PROTEIN-QUALITY OF PEAS AS INFLUENCED BY LOCATION, NITROGEN APPLICATION AND SEED INOCULATION

A study was conducted to evaluate the contribution of location, N appl ication and Rhizobium seed inoculation to variations in seed protein c ontent and amino acid (AA) composition of field peas. The magnitude of AA variations with protein level and the nature of the relationships that are involved were determined. Regression equations to predict AAs from protein were developed for the cultivar Bohatyr. The experiments were carried out al two locations in southern Manitoba in 1994. The l evels of N fertilization investigated were: 56, 75, 100, 125, 150, 200 , 250 and 300 kg/ha. At each level of N application, seeds planted wer e either Rhizobium inoculated or not inoculated, The combination of lo cation, fertilizer treatments and inoculation yielded 192 samples for chemical analyses. The samples were analyzed for dry matter (DM), N an d AA contents. Location and N fertilization had significant (p less th an or equal to 0.001) effects on seed protein content and AA compositi on. Seed protein content increased with increasing levels of N applica tion. The response of protein to fertilization was not the same in bot h locations as evidenced from the presence of interaction (p less than or equal to 0.01) between location and N application. Except for meth ionine and cystine, percent AAs in DM increased with increasing levels of N application. The effects of N application on the concentrations of methionine and cystine were not consistent. On protein basis, the c oncentrations of AAs decreased with increasing levels of N application . The only exception was arginine which strongly increased in concentr ation. There was no effect (p greater than or equal to 0.05) of seed i noculation observed in this study. Strong positive correlations (I > 0 .80) between seed protein content and AA concentrations expressed as p ercent of DM were found for all AAs except for methionine (r = 0.76) a nd cystine (r = 0.51). When AA concentrations are expressed as g per 1 6 g N, 15 of the 17 AAs were negatively correlated to seed protein con tent. Only arginine (, = 0.78) and aspartic acid (r = 0.17) had positi ve correlations. The regression equations developed from this study co uld be used to predict the concentrations of AAs except methionine and cystine for the cultivar Bohatyr once the protein content is known.