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Effects of tillage on the quality and quantity of surface and subsurface drainage water: Uplands

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Title: Effects of tillage on the quality and quantity of surface and subsurface drainage water: Uplands
Author: Kachanoski, R. G.; Rudra, R.
Abstract: A study was undertaken to determine the effects of tillage system on the quantity and quality of surface runoff and tile drainage water. Previous studies have suggested that the increased infiltration and occurrence of macropores in no-till systems may increase the risk of movement of chemicals to the groundwater. Thus, no-till systems may solve one problem (surface water quality), but create another problem (groundwater quality). The study was carried out on the long term no-till - moldboard plough comparison established by Don Lobb, a conservation farmer near Clinton, Ontario. The soil at the site is a sandy loam. Three tile lines in each of the two tillage systems were instrumented for monitoring tile flow quantity and the concentrations of nitrate nitrogen and phosphorus. Multi-level groundwater samplers were also installed in each treatment, and soil coring and the application of tracers (chloride) was used to track the movement of soluble chemicals. Detailed solute transport experiments under controlled application of water were also carried out to characterize the soil transport properties. The installation of equipment was started in the fall of 1988 and finished in spring of 1989. The site was planted with corn in 1989 and soybeans in 1990. Surface runoff was monitored by installing runoff collection flumes on selected soil landscape positions within the study field. Rainfall simulation studies and characterizations of the hydraulic soil properties controlling surface runoff were also carried out in cooperation with other studies. No significant tile flow was recorded until late fall 1989. From Oct. 1, 1989 to Oct. 1, 1990 a total of 121 cm of precipitation was recorded. Total tile flow amounted to approximately 19.0 cm with no significant differences between tillage systems. Movement of water below the tile line was significant and estimated at 49 cm of water. No-till had significantly higher average concentration and water flux averaged concentration of NO3-N in the early spring and fall periods compared to moldboard, but the reverse was true in the late fall. The average concentrations in both systems exceeded the drinking water quality limit of 10 mg NO3-N/L. The average concentration was 10.7 mg NO3-N/L in both systems. Total nitrogen leaching from the 1989 corn crop was estimated at 80 kg N/ha and 50 kg N/ha in the no-till and conventional till systems respectively. The increased N leaching in the no-till was attributed to a higher N soil test in the no-till system and a requirement for less N fertilizer than the moldboard systems. Both systems had the same fertilizer applied (160 kg N/ha). The amount of N lost by leaching in each replicated plot was significantly correlated to the difference between the fertilizer N applied and the fertilizer amount required according to the N soil test. Detailed transport studies indicated more macropore transport in the moldboard plough system than the no-till system. However, the average solute transport velocity was faster in the no-till, which was attributed to increased occurrence of blocked pore domains. The no-till system should not result in an increased risk of chemical contamination of our groundwater resource. If the nitrogen soil test is used to determine fertilizer requirements then the occurrence of over-application of N fertilizer should be significantly reduced in all tillage systems. Surface water runoff from both the no-till and moldboard treatments was negligible at this site. This was attributed to the very high infiltration rates of the sand-loam soil. Runoff simulation indicated that increase water runoff would be expected in the no-till treatment for very large rainfall events. However, total phosphorus loss would be 2 to 4 times lower than the moldboard treatment. Dissolved ortho-phosphorus and nitrate N in runoff water was also very low in the sandy-loam textured soil. However, runoff simulation on a clay-loam textured part of the field indicated that ortho-phosphorus in the runoff was significantly higher in the no-till compared to moldboard treatment. This, combined with an increased runoff volume from the no-till may be a problem in heavier textured soils.
URI: http://hdl.handle.net/10214/14817
Date: 1992
Rights: In Copyright - Non-Commercial Use Permitted
Rights Holder: Agriculture Canada


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