Effects of biochar, hydrochar, zeolite, and hydroxyapatite nanorods as urea carriers on some agronomical traits and water use efficiency of rice plant

Abstract

This study was mainly aimed to investigate and compare the effects of rice straw, biochar, hydrochar, urea-impregnated biochar (UB), urea-impregnated hydrochar (UH), urea-impregnated zeolite (UZ), and urea-hydroxyapatite nanohybrids (U-HAP) on rice cv. ‘Gohar’ growth characteristics, leaf chlorophyll index (LCI), and water use efficiency (WUE) in a sandy loam calcareous soil. A greenhouse experiment was performed based on a completely randomized design with three replications and 35 treatments, including control, urea-alone, UH, UB, UZ, U-HAP, sulfur-coated urea (SCU), amendments (rice straw, hydrochar, biochar, and zeolite) with and without urea at two rates of 435 and 870 mg kg^− 1 and two application methods of split and single. The results showed that zeolite, rice straw, and its derived hydrochar and biochar had no significant effects on root and shoot dry weights, root volume, tillers number, leaves number, LCI, and WUE. However, the applications of urea, UB, UZ, and U-HAP at the urea rate of 870 mg kg^− 1 significantly increased LCI, number of leaves and tillers, plant height, and WUE. The shoot dry weight of the rice plant in the treatments of UB, UZ, U-HAP, and SCU at the urea rate of 435 mg kg^− 1 had no significant differences with the split application of 870 mg kg^− 1 urea. In conclusion, the UB, UZ, and U-HAP can be utilized instead of the SCU as nitrogen slow-release fertilizers to improve rice growth and increase WUE. However, further studies and field experiments are required to evaluate the residual effects of these promising fertilizers on the environment.