In this paper, the impact of public R&D investment on agricultural productivity and long-term food security via R&D driven endogenous technical change is analysed. The findings show that R&D growth rates at the level reached in 2000s, particularly those for China, would not be expected any longer. Concerning the impact of projected R&D investments on agricultural productivity, it is found that endogenous growth rates of land-augmenting technical change are comparably lower than the standard exogenous rates used in long term projections of agri-food markets. This suggests that public R&D investments are not able to stimulate agricultural production to the levels that would be expected from the standard baseline outcomes.