VARIABILITY IN THE NUTRITIVE-VALUE OF STRAW CULTIVARS OF WHEAT, RYE AND TRITICALE AND RESPONSE TO UREA TREATMENT

Twenty-four cereal straws, comprising six cultivars of wheat, rye and triticale grown at four locations, were compared for chemical composition and dry matter loss (DML) in sacco. Significant differences (P < 0.001) were observed in crude protein (CP), neutral detergent fibre (NDF) and DML due to cultivar, location and to the cultivar × location interaction. The extreme values found for CP, NDF and DML were, respectively, 23.2 and 59.5, 736 and 873, and 339 and 592 g kg-1 dry matter (DM). Grain yield was not significantly correlated with CP or DML values of the straws. Following ammoniation with urea (55 g kg-1 air-dry straw) in sealed bags at 22°C for 60 days, the average increase in DML was 137 g kg-1 DM (range 87-192). No significant relationship was found between the initial DML of the straws and the increase in DML with urea treatment (r = -0.39; P > 0.05). A high negative correlation was observed between buffering capacity and response to urea treatment (r = -0.96; P < 0.001). The prediction of DML of the untreated and treated straws from saponification values was adequately described by a single, linear regression (r = -0.97; P < 0.001). The results are interpreted as showing that genotype and location can greatly affect the nutritive value of cereal straws, and that knowledge of buffering capacity may be important to predict the optimum level of urea application. © 1990.