EVALUATION OF SEED TREATMENTS FOR ORGANIC CORN: 2006 Janet Hedtcke, Bill Stangel, Gregg Sanford, John Hall

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1 EVALUATION OF SEED TREATMENTS FOR ORGANIC CORN: 2006 Janet Hedtcke, Bill Stangel, Gregg Sanford, John Hall INTRODUCTION In 2003, to comply with the National Organic Program (NOP) standards, we started using certified organic seed (untreated, non-gmo) for our organically managed systems on the WICST plots. In both organic systems (CS3 & CS5), the corn phase followed a plowdown legume, typically tilled the previous fall. Even with delayed planting we consistently had poor stands at emergence (refer to Addressing Organic Corn and Soybean Plant Populations in the WICST Trial paper in this report). Not only did we suffer severe yield decline on these plots but we also had increased weed pressure resulting in increasing weed seedbank numbers. The rule of thumb is that corn needs 110 GDD (base 50 F) from planting to emergence. Typically in southern WI, we get wet and cool weather in early to mid-may delaying corn emergence for 2-3 weeks and sometimes halting field operations all together. The long-term minimum soil temperature data at 2 depth at Arlington shows that mid-may is the average time when soil temperatures reach 50 F (Fig. 1) yet the variability over years is significant. From Fig.1, one can see that there are many years with minimum soil temperatures falling below 50 F even into late May. Most organic farmers don t consider planting corn until the third week of May to reduce their risk of cold soil, particularly if they are on soils less well drained than those at Arlington. A common practice among organic farmers is to plant corn seed when soil temps have warmed to average of at least 50 F to allow for rapid germination and emergence (ideally emerging in less than one week). Delayed planting allows for early weed flushes to be managed with tillage while also allowing soil temperatures to warm. While delayed planting allows for improved weed control and reduces the risk of untreated seed loss (from insects and disease), it has been shown to negatively impact yields with each day beyond May 15 (Fig. 2). By missing early planting windows, farmers can miss timely planting and be forced to plant late, forcing them to switch hybrids, or change crops altogether. Unlike conventional corn that can be treated with tested fungicide and insecticide, these options are unavailable to the organic producer. The objective of this trial was to evaluate seed treatments approved for organic corn production on their effect of stand density and yield and to determine if seed treatment is effective in early planting situations. METHODS In 2006, a trial was established at two locations in southern Wisconsin Arlington and East Troy. At each location corn was planted at two dates early and late May. The combined location-planting date gave us 4 environments to test the following seed treatments: Untreated Natural II TM T-22 Planter Box TM Cinnamon oil (East Troy only) Natural II has been tested in a number of locations in the upper Midwest with varying results (Delate et al., 2005, 2006 in IA; Vigue and Clayton, pers. comm in IL; Albert Lea

2 Seedhouse in MN, 2005). T-22 planter box has been on the market for several years and is thought to be beneficial in warmer soils not excessively high in nitrate-n (Gries and Blackmer, 2002). Cinnamon oil has shown promise in laboratory experiments at Iowa State (Christian, pers comm. 2005). Details of each treatment are shown in Table 1. The plots were laid out in a RCB design with 3-4 treatments/rep and 4 reps by planting date (Fig. 3). At both locations, field-sized equipment was used (6 row planter, cultivator, combine, all based on 30 spacing) so plots were large at approximately 0.10 a (15 x 300 ). The corn hybrid used in the trial was Blue River 48F27, a 102-d maturity. Seeding rates were between 34,500 and 38,000 seeds/a across the environments. Plant density data was collected from the 4 inner rows (4 stations of 17 5 length; 1 station/row) in each plot. Yield was measured on all 6 rows with a weigh wagon. The agronomic information for each location is reported in Appendix 1 and 2. RESULTS Agronomic Performance. Due to the cold and wet conditions that prevailed in early May of 2006, the early-planted environments were under substantially unfavorable conditions. Figure 4 shows that it took nearly three weeks for the corn to emerge in the Arlington early environment vs. just 5 days in the late environment. As a result, the stands across all treatments were poor with less than half of the seed planted emerging (Table 2). Seed corn maggot was observed at the Arlington location and was thought to be the main cause of the extremely low stand counts. It appears that Natural II provides some protection from cold, wet soils and perhaps has some insecticidal qualities as well. At both locations, Natural II had improved stands over the other treatments by 1.5-2x and higher yields by about 50 bu/a (Tables 2 and 3). In the later planting, there were less stand and yield differences observed at Arlington but at East Troy, Natural II had 30% higher yields than the other treatments (Tables 2 and 3). The cinnamon oil treatment may have damaged the seed or somehow contributed to seed death (dessication, pest attractant?) as it performed worse than the untreated check (Tables 2 and 3). T-22 planter box was inconsistent across environments. The earlier planted corn due to relatively poor corn stands allowed in-row weeds to emerge and all treatments had heavy weed populations (general observation). In addition to affecting yield, these weeds added to the weed seedbank, potentially affecting following crops in the rotation. Economics. With a market price of $5 for each bushel of organic feed corn, an additional 1-2 bushels is all that is need to get a return on the investment of these seed treatments. Natural II seed treatment gave a clear advantage over all the other treatments but T-22 paid for itself in the early planting at the East Troy location. SUMMARY Early and late planting dates represented dates to capture weather variability in a typical May days to emergence in early planting (May 5) and only 5 days to emergence in late planting (May 23). The early planting at each location had poor stands across treatments but the Natural II was 1.5-2x higher than the others and was the highest yielding in the early planting environments. Due to the warm conditions for the late planting, there was no treatment effect

3 observed at Arlington but Natural II yielded best at East Troy in the late planting. At a nominal fee, some seed treatments are worth the cost if only for insurance. CITATIONS Delate, K., A. McKern, and B. Burcham Comparison of organic seed coating in corn- Neely-Kinyoun Trial. Iowa. Gries, G.C., and A.M. Blacmer Field testing T-22TM Planter Box for corn in Iowa. Vigue, J. and A. Clayton unpublished data. Western Illinois University. White, B. Albert Lea Seed Farm Seed Catalog.

4 Fig. 1. ARS minimum soil temp at 2" depth Temp (degrees F) y = x R 2 = /1 4/8 4/15 4/22 4/29 5/6 5/13 5/20 5/27 6/3 6/10 6/17 6/ date 16-yr mean Linear (16-yr mean) Fig. 2

5 Table 1. Treatment descriptions and costs Treatment Supplier Coat ingredient Method of application Application rate Control -- untreated Natural II TM AgriCoat LLC. Actinomyces Seed film Pre-treated spp. etc coating 3oz / 80,000 T-22 TM Bioworks Inc. Trichoderma harzianum Cinnamon Oil USDA ARS: Cinnamomum Iowa State zeylanicum Oil Planter box 2oz / 80,000 Planter box 5 oz / 80,000 $ / 80,000 $12.00 (~$6/a) $11.40 (~$5.70/a) $3.31 (~$1.65/a) Fig. 3. Visual of the field layout of the RCB design at Arlington EARLY PLANTING DATE LATE PLANTING DATE REP 1 REP 1 REP 2 REP 2 REP 3 REP 3 REP 4 REP 4 Accumulated GDD Arlington Fig GDU on early planting at ARL 2006 GDU on late planting at ARL Acc GDU (base 50F) /6 5/7 5/8 5/9 5/10 5/11 5/12 5/13 5/14 5/15 5/16 5/17 5/18 5/19 5/20 5/21 5/22 5/23 Day Acc GDU (base 50F) /24 5/25 5/26 Day 5/27 5/28 5/29 ~GDU s necessary for corn emergence

6 Table 2. Corn stand density in four environments in Arlington East Troy Planting date Treatment Early Late Early Late Plants/acre at V5 stage Untreated check 8,930b 30,601a 16,625c 28,677 Natural II TM 15,754a 29,330a 28,496a 29,076 T-22 Planter Box TM 8,131b 27,152b 18,912b 27,987 Cinnamon oil n/a n/a 11,507d 25,918 p-value < < Table 3. Corn yield in four environments in 2006 Arlington East Troy Planting date Treatment Early Late Early Late bu/a Untreated check 125.6b c 98.5b Natural II TM 168.8a a 146.4a T-22 Planter Box TM 114.1b b 100.9b Cinnamon oil n/a n/a 92.9c 102.6b p-value < < <0.0001

7 Appendix 1. Agronomic calendar for the Arlington site, 2006 Previous crop Alfalfa Fall 05 practices Manured (6,000 gal/a) October 11, 2005 (surface applied) Area of field Early planting (North ½ of field) Late planting (South ½ of field) Spring 06 Practices Chisel w/sweeps and prepared seedbed on April 27 th, disked April 27 th, soil finished May 4th Variety Date Rate May 5, ,500 seed/a May 23, ,000 seed/a Rotary Hoe , , Tine Weed Tried , pulled out None Cultivation , (disk hiller) Scout/data Took aerial photos, stand counts and yield comparisons Harvest October 9, 2006 Fall Practices No fall tillage due to slope length and channels in field Appendix 2. Agronomic calendar for the East Troy site, 2006 Previous crop Wheat Area of field Early planting (North ½ of field) Late planting (South ½ of field) Spring 06 Practices Variety Date Rate Manured (poultry manure) May 4, 2006 at 3 tons/a (box spreader); Mulchmaster 3x to incorporate wheat and manure; field cultivator May 8 and May 23 for seedbed preparation May 8, ,600 seed/a May 23, ,600 seed/a Rotary Hoe None None Tine Weed , Cultivation 1x 1x Scout/data soil erosion in late May, heavy weed pressure, stand counts and yield comparisons Harvest November 8, 2006 Fall Practices No fall tillage