Abstract: An investigation was made on the yield component, dry matter allocation, root distribution in 0-100 cm soil layer, and soil physical and chemical properties in two high yielding (>19500 kg·hm^-2) spring maize fields of Yulin, Shaanxi Province. In the two fields, the planting density was from 105000 plants·hm^-2 to 123000 plants·hm^-2, spike rate was from 97.7% to 102.2%, 1000-grain weight was >320 g, and the dry matter allocation in ears occupied 60.2%-65.5% of the total. The average bulk density in 0-100 cm soil layer was from 1.28 g·cm^-3 to 1.33 g·cm^-3, and the soil bulk density, porosity, and field water-holding capacity along the profile all changed in M type. Maize roots were mainly distributed in 0-60 cm soil layer, and those in 0-20 cm and 20-60 cm accounted for 64.8%-72.1% and 23.30%-28.17% of the total, respectively. There was a close relationship between root distribution and soil physical-chemical properties. Root dry mass in 0-20 cm soil layer had a significant positive correlation with soil organic matter, total nitrogen, and total phosphorus, while that in 20-60 cm soil layer was significantly correlated with soil bulk density and field water-holding capacity. Therefore, to select soils with good permeability and high maintenance capacity of water and nutrients would be the key in obtaining high maize yield.

Key words: spring maize, yield component, soil, physical and chemical properties, root distribution, plant density, winter wheat, ¹⁵N labeled, nitrogen level, nitrate nitrogen content.