Temporal Variations in the Production—Quality and Optimal Cutting Date of Hay Meadows in the Central Pyrenees (Spain)

The production and forage quality of semi-natural hay meadows of Arrenatheretalia in the southern central Pyrenees were studied according to the time of mowing within the vegetative cycle, to determine its optimum moment. The results show important variations according to the meadows and the year. Higher productions (56% in kg DM ha−1, 42% in UFL ha−1) and lower qualities (−12% in CP, −11% in UFL kg DM−1, −7% in PDI and −17% in RFV) were obtained in the year in which temperatures and rainfalls were the highest. It is concluded that the timing (advance or delay) concerning the maximum value of production and the quality (two years) do not have a direct relationship with the variations of accumulated rainfalls and the growing degree days. The decreases in production (18% in kg DM ha−1 and 25% in UFL ha−1 until 24 June) and quality (26% in CP, 16% in UFL kg DM−1, 13% in PDI and 20% in RFV until 24 June) were also quantified from their maximum values within the traditional mowing period. The optimal time for mowing is between 20 May and 20 June, depending on the annual weather and the meadow characteristics