Potassium Cycle, Fertilizer, and Organic K Sources. Fundamentals of Nutrient Management Training. August Morgantown, WV. Ed Rayburn West Virginia University Extension Service

Potassium K is potassium, the mineral used by plants to move sugars, to regulate transpiration, and is high in milk. K 2 O is the measure of the fertilizer plant nutrient potash. K 2 O = 1.2 x K

Forms of potassium in soils.

Mineral5,000 to 25,000 ppm Non exchangeable50 to 750 ppm Exchangeable40 to 600 ppm solution 1 to 10 ppm

Mobility of potassium Roots absorb K as K + No organic coordinated compounds of K Leaching low in soils having some clay content Mobile in plants deficiency symptoms appear on older leaves

Fixed potassium

Factors controlling K availability Clay minerals type and amount Cation exchange capacity Amount of exchangeable K Soil moisture Soil temperature Soil pH Recent lime applications

Minerals for K supply and retention Primary minerals Mica and Illite Illite Vermiculite –Surface –edge –interlayer

Effect of amendments on K Liming increase CEC so increases a soil’s capacity to retain K and may interfere with K release from clay Application of gypsum increases K in soil solution Ca cannot remove Al, but easily replaces K

Forage yield response to soil test K.

Fertilizer K affect on forage yield when soils test low in K.

Fertilizer K affect on forage yield when soils test medium to high in K.

Converting to Mehlich 1 K Ammonium Acetate K, ppm x 0.67 = Mehlich 1 K, ppm Morgan K, ppm x 1.0 ~ Mehlich 1 K, ppm

Components of nutrient cycling Mass Balance = Import – Export –Import = forage + grain + minerals + fertilizer + rainfall –Export = animal products + crops + run off + erosion + leaching Recycling within farm –Nutrient content of pasture, crop, and supplements –Nutrients excreted by animal vs. removed in product –Recovery of urine and feces –Uniformity of return to area removed from –Location of areas having a net import or export

Nutrient value of pasture, hay, silage, and grains.

Nutrient content of pasture crops in terms of fertilizer nutrients. Pounds/Ton at 90% Dry Matter NP2O5P2O5 K2OK2OCaCO 3 MgCO 3 Pasture, grass Pasture, mm grass Pasture, mm legume Pasture, legume SD

Nutrient content of hay crops in terms of fertilizer nutrients Pounds/Ton at 90% Dry Matter NP2O5P2O5 K2OK2OCaCO 3 MgCO 3 Hay, grass Hay, mm grass Hay, mm legume Hay, legume Hay, small grain Straw corn stalks62773 SD

Nutrient content of silage crops in terms of fertilizer nutrients Pounds/Ton at 33% Dry Matter NP2O5P2O5 K2OK2OCaCO 3 MgCO 3 Silage, corn Silage, grass Silage, mm grass Silage, mm legume194 6 Silage, legume Silage, small grain Silage, sg and leg SD31541

Nutrient content of grain crops in terms of fertilizer nutrients Pounds/Bushel at 85% Dry Matter --- NP2O5P2O5 K2OK2OCaCO 3 MgCO 3 Corn, shell Wheat Oats Barley Soybeans SD

Average nutrient content of manure. Source and FormNP2O5P2O5 K2OK2OCaMgS Poultry (broilers, lb/t) Poultry (layers, lb/t) Dairy (solid, lb/t) Dairy (liquid, lb/1000 gal) Swine (liquid, lb/1000 gal) Horse (solid, lb/t)

Animal (mineral) vs. fertilizer (oxide) forms of nutrient measurements

CP = 6.25 N P 2 O 5 = 2.29 P K 2 O = 1.20 K CaCO 3 = 2.50 Ca MgCO 3 = 3.47 Mg Conversion from fertilizer nutrient to mineral form.

Nutrient value of fertilizers.

Potash sources potassium chloride (0-0-60) potassium sulfate (0-0-53) sulfate of potashmagnesia (0-0-26)

January 2009 fertilizer prices N from urea $0.50 / lb P2O5 from TSP $0.50 K2O from KCl $0.75

Nutrient value of a 1 ton hay crop (lbs./acre): 30 N 12 P 2 O 5 45 K 2 O

The dollar value of plant nutrients (N, P 2 O 5, and K 2 0) passing through a 1000 pound cow each year is ~ $150 to $250.

Nutrient value of milk, meat, and wool

Nutrient value of animal products

Magnitude of nutrient cycling by a 1000 lb. cow.

Magnitude of nutrient removal by a 500 lb. steer.

Magnitude of nutrient removal by a dairy cow making 10,000 lb. milk.

Majority of K is excreted in the urine by livestock (75-90%).

Annual nutrient cycling or removal by different classes of cattle.

Nutrient cycling in grazed areas.

Manure distribution in a 3-paddock system

Manure distribution in a 12-paddock system

Manure distribution in a 24-paddock system

Manure distribution across landscape Flat Gullied

In WV, rotationally grazed pastures having woods covering about 33% of the landscape, have about 66% of the manure deposited under the trees.

Grazing time affect on manure distribution.

Count cow pies in different areas to estimate efficiency of manure cycling in pastures and meadows.

Divide the pasture into different areas based on slope, aspect, shade, water, mineral feeder, and other cow use factors. Count the number of cow pies per acre in the different areas.

Two sampling methods for counting cow pies per acre Count cow pies within 10 feet of a transect line 43.5’ long, multiply by 100 to get cow pies per acre. Count cow pies within a circle having a radius of 11’9” from a center pin, multiply by 100 to get cow pies per acre.

To improve nutrient cycling in pastures Use rotational grazing. Use relatively small pastures on uniform areas of the landscape (soil, slope, aspect). Use moveable water and salt feeding sources. Have no shade or numerous uniformly spaced shade trees or movable shade in the pasture. Use strategic fertilization within pastures

Summary : Components of nutrient management Mass Balance = Import – Export –Import = hay + silage + grain + minerals + fertilizer –Export = milk + meat + wool + surface loss+leaching Recycling in pastures and meadows –Nutrient content of pasture –Uniformity over area (or lack of) –Location of areas having a net manure import –Location of areas having a net manure export

Take home lesson Effective recycling of nutrients in manure is an important way to reduce fertilizer cost and prevent environmental contamination.