Inhibition of urea hydrolysis in flooded soils and its significance in the molecular absorption of urea by rice

• Published in: Soil biology & biochemistry Vol. 23; no. 2; pp. 125 - 129
• Main Authors: Saraswathi, P., Balachandran, P.V., Wahid, P.A.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 1991; New York, NY Elsevier Science
• Subjects: absorption; Agronomy. Soil science and plant productions; Biochemistry; Biochemistry and biology; Biological and medical sciences; Chemical, physicochemical, biochemical and biological properties; flooding; Fundamental and applied biological sciences. Psychology; hydrolysis; Inceptisols; inhibition; Oryza sativa; Oxisols; Physics, chemistry, biochemistry and biology of agricultural and forest soils; quantitative analysis; Soil science; urea; Vertisols; India; Asia; Kerala; Nitrogen fertilization; Monocotyledones; Nutrition; Tropical crop; Rice soils; Oxisols; Cereal crop; Hydrolysis; Tropical soil; Soils; Oryza sativa; Urea; Vertisols; Absorption; Gramineae; Angiospermae; Spermatophyta; Application method; Flooded soils; Inhibition; Nitrogen fertilizer; Inceptisols
• ISSN: 0038-0717; 1879-3428
• DOI: 10.1016/0038-0717(91)90123-2

Urea hydrolysis was studied in six major types of rice soils of Kerala, India, namely, laterite (Oxisol). karappadam (Inceptisol), kari (Inceptisol), kayal (Inceptisol), kole (Inceptisol) and black soil (Vertisol). in three situations namely, at 60% WHC, submergence and in pre-flooded soil. Hydrolysis of urea applied to soil at the time of submergence or to soil kept at 60% WHC was complete by 5 days in all the soils except kari in which the hydrolysis proceeded for up to 30 days. On the other hand, urea applied to pre-flooded soils virtually remained unhydrolysed during 5 h exposure. The increases in soil pH and Fe(II) concentration or the decrease in Eh consequent to flooding did not explain the absence of urea hydrolysis in the soils. Autoradiographs of rice plants fed with 14C-urea confirmed the molecular absorption of urea. Quantitatively the accumulation of 14C amounted to 1.8 μg urea h −1 g −1 plant tissue. The results suggest that molecular absorption of urea can be significant from top-dressing.