A ground cover sheet material for use in agriculture is woven from warp and weft tapes of a plastics material and at least some of the warp or weft tapes have a greater width and/or thickness than the weft or warp tapes, or the material comprises a higher density of warp or weft tapes relative to the weft or warp tapes per unit area, or comprises slits through the tapes, or the tapes are folded lengthwise, all optionally in one or more high water flow through lengthwise extending parts of the material. In one embodiment the material is woven from warp or weft tapes some haλάng a rectangular or square cross-section and some having a circular or oval cross-section. In some embodiments the material is also a reflective material.