Objectives This study explored the influences of applying paclobutrazol on seed yield and seed setting characteristics of Chinese milk vetch (Astragalus sinicus L.), in expectation of providing reference for the efficient use of paclobutrazol in practical production.
Methods Using Chinese milk vetch cultivar ‘Xinzi1’ as tested material, field experiment had six foliar application levels of paclobutrazol, as 0, 200, 300, 400, 500 and 600 mg/L, recorded as CK, T1, T2, T3, T4, T5 in turn. The foliar application was conducted once at pre-flowering stage, and the spraying rate for all the six treatments was 750 kg/hm2. At the mature period of milk vetch, we recorded the number of inflorescence, pods and seeds at different inflorescence layers, the number of plants and branches per unit area using conventional test methods.
Results In comparison with the control, the inflorescence and pods numbers in unit area, the seed-setting rates of pods and seeds per pod at all the six inflorescence layers were increased in different degrees in all the five paclobutrazol treatments, with the best effect in T3 treatment. From the 1st to 6th inflorescence layer in T3 treatment, the number of inflorescences per unit area was increased by 34.1%–59.0%, the number of pods per unit area increased by 39.7%–68.4%, the seed number per pod increased by 44.3%–53.7%, the seed-setting rates of pods increased by 1.84–4.89 percentage points. The seed yield of Chinese milk vetch was significantly and positively correlated with the inflorescence numbers per unit area, the inflorescence numbers per branch, pod numbers per inflorescence, seed set rates of pods and seed number per pod.
Conclusions At pre-flowering stage, foliar application of paclobutrazol can significantly increase the inflorescences number, pod number, seed-setting rates and seed number per pod at all the six inflorescence layers especially at the 5th and 6th layers, and high seed yield was achieved at last. The best application concentration is paclobutrazol 373 mg/L.
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