Background: There is a lack of biochar field trials in temperate climate regions. Wood biochar was applied during 2009-2011 to seven field experiments on five working farms in the UK, for arable, legume, horticultural and root crops. Results: Three trials showed no significant (p > 0.05) effect on crop yield, two showed positive effects of 5-6%, one showed a very strong increase of 100% and one showed a decrease of 2-16%. A meta-analysis of effect sizes was conducted for all treatments (n = 47), which showed a significant (p < 0.05) positive effect, increasing average yield by 0.4 t ha-1. Biochar application rates of 20 t ha-1 or under led to the greater benefits. Conclusion: This paper shows that, in some situations, biochar can bring benefits in modern temperate farming.