Updated September 23, 2020:
A small plot field trial was planted on MSU campus as part of a multi-state trial. Off-campus location plantings (and sampling for native rhizobial populations) were not conducted due to covid19 restrictions, however intensive data collection will occur at campus location and data from other states will be leveraged to make broader conclusions. Treatments were laid out in a randomized complete block design (RCBD) with five replications, and included: non-inoculated control, seed inoculation with Bradyrhizobium japonicum, seed inoculation with Azospirillum brasilense, and seed co-inoculation with both bacteria. Ongoing data collection includes: stand counts, in-season biological N fixation using ureide analysis (RAU- relative abundance of ureides), yield components, and final yield and seed quality.
Additionally, three locations were planted with seeds of a non-nodulating soybean variety to quantify biological N fixation (BNF or Ndfa) against a commercial check and unfertilized corn, part of a multi-state trial to collect data for modeling BNF. Whole plant samplings were done at R2 and R6 (before leaf senescence) to determine total biological N fixation by comparing N levels of non-nodulating and nodulating soybean or unfertilized corn. Bulk seed from non-nod plots will be saved for planting multiple locations next year.
We are collaborating with 2 farmers in southwest Michigan under light textured soil and irrigation. Treatments were replicated four times in an RCBD in strips and included: no seed inoculant, seed inoculation alone, seed inoculation + in-season inoculant at V2-3, seed inoculant + in-season inoculant at R1 of Bradyrhizobium japonicum (from TerraMax, Inc., Bloomington, MN). In-season inoculant treatments were applied on the soil surface as a liquid using drop-nozzles and was then watered in with irrigation. A subsample of soybean plants (12 per strip) and leaflets were collected around R2 and R5 to determine biological N fixation (using RAU method) and tissue N concentration. A clean combine pass from each strip will be used to determine soybean yield. This data will be compiled with other states to evaluate the potential benefits of in-season inoculation application.
Field trial are part of a national protocol conducted across 12-15 states (20-30 sites) in the US, similar to trials conducted in 2019. Field trial were planted at MSU campus in a randomized complete block design with five replications. Treatments for objective 3 included 6 foliar fertilizer products containing multiple nutrients. These are commonly marketed products containing multiple nutrients for foliar fertilizer use in soybeans with a national footprint. Similar to common fungicide and/or insecticide application timing, products were applied at the R3 growth stage. Soil samples were collected at planting and measured for physical and chemical properties (texture, CEC, P, K, Ca, Mg, organic matter, and pH) using A&L labs. Within 24 hours prior to foliar product application and 2 weeks after application, the uppermost fully developed trifoliate was collected (petiole removed) from approximately 20-25 soybean plants per plot. Trifoliates were placed in paper bags and dried at 140°F (60°C) for 72 hr to be analyzed for macro- and micronutrient conc. For objective 4, 3 different fertilizers were broadcasted immediately after planting at three rates. Two fertilizers (AMS and gypsum) were applied to provide 10, 20, and 30 lbs/acre of sulfur. In addition, a non-sulfur nitrogen check (using urea) was included to separate any S response from the N- containing sulfur fertilizer (3 checks for the three S rates). A no-fertilizer control was also included. Soil samples were collected at planting and analyzed for various nutrients. Plots will be harvested for grain yield and a grain sample will be collected from each plot for protein and oil analysis. Data from these trials will be analyzed both locally and nationally to determine trends across broader scales.
A larger field experiment with 3 planting dates (early, mid, and late) and multiple management practices (e.g. maturity group, seed treatment, seeding rate, row spacing, inoculation, and fertility) was planned, however covid19 restrictions resulted in a change of plans. Two separate trials were planted. The first trial focused on evaluating 10 different maturity groups (1.1 to 3.5) under early (May 13) and late (June 17) plantings. Biweekly phenology data collection is ongoing in these trials. The second trial evaluated row spacing (15’’ vs 30’’) at six different seeding rates (40,000 to 190,000 seed/ac in 30,000 increments) under early (May 13), mid (June 2), and late (June 22) planting times: 144 total plots. Ongoing data collection includes phenology and canopeo for canopy closure estimates.