Nitrogen Uptake by Faba Bean from 15N-Labelled Oilseed-Rape Residue and Chicken Manure with Ryegrass as a Reference Crop

Abstract

The effects of soil amendment with oilseed-rape residue (OSRR) and chicken manure (CM) on the growth and nitrogen (N) uptake of faba bean (Vicia faba L.) were assessed in a pot experiments with Italian ryegrass (Lolium multiflorum Lam.) as a reference crop. A 15N isotope dilution method was used to estimate the amount of N derived from the residue (OSRR and CM) and from atmosphere through N2 fixation in the plants. Dry weights (DW) of shoots and whole plants were heaviest in the plants grown on the soil amended with CM (CM plants) followed by the plants grown on the soil amended with OSRR (OSRR plants) and control plants in this order. There were significant differences (p<0.05) in dry weight between CM, OSRR and control plants. DW of roots was also increased by amendment with either CM or OSRR in faba bean, but it was decreased in ryegrass. The amount of total N in both roots and shoots were increased by application of either CM or OSRR in both faba bean and ryegrass. The amount of N2 fixed by faba bean cultured on 1.2 kg soil amended with 10g residue (CM or OSRR) was 85.9 mg pot-1 but total N in faba bean derived from OSRR and CM was 192 and 374 mg pot-1, respectively. The percentage of N derived from atmosphere to total N in faba bean plants ranged from 15.9 to 26.5%. The amount of N taken up by faba bean and ryegrass plants from CM were larger than those from OSRR by 81.0 and 54.3%, respectively. Soil N balance was calculated as the difference between the amount of N applied (including fixed) and taken up by the plants. The N balance of soil amended with OSRR after cultivation of faba bean was 72.2% higher than that of the soil amended with CM, and that after cultivation of ryegrass was 89.9% higher.