| A major challenge facing agriculture is to improve water use and minimize environmental impact while increasing productivity levels. This study, carried out in Winkler, Manitoba, tested four water management treatments: no drainage and no irrigation (NDNI as control), no drainage with overhead irrigation (NDIR), free drainage with overhead irrigation (FDIR), and controlled drainage with subirrigation (CDSI). Each treatment was replicated in three plots during two growing seasons (April-October) in 2010 and 2011. The monitored variables included soil moisture content, water table depth variation, drainage outflow volume and quality, weather parameters, and agronomic indices. In 2010, yields were 8.48 (NDNI), 10.36 (NDIR), 10.10 (FDIR), and 9.22(CDSI) Mg ha-1 with only the mean yield difference for the NDIR and the CDSI treatments being statistically significant (p = 0.014). In 2011, yields were 9.25 (NDNI), 10.47 (NDIR), 11.28 (FDIR), and 9.49 (CDSI) Mg ha-1 with no statistically significant differences in yield. In 2010, the exports of NO3-N (138 kg ha-1), PO4-P (0.6 kg ha-1) and salts (2.34 Mg ha-1) from the FDIR treatment were significantly larger (p <0.05) than exports from CDSI, which were 0.07 kg ha-1, 0.08 kg ha-1, and 0.41 Mg ha-1, respectively. In 2011, the exports of NO3-N (36 kg ha-1), PO4-P (0.27 kg ha-1), and salts (1.1 Mg ha-1) from FDIR were significantly larger (p < 0.05) than the exports from CDSI which were 10 kg ha-1, 0.08 kg ha-1, and 0.39 Mg ha-1 , respectively. These results indicate that irrigation was the main factor driving corn yields under the conditions prevailing in the Canadian Prairies, while subsurface drainage had a beneficial impact when the beginning of the season was wet. Also, this study showed the advantage of controlled drainage over free drainage in reducing the nutrient and salt exports. |
