There are approximately 12,000 small farms in Idaho, Oregon, and Washington, mostly near large cities and towns. The number of small farms is growing rapidly and may double by the end of the decade. Small farms range in size from 1 to 20 acres. Many small farm owners have horses or other livestock which are fed by intensive management of the farm, often using quantities of fertilizers and chemicals far exceeding quantities used on large scale farms (on a per acre basis).
Small farms can have a significant impact on water quality. Most small farms are concentrated near the larger cities and towns in Idaho, Oregon, and Washington. These farms, or ranchettes, often contain several horses and other livestock. The owner tries to produce all feed for these animals on this small acreage. Thus forage crops are important. Because most small farm owners are relatively affluent and derive most of their income from off-farm sources the cost of chemicals used in the production of forage crops is often not a limiting factor in management. This results in a very high chemical use rate per land unit area.
Large numbers of small farms are appearing in King, Spokane, Pierce, Thurston, and Snohomish counties in Washington; near Portland, Medford, Bend, and in the Willamette and Rouge River valleys in Oregon; near Boise, Coeur d'Alene, and in Canyon county, Idaho. Because of their proximity to urban areas these farms are often situated on or near some of the most sensitive aquifers and surface waters in the Pacific Northwest.
Most small farm owners are environmentally sensitive; however, this group has totally been neglected as far as educational programming for pollution prevention. Numerous programs are in place to educate the urban dweller on home and garden chemicals. Massive federal programs are targeted at the larger farmer. However, since small farms are not eligible for cost share programs, these people often fail to get technical assistance supplied by agencies such as the Soil Conservation Service.
The purpose of this slide set is to provide a background that will enable a small landowner to utilize phosphorus best management practices on his or her small farm.
|1. Slide Title|
This slide set is entitled "Phosphorus best management practices for small farms in the Pacific Northwest." Funding for the development of this slide set was provided by a grant from the Pollution Prevention Program of EPA Region 10. Owners of small farms that utilize the best management practices introduced in this slide set will help protect both surface water and groundwater quality in the Pacific Northwest.
|2. Humans Need
Phosphorus (P) is an element essential to all forms of terrestrial plant and animal life. Fortunately, P is widely distributed over the surface of the earth in biologically available forms.
|3. The Phosphorus
The complex cycle of chemical pathways that trace P movement within plants, animals, soils, and water is known as the P cycle.
|4. The Phosphorus
This diagram shows a simplified version of the P cycle. The majority of P is located in the soil and can be found in both mineral matter and in soil organic matter. Plant roots remove P from soils and can cycle P directly back to the soil, or P can be eaten by animals, including humans. Soil washed into streams by erosional processes cycles P into water ecosystems.
|5. Phosphorus Cycle
Too much P movement from land to water is undesireable. To protect surface waters we should minimize both the amount of surface water runoff from fields and soil erosion losses from croplands.
|6. Phosphorus and
By itself, excess P is not harmful to plant, animal, or human life. Rather -- the problem occurs indirectly. Too much P causes rapid growth of algae and aquatic plants in water ecosystems. This growth upsets nature's balance -- and leads to undesireable side effects.
|7. Nitrogen Cycle -- Losses|
In water ecosystems P is often the most limiting element. That is, P controls the rate of plant growth in water ecosystems. If you artificially add P to these water systems -- plant growth can drastically increase. One undesireable side effect is that growing aquatic plants deplete the oxygen supply in water. This lack of oxygen is detrimental to fish.
|8. Phosphorus and Water Pollution
Excess P causes eutrophication of a water body. Eutrophication is the response of a water body to overenrichment by nutrients.
Eutrophication is a natural aging process in lakes. This is generally a slow process; however, the addition of P to surface waters can greatly accelerate this process. Elevated levels of nutrients -- particularly P -- often results in abnormally heavy growth of algae and aquatic plants. Examples of symptoms include: algal blooms, heavy growth of aquatic plants, and algal mats. These symptoms result in deoxygenation of surface waters. This is detrimental to fish populations and may result in fish kills.
|10. Phosphorus and
We have already seen that excess P is detrimental to surface waters. Phosphorus applied to soils does not leach -- the P is held tightly by soil particles. Consequently, P contamination of groundwater by human influence is rare. We do not consider agricultural use of P to be a threat to groundwater pollution.
|11. Phosphorus Use in
Phosphorus is one of the seventeen essential nutrients required for plant growth. Plants generally contain about 0.2% P on a dry weight basis. To supply adequate P to crops, application rates range from 20 to 100 lbs/acre depending on the crop. Even the home gardener that uses compost may be adding upwards of 25 lbs P/acre.
|12. Phosphorus Forms
in the Soil|
Phosphorus can be found in three forms in the soil. These forms include soil P, organic matter P, and soil solution P. The soil P and organic matter P forms are not available for plant use. The soil P must undergo a series of chemical reactions before it can enter the soil solution. Organic matter P must be mineralized by microorganisms before it becomes plant available. The P in soil solution is plant available; however, at any given time less than 1% of all the P in the soil is plant available in the soil solution. This makes leaching losses of P unlikely.
|13. Soil Phosphorus|
At any given time in a soil over 99% of the P is fixed. By fixed we mean attached to soil particles. The P is tied up by the soil particle and will not move. If you keep the soil in the field -- keeping it from running off the field and into surface waters you keep P out of surface waters. Simply, if you keep soil in its place, P does not become an environmental problem.
|14. Proper Phosphorus
Proper phosphorus management on small farms is important for four reasons. Proper phosphorus management improves crop quality. Proper phosphorus management improves farm profitability. Proper phosphorus management improves crop water use efficiency. And proper phosphorus management protects the environment.
When we talk about proper phosphorus management to prevent water pollution there is one key concept you need to become familiar with. This concept is called best management practice, commonly abbreviated as BMP.
|16. Phosphorus Concept|
Best management practices can be defined as implemented strategies which eliminate or minimize non-point source agricultural pollution. There has been extensive research to design best management practices for phosphorus management.
|17. Phosphorus Concept|
Best management practices have been designed to be compatible with agricultural ecosystems. Best management practices that you will see in this slide set can protect the environment without compromising the profitability of agricultural enterprises.
|18. Phosphorus BMP --
Soil Erosion Control|
There are six important phosphorus best management practices that should be considered for adoption on small farms. In fact, these BMPs are more easily implemented on small farms than on big farms. The first and most important phosphorus best management practice is soil erosion control. Numerous BMPs for the control of runoff and soil erosion are available. Runoff and soil erosion from agricultural lands are major causes of phosphorus pollution of surface waters. In addition to reduced cropland productivity through removal of fertile topsoil, the consequences of soil erosion include accelerated eutrophication and sedimentation of surface waters, destruction of fish and wildlife habitat, and decreased recreational and aesthetic values of surface waters. Sediment is a prime carrier of phosphorus. Practices for runoff and soil erosion control include both management and physical structures.
|19. Erosion --
Several management practices can be implemented on small farms to control runoff and prevent soil erosion. You should use a combination of two or more management practices to prevent soil erosion. Eight possible management measures are presented here. Use the ones that best fit your situation. One management option is to protect your soil by having permanent vegetative cover. With this management option you would establish and maintain a cover of permanent perennial cover to protect both soil and water resources.
|20. Erosion --
Another management option is to use conservation cropping sequences or rotations. Here the sequence of crops employed produces organic residue which reduces water runoff and protects the soil from erosive processes.
|21. Erosion --
This diagram illustrates some crop rotations that produce organic residues that protect the soil. This illustration is for a four year period. In example A normal row crops are grown in years 1 and 2. This is then followed by a meadow cover which protects the soil for years 3 and 4. The organic residues produced during these two years will help prevent soil erosion when the rotation again reverts to row crops.
|22. Erosion --
Conservation tillage and residue management is another BMP that can be used to reduce both runoff and soil erosion. Utilize tillage practices that leave residues from the previous crop on the soil surface. These residues will reduce water runoff by encouraging infiltration of water into the soil. In addition the residues protect the soil surface, and thus reduce soil erosion.
|23. Erosion --
Contour farming is another BMP that will help prevent soil erosion and runoff. Contour farming is the tillage, planting, and cultivation of sloping land performed on the contour of the landscape perpendicular to the slope of the land.
|24. Erosion --
Strip cropping involves farming operations with alternating strips of row crops, hay, or grain. Strip cropping can be an effective deterrent to soil erosion.
|25. Erosion --
Strip cropping can be effectively utilized on small farms. In this example the farmer is growing two different crops. By alternating strips of the crops both water runoff and erosion are decreased. In most cases on small farms a row crop and hay are alternated in strips.
|26. Erosion --
Cover crops can be used to prevent soil erosion. Cover crops are ground-hugging plants seeded after a row crop is harvested. Cover crops prevent the exposure of the soil surface to erosive events. Cover crops are often used to protect the soil over the winter. They can be grazed by livestock.
|27. Erosion --
Buffer or filter strips are BMPs which reduce soil erosion. Buffer strips are areas of close-growing vegetation, usually a grass, that is used for removing sediment, organic matter, and other pollutants from runoff and wastewater draining from a field.
|28. Erosion --
Mulching is a practice that helps reduce both water runoff and soil erosion. Mulching is simply the use of residue gathered from an off-site source which is used on a field for erosion prevention.
|29. Erosion --
In addition to management practices, physical structures can be used to prevent soil erosion. There are several types of structures that can be used to prevent soil erosion. One such structure is called a diversion. A diversion is simply a channeled ridge perpendicular to a slope. The diversion reduces the speed of water flow -- which in turn allows sediment to settle out from the water and allows extra time for water to infiltrate into the soil.
|30. Erosion --
Fencing is another structural practice that can be used as a BMP to prevent soil erosion. Fences are simply barriers that enclose or divide land areas and prohibit stock access to critical streambank areas. It is important to keep stock out of critical streambank areas for two reasons: (1) the physical movement and grazing by stock cause erosion along a streambank, and (2) wastes generated by stock are rich in P and pollute surface waters.
|31. Erosion -- Structural Practices
Grade stabilization structures are BMPs designed to reduce erosion losses of soils. Grade stabilization structures stabilize slope gradients, control erosion, and prevent the formation of gullies.
|32. Erosion --
Grass waterways reduce erosion losses of soil from fields. These structures are graded, vegetated channels for water runoff. The grass at the bottom of the channel prevents soil erosion by the water runoff stream.
|33. Erosion --
Ponds and sediment basins are structural BMPs that control both water runoff and soil erosion. These structures trap runoff waters and sediments before they leave the small farm. Consequently, major surface water sources are protected from agriculturally generated phosphorus.
|34. Erosion --
Terraces are earthen embankments of channels and ridges, perpendicular to the slope, designed to intercept and transport runoff at non-erosive velocities. As a structural BMP, terraces effectively minimize soil erosion.
|35. Erosion --
This diagram shows a cross section of a terrace. These structures are expensive and must receive routine maintenance; however, they are very effective at reducing soil erosion on sloping land.
|36. Phosphorus BMPs --
An important best management practice for phosphorus is to make sure that the fertilizer rate applied is sound -- based on research. Phosphorus application rates should be based on scientific information. The three Northwest land grant universities -- Oregon State University, Washington State University, and the University of Idaho have developed fertilizer guides for over 50 crops grown in the region.
|37. Phosphorus BMPs --
Fertilizer guidelines developed by university research are the best source of phosphorus fertilizer information. These fertilizer guides take into account both the crop to be grown and the residual amount of plant-available phosphorus that is already in the soil. The appropriate fertilizer guide for your crop of interest can be obtained from your local county Extension office. Your agricultural Extension agent can help you use the appropriate guide.
Correct phosphorus fertilizer placement is another best management practice that can help protect water quality. This strategy is very simple -- put phosphorus in the vicinity of plant roots to maximize phosphorus uptake. Do not apply P to the soil surface -- unless there is no other choice -- as with permanent pastures. The two most often employed placement strategies are banding and broadcast placement.
This diagram shows two forms of phosphorus fertilizer placement -- banding and broadcast. Banding can be defined as placing fertilizer in a small area, a band. The fertilizer is usually placed 2 to 5 inches below and to the side of the seed at planting. In contrast, broadcast refers to a uniform placement of fertilizer. Broadcast can occur either before or after planting. If before planting, it is uniformly applied to the soil surface and then mixed into the soil with an implement. If applied after planting -- it is uniformly applied to the soil surface. We do not want to place phosphorus on the surface because of the potential of environmental damage via runoff and erosion. Clearly, banding is the preferred method of phosphorus application.
Some advantages of banding phosphorus fertilizer compared to broadcast placement include: prevention of phosphorus losses by erosion; protection of surface water quality; placement of fertilizer where crop roots rather than weeds get the phosphorus; the phosphorus is close to plant roots so that under cool weather conditions you get enhanced early season crop growth.
|41. Manure Management|
Many small farms are diversified and have animals as a significant component of the overall farm operation. Whether horses, cows, cattle, or poultry these operations tend to produce a significant quantity of manure. The manure is valuable as it is a significant source of plant nutrients including phosphorus. Correct management of manure is a best management practice. Manure management should consider the following: application methods, application rates, timing of application, consideration of the application site, and manure storage.
|42. Manure Management|
The application strategy for manure is important. Threats to surface water sources are minimized if manure applications are incorporated or injected below the soil surface. Manure applied to the surface of the soil is likely to runoff during a rainfall event. Nutrients, especially P in the resulting runoff water, can contaminate surface waters. Manure incorporation into soils is most critical on sloping land. On sloping land all manure incorporation systems should follow the contour.
|43. Manure Management|
Consideration of manure application rates are critical for proper P management. Manure can supply part or all of the phosphorus needed by crops depending on the manure composition and the actual rate of manure applied. Use published tables to determine the phosphorus content of the type of manure you are applying.
|44. Manure Management|
Animal manures applied to soils can provide substantial amounts of phosphorus to plants. Only a portion of the phosphorus in the manure would be mineralized by soil microbes during the first growing season after application. This table provides information on phosphorus credits for manure for the first season after application. For example, if one ton of solid poultry manure had been applied over an acre the phosphorus credit would be 14 pounds per acre. If 3,000 gallons of swine manure had been spread across an acre, the phosphorus credit would be 30 pounds (10 x 3 = 30).
|45. Manure Management|
Timing of the manure application is also important. Manure should never be applied to the surface of sloping land when a runoff event is likely. In addition, manure should never be applied to frozen ground.
|46. Manure Management|
Incorporation of manure into the soil is always desireable; however, it isn't always practical. There are a few situations where manure must be incorporated into the soil. You should always incorporate manure on 15-year floodplains. In addition, manure should always be soil incorporated on land that is within 250 feet of lakes and streams.
|47. Manure Management|
Environmental conditions often cause manure storage to be a consideration. Manure should be stored when soils are frozen or saturated. Manure storage facilities should be covered and be designed to minimize nutrient losses until soils become suitable for application.
Barnyard/feedlot runoff control is a best management practice that protects surface waters. Runoff from barnyards and feedlots can contribute significant amounts of phosphorus to nearby surface waters. Water quality impacts from barnyards and feedlots increase with decreasing distance to a surface water body. Barnyards and feedlots produce substantial quantities of manure. If the manure is not properly handled, phosphorus can move off site as both runoff water and as eroded organic materials.
There are several types of BMPs that can be utilized in barnyards and feedlots to control phosphorus losses. The two major broad BMP categories are clean water diversions and runoff treatment practices. Clean water diversions include diversions and the utilization of roof runoff systems. Runoff treatment practices include: yard shaping, settling basins, outlet boxes, and filter strips.
|50. Barnyard BMPs|
This diagram of a small farm illustrates several clean water diversion techniques and runoff treatment practices. Illustrated diversion techniques include diversions and a roof runoff system. Illustrated runoff treatment practices include yard shaping, a settling basin, an outlet box, and a filter strip. A grass waterway for erosion control is also shown.
Conservation tillage practices are best management practices to protect surface water quality. Conservation tillage can be defined as any tillage practice that leaves plant residue on the soil surface. Conservation tillage practices are best management practices because they reduce both runoff and erosion when adequate levels of residue remain on the soil surface.
|52. Phosphorus BMPs|
The best management practices presented in this slide set are practices designed to protect water quality and to still provide an acceptable economic return. Remember the following. Use soil erosion control practices to minimize runoff and soil loss. Test you soil and apply phosphorus at recommended rates for crop production.
|53. Phosphorus BMPs|
Credit phosphorus contributions from manure and other organic wastes. Band phosphorus below the soil surface or broadcast and incorporate it.
|54. Phosphorus BMPs|
Control runoff from barnyards and feedlots. Install buffer (filter) strips adjacent to surface waters receiving runoff from croplands.
|55. Phosphorus BMPs|
Limit manure applications on untilled lands. Avoid manure applications to sloping, frozen, saturated, or eroding soils.
This slide script, WQ-21, was prepared by R. L. Mahler
and K. A. Mahler of the Soil Science Division, University of Idaho,
Moscow, Idaho 83844-2339.
This slide set and script was funded by a grant from the Pollution Prevention Program of the Environmental Protection Agency, Region 10.
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All contents copyright © 1997-2003. College of Agricultural and Life Sciences, University of Idaho. All rights reserved. Revised: January 3, 2003