Effect of tillage below the seed on emergence of wheat seedlings in a hardsetting soil

Two field experiments investigated the effect of tilled and untilled soil below the seed and the effect of a press wheel on the emergence of wheat (Triticum aestivum L.) seedlings on a hardsetting soil at Tatura, Victoria, Australia. Soil physical properties of the seedbed including penetrometer resistance, temperature and water content were recorded. The fate of seeds and seedlings and the length of roots were determined. In the experiments, germination was high (over 90%) and was not affected by the depth of tillage, the press wheel or by temporary waterlogging, but several physical conditions of the soil restricted emergence. In the first experiment, the rate and final emergence (at Day 10) was increased by tillage below the seed (e.g. at 46–90 mm depth) in spite of the penetrometer resistance of soil at 0–20 mm depth being 50% greater than that in the treatment untilled below the seed. The roots of the seedlings in the treatments untilled below the seed were temporarily waterlogged (at Days 0–1) and grew in soil that was drier (at Days 3–9) and harder than in treatments tilled below the seed. In the second experiment, the press wheel increased the rate of emergence by decreasing the sowing depth by 10 mm. Tillage below the seed increased the rate of emergence by decreasing the penetrometer resistance of the soil to less than 2.0 MPa.