THE EFFECT OF NITROGEN QUANTITY AND APPLICATION TIMING ON FURROW-IRRIGATED RICE

Furrow irrigation can be a viable alternative to flooded irrigation systems used for rice (Oryza sativa L., cv. Lemont) production, especially where water supply is limited, or where soil textures are not conducive to seasonal flooding. The fluctuating aerobic/anaerobic soil conditions inherent with the furrow-irrigated rice system may facilitate increased N losses. The purpose of this research was to evaluate N management in furrow-irrigated rice including N quantities and application timings. Treatment responses of furrow rice to three N quantities, applied at five application timings, were examined under field conditions. Total quantities of 120, 180, or 240 lb N/acre as urea were evaluated with each quantity applied as follows: (i) entire quantity applied 4 wk after planting (4WAP); (ii) 50% 4WAP, 50% panicle differentiation (PD); (iii) 33% 4WAP, 33% PD, 34% 14 d post-PD; (iv) 66% 4WAP, 17% PD, 17% 14 d post-PD; (v) 50% 4WAP, 16% PD, 17% 14 d post-PD, 17% 28 d post-PD. The 120 + 30 + 30 treatment, the current recommended N quantity and application timing for flooded 'Lemont' rice, was in the top yielding group in 1988 and 1989 (128 and 121 bu/acre, respectively). Soil-and plant-N concentrations indicated most efficient N application for furrow-irrigated rice occurred when the majority of N was applied 4WAP, with no advantage to N inputs later than 14 d post-PD. Although no direct comparisons were made to flooded rice in this study, based on published literature, optimum N management for furrow-irrigated rice appears to be similar to flooded rice.