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| Drainage is commonly mis understood. Remember your only removing gravitational water -- that is water that is held too losely by the soil particle so its actually restricting root growth. So yes in a dry year you do have more water in the soil --- HOWEVER - it is not plant available because it has no oxygen, or reduced oxygen levels so root growth down to those areas is greatly restricted. I farm next to a creek and you can see the water does "wick" up the soil about 6 in to a foot. However you have to get root development to happen to that level -- so if like normal the water level goes down as the season progresses - the roots cannot grow into the current "wicking zone" until the water level is below that zone. So yes on an untiled field you may have the water level down say 2 ft -- however your roots may only go down 18 in - of which only the last 6 in may have useable water. In the same scenerio in a tiled field the water level may be down 4 ft and the roots down 3-1/2 ft -- so the same 6 in is available to the plant as well as any water holding capacity in the additional 1-1/2 foot of soil the roots explored. Now if we entered an expented period of dry years where the water level moved down - then itd be kinda different. We look as tile as a way to drain water out when in all actuality what were really doing is letting the air in -- getting that balance of 50% soil, 25% water, 25% air -- you're just letting the water out to get to the 25% air level which would be "field capacity" down to the level of the tile. In NW iowa its interesting to watch an area like Spencer which has alot of sand -- water standing on top and 3 weeks later its toast. We cannot raise the water level to force water into the plants - it all depends on the ability of the soil to hold the water in a "plant available" form. Now I do think on heavy flat ground that these new valves are an interesting concept -- drain it out in the spring and seal it off when its dry -- let the heavy soil (with better wicking ability) move the water into an aerated root zone where the roots have already developed. | |
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question on tile in drought
