Arts: Now that's what I call organic sculpture

Look down the valley from Roche Court, near Salisbury, and you will see a row of hay bales glinting sculpturally in the sun. The bales' resemblance to art may have something to do with their scale or shape or with their man-made form. On the other hand, it may be to do with context: the bales are sitting next to a large Barbara Hepworth and, just beyond, a matching pair of Joel Shapiros. (Roche Court, a handsome Georgian house, has been converted into a sculpture park by its owners.) Actually, the explanation for the bales' sculptural look is that they are a sculpture called Harvest, the final act in a piece of landscape art by the young British sculptor Tania Kovats.

Over the summer, Kovats planted a swathe of oats along the side of a valley on Salisbury plain. A photograph of the outcome, called Contour, is included in a small but excellent exhibition of the artist's new work at Roche Court. It shows a formal sweep of green along the valley bottom, an intervention that is both in the landscape and not quite of it; chameleon- like and yet intrusive, obviously natural but just as clearly artificial.

The work respects the idea of the landscape in art and turns it on its head. Turner and Samuel Palmer used paint to represent the countryside; Kovats uses the countryside to make something that looks very like painting. Add to this the distance from which Harvest is now seen, and the work is rich and strange.

What it is not is tricksy. Kovats's work may equivocate, but it doesn't tease. It is serious, concerned with its role as art and with the traditions of art (which may explain the continued absence of Kovats's name from Turner Prize shortlists).

Take Sunk, a white cube some four feet high. It seems to be playing with ideas of the plinth and, by extension, of art galleries and how they work. But it doesn't have any art on top: rather the opposite, since Kovats has mined down into the plinth, leaving a deep black hole.

Sunk is not about anything. Yes, there are a number of ways in which you can interpret the work. You might like to see it as being to do with decay - a metaphor for the eventual triumph of organic nature over art- making man. Or you can view it in formal terms. Are we meant to see it as a plinth with a bite taken out of it, or does the white cube support a work of art - a landscape, maybe - which merely happens to exist inside it rather than on top of it? The truth is that Sunk is open to any of these ways of being looked at, and possibly to all of them.

So too with Rocky Road. See it as an allegory; a series of nearby drawings called Pilgrim might suggest an interpretation in the manner of John Bunyan, and the piece begins to seem silly. Its shape, a figure of eight that constantly turns back on itself, is just too heavy-handed a symbol for tough journeying; read the white forms on which the road is borne as a series of cliffs and the whole thing turns into portentous Scalextric set. Clear your head of all of these things, though, and Rocky Road simply tells the story of getting from a place to another place, the difficulties the artist had in taking her abstract form from one point on the gallery floor to a different point on that floor. What Kovats's work is about, in other words, is itself - a quality that gives it enormous gravitas, and which will probably see it excluded from next year's Turner list as well.

`Tania Kovats: New Work': Roche Court, Salisbury (01980 862244), to 12 December