Simulated growth and nitrogen dynamics of a perennial rye grass

Abstract

The growth and nitrogen uptake of Italian Rye Grass ( Lolium multiflorum Lam.) used as a catch crop were studied in 1988/1989 and 1990/1991 with the aim of determining the extent to which differences between the two years could be explained by variation in climatic conditions. The experimental field was situated about 50 km south of Halmstad close to the Swedish west coast (56°30′N; 13°00′E, 10 m elevation). The SOILN model, which considers the major flows of nitrogen and carbon in both plant and soil, was used to evaluate the importance of three growth factors, i.e., solar radiation temperature and nitrogen status, under autumn and winter conditions. The model was calibrated against measured total plant biomass ( r 2 = 96%) and nitrogen ( r 2 = 95%) together with soil mineral nitrogen in 1988/1989 and validated on an independent dataset in 1990/1991. Measured increases in biomass and nitrogen were much lower in 1990 than in 1988 (79% and 68% lower, respectively). The simulations were able to explain 90% of the observed between-year variation in relative growth rate. The higher maintenance respiration in 1990 was the main factor responsible for the differences observed. In 1990, plant N was well simulated ( r 2 = 89%), whereas estimates of plant biomass was high ( r 2 = 76%).