Soil Fertility Considerations Part of the Ruminant Livestock: Facing New Economic Realities Meetings

Fertilizer Prices Late January 2008: Nitrogen = $0.65/lb, P 2 O 5 = $0.65/lb, K 2 O = $.0.41/lb Future Projection: Increasing costs! Management Options? Continue as before Quit using synthetic fertilizer Use strategically

pH Effect on Element Availability When talking about fertilizers and fertility, begin by looking at soil pH. Soil pH has an effect on fixation and release mechanisms in soil Lime may be the cheapest “fertilizer”

Soil pH: Legume species SpeciesTolerance to pH < 6.0 pH Goal AlfalfaLow> 6.5 Alsike CloverHigh> 5.5 BFTHigh> 5.5 Red CloverMedium White CloverMedium Kura CloverMedium Source: Ohio Agronomy Guide, bulletin 472

Soil pH: Grasses SpeciesTolerance to pH < 6.0 pH Goal Kentucky BGMedium6.0 – 6.5 OrchardgrassMedium6.0 – 6.5 Tall FescueHigh> 6.0 Perennial RGMedium6.0 – 6.5 TimothyMedium6.0 – 6.5 BromeMedium6.0 – 6.5 Source: Ohio Agronomy Guide, bulletin 472

Soil pH and Lime Application Apply lime when soil pH is below optimum It is the buffer pH number that determines the lime application required to get the desired response Agronomy Guide recommendations are based on tons/acre of ag lime with an ENP of 2000 lbs/ton Lime is not very soluble, surface applications neutralize acidity slowly (may move downward approximately 1 inch/year) Implications for nitrogen fertilization (can increase losses)

Nitrogen Fertility Rate of nitrogen application is directly related to yield potential Nitrogen sources include synthetic fertilizer, livestock manure, compost, and organic matter release in the soil Cool season grass response is greatest in spring and in fall Pasture and hay fields with > 25% evenly distributed legumes do not need nitrogen application

Phosphorus (P) Needed at critical soil test level to ensure maximum forage production Rate recommended is not directly related to yield potential For every 7.5 – 10 lbs/acre of P 2 O 5 added or removed from the soil, soil test P will change by 1ppm Source: Robert Mullen, presentation to Athens Grazing Council

Potassium (K) Poor potassium nutrition can result in poor forage production Application not related to yield potential For every 2 –6 lbs/acre of K 2 O added or removed, soil test K will change by 1 ppm High levels of soil K can be a problem: Luxury consumption and high forage concentrations Can suppress magnesium uptake Source: Robert Mullen, presentation to Athens Grazing Council

Critical Soil Nutrient Levels for Forages: P and K KatCEC: CropP51020 ppm (lbs/acre) ppm (lbs/acre) Legumes25 (50)88 (175) 100 (200) 125 (250) Grasses15 (30)88 (175) 100 (200) 125 (250) P critical levels based on crop, K critical levels based on CEC Source: Robert Mullen, presentation to Athens Grazing Council

Role of Soil Organic Matter O.M. increases the water holding and nutrient storage capacity of the soil Critical to soil organisms that play a role in nutrient release, decomposition, and breakdown of chemicals Release nutrients and increase nutrient availability to plants Buffers the soil system: in high organic matter soils macro nutrients are more available compared to low pH soils (What is a “high” OM soil?)

Pastures: Nutrient Cycling Removal rates for pasture are lower than for hay crop, but… Grazing livestock move nutrients and concentrate nutrients into patches Nutrients are lost from pastures as animal product, through volatilization, leaching, erosion, but… Purchased feeds and stored feeds fed to livestock on pasture can add nutrients

Pastures: Nitrogen Cycling 70% of nitrogen returned to pastures is in the form of urine The nitrogen application rate can be the equivalent of 1000 lbs/acre in a urine patch Leaching losses can approach 50% and 22% of nitrogen is lost to volatilization Negligible N-fixation under a urine patch Source: Dave Barker, OFGC conference presentation

Pasture Nutrient Cycling: Feces/Dung Phosphorus applications can amount to 220 lbs/acre in dung patches Soil K in camp areas are commonly 4 to 10 fold higher than the overall pasture average The nitrogen in dung can approximate urine N levels but is in an organic form and is more stable: volatilization losses about 5% and leaching losses about 4% Source: Dave Barker, presentation to OFGC conference

Nutrient (manure) Management in Pastures Higher stock density = better distribution Shorter occupation periods = better distribution Shade, water and minerals can concentrate manure Use water and minerals to spread distribution More intensive management can reduce fertilizer costs