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Annual Manure Application Schedule for Western Oregon EM 8724 January 1999 M. Gangwer, B. Wilson, and M. Gamroth Do you want to print a copy? We recommend downloading the print version (97 K). First download the free Adobe Reader, if you don't already have it. Contents Agronomic considerations Nitrogen (N) Phosphorus (P) Potassium (K) Summary Example Manure Application Calendar The overall objective of manure management should be to take as many excretable manure nutrients to the soil and have them used by plants for optimal crop yield. This reduces the need to purchase feed and inorganic fertilizer. The usual outcome of manure management is finding as many acres as possible for manure application. Manure application scheduling depends on the type of manure. Apply liquid manure on a schedule that provides nutrients in the soil root zone in anticipation of crop growth. Apply when soils are at field capacity or less moisture content, i.e., some air space exists in the topsoil. (See Figure 1.) There are several ways to measure soil moisture. You can squeeze a handful of soil and see whether it clumps together. If it does, it probably is at least at field capacity. If water runs out of your hands, then the soil probably is near or at complete soil saturation. You also can measure soil moisture with portable soil meters, tensiometers, watermarks, or other sensory devices. Apply solid manure in such a manner that it will not leave the field surface during rainfall events or flooding. Spring and summer are the best times for manure application. Empty all storage facilities by October 1 of every year in preparation for the winter storage season. Soil testing is an important part of manure application scheduling. A fall test is especially important as it serves as a report card to evaluate crop yield during the previous growing period in relationship to plant-available nutrients, especially nitrate-N. If excessive soil nutrients (N, P, K) are measured, plan a strategy for reducing these values by reducing manure application, changing crop variety, and/or increasing yield. Soil tests also help you decide where to apply manure. They help show whether you are distributing manure on enough crop acres to result in optimal crop yield per acre. Placing too many manure nutrients on too few acres results in excess soil concentrations and reduced nutrients used for crop growth. Figure 1.--Topsoil profile: blue indicates soil moisture, white indicates air space (capacity for liquid to fill), and soil particles are brown. top Agronomic considerations Nitrogen (N) Take a fall soil sample from manured fields. Any concentration of 100 lb (27 ppm) nitrate-N or higher is excessive and indicates less agronomic uptake than the sum of organic mineralization, fertilizer input, and manure application. A goal for this report card test is 55 lb (15 ppm) soil nitrate-N in the top foot. Reduce manure application the following year and increase crop yield (or change the crop) in order to reduce fall nitrate-N. A spring nitrate-N analysis generally is not required because winter rainfall, high water tables, and denitrification leach nitrate-N out of the soil. A cover/relay/ double crop or permanent grass will scavenge some of this leftover nitrate-N. A spring application of manure-N is highly recommended due to the winter losses. This application is especially important for annual and perennial grass. In corn fields, the pre-sidedress soil nitrate test (PSNT) will indicate whether further manure is required. Manure excretion N is half organic and half ammonium. There is no nitrate in manure. Phosphorus (P) You can take a soil test for P at any time. The soil test for P shows extractable P, or plant-available P. It indicates the amount of P in the soil that can be used for plant growth at a given time. Heavily manured fields usually have higher levels of soil test P than do nonmanured fields. Any concentration of 100 ppm or higher of soil test P is excessive. Do not add P to these fields. However, storage pond supernatent contains very little manure P; applications can be made based on N or K requirement. If soil test P is excessive, reduce manure application the following year so P can be mined out of the soil by plants. However, fields with high levels of organic matter can buffer P so that soil test P does not drop rapidly. Mining will occur slowly in these fields. Excessive P in the soil in any form can have a negative impact on water quality if soil erosion moves topsoil into surface waters, carrying with it all forms of soil P. Excessive P in surface water increases aquatic plant growth and reduces the amount of oxygen in the water available for fish. Potassium (K) You can take a soil test for K at any time. The soil test for K indicates plant-available K. Heavily manured fields usually have a higher level of K, especially fields receiving liquid manure. Any concentration of 800 ppm or higher of plant-available K is excessive. Problems with excessive K in the soil can cause high plant K concentrations that can have a negative impact on herd health, especially in fresh and early lactating cows. Excessive K, if leached into groundwater, can increase the salt concentration of water. Also, like sodium, excessive K can reduce water infiltration through soil by hanging onto water. Therefore, managing K on the basis of ration makeup is a good strategy. If feeds low in K are needed for a particular ration, you may need to avoid applying liquid manure on one field until K is mined out. Summary Apply liquid manure on a schedule that provides nutrients in the soil root zone in anticipation of crop growth. Apply liquid manure when soils are at field capacity or less moisture content, i.e., some air space exists in the topsoil. A soil moisture sensor/meter or field hand-grab sample is useful. Apply solid manure in such a manner that it will not leave the field surface during rainfall events or flooding. Empty all storage facilities of any size by October 1 of every year. Use soil testing, especially the fall test, as a report card to evaluate crop yield during the previous growing period in relationship to plant-available nutrients, especially nitrate-N. If excessive soil nutrients (N, P, K) are measured, plan a strategy for reducing these values by reducing manure application, changing crop variety, and/ or increasing yield. Soil tests will help you decide where to apply manure. They will help show whether you are distributing manure on enough crop acres to result in optimal crop yield per acre. Placing too many manure nutrients on too few acres results in excess soil concentrations and reduced nutrients used for crop growth. The overall objective of manure management should be to take as many excretable manure nutrients to the soil and have them used by plants for optimal crop yield. This reduces the need to purchase feed and inorganic fertilizer. The usual outcome of manure management is finding as many acres as possible for manure application. top Example Manure Application Calendar top Prepared by Mike Gangwer, Extension agent, Marion County; Bruce Wilson, conservation planning engineer, USDA-NRCS; and Mike Gamroth, Extension dairy specialist; Oregon State University. January 1999.

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