Organic Cropping Systems January 2014 George Nelson University of Minnesota West Central Research and Outreach Center, Morris MN Introduction The University of Minnesota West Central Research and Outreach Center (WCROC) in Morris, MN established an organic dairy herd in 2008; subsequently, we began transitioning selected fields from conventional crop production to organic crop production in effort to support the organic dairy herd. Currently, approximately 300 acres are under organic management with the goal of producing 1) forages: alfalfa haylage, wheatlage, and corn silage, 2) corn and wheat feed grains, and 3) straw for livestock bedding. One of the biggest challenges with organic production is weed management and its impact on yield. In organic systems repetitive tillage is frequently required for successful weed control. While our organic crop production was mostly successful, it was tillage intensive and counterproductive to promoting soil sustainability, a tenet embedded within the organic production philosophy. Repetitive tillage leads to increased fuel consumption, soil carbon loss/organic matter decomposition and soil erosion. Our challenge is to produce organic crops in a sustainable manner while adhering to organic production principles; thus, a revised, less tillage intensive production system was initiated. This paper will contrast a more tillage intensive organic crop production system (MT) for dairy feed production, with a less tillage intensive organic crop production system (LT) for dairy feed production. The MT system utilizes mostly tillage for weed management and crop production. The LT system will increase the utilization of minimal soil disturbance, crop competition, and continuous residue cover operations in its weed management and crop production system. Both the MT and LT systems will have the same diverse crop rotation. Weed control effectiveness, grain/forage yield, overwinter field cover, and diesel fuel consumption was assessed and recorded for both cropping systems. Procedures: A brief description Contrasting MT and LT crop systems Both cropping systems are in the same six-year rotation: 1) Silage Corn, 2) Winter Wheatlage/Soybeans, 3) Grain Corn, 4) Spring Wheatlage/Alfalfa, 5) Alfalfa, and 6) Alfalfa. In year one of the rotation, corn is chopped for corn silage and ground is seeded to winter wheat. Year two: winter wheat is chopped for wheatlage and ground is seeded to soybeans. Year three: corn is seeded for grain harvest. Year four: alfalfa is seeded with spring wheat (the spring wheat
is chopped for wheatlage along with the alfalfa at first cutting). Years five and six remain in alfalfa, and are chopped as haylage. In the MT system, tillage separates the crops in rotation. In the LT system, more crop competition and reduced/no tillage seeding operations are used for weed management. Weed pressure and yield were assessed in both systems where they differ operationally. During the first three years (CN-SB-CN) of the six-year rotation, the MT and LT systems are identical in year one, while they differ in years two and three. For annual crops in our organic production system, two spring tillage (field cultivation) operations are used prior to seeding crops. The first tillage operation occurs in the spring as early as possible to coincide with conventional corn spring tillage, and a second tillage operation 7-10 days later to eliminate the early spring flush of weeds. Early in-season weed control is achieved with rotary hoeing, harrowing, or a row flaming operation prior to or closely after crop emergence for germinating or just emerged weeds. Later season weeds are controlled with row cultivation when the crop is well established. Differences between the MT and LT systems began after the first year of corn silage harvest, by tillage for seedbed preparation for fall winter wheat seeding in MT, verses fall no-till seeding of winter wheat in LT. The winter wheat is harvested in year two as wheatlage in boot stage. The winter wheat stubble is then tilled under in both MT and LT systems (biennial/perennial grass crops are notoriously hard to kill without tillage or herbicides). After wheatlage, harvest soybeans are seeded and weeds are controlled using appropriate organic methods as described for annual crops. In the MT system, after soybean harvest, the soybean ground is tilled (probably chisel plowed) in the fall and then tilled twice in the spring and seeded to corn in the third year. By contrast, the LT system has no fall soybean ground tillage and the corn is no-till seeded. In both systems, fall tillage is performed at the end of the third year after corn grain harvest. In the fourth year, tillage is performed then spring wheat/alfalfa is seeded for both systems. Forage (wheatlage) is harvested when the spring wheat is in the boot stage and a second cutting alfalfa haylage crop is harvested in August. The field remains in alfalfa for the fifth and sixth years and is harvested three times each year as alfalfa haylage. Results of the MT and LT systems are identical in years four through six and will not appear in this report.
Organic Rotation Differences MT Y1 Corn (silage harvest) then tillage and seeding of Winter Wheat. Y2 Winter Wheat (wheatlage harvest) then tillage and seeding of Soybeans. Soybean harvest, liquid manure injection or solid manure, then fall tillage of soybean ground. Y3 Spring tillage (two passes) and then seeding of Corn (grain). LT Y1 Corn (silage harvest) then no-till seed Winter Wheat. Y2 Winter Wheat (wheatlage harvest) then tillage and seeding of Soybeans. Soybean harvest, liquid manure injection. Y3 No-till seed corn (grain). NO Organic Rotation Differences Y4 Spring Wheat/Alfalfa (first cutting wheatlage, second cutting haylage). Y5 Alfalfa, three cuttings (liquid manure after second cutting). Y6 Alfalfa, three cuttings. Fall tillage.
2013 Data Table (First year results and three year estimates) MT and LT systems in a Silage Corn-Soybean-Corn rotation. MT LT Tillage Operations (3 yr. est.) 16 10 All Other Passes: seeding, manure 10 10 application, etc. (3 yr. est.) Total Field Passes (3 yr. est.) 26 20 Overwinter Field Cover (live plants or intact stubble) 2013 2014 2014 2015 2015 2016 Total Diesel Fuel: Fall 2012 to Fall 2013 1 year of 3 2 years of 3 13.81 gal/ac 11.86 gal/ac 2013 Corn Silage (E16) 18.5 Tons 31%DM same operationally 2014 Corn Silage (SM) 2014 Soybeans (E16) 2015 Corn (E16) 18.5 Tons 31%DM same operationally 2013 Corn Weed Control Good Good 2014 SB Weed Control 2014 Corn Weed Control 2015 Corn Weed Control Nitrate Nitrogen (NO 3 -N) in tile line water Concentration (ppm) 2013 Silage Corn (Baseline) 20.5 20.5 2014 Till WW/SB Fall Till 2014 NT WW/SB no fall Till 2015 Tillage for Corn 2015 NT Corn
2013 Preliminary Results: From Data Table (year one of three) Tillage operations and all other field passes for the number of total field passes are an estimate/goal for the three year corn-soybean-corn rotation. After the first year, plus fall seeding of winter wheat, tillage projections and overwinter field cover are on track. Diesel fuel consumption (only fuel required by equipment for crop production purposes) was based on fields ranging from 38 ac to 148 ac. Fuel consumption records are used for the sole purpose of measuring differences in fuel use between MT and LT production systems with our sized equipment, but should be relevant to other equipment lines. Tractors and other equipment were fueled prior to entering the field and immediately after exiting the field. The LT system used 2 gal/ac less fuel than the MT system. Corn silage yields (2013) were based on field totals. The MT and LT systems were the same operationally (18.5 T/ac 31%DM). In 2013, weed control ratings for corn were based on a total field subjective assessment (excellent, good, fair, poor) by a research plot technician after all weed management operations for that system were completed. Good weed control was achieved in the organic systems with two spring field cultivations, one by in-season harrowing, and the other as in-season row cultivation. Nitrate-nitrogen concentrations were derived via tile line water flow measured with automated Isco 4230 Bubbler Flow Meters and automated Isco water samplers. In the fall of 2012 the site had solid dairy manure applied at 152 lbs of available N/ac. The average nitrate-nitrogen concentration of all tile line discharge water (14 acre pattern tiled field, 790,000 gallons) throughout 2013 was 20.5 ppm. This baseline will be used to differentiate nitrate-nitrogen concentration discharge between the MT and LT systems. 2014 Plans All 2013 fall operations (fall tillage, manure application, and successful winter wheat establishment) are in place for 2014. Organic soybean weed control will most likely be achieved with row flaming and row cultivation. Isco flow meters and samplers will be installed in late winter/early spring to record differences in nitrate-nitrogen concentration in tile water between the MT and LT systems.