Drainage Management Systems
April 7, 2014, Ohio – State conservation engineers in Ohio are seeing the benefits of Drainage Water Management, an option from the USDA's Natural Resource Conservation Services, writes FarmersAdvance.com. | READ MORE 
Dec. 11, 2013, Algoma, ON – The Agricultural Tile Drainage and Storage Study for Algoma District has identified investment needs of approximately $6.5 million for agricultural infrastructure improvements, including land drainage, according to Wawa-news.com. | READ MORE
Nov. 21, 2013, Illinois – A farmer in Illinois turned to different strategies when traditional tile drainage methods didn't work for his soil, writes AgWeb.com. | READ MORE
Nov. 21, 2013, England – Clitheroe Golf Club in northern England has completed the drainage element of a substantial redevelopment program, which was delayed by bad weather last winter, according to GolfCourseArchitecture.com. | READ MORE
Sept. 13, 2013, United Kingdom – The North Wales Golf Club received an updated drainage system after last year's wet summer brought drainage problems to a head, writes PitchCare.com. | READ MORE
Sept. 9, 2013 – As Denis Rogerson, a drainage commissioner in Norfolk County, Ont., noted in the 1975 issue of Drainage Contractor, preventative maintenance is an important part of open-ditch drainage. Read more in this week's Forty-year flashback article.
May 16, 2013, Ireland – A farmer in Ireland has already seen the benefits of updating an outdated drainage system, writes the Irish Independent. | READ MORE
May 6, 2013, Ohio – An Ohio State University scientist has created a two-stage ditch design, earning him the Ohio Agricultural Research and Development Center's 2013 Innovator of the Year Award, according to Ag Answers. | READ MORE
The agricultural drainage lines that drain water away from individual farmland tile systems are being replaced in a carefully orchestrated program that is expected to take 10 to 15 years.  According to Tom Cummins, Montgomery County surveyor, “In a county like this, drainage is paramount because of the loamy and water-bearing soil. We have more than 200 regulated drains and somewhere between 360 to 400 miles of tile, and during the past five years this drainage infrastructure has just been falling apart.” Montgomery County, whose county seat, Crawfordsville, is 50 miles northeast of Indianapolis, has 505 square miles that is mostly farmland, mainly corn and soybeans.In Indiana and the Midwest, recognizing the need to drain the large numbers of watersheds dates to the late 1800s and early 1900s. Montgomery County landowners realized that it would be mutually beneficial to pool their money and construct common pipelines that would carry water away from their land. Now there are a combination of open ditches and subsurface drains that landowners pay taxes to maintain. It is not uncommon to have a large-diameter 18-, 24- or 30-inch clay or concrete tile or an open ditch that would be as long as three or four miles. Cummins has found that those clay and concrete tiles have outlived their useful life, have started to break down and collapse and today are being replaced with pipe made from high-density polyethylene (HDPE). “We started recognizing the problems that needed to be addressed,” he continued. “I spoke with all the contractors who are on my list for doing the repair work and got their feel for what was the best product out there. I had three or four who were actual tile installers, and got a lot of good information from them, what seems to be doing the best job and that led me to the HDPE pipe.”Mostly used in this county project is perforated, corrugated, smooth inner wall HDPE pipe made with virgin resin supplied by local manufacturer Fratco, Inc. (Francesville, Indiana). Pipe diameters range from 10 to 30 inches. The bidding contractor who was awarded the project selects the brand of pipe as long as it conforms to the specifications and any additional criteria set out by the surveyor’s office. “We have never had a problem with the Fratco HDPE pipe,” stated Cummins. “It meets AASHTO and ASTM specifications.”“Corrugated HDPE pipe is rugged because the material itself is rugged,” stated Tony Radoszewski, executive director of the Plastics Pipe Institute, Inc. (PPI), (Irving, Texas). “HDPE is abrasion resistant and will not corrode. Used since the mid-1960s for agricultural applications, the pipe is a flexible conduit for water that has continued to evolve to provide for the demands of an efficient farming operation and the environment of soil and water conditions.  Today we have pipe that is delivered to the field on mega-size coils of thousands of feet, and on some reels there’s nearly a mile of three-inch-diameter pipe. This enables a contractor to tile acres of land rapidly. The very design of the HDPE pipe that permits perforations, which allow water to enter the system and be drained away, is the key.” PPI is the major trade association representing all segments of the plastic pipe industry.Today, installing a system is vastly easier due to advances in machinery and the pipe. “I’m a fourth-generation drainage contractor,” said Bart Maxwell, Maxwell Farm Drainage (Crawfordsville, Indiana). “We started in 1910, and we’ve seen a lot of things happen over the years. We started with clay tiles and cement, and some of the first plastic tile was put in by my dad, Bart Maxwell, Sr.”According to PPI’s Radoszewski, “The concrete folks like to say that their 100-year product life cycle is proven, because some of it has been in the ground for 100 years. But now it’s not automatic to replace it with reinforced concrete pipe (RCP), which is heavy, difficult to work with, and some contractors report there could be as much as a 30 percent cost advantage of HDPE pipe in labor and materials verses RCP. Installation of HDPE pipe can be done with an excavator, chain digging machines or a trencher.”“We experience so many different soil types and conditions,” Maxwell commented. “We usually try to look at it from the standpoint of ‘if there wasn’t any tile, how would we tile this field?’ You can’t of course do it without factoring in the course of the old concrete or clay tile.“One factor is the grade we use installing the pipe . . . . It could be a tenth of a foot per 100 feet of fall, or five-tenths of a foot per 100 feet. The grade is based on each job,” Maxwell said. “We are very cognizant of the need to increase the size of the pipe based on the lack of grade. Using GPS, we survey the field and plot the topography, lay the main in the lowest parts of the field and keep at least two feet of cover over the pipe just because of the depth of some of the farming tools. Three feet would be great on a 24-inch tile. Sometimes we’re 12 feet deep to catch really low areas such as at the end of the tile run. When you’re doing gravity drainage, and you’re not able to pump, you have to have constant flow through that pipe.”Maxwell generally uses a trencher machine wherever possible instead of an excavator.  “A key factor is that we can cut the trench with a contoured bottom so the soil is not disturbed on the sides and putting some gravel backfill is the extra insurance and then the native soil.  There are some places you can’t use the trenching machine and have to use a bucket excavator and this means more stone has to be used.  Our trencher also grinds the soil finer than just excavating out.  So when you push it back in you don’t have large chunks.  We backfill with number 8 gravel or stone to bed the pipe.”  To allow the trencher to more easily follow the natural contour of the land, Maxwell fitted it with a shorter boot. To facilitate a safe installation with this shorter boot behind the trenching machine, he used shorter lengths of pipe – 13 or 14 feet, and as short as 8-1/2 feet.  Maxwell uses a 1971 Buckeye Super 7 Trencher. “Buckeye is building me a new one that will be delivered in October that will lay up to 36-inch-diameter pipe. The one we have now is slow by trenching standards, but as far as someone digging with an excavator or a backhoe goes, it’s very fast . . . about six feet a minute, that’s 36 inches wide, six to seven feet deep. In a day’s time, it’s no problem to do 2000 to 2500 feet, a half-mile of 24-inch or 30-inch-diameter drainage tile. We run Fratco XD Class II perforated pipe. On the farm field, we want perforated all the way around, which really drains the field.”“Once we install the new HDPE pipe,” continued Maxwell, “we go back and destroy the old tile, cut another trench on the opposite side of it to find any laterals coming in, so we can hook those in to the new system. It’s typical to lay about three trenches total to accomplish the job and we usually have a crew of seven to operate the trencher, feed the pipe and backfill.”Developing the planCummins and the five-member Montgomery County Drainage Board mapped out a program that included pinpointing the drains to be rehabilitated and a fair tax assessment plan. “It was a matter of going over what drains were taken care of during the past 20 years and seeing how much money came out of the assessments for these new ones,” he said.  “We don’t assess people so that as soon as the money comes in we can spend it and then be broke until the following year when the assessments come in again. In the process of examining the books, it became evident that we were spending money as fast as it was coming in. The county collected taxes over the years and at this point in time they figured out that we spent more in repairs and maintenance on fixing broken clay or concrete tile, than it was really worth. We changed the method. Now we identify the drains that are needing constant maintenance and are getting to the point of doing a reconstruction, and fixing it from top to bottom. With a new drain we can keep the landowner’s assessment at a lower rate because it will be decades before any maintenance is needed on that drain. The determining factor is the number of acres in the watershed. Let’s say we have a 200-acre watershed; one farmer might own 20 acres, another 150, and so they figure the percentage of the watershed that they own and that’s the percentage that they will pay on that project.“It’s been during the past four to five years that we have started going gung-ho on the drain reconstructions,” Cummins explained. “We’ve put in close to 50,000 feet. That’s anywhere from 10- to 12-inch all the way up to 30-inch diameter-pipe. We have averaged four to five reconstructions a year with the smallest, generally, about 2000 feet. The longest one we’ve done to date was 6000 feet, completed during the summer of 2012 up in Crawfordsville, which is the main city in Montgomery County.”  According to contractor Bart Maxwell, “A lot of people didn’t think anyone would spend money on these projects, they just wanted to patch up the bad areas. And then all of a sudden when progress was being made, people began showing up at the Drainage Board meetings, and were willing to spend the money to get new mains so they could expand their farm drainage system, and that turned this county around. Before, some people wouldn’t do a drainage system because they didn’t have a good outlet and they were never going to spend money on this tile even though it would help them grow more crops. Now at every meeting there are several landowners saying they have a problem and want the county to fix it because they see the success of the program and the way the tax assessment is handled.” For Maxwell, the past is truly prologue. “A customer of mine bought a farm the other day and he got a packet with information about the farm from the early 1800s,” he said. “There was also the original tile paperwork that showed it was my great-grandfather and his brother who had laid 18-inch tile across this farm. Tom Cummins plans showed that the tile is now coming up for reconstruction. It was installed in 1918 and now four generations later, I may very well be the guy who gets to redo my great-grandfather’s work.” 
Although drainage is usually meant to draw water away, Canadian researchers are successfully irrigating through tile drainage and are improving crop yields not only through increased water uptake but also by reclaiming lost fertilizer nutrients.At the Greenhouse and Processing Crops Research Centre in Woodslee, Ontario. Agriculture and Agri-Food Canada scientists have developed water management technology that combines tile drainage, reservoir and controlled drainage with sub-irrigation systems. Designed by Dr. Chin Tan, research scientist and water management specialist, the two facilities are fully automated, remotely monitored, and equipped with the most extensive and sophisticated water sampling capabilities.The first of the two systems, the Long-term Crop Rotation Water Quality site, was established in 1959 to demonstrate the benefits of crop rotations, whereas the Great Lakes Water Quality site was constructed in 1991 specifically to study controlled drainage and sub-irrigation, and water recycling. On the Great Lakes site, riser pipes that were installed on existing tile drainage systems control drainage. Both sites were upgraded in 2008, with the addition of four storage reservoirs to capture and recycle surface runoff and tile drainage water at the Great Lakes site. Additional “real-time” measuring equipment was issued to the long-term site. Using these instruments, Tan and his team can now measure surface runoff and sub-surface tile flow year round. “Water has to balance and if you do not measure, you do not know,” says Tan. “If you look at the entire water balance, then you know where you want to control and where you want to reduce nutrient loss.”Tan says that with his background in hydrology, it didn’t take long to establish that the prime conditions for nutrient runoff are when there’s residual nutrient left in the soil leading into the winter. With 70 percent of rainfall occurring outside of the cropping season in southern Ontario, it was easy to conclude that capturing and storing surface and tile drainage water during the non-cropping season would be the only means of intercepting sediments and nutrients. By pumping the same water back out of the reservoir during the next cropping season, all these nutrients, particularly phosphorus and nitrates, can be reused.  “In the summertime, you don’t have that much runoff so you want to encourage the crop to use water,” says Tan. “If the crop is using more water, it’s going to produce higher yields.”In tests conducted from 2000-2005 on a Conservation Authority demonstration farm, Tan and his team demonstrated yield increases of 50 percent in soybeans and nearly 90 percent in corn with the controlled drainage and sub-irrigation combination. In a commercial growers’ field, processing tomato yield also increased 40 percent. The increase in production and cost savings makes up for the cost of taking land out of production for water storage. “There’s no question about it from my point of view,” says Tan. “This is not only good for crops, it is good for the environment.” Water quality and environmental impactsSubsurface tile drains are installed to remove excess soil water from agricultural fields so that crop productivity isn’t compromised by wet soils during spring planting. In Ontario, tile drained farms account for 70 per- cent of land in agricultural production. But from an environmental perspective, tile drains also remove excess nitrate during the non-cropping season and this can impair water quality. Tan says phosphorus loss in tile drainage water, especially in the poorly structured clay soils he often works with, has increasingly become a concern. Protecting water quality becomes even more important to the team as more farmers adopt conservation tillage practices, says Tan. “There’s no question about it, conservation tillage has a lot of advantages besides reducing soil erosion; you improve soil structure and use less energy,” says Tan. “But the disadvantages include nutrients coming out, in particular if you have tile.”The improved storage of no-till soils promotes higher water in the upper levels of the soil profile, says Tan, which is a good thing during the cropping season but not during the non-cropping season. Dr. Dan Reynolds is one of the members of the research team who has been heavily involved in studying the relationship between tile drainage and nutrient loss. After conducting an experiment that followed N fertilizer and a chloride tracer in the fall and winter through five agricultural soils, Reynolds was surprised by how fast and deep these nutrients moved down the profiles. “We found, for all five soils, between 60-96 percent of the chloride tracer leached below the 60-centimetre depth over the fall, winter and spring,” says Reynolds. “So based on that, we’d have to say that the N leaching risk was high for all five soils, even though some of the soils had hydrologic soil group designations which suggested low leaching risk.”In Ontario soils are classified by the Nitrogen (N) Index, which rates the risk for contamination of surface and ground waters by nitrate leached out of the crop rooting zone. Reynolds says that in the States they’ve been using N indexing for 20 to 30 years in various forms and Ontario’s version is a hybrid of the two main tiers. But it’s still based on hydrologic soil group and his research is making him think the soil survey information these designations are based on might be lacking.“Water and nutrient movement are strongly affected by the cracks and worm holes making up the soil’s structure, not just the proportions of sand, silt and clay making up the soil’s texture,’’ says Reynolds. ‘‘But soil surveys tend to focus on texture as opposed to structure, because structure is hard to quantify numerically, while texture is relatively easy to quantify.”Reynolds says farmers and drainage contractors need to have a better feeling for just how permeable the soil is and suggests collecting more of the fundamental data, such as saturated soil hydraulic conductivity, and designing your drainage systems partially on that, as opposed to solely soil texture, topography or tradition. To address nutrient leaching, he thinks controlled drainage is worth considering in fairly flat areas and where precipitation can be erratic. “Controlled drainage will definitely decrease nutrient leaching losses, partially because it changes the hydrology of the field by slowing down the rate in which the water moves,” says Reynolds. So far, Tan says, the system they have designed can reduce total nitrate and phosphorus losses by up to 40 per cent. But he warns that controlled drainage with sub-irrigation still requires care in order to avoid making higher surface run-off problems worse.“Once you do sub-irrigation, the soil becomes moist and, with a heavy rainfall, you create more surface runoff,” says Tan. “But when you think about it, you really have a win-win situation in terms of improved nutrient management and increased crop productivity.”Expanding sub-irrigating technology beyond bordersTan says there is renewed interest in drainage management outside of Ontario and even Canada. He says that in much of the Lake Erie basin, the majority of corn production areas have tile drainage and that his research is earning him some new attention, particularly in dry years.“Our climate is changing to be drier but even if you only get 600-700 millimetres a year of rainfall, about 40 percent goes into the tile and surface runoff during the off season,” says Dr. Tan. “With that amount of water we collected in the storage reservoir, you can irrigate for two months, every day, without drying out.”  One of Tan’s colleagues in neighbouring Manitoba recently came to see the Ontario facility in operation. Bruce Shewfelt, a senior water and biosystems engineer, is developing parallel research and development activities on controlled drainage and sub-irrigation. He says addressing drainage management is becoming a hotter topic west of Ontario and to the south of him in the Dakota states.“There’s been a lot of interest and uptake in tile drainage in the last three to four years and the industry is growing very rapidly here,” says Shewfelt. “Dr. Tan’s experimental setup is second to none and provides a great deal of information in a very controlled environment.”Shewfelt says that in their own trials, they address the technical differences between the clayey soils Tan has worked with in Ontario and the fine sands of Manitoba’s special crops areas. Seasonal rainfall variations make drainage in the spring extremely important but in those same locations there is often a need for water by July and August. Manitoba growers of high-value crops could be particularly interested in sub-irrigation and controlled drainage says Shewfelt, if the large-scale studies he is conducting continue to support and build on Tan’s findings.“In a year like this year when we didn’t really get much for spring moisture, if you’re considering means of adding water to the soil and you don’t have overhead irrigation, sub-irrigation might be a method to supplement water available to the crop,” says Shewfelt. “Our contractors and producers are certainly watching what we’re doing and waiting to see what the advantages or disadvantages might be.”
On Jan. 19 a large and interested group heard Larry Brown of Ohio State University discuss “Drainage Water Management for Water Quality and Crop Yield” at the Land Improvement Contractors of Ontario conference in London, Ont. Brown sought to stimulate some new thinking about drainage strategies by presenting photos and discussion of several farms he has toured as part of his work with academic groups from several colleges.Brown started by laying out the problem he and his fellow academicians are seeking to alleviate: worrying levels of nitrates and phosphates that are draining into major water systems from cropland and causing drops in water quality and deadly algae blooms. He noted that agriculture was a major source of nitrates, but not the only source, and that the problem stems mainly from the Midwestern U.S. farm belt and subsurface drainage. Runoff from agricultural lands is causing problems in the Gulf of Mexico and the Great Lakes.In a nutshell, Brown described the solution as better management of drainage, shallower drains, bioreactors, and more use of wetlands as filters for nitrates. He pointed to the NRCS standards 554 and 587 for controlling drainage from a field and noted that of the three kinds of drainage – conventional, controlled and subirrigation – he would primarily be discussing controlled. While controlled drainage has been around since the 1950s to control subsidence on organic soils, groups like Brown’s from across the Cornbelt have met resistance since they started promoting it as a general drainage tool in the 1990s. Contrary to the fears of many landowners, Brown says his studies have found that nitrate concentrations in soil do not fall measurably with controlled drainage whereas water outflows decrease dramatically. He admitted that we do not fully understand where the water and nitrates go. Scientists speculate that because controlled drainage leaves the water table higher, nitrogen may get reintroduced into the soil after the surface water is drained off. His group has measured up to a 50 percent reduction in nitrogen loads in corn and soybeans in controlled drainage operations with subsurface flow reduced by a similar amount. The group does not yet have enough research to say definitively if controlled drainage will increase crop yields. Brown said concerns about using controlled drainage in the winter are mostly due to misunderstandings about the technology. Blocking drains is not an aspect of a controlled drainage management system; instead, the group is adjusting the outlet “elevation” at which water can leave the field. Local practices would have to be adapted to regional climate variations, but he said that controlled drainage has been demonstrated to work as far north as Minnesota and as far south as North Carolina and Louisiana. The practice involves installing water table control structures at drainage outlets.Brown showed an example from a farm that had been converted from beef production to grains. The new drainage system used an existing wetland to take the overflow, and this excess water was used in a lower portion of the field that was under controlled drainage. He pointed out that controlled systems can be retrofitted onto existing drains. Brown said it was true that controlled drainage was not the perfect solution in all situations, but that systems should be designed for the particular cropping system and soils the farmer manages.Brown then moved on to offer some general guidelines for controlled drainage systems. He said the best results are achieved when the water table control structure is installed on solid ground without gravel. Contractors should use an anti-seep collar and hand backfill around the structure after retrofitting. He said it is important to use the manufacturer’s recommended fittings, pipe and watertight joints, and use non-perforated pipe on either side of the structure for a distance of about 20 feet, or half the drain spacing.For good system management, Brown recommends adjusting the outlet elevation in the fall and reducing the drainage outflow until early spring the next year. The outlet elevation should be adjusted again after planting, and unless there is rainfall, allow the crop to slowly lower the water table. The next step on appropriate crop fields is to couple controlled drainage with subirrigation systems, where remarkable increases in crop yield may be achieved, according to Brown’s studies. Forty- to 50-bushel increases in corn production were seen in some instances, with 10-bushel increases in bean production.  Brown faced a number of skeptical questions from the Canadian audience about how such a system would work in the harsh winters. He allowed that more demonstration in northern climates was probably needed.
As much as 85 per cent of the tile installed in Ontario these days is laid using GPS. Despite widespread uptake of the technology by contractors, there is still room for improvement. That was the takeaway message from a talk called “Installing Tile with GPS: A Panel Discussion on What We Have Learned,” held Jan. 18 during the Land Improvement Contractors of Ontario (LICO) 53rd Annual Convention in London, Ont. During the half-hour session, Premier Equipment’s Philip Horst, GeoShack’s Dale Stephenson and  Steve Pym, and AGPS’ Nate Cook shared the lessons they have learned from working with GPS technology over the years. Moderator Gerald Neeb of Roth Drainage opened the session with a discussion about poor and dropped satellite signals. A number of contractors reported encountering bands of interference that caused signals to drop in roughly the same area on each pass across a field.  This phenomenon wasn’t news to panel members.“The only thing I’ve been able to figure is some sort of radio transmitter – directional antenna – through that area floods the spectrum enough that it doesn’t get all of [the satellites] cleanly,” Cook said.One contractor in the audience speculated that the problem was with the radio signal rather than the satellite signal. While working a job near a small airfield, he found that his newer, 450-megahertz system was having difficulty talking to his base and getting a satellite lock. Meanwhile, his old 900-megahertz system still worked. What he first thought to be a problem with his equipment turned out to be a problem with the frequencies in use in the area.GeoShack’s Stephenson agreed that frequencies are a likely culprit in this scenario. He noted that there’s more potential for interference in the 450-megahertz frequency range than in the 900-megahertz range.Technical difficulties with user interfaces were also up for discussion. One contractor reported that over the summer, his equipment kept generating error reports. On three occasions, the only way to get everything up and running was to perform a dealer refresh. The refresh dumped all of the custom parameters installed on his system; they had to be reinstalled after each refresh. To minimize downtime in the future, the panelists advised that custom parameters should be backed up to a database. This way, a contractor can get his equipment up and running more quickly after a dealer refresh.Stephenson then steered the group into a conversation about features and tools they would like to see incorporated into future equipment and software releases. Horst recommended a feature that sets target elevation at a point in the line. That point could then be used as a frame of reference to calculate the slopes for all other points along the line. The audience offered up suggestions too, including a feature that lets users cross-reference top and side views of the terrain, snapping between views in order to better understand a field’s landscape.While on the topic of future tools for the industry, Neeb wondered if lateral spacing controls might one day allow a contractor to put a machine on automatic and make a run while maintaining a predetermined distance between rows of tile. Cook explained that an experimental, real time kinematic (RTK) auto-steer plow directed by a second, front mounted antenna is currently under development in the U.S. At the moment, there are some bugs that need to be worked out of the system.“We’ve had a little bit of trouble with lost accuracy where it drifted a little bit and wasn’t holding the line as close,” he explained. “The best way is to go full RTK – of course, it’s more expensive that way.”Cook advised that the main expense associated with this feature will likely come down to the cost of investing in a second GPS system; the investment in software will probably be minimal.Several contractors in the audience wondered whether this type of system would create problems for users operating their base station through a cellphone. Cook said that this depends on how far the cellphone is from the cell tower.“RTK accuracy still depends on how far away you are from your base station. Whether you get your connection through a radio or through a cell phone, it’s just a difference in the wireless technology,” he explained.Toward the end of the session, one audience member asked about limiting factors, questioning whether it is GPS technology, electronic capability, hydraulic flow or machine speed that currently sets a ceiling on how much tile can be installed, and how precisely it can be installed.Cook speculated that the number of satellites currently available to GPS units on the ground is the main limiting factor at the moment. He pointed to the interference and dropped satellite issues discussed earlier as evidence.Pym argued that machine capability and field conditions are the main limiting factors facing the industry. “GPS we take from the construction industry, and we can basically run the dozer as fast as you want to drive it and control the grade. I would say at this point it’s conditions of the field, conditions of the job, things like that that are going to be your limiting factor as far as GPS grade control.”Cook suggested that integrating more pitch and roll sensors into equipment may help here, as sensor data may allow users to anticipate grade changes before GPS detects them.Although this year’s convention highlighted issues that still need to be ironed out, Neeb said that GPS technology will probably take a hiatus from the LICO convention agenda for a while, until there are new developments to discuss.
For quite a few years farmers and drainage contractors have been hearing about pollution issues in the Gulf of Mexico. There have been calls for farmers to do more to control their use of inputs and an alarming amount of negative press aimed at drainage contractors, merely for installing drainage tile for much of the past two to three years. And not to be mistaken, the pollution problems at the mouth of the Mississippi River, and along other waterways across the US, are in fact, serious and must be addressed. Yet the truth is, there is an overwhelming amount of research that proves drainage is a tremendous asset to the farmer. Furthermore, as the world’s population continues to grow, there is greater demand for corn and soybeans, and that means continued use of inputs in order to boost yields.The good news is, there is a solution; one that is feasible, workable and the latest research indicates it can reduce nutrients by as much as 60 percent. The development of bioreactors is the latest innovation that has shown significant potential to curb some of the concerns regarding nitrate pollution. Basic designsIn its simplest form, a bioreactor is a buried trench which is filled with some sort of carbon substrate – usually wood chips, although there are other options. The wood chips provide an excellent medium for the growth of micro-organisms which use the carbon source as food, and break down the nitrate in any tile water that is run through the buried biomass. The nitrates are broken down by the micro-organisms and expelled as dinitrogen gas (N2), which is a primary – and harmless – component of the Earth’s atmosphere. The Iowa Soybean Association has been doing a considerable amount of field research into bioreactors, joining other states such as Minnesota and Illinois. The move to introduce bioreactors has been gaining strength, especially since much of the agricultural land in north-central Iowa has been tile-drained. And being near the headlands of the Mississippi River, there has been a greater focus on trying to reduce the amount of nitrates flowing out of drains into streams and rivers that feed the Mississippi. “Getting implemented on a field scale, it’s probably been growing within the last three to five years in the Midwest,” says Keegan Kult, watershed management specialist for the association. “And only in the last couple of years has it been gaining a lot of momentum.”The Iowa Soybean Association has taken something of a leadership role in the study of bioreactors, including participation in a Conservation Innovation Grant worth more than $350,000 from the US Department of Agriculture’s Natural Resources Conservation Service. “That’ll pay for additional monitoring on some of these bioreactors, and we’re matching some of the other funding sources up with that,” says Kult, noting that such matching of resources will pay for additional installations. “Part of the grant’s purpose is also to work with NRCS and the different stages that make it an equal and eligible practice. It already is in Iowa, but we’re still at an interim standard and we’re trying to move that standard along.” The NRCS has administered this money as part of a three-year study and a total investment of nearly $22.5 million in conservation programs and research aimed at addressing issues that affect natural resources in the US.For now, the focus of the Iowa project is on agriculture and working together with drainage contractors, since both groups are so well connected. “I haven’t really separated the two,” explains Kult. “I always say that we work so closely together and we work under that ‘tile drainage is necessary for agriculture’ notion, especially where these projects are focused at. Right now, we have this Mississippi River Basin Initiative (MRBI) to address the nitrates reaching the Gulf of Mexico, so it’s listed as one of the core practices there to address nitrate issues.” It is no coincidence that bioreactors have become a topic of interest among universities, grower organizations and associations, and industry groups such as the Agricultural Drainage Management Coalition (ADMC). The pollution issue is gaining strength and coverage across much of the US, particularly along the Mississippi River, and many interests within the drainage industry are looking for answers. In the past, buffer strips were thought to be a solution to higher levels of nitrates and other pollutants; however recent research has indicated that beyond significant rain events, most water leaving fields comes through subsurface drainage systems. Furthermore, that flow almost never comes in contact with surface-level filter systems such as buffer strips. Although the installation of wetlands is another option to offset pollution levels, it is often cost prohibitive to the farmer, with a corresponding loss of production on some portion of the field. Involving farmers and contractorsAs explained on the Iowa Soybean Association’s website (www.iasoybeans.com/environment/programs-initiatives/programs/bioreactors/basics), installation of a bioreactor means there is no adverse effect on a farmer’s field; there is no impact on yield, production or quality of the crop. From a drainage perspective, a control structure on the bioreactor ensures flow across the trench is kept at an optimum level to reduce pollution, without affecting the drainage of water off the field. During times of the year when the flow is high, excess water can bypass the bioreactor and continue its course through existing field tiles. When combined with other environmental control initiatives, such as nutrient management, bioreactors can reduce the nitrogen load between 40 and 60 percent. As for the lifespan of a bioreactor, the wood chips can last as long as 20 years, depending on the consistency of the flow of water from the drainage tiles. “The more consistent flow you have through that bioreactor, the longer-lasting that carbon source is going to be,” says Kult. “It’ll get spent faster the more you get through the wet-dry cycles or if they’re dry, the faster that carbon will decompose.”Some of the other advantages cited by the Iowa Soybean Association include: Nitrates are removed immediately after completion of the water flow; A bioreactor is an option where wetlands cannot be built; Bioreactors can be targeted to a specific location in a field, thereby maximizing the impact; Use of bioreactors is becoming more acceptable in the eyes of producers. That last point is especially important, and Kult acknowledges the need to get drainage contractors to be confident in installing bioreactors is just as vital as convincing growers such an installation is a benefit to them. “Part of the grant is also to get education material out there, along with training days, so that contractors would be comfortable recommending a bioreactor to a landowner,” says Kult. “Then it’s a matter of adding a piece of marketability to the contractor on how to install the bioreactors.”That is one place where ADMC can help. In 2011, the organization held a certification class for bioreactors, and Kult believes there will be more to follow for 2012. “Once they have one installed, I think contractors are fairly confident on how to do the work,” he notes. “And once you get the plan (for the bioreactor), it’s pretty straightforward on how to install it, but as of right now, it’s probably not too high on a contractor’s priority list with as much other work that they have going on at the same time.” Monitoring mercury contaminationAccording to monitoring of bioreactor demonstrations in other states, contamination from methyl mercury (MeHg) can be a problem. And while analysis of soils has not found the same levels of background mercury that exists in other states, it is being monitored nonetheless. Stop logs in the control structures can be adjusted to get an appropriate flow rate that will not fully reduce nitrate levels, but will leave about one to two parts per million in treated water. This design adjustment will limit sulfate reduction in the water, which occurs after complete nitrate removal. That affects sulfate-reducing bacteria, to the point where it also reduces the potential for methylation of any mercury. Further monitoring of the water flow will ensure nitrates in the treated water area not completely depleted.
Land improvement by drainage is not quite what it used to be in Manitoba. A potato grower with extensive tile drainage and a municipal official gave two views of the complex story to a packed house at Ag Days 2011 in Brandon, Manitoba.
Installation of agricultural subsurface drainage tile in the Mexicali Irrigation District (MID), Baja California, Mexico, began in 1971 with the installation on 100 acres. Later, in 1991, the University of Baja California (UABC) installed five in its experimental field located in the ejido (communal) Nuevo León, and another 45 in the year 1995. During the spring of 1998 in a pilot program, the state government of Baja California gave funds to farmers to install tile in four fields with a total area of 145 acres, to 2010, where there are now about 14,000 acres with tile.This made it necessary to develop a field evaluation in the year 2008 with the objective to review the impact that have such systems in soils and agricultural production, as well as the current conditions of these systems.IntroductionThe MID is located in Mexicali, Baja California, Mexico, and receives water from the Colorado River. This district is on border with the state of California, and particularly with the Imperial Valley Irrigation District (IID). This is an arid zone with 513,698 acres in production. In summer, the temperatures can reach 123 degrees F and lows of 21 degrees F, with an annual precipitation of 15 inches and evaporation of around 95 inches per year. These characteristics mark the conditions of an arid area, plus the poor drainage and salinity concentration of the irrigation water of 1200 parts per million (ppm) represent a challenge to maintain adequate soil conditions.At this moment the tile installation is focused to reclamation of land with shallow water tables and progressive soil salinization, and due to this, it is necessary to conduct an evaluation of existing drainage systems to verify their impact on the crop production and the physical-chemical status of soils in a complementary way.The objectives that had been raised were: To evaluate the agricultural subsurface drainage systems of Mexicali Irrigation District, Baja California, Mexico, and To analyze the condition of the pipe filters. Figure 1.  Location of evaluated fields. All figures and photos courtesy of Carlos R. Orozco-RiezgoField workField tours were carried out in holdings with subsurface agricultural drainage projects installed in the District of Irrigation 014, along the Colorado River, for organization and processing into a data base using GIS, whereby information was collected.Soil profile was developed in Field 36 in the ejido (communal land of) Oaxaca, where it had four layers differentiated by color. The first horizon was observed loose and dry, but deeper soil aggregates were more defined and generally have greater resistance to the degree of deformation, as noted in the description of horizons is presented below (Figure 2).Figure 2. Soil profile of Field 36 at Oaxaca. Agronomic evaluation allows us to determine qualitatively if spacing between lateral tiles is working based on the design, which notes the development of cultivation. If in the middle of two laterals, the plant size is smaller than the size of the plants on top of it, then we can infer the separation between drains is incorrect. Seventy-two fields were agronomically evaluated and 59 (82 percent) were working very well; in recovery process were 11 of the fields (15 percent) (Figure 3).Figure 3.  Field with sodium problems.Subsurface drainage systems analysisSedimentation was found in some drainage systems; up to 75 percent of pipe capacity, specifically in soils that have much silt and fine sand. There were root problems in 10 fields, specifically when the open ditch had weeds and bushes in the area were close to the collector discharge.Abrasive deposits of iron (Fe) and manganese (Mn) of one millimeter thick were found both in laterals in the middle of the field and on the main collector. In a total of 172 fields evaluated, five had these problems (Figure 4).Figure 4. Sheath materials analysis.With a portable device, it was determined that the electrical conductivity (EC) of drained water from 45 fields, using pH values, varied from 1.02 to 27.4 dS/m (deciSiemens per meter). The maximum value has an electrical conductivity level similar to seawater salinity data. High salinity detected means that soils are in the process of leaching salt.As stated previously, of 72 fields evaluated, 82 percent were working very well, with 15 percent in the recovery process. The design of geotextile filters was based on the grading curve and a recommended 400-micron size, and systems to a depth of 46 inches for the filter (3.83 feet) on average. The pipe in some cases had up to 75 percent sedimentation, including iron and manganese sediments, and an invasion of roots, so it is recommended to perform maintenance on these systems. Sedimentation in drainage systems was present in soils with silt or fine sand, and in loamy-clay or clay soils.Added conclusionFollowing an analysis of the field information generated, we have the followings conclusions:The maximum water flow in the outlet collector was 158.5 gallons per minute (gpm) and the minimum of 2.9 gpm of salt that is extracted under these conditions is equivalent to 7.38 tons per day and 0.02 tons per day, respectively.RecognitionsTo do this work we had the participation of Rodolfo Namuche, the Mexican Institute of Water Technology (IMTA), the National Water Commission (CONAGUA) and the State Government of Baja California, México.*Carlos R. Orozco-Riezgo is a soil and drainage consultant, and is working on his PhD in subsurface drainage. He is based in Mexicali, Baja California, Mexico.
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