Year, Location, and Nitrogen Effects on Maximum Node Production Rate and Main Culm Node Number in Rice.

Maximum node production rate (MNPR) and main culm node number (MCNN) affect yield and yield-related traits of rice. However, there is limited literature on the effects of environment on these traits. The objective of this study was to determine the significance and magnitude of the effects of year, location, and nitrogen on MNPR and MCNN. Rice cultivar Cypress was planted in plots at Beaumont and Eagle Lake, TX, on 14 April 2000 and 2001. The N treatments were 0, 9, 18, 27, and 36 g m^-2 N, with the N applied at preplant, preflood, panicle differentiation, and heading, respectively. Data estimated included: MNPR (obtained during the pre-tillering stage, it is the slope obtained by regressing the leaf stage of the main culm against the no. of ^od > 10^oC from planting); MCNN (obtained from main culms, the node number on which the panicle is borne); and the N concentration of main culm structures (panicles, leaves, stems, and roots). MNPR was not significantly affected by year (Y), location (L), and N, but it was significantly affected by L x N, Y x N, and Y x L. MNPR (averaged across Y) ranged from 0.01222 node ^od > 10^oC for the Beaumont-0 N treatment to 0.01523 node ^od > 10^oC for the Beaumont-18 N treatment. Only the 0, 9, and 18 N treatments had been applied during the period used to estimate MNPR. MNPR, leaf N concentration, and N applied were significantly and positively correlated with each other. MCNN was not significantly affected by Y and L, but it was significantly affected by N and Y x L x N. MCNN (averaged across Y and L) ranged from 14.0 for the 0 g m^-2 N treatment to 15.4 nodes for the 36 g m^-2 N treatment.