Abstract:

In order to explore the effects of applying different water-retaining agents under drought stress on the growth and development of soybeans and provide a reference for dryland cultivation of soybeans in the Hulunbuir region, a two-factor pot experiment was conducted with ‘Tongdou No. 2’ as the material. The first factor included four water gradients: normal water supply, mild drought, moderate drought, and severe drought. The second factor involved three types of water-retaining agents with different particle sizes, namely powder (SAP-A), 0.6-1 mm (SAP-B), and 2-3 mm (SAP-C), with no application of water-retaining agent as the control (CK). A total of 16 treatments were set up. The differences of various growth indicators of soybeans were analyzed at the V2 stage. The results showed that with the intensification of drought, all agronomic indicators of soybean seedlings showed a decreasing trend. The application of water-retaining agents could alleviate the adverse effects of drought stress. Under mild drought, SAP-A had a better effect on improving the agronomic traits of soybean seedlings than other treatments. Compared with the control, the plant height, stem diameter, SPAD value, total root length, root surface area, root volume, and dry weight per plant increased by 19.90%, 10.28%, 7.81%, 19.81%, 8.91%, 24.38% and 20.09%, respectively. Under moderate drought, SAP-C had a better improvement effect. Compared with the control, the above indicators were increased by 17.45%, 10.77%, 5.04%, 38.27%, 18.13%, 43.63% and 31.85% in turn. However, under severe drought, the improvement effect of applying water-retaining agents was not obvious. In soybean production in the Hulunbuir region, applying powder water-retaining agent under mild drought and 2-3 mm large-particle water-retaining agent under moderate drought had better effects.

Key words: drought, water retaining agent, particle size, soybean, seedling stage, growth and development, root morphology, dry matter