Influence of boron on seed yield and seed quality of organic white clover (Trifolium 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 <1mgBkg(-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 22mgkg(-1), 73% germinated as normal seedlings and 14% were assessed as hard seeds; corresponding values for seeds with an average B concentration of 17mgkg(-1) were 60 and 38% respectively. The results indicate the need for further studies of factors determining B uptake in white clover.