There are many jobs in agriculture which simply cannot be done by mechanical means SH. Agriculture (including forestry) is a special case in as much as that it only employs 1.13% of the British workforce full time, only contributes around 1% to the GDP. of the UK. yet uses 71.23% of the land area (this includes forest area, permanent pasture land, temporary meadows as well as arable land). The rural population growth of the UK. stands at - 0.614% yearly, in other words it is going down. There is not the rural workforce to fill this gap. If you are going to talk about replacing immigrant workers with machines then you should also consider that agriculture is already responsible for 39.53% of methane emissions and 60.9% of nitrous oxide emissions - much of which is a product of agricultural mechanisation. Replacing workers with machines also means bigger fields, even less crop rotation, even more ripped out hedgerows etc. etc. There is no replacement there for immigrant workers. The length of this 'seasonal' work is also much higher than is presumed - if you consider that the first harvest (asparagus) through to the last (late fruit such as apples) is around 6 months. In between time we have help with hay making, tree pruning etc. and a host of other things. Even the slurry which is taken out on the fields is done mostly by seasonal workers. Agriculture will always have a fluctuating demand for labour which, in the past, would have been done by lending workers from one farm to another but which is no longer viable. I would love to go down the road of organic, small scale farming, with proper crop rotation, smaller fields etc. all done by locals and by families, but.....this would involve increases in food prices and the role of agriculture in capitalism is to keep food prices as low as possible so as to protect spending power in other areas.