Yellow field peas (Pisum sativum L.) recently gained popularity across Nebraska due to their rotational benefits and increase in consumers' demand for plant-based alternatives to meat and dairy products. Protein isolate manufacturers have a special interest in grain with high protein content as it reduces the amount of raw material being processed and increases the efficiency of the protein isolation process (Figure 1).

The objective of this project was to identify the impact that location, variety selection, irrigation, tillage and fertility programs have on yellow field pea protein content in Nebraska (Figure 2).

2019 grain protein studies

Four field experiments were conducted at Henry J. Stumpf International Wheat Center near Grant, NE to evaluate yellow field pea grain yield (t/ha) and protein content (%; Near-Infrared (NIR) Spectroscopy - method):

1. Variety evaluation of 20 yellow field pea varieties at 3 sites:
   • Grant, NE dryland – non-replicated strips
   • Grant, NE irrigated – 4 reps
   • Mead, NE dryland – 4 reps
2. Irrigated study at Grant, NE had 3 treatments using field pea variety Durwood (Pulse USA):
   • Dryland (11.9 inch of rainfall)
   • Deficit Irrigation (11.9 inch of rainfall + 2.2 inch irrigation)
   • Full Irrigation (11.9 inch of rainfall + 4.4 inch irrigation)
3. Tillage study at Grant, NE had 2 treatments using field pea variety Durwood (Pulse USA):
   • Tillage (conventional - disk)
   • No-till
4. Fertility study at Grant, NE had 10 treatments including combinations of seed and in-furrow applied rhizobia inoculants and foliar products (Table 2). Salamanca (Valesco Genetics) field pea variety was used in the study.

Key findings from each study

• AAC Profit had the highest grain protein content (28.1%) across three sites (Table 1). AAC Profit was also the highest yielding variety among 20 other yellow field pea varieties evaluated.
• Tillage had no impact on yellow field pea protein or yield (Figure 3).
• Irrigation had no impact on yellow field pea protein. Deficit irrigation increased field pea yield by 4.5 bu/ac compared to dryland treatment, while no yield increase was observed with full irrigation (Figure 3).
• Fertility treatments caused no significant change in grain protein content (P-value 0.098). Grain yield ranged from 25 to 48 bu/ac depending on the treatment (Table 2). Rhizobia inoculant product selection and mixing were critical in achieving high nodulation scores and high yields (Table 2). Foliar products had a positive impact on yield when applied at reproductive stages (R1-R4).

Conclusions

• There was no evidence that a higher grain yield of yellow field peas causes a reduction in grain protein content (Figure 4).
• Variety selection is the most important factor influencing grain protein content of yellow field peas; AAC Profit consistently provided high protein content and high yields.
• Farmers should make every effort to follow the best irrigation, tillage, and fertility practices to increase grain yield and profitability.