The experimental network will be integrated by 8 to 12 sites with contrasting edapho-climatic characteristics around Minnesota soybean crop land area. All the experiments will be carried out under rainfed conditions.
Crop management: The trials will be planted with the technology available by the producer. Planting date will be the earliest recommended for each site. Plant density and row spacing will be adjusted considering local recommendations and seed will be treated. Crops will be maintained free of weed, insects, and diseases. At each site, two modern varieties of contrasting maturity groups will be evaluated. Maturity group selection would change depending
on the target environment (latitude and planting date used by the producer). At each site the fertility management program will be compared against a full nutrition treatment.
Experimental design: A split plot design with at least two replicates will be used at all sites, where the maturity group will be the main plot and nutrition management the sub-plot. The plots will be sized on a farm-by-farm basis based on each farmer’s planting and harvesting equipment. The Naeve project will visit each site after planting to apply additional fertilizer treatments to ensure no fertility-based yield limitations.
• Treatment factors are presented in the table below:
Treatment Number
Treatment Number
Maturity Group
Nutrition
1 short full
2 long full
3 short control
4 long control
Field measurements:
Pre-planting characterization:
• With help from our staff, each producer will fill out a detailed (~6 page) summary of field history and current management practices as part of the larger NCSRP project. This background field data is also important for this more detailed Minnesota-specific project.
• 0-6" soil cores will to characterize texture, SOM, P, CEC, and pH;
• 0-24" soil cores will be used for initial water content, NO3, NH4, and SO4 analysis. In-season samplings:
• Biomass sampling stages will be R3 and R6, to determine crop growth rate during the critical period: 5-foot sample for recording fresh weight and number of plants;
– From the 5-ft sample, 5 whole plants will be kept (fresh and dry weight);
– From the same 5-ft sample, 5 main stems from 5 plants (fresh and dry weight).
• Fraction of soil cover at R3 and R6: Two photographs per plot taken from above and at a minimum distance of 1.5 m from the top of the canopy will be analyzed using Canopy application to obtain fraction of soil cover (%). This variable will be an estimator of the fraction of intercepted radiation that will be also useful to indirectly estimate radiation use efficiency during the critical period.
• Remote-sensed data will be captured from each site after emergence, at canopy closure, and at additional time sequences as frequently as possible. Multispectral imagery will be employed to capture NDVI as well as to evaluate for disease and water stress.
Crop harvest (R8 stage):
• Seed yield will be recorded from combine yield monitor data.
• A 2-lb seed sample per plot will be collected for seed compositional and seed size analysis. Additional information:
• Location descriptors (coordinates, previous crop, amount of residue, tillage system);
• Phenology (VE, R1, R3, R6, and R7) and fertilization records (dates);
• Weather data (temp., prec., radiation, RH, ET). Laboratorial analysis:
• Soil samples:
– as noted above.
• Seed samples:
– Protein, oil, and amino acid concentrations.