Net Primary Production of a Perennial Grass Ley (Festuca pratensis) Assessed with Different Methods and Compared with a Lucerne Ley (Medicago sativa)

Abstract

The above-ground production of an established perennial grass (meadow fescue) ley in C Sweden was analysed by repeated clipping. Depending on the calculation method, annual net above-ground primary production (NAPP) of ash-free dry mass varied between 903-985 and 810-1039 g m -2 in 1982 and 1983, respectively. Methods which included biomass turnover gave the highest production values. Underestimation in NAPP due to decomposition of litter between samplings was <10%. Mean daily growth rates of above-ground crop were 4.7 and 6.0 g m -2 in 1982 and 1983, respectively. Maximum recorded daily crop growth (22.0 g m -2) occurred in early June 1983. Mean annual total net primary production (NPP) was 1468 g m -2. Amount of organic matter input to the soil system via litterfall was a minor part of the NPP but a significant part of the total organic matter supplied to the soil organic matter pool during a year. Growth pattern and total NPP were compared with those of a lucerne ley grown in parallel with the meadow fescue ley. A severe drought in 1983 affected the grass ley more than the lucerne ley. Average annual NPP was similar in both crops, but amount of standing dead was higher in the grass ley than in the lucerne ley. The allocation below ground was similar, c30%, but root death was higher in the grass ley. -from Authors