ABSTRACT
Summary Chemical composition of berseem (Trifolium alexandrinum L.), produced in winter and spring under irrigation in Morocco, was investigated in a 4-year study. Berseem was planted at various dates, and after the first cut had been harvested, samples were taken from each regrowth at weekly intervals. Total plant samples and leaf and stem samples were analyzed for dry matter 476(DM), ash, crude protein (CP), and crude fiber (CF). A total of 172 samples of above-ground regrowth were analyzed and used to calculate multiple regressions of chemical composition on age and date of cutting. Date of cutting was defined as number of days after August 1. Regrowths remained vegetative from November to early May, after which time flowering occurred. Dry matter remained low (8% to 12%) during winter and spring and reached 20% only in June. Ash was always high (12% to 20%), while CF did not exceed 30%. Crude protein varied between 18% and 30%. At a given date of cutting, CF increased and ash decreased 0.19 and 0.06 percentage units/day of age, respectively. DM increased rapidly when plants grew old, while CP decreased while they were still young. At constant ages of cutting, regrowths showed a slight decrease in DM from November to the end of January and then increased until June. Ash decreased more rapidly than CP with the advancing season from November to June. Crude fiber increased dramatically during the same period. The effects of date of cutting appear to be a combination of effects of regrowth number, stage of maturity, and temperature. When samples of the same regrowth number and stage of maturity were compared, there was considerable variation from year to year of samples of similar ages for leaf percentage and chemical composition. For CF, variation exceeded 6 percentage units. Multiple linear regressions between morphological or chemical composition, age, and average temperature showed that temperature partly explained these variations. Elevated temperature decreased leaf percentage for both the first and second regrowths, but not for the fourth. It also increased DM percentage rapidly in the last regrowth. Partial regression coefficients between CF and average temperature were 0.38, 1.75, and 0.92 for first, second, and fourth regrowths, respectively, while those with ash and CP were always negative. Leaves appeared to have nearly constant CF contents. Temperature appeared to increase CF of berseem by stimulating its maturity but also by a specific action on the fiber content of stems.
