Monday, February 20, 2012

Farmers have a major role in drought and flood issues

Todays DEFRA conference should be looking at soil management

The up-coming drought in the S-E of England is worrying farmers, who are demanding concessions to any drought orders in order to protect their crops and livelihoods. Yet it is on their land that the rain mainly falls. Is modern land management, that is, the way farmers work the land, in any way responsible for the problems of drought and flood?  And if so, is there anything which can be done to help solve the problem? 

Practical Farm Ideas thinks there is.  For years
government has commissioned many studies on drought and flood creating a mass of information, but few take notice of land management in the watershed - the area upstream which catches the rain in the first place. It's time for some conclusions. 

There's a simple view that says drought as a lack of rainfall and flooding as a surfeit - so how can anyone say the two could in any way be connected? 

Flood and drought are connected because both are partly caused by less rainwater being absorbed by the soil. So when the clouds open and it tips down with rain for days, all but a small proportion runs off the land into ditches, streams and rivers. Farmers don't want water standing on their land so they clear ditches, and with the growing ownership of tracked diggers and JCBs, plus the fact that it's good farming to have clean ditches, water doesn't hang about like used to. So the rainfall in the Severn catchment area of maybe 4000 sq miles soon runs down into the river to accumulate in places such as Tewkesbury. 

If water doesn't stand it has little chance of being absorbed, and that surely means less reaching the underground aquifers that criss-cross the land beneath our feet. Aquifers are an important source of water for rivers and water supplies. 

Increasing the quantity of rain water which is absorbed by the land will allow a greater proportion to seep down into the substrata, which means there's less to run off over the soil surface. Has anything changed to make farm land less absorbent?

We're certainly driving bigger, heavier tractors now than we were 20 years ago, and today's machines are monsters in comparison to those in use in the 1960s and 70s. Heavier machines create greater soil compaction, particularly in wet soils (see Practical Farm Ideas Issue 20-3 pgs 32 and 33 - Science into Practice 'Soil and its Compaction'). Compact soil has reduced absorbency. Weight, be it a 250HP tractor on min-till or with a plough, or a 150HP tractor towing a silage trailer with 15 tons on board, exerts a force on the soil which extends 24 inches below the surface, and when tyres have slippage they smear the top as well. 

How could farming help reduce flooding and increase water absorption? Aerating grassland is a simple measure. Reducing the weight of tractors, with more on tracks, is another.  But above all, farmers would find a useful means of measurement valuable. So they could see how their farm scored against the norm, and how various parts of their farm compared. 

Water absorbency is a vital part of the soil, and one which has been all but neglected.

Will today's (Feb 20, 2012) top level Defra enquiry into the up-coming drought have much on soil absorbency? It's highly doubtful. 

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