Effects Of Irrigation On White Clover (Trifolium Repens L.) Reproductive Growth And Seed Yield And Quality

The researches of water management in white clover {Trifolium repens var Haifa) seed production at the experimental field at Yunnan Sheep Farm and the green house for the effects of soil water status on white clover flowering in Beijing were carried out from November 2003 to June 2005. Five water treatments were designed to determine the crop water requirements and irrigation timing, and the effects on white clover seed yield and yield components, white clover growth development, seed development and seed quality by different water supply. The results were shown below:Treatment w3, which is the Available Soil Water Depletion (ASWD) ranged from 42% to 48% and the Crop Water Stress Index (CWSI) from 0.66 to 0.68, reached the highest seed yield averaged in 2 years. Treatment w2 that the ASWD was about 20% reached the highest seed yield and harvest index of 449.7 kg.hm'2 and 8.7% in 2004 and w3 did 434.9 kg.hm^-2 and 6.63% in 2005, respectively, and 7% of seed yield for w2 and 20.67% for w3 higher than control. The seed yield was mainly affected by seed weight in 2004 and by flower density, pod per flower and seed per pod in 2005, according to the seed yield components responses to different irrigation treatments affecting seed yield by path-coefficient analysis.The growth stage was delayed and growing rate increased significantly by water supply. The ASWD decreased stolon density, leaf area, internode's length, and peduncle and petiole length but increased the number of reproductive nodes. Biomass accumulation did not affect seed yield. The ASWD affected the distributions of aboveground dry matter and increased percentage of reproductive organs.The photosynthetic rate affected white clover seed yield in only pod stage in 2004, but in both initial flowering stage and pod stage in 2005. Total soluble sugars at different stage distributed mainly in stolon. Soluble sugars of root in bud stage and leaf in flowering stage affected white clover seed yield. Being increased the total soluble sugars of stolon and leaf, the photosynthetic rate of white clover would decrease. White clover flowering time was short, and centred by the ASWD. Total soluble sugars in peduncle and flower head affected ripe flowering head per unit area. In addition, the contents of soluble protein, free amino acid, soluble sugar, GA and ABA of stolon and leaf were affected by the ASWD before and after flowering, and then the flower development done.The seed mature time was short, and percentage of hard seed of white clover increased, and 1000-seed weight decreased, by the ASWD. Germination trend and percentage of normal seedling in w2 and w4 that the ASWD was about 60% were different significantly. Seed vigor was not affected by water treatment. Being increased the content of GA and ABA in white clover seed, the percentage of hard seed would decrese and increase, respectively.