Influence of boron on seed yield and seed quality of organic white clover ( T rifolium repens L .)

The effects of boron (B) application on flower development, nectar production, germination and seed yield were investigated in organic seed crops of white clover grown in soils with <1 mg B kg −1 . Application techniques of a liquid B product were studied in two field experiments in 2009–2011. Three rates of B application to the soil at sowing and three rates of B as a foliar application in the harvest year were compared with untreated control plots. None of the B treatments had a significant effect on seed yield, relative to the control. In one experiment, with a dense crop stand, the results indicated a small (10%) yield increase with B applied to the soil. Seed germination and B concentration of shoots, roots and seeds were unaffected by B application, although the soil concentration increased. In seeds with an average B concentration of 22 mg kg −1 , 73% germinated as normal seedlings and 14% were assessed as hard seeds; corresponding values for seeds with an average B concentration of 17 mg kg −1 were 60 and 38% respectively. The results indicate the need for further studies of factors determining B uptake in white clover .