An Analysis of N Nutrition on Yield and Yield Components for the Improvement of Rice Fertilization in Korea

Abstract

AbstractThe statistical procedure of path coefficient analysis was applied to five field experiments conducted in Korea to help set criteria for the development of new controlled‐release fertilizers and fertilizer management practices tailored to flooded rice. The yield components which are most sensitive to N nutrition and the growth stages when N uptake is most efficiently translated into yield component development were identified.The experiments were conducted over a period of 2 years using two varieties of rice (Oryza sativa L., var. Tongil and Jinheung), two water management regimes (continuous and intermittent flooding), and three fertilizer sources (regular urea and two sulfur‐coated ureas) applied at four or five different levels of N. Continuously flooded experiments were conducted on an Aquic‐Fluventic Eutrochrept and the intermittently flooded on an Aquic‐Udipsamment. Yield response to N and apparent fertilizer N recovery varied with N source, rate, and variety, but in an inconsistent pattern. Close examination of yield component development as a function of N uptake revealed that variations in yield were mainly determined by panicle density and number of spikelets per panicle; the product of these components can serve as a potential yield index (PYI). The PYI is, to a large extent fixed by heading time and is closely related to the amount of N taken up between transplanting and heading. Path coefficient analysis was used to ascertain that N uptake during the period between 2 weeks after transplanting to maximum tillering most critically influenced PYI.