Abstract: To examine the effects of different groundwater depths on dry matter accumulation and root growth of maize, seven groundwater depth treatments (1.0 m (D1.0), 1.5 m (D1.5), 2.0 m (D2.0), 2.5 m (D2.5), 3.0 m (D3.0), 3.5 m (D3.5) and 4.0 m (D4.0)) were set up with groundwater simulation system at the Irrigation Experimental Center of Liaoning Province, Shenyang, China. We measured maize dry matter accumulation, maize root growth and yield. The results showed that: (1) Root length, root surface area and root volume increased with maize growth under all treatments. There were significant differences among the treatments. Root diameter increased first and then decreased at the filling-mature stage. (2) Dry matter accumulation of stem and leaf decreased first and then increased with increasing groundwater depth in jointing stage and fillingmature stage of maize. Dry matter accumulation of maize stem and leaf under D2.0 treatment was the lowest, with a decrease of 7.2%-19.5% compared with other treatments. The dry matter accumulation of maize ear under D2.5 treatment was the lowest, being 9.8%-24.8% lower than other treatments. Dry matter of roots under D2.0 treatment at tasseling and silking stage was the highest, being 7.2%-54.2% higher than other treatments. (3) Maize yield decreased first and then increased with increasing groundwater depth. The D1.0 treatment attained the highest yield, which was 365-1790 kg·hm^-2 higher than other treatments. The D3.0 treatment had the lowest yield. (4) Results from multiple regression and path analysis showed that groundwater affected maize yield by affecting root growth and dry matter accumulation. Maize yield had a significantly positive relationship with root length and root diameter at tasseling and silking stage, and a significantly negative relationship with root surface area, dry matter accumulation of stem and leaf at tasseling and silking stage, and root surface area at filling-mature stage of maize. Our results can provide theoretical basis for improving maize yield in Liaoning plain and similar areas under different groundwater depths.

Key words: 16S rDNA, bio-control., Streptomyces rochei, Cytospora sp., inhibitory activity