Abstract:

Effects of nutrients (compounds of macro- and micro-elements) supply without sulfur (T₁) and with sulfur (T₂) on the competition between Stipa grandis L. (C₃) and Cleistogenes squarrosa L. (C₄) were examined using a replacement series design in a greenhouse experiment over a period of 80 d. Blank treatment (nothing applied) (T₀) was conducted simultaneously. It seems to be no inter-competition between S. grandis and C. squarrosa in all treatments. There was also no intra-competition for S. grandis in all treatments, and for C. squarrosa under T₀ treatment because of low productivity. However, the intra-competition of aboveground of C. squarrosa was significant when nutrients were supplied regardless of sulfur (S) application. The interaction on dry weight of C. squarrosa per pot between S supply and proportion of C. squarrosa was observed. Under the treatments of T₁ and T₂ the shoot growth of S. grandis increased significantly compared with T₀ treatment, but there was no significant difference between T₁ and T₂ treatments, indicating S had no effect on it. Root morphologies of S. grandis was not sensitive to nutrients added. Nutrients supply (T₁ and T₂ treatments) not only increased significantly the shoot growth of C. squarrosa, but also increased significantly its root growth. Sulfur increased significantly growth of the shoot and root of C. squarrosa. Nutrients supply decreased significantly ratio of root to shoot dry matter (RRS) of C. squarrosa regardless of S application, but the RRS of S. grandis was not affected by nutrients applied. Sulfur also decreased significantly the RRS of C. squarrosa in 100% and 75% proportions of C. squarrosa. The RRS of C. squarrosa was greater significantly in the 100% proportion than that in the 25% proportion of C. squarrosa for all treatments. Therefore, photosynthesis is more allocated to root in infertility soils than in fertility soils and the competition for nutrient resources stimulates root production. The degree of leaf greenness of C. squarrosa in T₁ treatment was less significantly than that in T₀ and T₂ treatments, and it was greater significantly in the 25% proportion than in the 100% proportion of C. squarrosa under T₁ and T₂ treatments, indicating that nutrients supply increase chlorophyll content in plant and may accentuate S deficiency or low plant productivity alleviate S deficiency.

Key words: Stipa grandis , Cleistogenes squarrosa , competition, morphology, sulfur (S) and other all nutrients application