Regrassing flood-damaged pastures

Abstract

On the night of February 14th 2004 the lower North Island was hit with a storm system, which would cause the biggest flood seen in the region for over 100 years. The hardest hit areas include the Manawatu, Rangitikei, Horowhenua, Wairarapa and Wanganui regions. In the summer after the event, a survey was conducted of the affected areas. Semi-structured interviews of 52 individual farmers focused on their farm operations, the impact of the flood, and their regrassing strategies. The interviews established the state of the pastures postflood including depth and texture of silt deposit; water levels and flow; duration of inundation; and soil surface condition. The regrassing strategies included seedbed preparation, sowing technique, fertilizer use and weed control. Site measurements made were: pasture cover and species content, and that soil profiles revealed rooting depth and silt depth (if not cultivated). General trends that emerged were that the more thoroughly a seedbed was prepared the lower the risk of pasture establishment failure. Nitrogen (N) applications of 75 kg/ha over the intervening period did not have a significant effect but where deep sediment was encountered two or three applications of N was reported to produce feed and start inputting organic matter (OM). The use of a roller drill increased the reliability of establishment and was essential for the establishment of pasture legumes. Double normal seeding rates (30-40 kg/ha) increased the reliability of success where the seed was broadcast. Many farmers that had no sediment reported perennial weed problems including couch, creeping buttercup and a variety of thistles. Small scale surface cultivation was reported to decrease drying time dramatically in extremely wet areas. Keywords: ground cover, pasture cultivars, pasture establishment, seedbed preparation, weeds and pests