ISSUE 14 August 2, 2001
DRAINAGE- MYTHS, LEGENDS AND REALITY
I have lived in North Dakota since 1994. I missed the dusty 1988-1990 period and for that I am grateful, although it was plenty hot and dry in Illinois those summers and in 1989, I saved my neighbors’ house from burning after his toasty brown lawn caught fire from an unattended burn barrel. When I moved here, I was told it was dryland country. And I suppose for most of pioneer history until now it was. But it isn’t now. Every year, it seems that North Dakota is more and more like Illinois- more corn, more soybeans, more water, and more talk of tile and drainage.
In the mid-west, and it was particularly true in east-central Illinois where I spent most of my fertilizer company agronomist career, tile are abundant and it is evident why they are abundant from areas in fields where they break, or in fields where they were never put in. If you look at old maps of Illinois in the early 1800's, you will notice the large area in the east, where hardly anyone lived except on the morainal ridges. This was a huge area of swampy ground filled with mosquitos that Native Americans and pioneers vigorously avoided.
In the late 1800's, some people from northern Germany and lower Holland, familiar with land drainage, came over to visit and seeing the wonderful soil underneath the swamp, decided to call their relatives and drained the region. They used steam boats with dredges, steaming into the middle, deepest part of a shallow lake and steering for the nearest stream, producing channels that were the first step in draining the areas. The channeling was perhaps the simplest and cheapest step. The next project was running tiles, usually clay at that time, from the field into the channels. I talked to several older people who actually made a living in the 20's and 30's digging tile lines for 4-8 inch tile with a spade, going down about 16-18 inches and laying them in by hand. It took a long time to do, but the results were amazing. That area is now one of the productive corn and soybean areas in the world.
One has only to fly around the state briefly to look at what excess water can do to a region that has no effective drainage strategies. Land that was cropped in the 1980's now has some of the best northern pike fishing around. The low, black fertile ground is now covered with cattails. Areas with no salt ten years ago now grows kochia and little else and is surrounded with still more white crusty land. Is there anything that can be done?
Drainage can be approached two ways- get rid of the surface water as soon as possible, and/or tile drain so that water moves slowly from the land and the surface dries enough between rains so that surface flooding due to already saturated soils is not as severe.
In high clay soils, such as are present within five miles east and west of the Red River Valley, we are stuck with the first option. This is also the option that distresses most urban people within the region, because the more surface drainage, the faster the water moves to the river and the higher the river might reach in height. Tile drainage is possible in clay soils, but the distance that must be maintained between the tile lines is very close, perhaps 40 to 50 feet apart. The cost of achieving this drainage is very high. The other consideration in clay soils is that the immediate benefit from having removed free water from the upper 18 inches of soil or more is not as great as in soils with higher permeability. Drier surface soils may allow another 1/4 inch of rain to penetrate the soil, but movement downward is so slow that runoff potential is still very high.
In medium and moderately fine textured soils, tile drainage makes more sense than surface drainage, because it results in slower release of water to swollen streams and rivers, and because the loss of water is continuous for a long period of time, keeping streams and rivers flowing perhaps during times that they normally would not. Lateral tile lines within fields will normally be between 150 and 200 feet, making the cost of installation far less expensive than in clay soils, although in many cases it might cost as much as a person paid for the farm originally to install them. Tiling does not eliminate all water from the soil, it only gets rid of free water to the depth of the tile. Most plants use only a small amount of free water, since roots of our normal crop plants also need oxygen to grow and do not grow into saturated soils on purpose. What tiling will do, is lower the water table, cause salt problems to diminish, and provide a more stable moisture environment for crops. Fields can be seeded earlier in the spring, and harvest rains are not as devastating, because tile helps to dry the fields out even when crops are not using water anymore.
There are practical considerations that must be addressed before tiling. First is where the outlet might be. There are many areas in the state which are essentially land-locked to drainage. In other areas, the crop to a ditch or stream might be too shallow. There might be neighbors whose land must be crossed to reach an outlet. In states where drainage is a way of life, there are drainage districts established where there are agreements regarding who has rights and who does not and this helps to solve these social issues with limited hard feelings. But working with neighbors is an important issue and may often restrict what can be done. Many people want to get rid of their water, but do not want anymore upstream water if they can help it.
The second issue is regulatory. Before going to far into the process, wetlands are protected. There are firm guidelines, mostly defined by soil series and soil development under these areas, of what a wetland is and is not. Working with NRCS, there may be ways to mitigate certain lands to create wetlands somewhere else and allow drainage of large parts of fields through the original wetland.
The third issue is cost. Drainage is not cheap. If it was known that the current wet period (I dislike the word cycle- every year is different, not a repeat of another time) would last for another fifty years, tiling might have begun faster than it has. However, might our climate revert to dryland next year? There is no way to know. So to spend $500/acre on tile drainage might be what keeps someone in business in a highly profitable way, or all it could do is hasten a farm sale.
The fourth issue is environmental. Currently, areas of the US with tile drainage experience large fluctuations in nitrate in surface waters. Low rainfall and slow tile drain activity result in low surface water nitrate. However, when it rainfall is high, the soil is "flushed out" of nitrates, because all the soil pore space is filled with water and the concentration of nitrate in water increases greatly. It would be more difficult in tiled fields to predict nitrate levels based on our fall soil testing. It might push us to use more spring soil testing or pre-sidedress testing for row crops. But the social effect would be that where our rivers and streams have relatively low levels of nitrates now, because movement through our soils is slow and excess nitrate tends to either stay in the soil or denitrify, with increased tile drainage, nitrate levels in surface waters would increase. There is already activity at the Federal level to limit N rates in some parts of the country. With increased nitrate in our water supplies, those coming regulations would surely be applied to our region as well.
SOIL SAMPLING FOR NITROGEN FERTILIZER PLANNING
As soon as the soil dries out from the recent rains, grain harvest will begin. Following closely behind, before the chisel plow gets to the field, should be a soil sampler. Soil sampling for N can proceed anytime following small grain harvest. There is no need to wait until October. The sampling date adjustment made by the state’s soil testing laboratories does an excellent job of predicting the ½ lb/day nitrate-N released until September 15 from decomposing barley and wheat straw/leaf residues. By waiting, there is an increased risk that volunteer grain regrowth will distort residual N differences, and by waiting until after deep cultivation, it is not as easy to obtain a consistent, uniform 0-6 inch core with a hydraulic corer for phosphate and micronutrient analysis.
Sampling following canola, field pea and other early harvested broadleaf crops should be delayed until September 15, since release of N from decaying residue is richer in N than small grains and is probably not predicted by our present sampling date adjustment. Following September 15, the soil test values would be most valid.
Consider sampling by topography this season, even if fertilizing uniformly. By sampling 8-12 cores each on hilltop, slope and depressional area within a field, as opposed to 20-30 cores in representative uniform areas to describe the field, the resulting sample report will provide three nitrate-N numbers and give support to any high testing values found in the field, or it will expose major differences in values that might lead to different fertilization strategies than might have been used if a composite sample for the field was taken. Costs will be similar to the composite approach, due to similar number of cores being taken, with some increased cost due to increases in the number of samples analyzed. Since nitrate is by far the most important nutrient tested for, and the one that usually makes the most difference in yield and quality of crops, this sampling is most appropriate for N. For more information on soil testing and zone sampling, see NDSU Extension Circular SF-990 (Revised) and SF-1176(2).
The most important input in raising a crop, except for seeding, is nutrient management. Soil testing is the best basis for accomplishing a successful fertilizer application, and should be the first thing done once the grain comes out of the field.
NDSU Extension Soil Specialist