Potassium Soil Test Calibration for Lowland Rice on an Inceptisol

• Published in: Communications in Soil Science and Plant Analysis 2010-01, Vol.41 (20-22), p.2595-2601
• Main Authors: Fageria, N.K, Santos, A.B. dos, Moreira, A, Moraes, M.F. de
• Format: Article
• Language: English
• Subjects: Agricultural production; Agronomic efficiency of K use; Agronomy. Soil science and plant productions; Biological and medical sciences; Efficiency; Fundamental and applied biological sciences. Psychology; grain yield; K uptake; Oryza sativa L; Rice; Soil science
• ISSN: 0010-3624; 1532-2416; 1532-4133
• DOI: 10.1080/00103624.2010.514377

Potassium (K) plays an important role in many physiological and biochemical processes in plants and its adequate use is an important issue for sustainable economic crop production. Soil test-based K fertilizer recommendations are very limited for lowland rice (Oryza sativa L.) grown on Inceptisols. The objective of this study was to calibrate K soil testing for the response of lowland rice (cv. Ipagri 109) to added K. A field experiment was conducted in the farmers' field in the municipality of Lagoa da Confuso, State of Tocantins, central Brazil. The K rates used were 0, 125, 250, 375, 500, and 625 kg K ha-1 applied as broadcast and incorporated during sowing of the first rice crop. Rice responded significantly to K fertilization during 2 years of experimentation. Maximum grain yield of about 6,000 kg ha-1 was obtained with 57 mg K kg-1 soil in the first year and with 30 mg K kg-1 in the second year. This indicated that at low levels of K in the soil, nonexchangeable K was available for plant growth. Potassium use efficiency designated as agronomic efficiency (kg grain produced/kg K applied) decreased significantly in a quadratic fashion with increasing K level in the soil. Agronomic efficiency had a significantly linear association with grain yield. Hence, improving agronomic efficiency with management practices can improve rice yield.