Subsurface Tile Drainage Advantages
Dr. Eileen Kladivko, agricultural engineer, Purdue University has conducted drainage research for 44 years. About 35 years ago, Purdue installed 4 inch plastic tile on hard to drain, clay resistant soils (Clermont somewhat similar to Paulding Clay). Clemont soil has a clay pan 2.5 to 3 feet deep which act like a bowl, filling up with water so the subsoil stays wet. This research started in the 1980’s using 5, 10, 20 meter spacings (16, 33, 66 feet) compared to no tile drainage (over 40 m or 132 feet).
Dr. Kladivko data shows that drainage pays, even on tough clay soils with a claypan. Benefits include more timely spring field operations; improved yields; positive results from other conservation practices; and improved cover crop, hay, and small grains crops growing in the fall and over the winter.
Kladivko found that even during dry times, there were positive benefits subsurface tile drainage. The first 10 years, the rotation was corn after corn due to farmers interest in that practice with chisel plowing in the spring. If they chisel plowed in the fall, the soil would seal over and that negatively affected all the tile drainage systems. The next 10 years they switched to a corn soybean rotation and went to no till plus a winter cover crop. Here are the results:
The first 10 years (continuous corn, spring chisel plowing) on the zero drainage; spring planting was delayed 1 to 15 days compared to the narrowest tile spacing (5 meters, 16 feet). Aerial photos show a lighter color over and around tile lines indicating better drainage compared to dark coloring on the undrained soils. A big change was the difference in corn grain moisture which averaged 21% on the drained plots compared to 23% moisture on the undrained plots. This is a reduction of 2% in reduced energy cost to dry the corn down, averaged over 10 years.
In some years, they had to replant 2 to 3X to get a stand on the undrained plots. The corn did not emerge or the stand was too spotty to keep. They got a stand a least 30 days later one year. Early planting has a significant effect on crop yield, especially when stands are good. Dr. Kladivko estimates the cost of replanting is $95 for labor, machinery costs, fuel oil plus about another $100 for high quality hybrid seed.
The biggest change was in improved crop yields, especially when they switched to no till and cover crops after 10 years. The no till and cover crops improved the soil structure on the clay soils with a claypan so that the subsurface tile worked better. Instead of having to wait for 6 to 8 inches of soil to dry out on the conventional chisel plowed soil, now they had to wait for only the top 1 to 2 inches to dry out. Now they can plant all the drained plots on the same day but still have to wait to plant later on the undrained plots. The undrained soil was consistently in the bottom on yield or tied with the bottom, all ten years, after no till and cover crops were initiated.
Over the course of the research (1984 to 2017), the 5, 10, 20 meter (16, 33, 66 feet) spacing averaged in the mid 160 bushel per acre range with a 24, 19, 18 bushel yield advantage over the undrained cropland (144 bushel). In some years like 2007 and 2011, there was almost no advantage, but in some wet years (2015) the advantage was 50 plus bushel per acre over undrained plots, no subsurface tile. On average, based on average corn prices for that time period, there was a $60 per acre economic advantage per acre for subsurface tile drainage.
Dr. Kladivko also noticed other positive results to tile drainage. On average, farmers expect about a 1.9% improvement per year in corn yields due to genetics. The tile drained plots allowed this improvement but the undrained plots did not see any improvement in crop yields over time. The first 10 years, the improvement in crop yields were not as good. At first, they thought that that decade was drier and the last 10 years were wetter. That was not true, the precipitation trends were quite similar. Then they looked at the change in tillage and cover crop installation. They found that the soil had more soil organic matter, the soil structure was better, and the drainage improved. Tile drainage allowed other conservation practices to work better. Also cover crop biomass increased 4X and fall and winter planted crops grew better with improved drainage. The average change in crop yields was probably closer to 30 bushel per acre on the tile drainage due to aid from no till and cover crops to improved sustained drainage.
