02222naa a2200289 a 450000100080000000500110000800800410001910000170006024500670007726000090014452015150015365000130166865000100168165000100169165000130170165000090171465300240172365300090174765300100175665300190176665300190178565300230180470000200182770000200184770000180186777300470188510735781993-08-31       1967    bl ---       0--  u    #d1 aMONKE, E. J.  aField study of subsurface drainage on a slowly permeable soil.  c1967  aThe readiness of a slowly permeable soil to drain was evaluated for replicated subsurface drains placed 25, 50, and 100 ft apart. The drains responded within a few hrs to the commencement of a discharge-producing storm and produced maximum discharge values quickly, after which long recession periods occurred. In general, the highest discharge occurred for drains which were placed farthest apart because of the likelihood of high antecedent moisture conditions. Percent-agewise, the difference between peak flow rates decreased as the magnitude of flow increased, suggesting that-when the soil becomes fully saturated these differences would be small. Peak rates could therefore be used to obtain an effecfive hydraulic conductivity value for the rational design of subsurface drainage systems, The response of crop production to different levels of drainage was evaluated form yield data and population stands. Corn yields were significantly different with respect to the spacing of the drains. Part of this difference wasdue to variation in corn population. In general, stands for the 25-ft spacing were  higherthan those at either the 50 or 100-ft spacing. How much of the yield differences, if any, should beattributed as a response just to drainage as opposed to total moisture environment thoughout the entire growing  season is unknown. Also before yield data can be used to justify a spacing criterion, the probability of the occurrence of yield-depressing drainage situations should be assessed. ...  adrainage  awater  aÁgua  aDrenagem  aSolo  aDrenos subterraneos  aFlux  aFluxo  aPermeable soil  aSolo permeavel  aSubterranean drain1 aFLUGGINS, L. F.1 aGALLOWAY, H. M.1 aFOSTER, G. R.  tTransactions of the ASAE, p.573-576, 1967.