Effect of Nitrogen Application and Cutting Frequency on the Yield and Forage Quality of Alfalfa in Seasonal Cultivation

Although nitrogen application and cutting frequency (CF) are two important factors affecting forage productivity and quality, their effects on alfalfa (Medicago sativa L.), particularly in humid areas, remain less understood. Here, we investigated the fertilization and cutting regimes for seasonal alfalfa cultivation in humid areas in southern China. Treatments performed over a 2-year period were of a split-plot design with four N application rates (60, 120, 180, and 240 kg N ha−1) and three CFs (five, four, and three times.). After cutting, forage components, yield, and quality were measured. In both 2-year cutting cycles, the effects of N application × CF interactions on forage yield and quality were non-significant. N application and CFs influenced plant height, mass shoot−1, leaf area shoot−1, and shoots plant−1. CF had remarkable effects on forage quality under different N applications, with forage cut five times having the best nutritive value and quality. However, neutral and acid detergent fiber contents were lower than when cutting three times, and produced the lowest yields. Forage cut four times had the highest in vitro digestible dry matter. In conclusion, to obtain high yields and desirable quality, the application of 180 kg N ha−1 and cutting three to four times in spring could be a suitable strategy for alfalfa forage production during seasonal cultivation in humid areas of southern China.