Effect of Tillage on Nitrogen Availability to Sugar Beets Years 1 & 2 Amber Moore and David Tarkalson University of Idaho – Twin Falls USDA ARS - Kimberly

Introduction Introduction of Round-up Ready sugar beets – Weeds no longer controlled by cultivation Opportunities for conservation tillage methods, such as strip-till – No-till meets moldboard plow – Only disturbs portion of the soil that contains the seed. Estimated 1800 acres of strip-till sugarbeets in Idaho in 2008

Introduction Advantages of strip till over moldboard plow – Reducing number of passes – Controls soil erosion – Water retention – Apply chemicals and fertilizers during tillage

Introduction Chisel plowing – Loosens the soil without inverting it – Residues are partially incorporated into the soil – Breaks into plow pan

Introduction  Concerns with strip till and chisel plowing  Organic matter lying on surface, no longer fully incorporated into the soil  Sugar beets highly sensitive to N release rates and release timing  Will reduction of carbon and aeration/mixing slow biological processes such as N mineralization?  Will reduction of carbon lower C:N ratios, thus speeding up N mineralization and slowing down immobilization?  Release of residue N

Introduction Tillage timing – Fall tillage Allows incorporated residues time to decompose – Potentially less tie-up of N – Spring tillage Can apply fertilizers and pesticides while tilling (for strip till) Prevents soil erosion over winter (chisel plow and moldboard plow)

Effect of Tillage on Nitrogen Availability to Sugar Beets Project goal - To determine the effect of tillage method and tillage timing on nitrogen available to sugar beets following a cereal crop

Experimental design Tillage study at USDA-ARS Kimberly – David Tarkalson and Dave Bjorneberg Three tillage methods – Strip till (ST) – Chisel plow (CP) – Moldboard plow (MP) Two tillage times – Fall and spring Five fertilizer N rates, including a control

Moldboard Plow

Chisel Plow

Strip Till

YearTillageBedding UAN application rate (lbs N/acre) lbs plant available N/acre Strip tillage Fall79.0 ab102.7 ab101.9 bc Spring91.7 a 81.0 b121.5 ab Chisel Plow Fall 66.2 ab96.6 ab156.8 a Spring 59.7 b 88.0 ab115.7 abc Moldboard Plow Fall 77.2 ab143.5 a138.8 ab Spring 63.1 b 69.4 b 77.3 c P>0.05/LSD NS 2009

YearTillageBedding UAN application rate (lbs N/acre) lbs plant available N/acre Strip tillage Fall79.0 ab102.7 ab101.9 bc Spring91.7 a 81.0 b121.5 ab Chisel Plow Fall 66.2 ab96.6 ab156.8 a Spring 59.7 b 88.0 ab115.7 abc Moldboard Plow Fall 77.2 ab143.5 a138.8 ab Spring 63.1 b 69.4 b 77.3 c P>0.05/LSD NS 2009 Strip tillage Fall103.7 Spring100.8 Chisel Plow Fall 90.2 Spring 97.5 Moldboard Plow Fall Spring P>0.05/LSD NS

YearTillageBedding UAN application rate (lbs N/acre) lbs plant available N/acre Strip tillage Fall79.0 ab102.7 ab101.9 bc Spring91.7 a 81.0 b121.5 ab Chisel Plow Fall 66.2 ab96.6 ab156.8 a Spring 59.7 b 88.0 ab115.7 abc Moldboard Plow Fall 77.2 ab143.5 a138.8 ab Spring 63.1 b 69.4 b 77.3 c P>0.05/LSD NS 2009 Strip tillage Fall Spring Chisel Plow Fall Spring Moldboard Plow Fall Spring P>0.05/LSD NS

YearTillageBedding UAN application rate (lbs N/acre) lbs plant available N/acre Strip tillage Fall79.0 ab102.7 ab101.9 bc Spring91.7 a 81.0 b121.5 ab Chisel Plow Fall 66.2 ab96.6 ab156.8 a Spring 59.7 b 88.0 ab115.7 abc Moldboard Plow Fall 77.2 ab143.5 a138.8 ab Spring 63.1 b 69.4 b 77.3 c P>0.05/LSD NS 2009 Strip tillage Fall Spring Chisel Plow Fall Spring Moldboard Plow Fall Spring P>0.05/LSD NS

YearTillageBedding UAN application rate (lbs N/acre) lbs plant available N/acre Strip tillage Fall79.0 ab102.7 ab101.9 bc Spring91.7 a 81.0 b121.5 ab Chisel Plow Fall 66.2 ab96.6 ab156.8 a Spring 59.7 b 88.0 ab115.7 abc Moldboard Plow Fall 77.2 ab143.5 a138.8 ab Spring 63.1 b 69.4 b 77.3 c P>0.05/LSD NS 2009 Strip tillage Fall Spring Chisel Plow Fall Spring Moldboard Plow Fall Spring P>0.05/LSD NS

Figure 3. Effect of tillage treatment and timing for soil carbon content at a one-foot depth for a Portneuf silt loam at planting, averaged over 2008 and 2009 and over nitrogen rates. CP = Chisel plow, ST = Strip-till, MB = Moldboard plow.

Conclusion It seems that tillage method and timing are more likely to impact nitrogen mineralization in growth limiting environments (lower N, higher C, etc.). Spring plowed and chisel-plowed soils show the greatest increase in carbon compared to fall plowed and moldboard or strip-tilled soils

Thank you!