Saw a program about soil on BBC 4 which was stating how agricultural land is being drastically eroded by rain fall and due to the planting in rows all the rain is being sent down the channel between rows and once it pick up speed it’s not draining any more and causing considerable erosion….this has been going on for along time now and has caused many farms to abandon certain fields as they now have no nutrients left in the soil ( or something)….. the answer for this was provided by an engineer and was simply to line between the rows with straw. The rain was diffused by the straw and then had time to drain and not turn into a running torrent. This is about as simple a solution as you could wish I would imagine, both cheap and possibly eco friendly.