Environmental benefits of kura clover living mulch in annual

cropping systems

Tyson Ochsner

USDA-ARS

Soil and Water Management Research Unit

St. Paul, MN

Exp. #1: R3

• Goal: – Integrated assessment of yield, GHG emissions, nutrient

leaching, and long-term changes in soil properties for various cropping practices

• Setting:– Rosemount, MN (4445’ N, 9304’ W)– Waukegan silt loam (0.66 – 1.16 m deep) – 879 mm avg. annual precip; 6.4C annual mean temperature

• Collaborators:– Rod Venterea (GHG emissions, N transformations, soil

properties)– Pam Rice (pesticide fate and transport)

Exp. #1: R3 (continued)

• Design:– Total of 39 large plots (76 m x 27 m)– 4 tillage practices, 3 crop rotations, 2 N sources, 3 replicates

• History:– Main treatments (4 tillage types, C/C, C/S) established 2000– Kura clover added 2006

• Instrumentation:– Static and automated chambers for GHG emissions– Automated equilibrium tension lysimeters for drainage and

leaching– Soil water content sensors– Soil temperature sensors– Recording rain gauges– 3 comprehensive weather stations within 2 km

Exp. #2: GRACENet

• Goal: – Field scale assessment of yield, carbon sequestration, water

use, and long-term changes in soil properties for various cropping sytems

• Setting:– Rosemount, MN (4445’ N, 9304’ W)– Waukegan silt loam (0.66 – 1.16 m deep) – 879 mm avg. annual precip; 6.4C annual mean temperature

• Collaborators:– John Baker (CO2 fluxes, water use, surface energy balance)– Tim Griffis, U of M (gas fluxes, partitioning CO2 exchange)

Exp. #2: GRACENet (continued)• Design:

– Three adjacent large fields (>40 acres each)– Three distinct cropping systems

• Conventional C/S• C/S with reduced tillage and rye cover crop after corn• Kura clover living mulch

• History:– Rye cover crop initiated fall 2003– Kura clover planted spring 2006

• Instrumentation:– Eddy covariance systems and tunable diode laser for water use and

GHG exchange– Comprehensive suite of meteorological sensors– Automated equilibrium tension lysimeters for drainage and leaching– Soil water content and temperature sensors

Exp. #3: Arlington

• Goal: – Initial assessment of nitrate leaching for corn produced in kura

clover living mulch

• Setting:– Arlington, WI (4445’ N, 9304’ W)– Plano silt loam

• Collaborators:– Ken Albrecht– Bob Berkevich

Exp. #3: Arlington (continued)• Design:

– Randomize complete block, 4 reps– Corn in living mulch with 0, 20, 40, 60, and 80 lbs/acre N– Corn without living mulch

• History:– Experiment initiated spring 2006 in mature kura clover stand– Second year corn in 2007

• Instrumentation:– Suction cup samplers for nitrate concentration– Tensiometers– Soil water content sensors– Nearby weather station

05/03/06 08/11/06 11/19/06 02/27/070

10

20

30

40

50

60

70

Nitr

ate

conc

entr

atio

n (m

g L-1

)

No kura + 80#NKura + 0#NKura + 80#N

Arlington results: nitrate concentrations

• NO3-

concentrations – 5X lower in

living mulch with no N

– 2.5X lower in living mulch +N

– Compared to corn in killed kura +N

Research needs

• Establishment methods and economics• Crop rotation and management• N rate, fixation, transfer, and losses• Water use and competition• Light use and competition• GHG emissions, carbon sequestration• N and P leaching• Pesticide transport• Erosion reduction• Ecological benefits• Net energy production