Growth dynamics of reed canarygrass (Phalaris arundinacea L.) and its allocation of biomass and nitrogen below ground in a field receiving daily irrigation and fertilisation

Biomass and nitrogen in the roots, rhizomes, stem bases and litter of reed canarygrass (Phalaris arundinacea L.) were repeatedly estimated by soil cor ing, and root growth dynamics of this potential energy crop was studied for two years using minirhizotrons. Results are discussed in relation to above -ground biomass and nitrogen fertilisation. Five treatments were used: C-0, unfertilised control; C-1, fertilised with solid N fertiliser in spring; I -1, irrigated daily, fertilised as in C-1; IF1, irrigated as I-1 and fertil ised daily through a drip-tube system; IF2, as in IF1 but with higher N fer tiliser rates. Biomass of below-ground plant parts of reed canarygrass incr eased between the first and second years. Up to 50% of total plant biomass and nitrogen were recovered below-ground. The highest proportions were foun d in C-0. The calculated annual input via root turnover ranged between 80 a nd 235 g m(-2). In absolute terms, up to 1 kg and 10 g m(-2) of biomass and nitrogen, respectively, were found in below-ground plant fractions. High i nputs of stubble and accumulated below-ground biomass will occur when the l ey is ploughed, which will result in a highly positive soil carbon balance for this crop in comparison with that of conventional crops such as cereals .