Evaluation of forage and nitrogen-supplying potential of hyacinth bean in Saudi Arabia

Field experiments were carried out under the irrigated semi-arid conditions of Central Saudi Arabia to examine the response of yield and quality of hyacinth bean to Rhizobium inoculation and N-fertilization complemented with or without phosphorus, and to determine the relationship between the chemical composition of some constituents of the bean and their mineralizable N capacity in soil. The results obtained indicated that possible yield and quality advantages may accrue to bean from inoculation and N-fertilizer plus P. Statistical analysis revealed that organic C and total N of the plant material were not significantly correlated with the cumulative amount of N-mineralized when the plant residue was incorporated into the soil. The relationship between the C : N ratio of the plant material and the percentage of N-mineralized showed a linear response (r = 0·93*** foliage fraction; r = 0·90*** foliage + stem fraction). This result supports the view that the C : N ratio is a poor index for the mineralization susceptibility.