The National Trust is worried that the Government may cave into pressure and preserve many subsidies to farmers. They and other green groups fear that the farm lobby has succeeded in ensuring that food production and agricultural productivity will also be listed as 'public goods'.
This would go beyond the definition of what is a public good in economics, but the definition tends to be elastic in public debate and tends to encompass what would properly be termed merit goods.
Of course, the political calculus behind using farm payments to incentivise environmental benefits was to appeal to the urban electorate (many of them members of the National Trust) and that calculation remains a powerful one.
I do not think that there is a general case for subsidies for food production (many food security arguments are spurious) but there is a case for doing more to boost agricultural productivity which is poor, particularly through encouraging the use of new technology.
There is a £60m Countryside Productivity Small Grant Scheme to assist the purchase of new farm equipment: Farming productivity fund. However, the maximum grant is £12,000 which doesn't go a long way to buying sophisticated kit. Also, farmers applying for the scheme consider that they get caught between demonstrating that the farm business is viable, but not too viable otherwise it would not need assistance.