine or a merlin. In 1999 and 2000, corncrakes have been sighted on the reserve. Level paths and boardwalks provide wheelchair access to the bird hide. Wellies are necessary off the boardwalk during flooded winter conditions.

The flora of the haymeadows is outstanding from late May to early July when tens of thousands of orchids, including heath spotted, early marsh, common-spotted, northern marsh and common twayblade, are in bloom. Yellow bartsia, yellow rattle, lousewort, purple loosestrife and cuckoo flower are among the other grassland species present. In the areas of peat, bog myrtle and purple moor grass are dominant.

Notable species include royal fern, bog myrtle, yellow bartsia and six species of orchids (May to July), corncrakes, hen harriers (western Europe's largest winter roost is close to the reserve).