Maximum Liquid Manure Spreading Rates on Sloping Land Ron Fleming and Malcolm MacAlpine University of Guelph Ridgetown Campus CSBE09-502

Funding Ontario Ministry of Agriculture, Food & Rural Affairs – Nutrient Management Research Program

Background Nutrient Management Act sets limits on spreading rates based on: ◦ Land slope ◦ Hydrologic Soil Group ◦ Application method (e.g. incorporated) ◦ Distance to surface water

Factors influencing runoff risk: Soil texture Soil structure Land slope Soil management Vegetative cover Soil moisture level Risk of rainfall after spreading Frost in soil Manure DM Rate of application Application method

Objectives Develop maximum land application rates for liquid manure. Assess the impact of post application rainfall events on runoff on different field slopes Propose maximum land application rates on pre-tilled and un-tilled land surfaces

Setup Small plots HSG = C 1 m x 1 m in m x 4 m in 2008 Swine & dairy manure & water Pre-tilled vs un-tilled 3 rates – 47, 94, 140 m 3 /ha Surface applied

Plot Layout in 2008 Slope Plots 1 m wide by 4 m long – manure on 3 m length

Setup FactorsNumberDetails Liquid applied3Swine, dairy, water Land slope33 to 5%, 6 to 8%, > 9% Application rate346.7, 93.5 and m 3 /ha Tillage2Un-tilled vs tilled Replications3 Total plots162

Setup FactorsNumberDetails Liquid applied3Swine, dairy, water Land slope33 to 5%, 6 to 8%, > 9% Application rate346.7, 93.5 and m 3 /ha Tillage2Un-tilled vs tilled Setback30 cm, 50 cm, 100 cm Replications3 Total plots486

Site 07-1, un-tilled section, 2.9% slope

Site 07-1, tilled section, 2.7% slope

Manure application

Rainfall simulation (in 2007) 1 in 5 year storm (25.5 mm in 30 minutes) 24 hours after manure applied On 2/3 of plots

Results Spreading after wheat harvest in August & September Soil: silt loam – mostly HSG C Dairy manure: >6% DM Swine manure: <3% DM

Sites 07-1 and 08-1: 2.5 to 3.0% slope Sites 07-2 and 08-2: 4.7 to 6.8% slope Sites 07-3 and 08-3: 9.2 to 15.2% slope

Results – Runoff

Results - Slope In general, the greater the slope, the greater the average volume of runoff

Results - Tillage Pre-tillage did not lead to a “significant” reduction in the volume of liquid runoff in 2007 – but it did in 2008 at the 2 steeper sloping sites ◦ E.g. Site 08-3 ◦ pre-tilled – mean runoff = 828 mL ◦ un-tilled - mean runoff = 2360 mL

Results – Liquid Applied Swine manure (DM 6%) in both years

Runoff volume – all plots

Runoff volume – all plots

Results – Application rate In general, the higher the application rate, the greater the volume of runoff ◦ E.g. 2008, Setback = 0 cm ◦ Applic. rate 140 m 3 /ha; runoff = 1730 mL ◦ Applic. rate 94 m 3 /ha; runoff = 1130 mL ◦ Applic. rate 47 m 3 /ha; runoff = 280 mL

Results - Rainfall Rainfall within 24 hours of spreading: ◦ Runoff liquid is dilute but represents a pollution risk ◦ Volume is un-related to initial liquid ◦ Volume is related to degree of saturation (i.e. initial application rate)

Results – Setback Distance Runoff was greatest where setback was 0 cm At Site 08-1, no liquid moved 50 cm downslope At Site 08-3, no significant difference in runoff as setback changed – quite variable

Conclusions The higher the application rate the greater the chance of runoff But – some rates tested were higher than allowed by the Nutrient Management plan The steeper the slope, the greater the chance of runoff Pre-tillage reduced the risk of runoff

Conclusions (Cont.) Any method used to predict maximum rates (before runoff occurs) needs to consider: ◦ Dry matter of the liquid applied ◦ Slope of land ◦ Application rate ◦ Pre-tillage

Conclusions (Cont.) Of less importance: ◦ HSG (esp. for high DM manures) ◦ Soil vegetation cover ◦ Direction of tillage/cropping

Questions