RELATIONSHIP BETWEEN ORANGE G DYE-BINDING CAPACITY AND TOTAL N CONTENT OF SIX GRASS SPECIES

Abstract

Six grass species were grown at four levels of N fertilizer and harvested at three stages of maturity. Two methods were used to estimate the protein content of the grasses: the Orange G dye-binding capacity and total N content. Values from the two methods were correlated to show the relationships between the two methods when species, levels of N fertilizer, and stages of maturity varied. The correlations between Orange G dye-binding capacity and total N were linear, positive, and highly significant. The variation about the regression lines was greatest when total N content was greater than 2.5% of plant dry weight; this condition was especially marked at early heading stage and high rates of N fertilizer. The precise relationships also varied among species. The Orange G dye-binding method for determining protein content is satisfactory for grasses where the total N content of the grass does not exceed 2.5%, but is not satisfactory for grasses with higher total N contents.