Effect of Water Table Management on Water Quality and Crop Yield at the Plot and Farm Scale Fields

Abstract

There is mounting evidence that water management systems which combine controlled drainageand subsurface irrigation (subirrigation) can mitigate growing-season water deficits and reduce nitrate leachinglosses in tile drainage water. This may in turn improve both crop yields and environmental quality. A 4-hafarm scale field on a sandy loam soil and a 0.4-ha plot scale field on a clay loam soil in southwestern Ontariowere instrumented with two water management systems: controlled tile drainage with subirrigation (CDS), andtraditional free outlet tile drainage (DR). The objectives of the study were to compare the CDS and DRsystems with respect to tile drainage volume, nitrate concentration in tile drainage water, total nitrate loss in tiledrainage water, and yield of tomato, corn and soybean.<br><br>From May, 1995, to April, 1997, the farm-scale CDS system in the sandy loam soil reduced flow weightedmean nitrate concentration in tile drainage water by 38 % and total nitrate loss in tile drainage water by 37 %,relative to the DR system. Total tile drainage volume was similar for both systems. In 1995, marketable tomatoyield on this soil was increased by 11 % under CDS relative to DR (64.9 t ha-1 for CDS, 58.4 t ha-1 for DR),while in 1996 corn yield under CDS was increased by 64 % relative to DR (11.0 t ha-1 for CDS, 6.7 t ha-1 forDR).<br><br>Between May, 1995, and April, 1997, the plot-scale CDS system in the clay loam soil reduced total tiledrainage volume by 50 %, flow weighted mean nitrate concentration in tile drainage water by 32 %, and totalnitrate loss in tile drainage water by 66 %, relative to DR. In 1995, soybean yield under CDS on the clay loamwas increased by 17 % relative to DR (4.2 t ha-1 for CDS, 3.6 t ha-1 for DR), and in 1996 corn yield wasincreased by 9 % relative to DR (8.6 t ha-1 for CDS, 7.9 t ha-1 for DR).<br><br>It consequently appears that the CDS system can consistently reduce nitrate leaching loss through tile drainageand increase crop yields, relative to DR.