No-till crop establishment on red earth soils at Katherine, Northern Territory: effect of sowing depth and firming wheel pressure on the establishment of cowpea, mung bean, soybean and maize

Abstract

The effect of sowing depth and firming wheel pressure of a no-till planter on the emergence and seedling growth of soybean, cowpea, mung bean and maize was examined in a red earth soil at Katherine, Australia. Each species was planted in a factorial combination of 3 sowing depths (60, 80, 100 mm) and 3 seed firming wheel pressures (1, 6, 11 kg/cm tyre width). Hot, dry conditions for 14 days after sowing resulted in rapid drying of the soil and high soil temperature. Most seed germinated but there was considerable variation in seedling emergence. Good seedling emergence of mung bean (96%) and cowpea (95%) contrasted with poorer emergence of soybean (57%) and maize (50%). Maize germinated more slowly than the grain legumes and unemerged seedlings had ceased growing when the coleoptiles were < 10 mm long. Soybean germinated rapidly and hypocotyls of the unemerged seedlings had stopped growing within 20 mm of the soil surface. The development of maize and soybean seedlings may have been retarded by high temperatures and severe soil water deficits. Deep planting slowed emergence but increased seedling growth in maize and soybean. The effect was most evident in soybean. Firming wheel pressure did not influence the soil strength below the planted seed and did not significantly affect seed germination, seedling emergence or seedling growth.