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Conservation Practices

Iowa’s farmers use a variety of conservation practices to ensure the best use of soil and water resources to reduce nutrients in water and ensure their long-term ability to farm. What is best for a particular farm depends on many factors, so a variety of practices are used to maximize results.

Some practices are considered every year and take place in the field. Others provide long-term water quality benefits and only require maintenance to keep working. These practices may be installed within the cropped area of the field or at the edge of the field, depending on the practice. 

Annual Practices

Cover Crops

Planting cover crops is a best management practice to improve water quality by retaining nutrients on farm that may otherwise leave the field via erosion, runoff or leaching.


Cover crops are non before or commodity crops planted into standing cash crops or bare fields following harvest, with the intent of improving soil health and water quality, increasing farm profitability, reducing fertilizer costs and improving weed control.


There are so many! Based on several years of research among the agronomist community, the following list equates to the many reasons cover crops are great:

  • Improves soil quality

  • Reduces erosion

  • Retains soil nutrients

  • Sequesters carbon

  • Breaks up soil compaction

  • Replenishes nitrogen

  • Increases organic matter

  • Combats weeds


Cover crops need to be planted early enough in the late summer or fall to allow for germination and growth before frost (aerial seeding can help with this), and they need to be terminated in the spring to prevent interference with the next crop. However, this can easily be accomplished through grazing, haying, tilling, spraying or a combination of these methods.

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No-till farming greatly reduces soil disturbance, which in turn reduces soil erosion, builds soil organic matter and helps reduce phosphorus entering waterways. Soil and crop residues are left undisturbed between harvest and planting, other than nutrient injection.

Strip-till is a modified form of conservation tillage where tillage is limited to a narrow zone in which the crop is planted. Soil disturbance is greatly reduced compared to conventional tillage. Strip-till reduces soil erosion, builds soil organic matter and helps reduce phosphorus leaving the field. 

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Extended crop rotation

Extended crop rotation is a planting cycle of different crops, such as grasses, legumes, small grains, corn and soybeans, to help improve soil health and decrease insect and disease pressure. The increased number of months that soil is covered with actively growing plants is the benefit to water quality and soil health.

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Nutrient management practices

The fertilizer rate, timing, placement and the source of nutrients applied are managed to maximize the nutrients that are taken up by the crop while minimizing the loss of nutrients – particularly nitrogen and phosphorus – to surface water, groundwater or to the atmosphere. The right source, rate, time and place make up the 4Rs of nutrient managements. 

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Drainage water management or controlled drainage is the use of a control structure to manage drainage of water from fields throughout the year. The practice reduces the loss of nitrates and can increase crop yields in some years.

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Long-term Practices


Bioreactors redirect tile water to an underground bed of woodchips where nitrate is removed naturally by microorganisms. Bioreactors can reduce nitrates by an average of 43 percent. Vegetation on top of the bioreactor can provide other benefits, such as wildlife habitat.

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Saturated buffer

Saturated buffers have a water level control structure that is installed near the outlet of a tile line, but within or immediately adjacent to an existing stream buffer. A portion of the water is diverted into a tile line parallel to the stream and within the buffer. Nitrates in the lateral tile are used by the vegetation around the buffer. 

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prairie strips

Strips of native prairie grasses and forbs are placed on the contour in crop fields, combined with filter strips of prairie grass strategically placed where runoff leaves the field. This practice results in large improvements in runoff water quality with only a small (10 percent) portion of the field taken out of row crop production.

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stream buffers

Stream buffers are grassy or native vegetation adjacent to streams that trap sediment from surface runoff. They reduce phosphorus entering a waterway, filter nitrogen as it moves in groundwater through the soil, stabilize stream banks and provide habitat for wildlife.

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constructed wetlands

Constructed wetlands are shallow vegetated pools that help filter nutrients, especially nitrates, control flooding and provide wildlife habitat. They have been shown to improve water quality by reducing nitrates by an average of 52 percent. Actual nitrate removal depends on rainfall, with greater removal in drier years and lesser removal in wetter years. In addition to removing nutrients, wetlands provide habitat, recharge groundwater, reduce flooding downstream by storing runoff and can provide recreational opportunities.

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grassed waterways

Grassed waterways are areas within fields that are maintained in grass to address areas of concentrated water flow. Grass waterways prevent soil erosion and associated phosphorus loss.

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Terraces are earthen embankments, ridges or ridges-and-channel built across a slope to slow water runoff, thereby reducing soil erosion and phosphorus loss.

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Water and sediment control basins

This practice is very similar to a terrace, but water and sediment control basins are generally short and straight, are placed at the lower end of slopes and do little to reduce slope length. They may be used to help control gully erosion and/or to prevent sediment accumulations farther downstream.

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