Location: Soybean and Nitrogen Fixation Research
Project Number: 6070-21220-070-065-R
Project Type: Reimbursable Cooperative Agreement
Start Date: Oct 1, 2024
End Date: Sep 30, 2025
Objective:
Potash, phosphate and nitrogen are the three most applied fertilizers to soybeans. The USDA reported that 3,150, 1,878 and 449 million pounds of potash, phosphate and nitrogen, respectively were applied to the soybean crop in 2020. In 2022, soybean fertilizer costs were more than double, $102/acre, compared to $45/acre in 2021. This increase in fertilizer costs was based on higher prices for DAP and potash and did not include adding nitrogen. In soybean, several super-nodulating soybean genotypes have been identified, which have been shown to form more nodules and exhibit a greater nitrogen fixation capacity under varying levels of soil nitrogen. However, very little data exists on the performance of super-nodulating genotypes under varying levels of nitrogen, phosphorus and potassium fertilizer applications. In addition, previous research has shown that salt tolerance in soybean is associated with greater nodulation and nitrogen uptake.
Objectives to which ARS investigator will contribute:
In an effort to improve growth and yield of super-nodulating soybean genotypes, we propose to: 1) evaluate the yield performance of recently developed advanced breeding lines under field conditions with varying levels of nitrogen, phosphorus and potassium and 2) to clarify the characteristics of growth and yield performance of these intermediate super-nodulating and super-nodulating breeding lines in comparison to commercial checks. Developing soybeans that can maintain high yield with limited inputs could reduce fertilizer costs for farmers and increase sustainability. In addition, we propose to: 3) to evaluate the yield performance of salt tolerant germplasm in response to nitrogen fertilizer.
Approach:
Objectives 1) & 2): The experimental design will be a randomized complete block. Treatments will include two factors: fertilizer rate and application timing. Soil samples will be collected before planting and sent to the NCSU soil testing laboratory for analysis. Treatments will be randomly assigned within blocks. Treatments will consist of three levels of P (0, 74, and Ill kg/ha), three levels of K (0, 186, and 279 kg/ ha) and three levels of N (0, 135, and 270 kg/ha). The treatments will be evenly applied by hand at-planting, at the fourth vegetative growth stage (V4), and at the second reproductive growth stage (R2). Individual plot size will be 4 rows, 3m wide by 7.6m long with a 0.76m row spacing. Agronomic characteristics evaluated will be seed yield, plant height, seed quality, seed weight, protein and oil concentration of the seed, and lodging. Seed yield will be measured from the two center rows in grams per plot (corrected to 13% moisture) and converted to kilograms per hectare. Seed quality will be visually evaluated and recorded on a scale of one (very good) to five (very poor). Seed weight will be determined by weighing a clean 100-seed sample. Protein and oil concentrations will be determined using a Perten DA 7250 and will be reported on a dry weight basis. Lodging scores will be recorded at maturity using the scale one (all erect plants) to five (all prostrate plants). Plants from 1m will be harvested from the two outside rows and nodules from each plant will be counted and rated for size.
Objective 3): The experimental design will be a randomized complete block. Treatments will include two factors: N fertilizer rate and N application timing. Soil samples will be taken before planting and sent to the NCSU soil testing laboratory for analysis. Treatments will be randomly assigned within blocks that will be replicated four times. The fertilizer N source will be urea (46-0-0), which will be applied by hand to each plot at one of three rates: 0, 135, and 270 kg N ha-1. The application of N fertilizer will be made at three different times: planting, fourth trifoliolate (V4), and full bloom (R2). Application timings were selected based on stages with the highest soybean N demand. Individual plot size will be 3m wide by 7.6m long with a 0.76m row spacing. Agronomic traits and nodulation will be acessed similar to objectives 1 and 2.
