Effect of New Innovative Water Management System On Nutrient Losses and Crop Production.

Nutrient (P & N) losses and their partition in various pathways may differ depending on water management practices. A study was conducted using large field plots equipped with automatic flow volume measurement and sampling systems over a 5-year period to determine the effectiveness of regular free drainage (RFD) and controlled drainage with sub-irrigation (CDS) for mitigating P and N losses and to identify the relative roles of surface runoff and sub-surface tile drainage in P and N losses. CDS produced 150 mm greater surface runoff, but 369 mm less tile drainage volume than RFD over the 5-yr period (2000-2004). CDS reduced total combined surface runoff and tile drainage volume by 19 % relative to RFD. For RFD, flow weighted means (FWM) of total P and nitrate concentrations over the 5-yr period were averaged at  0.741mg P L^-1  and 4.37 mg N L^-1  in surface runoff water and at 0.480 mg P L^-1  and 8.47 mg N L^-1 in tile drainage water, respectively. For CDS, FWM of total P and nitrate concentrations were averaged at 0.804 mg P L^-1 and 5.82 mg N L^-1 in surface runoff water and at 0.457 mg P L^-1 and 8.71 mg N L^-1 in tile drainage water, respectively. Relative to RFD, the CDS reduced total P and nitrate losses by12 % and 21 %, respectively. Of the total soil P and nitrate losses, about 5 % and 2 % were accounted for in surface runoff water, while 95 % and 98 % were accounted for in tile drainage water for RFD. For CDS, 30 % and 14 % of the total soil P and nitrate losses were in surface runoff water, while 70 % and 86 % were in tile drainage water. Subsurface tile drainage played predominant role in nutrient P and N losses. During the low rainfall seasons of 2001 and 2002, the CDS increased corn yield by 91% (2001) and soybean yield by 49% (2002), relative to the RFD. Thus, CDS can be considered as a beneficial management practice to reduce nutrients P an N losses and improving crop yield under the similar climate and relatively flat field conditions in Southern Ontario.