Dry Season Rice Yield Responses to Nitrogen Fertilizer in Central Myanmar

Abstract

Rice crop yields in central Myanmar are considered to be relatively low due to inadequate applications of fertilizer, and particularly of nitrogen (N). In this study, replicated field experiments were conducted at two sites, Taungoo and Yezin, in Central Myanmar to determine the crop yield responses to N fertilizer for dry season irrigated rice in 2017. The two field experiments were identical in design and conducted at the same time. The experiments had a randomized complete block design with 3 replicates of 8 treatments. The 8 treatments included 6 rates of N fertilizer (0, 30, 77.6, 100, 130, and 160 kg N/ha), applied as two split surface-broadcast applications at 10 days after transplant (10DAT) and at crop panicle initiation (PI) in accordance with local farmer practice. In addition a urea deep placement (UDP) treatment with placement of 2.7 g urea briquettes at IFDC-recommended spacing and soil depth at a N rate of 77.6 kg N/ha was included, as well as a nil input control. All treatments except for the nil input control received basal applications of P, K, S, and Zn. Mean grain yields at Taungoo ranged from 3.54 t/ha (0 kg N/ha) to 5.24 t/ha (160 kg N/ha) whilst at Yezin they ranged from 6.78 t/ha (0 kg N/ha) to 8.15 t/ha (130 kg N/ha). The Taungoo site may represent a typical low-fertility farm site whereas the Yezin site had a more fertile soil. The 77.6 kg N/ha application rate was found to result in a 33% increase (i.e. +1.18 t/ha) in grain yield (P<0.05) at the Taungoo site and a 12 % increase (i.e. + 0.84 t/ha) at the Yezin site (P<0.05) indicating benefits from this N fertilizer rate, depending on economic analysis. At the Taungoo site the UDP treatment (77.6 kg N/ha) produced yields consistently higher than the comparable 77.6 kg N/ha surface broadcast treatment, with a UDP mean yield of 5.23 vs 4.72 t/ha for surface broadcast. However, analysis of variance (ANOVA) found this not to be significant at P=0.05, with a t-test estimating P=0.054 for this comparison. This is sufficient to encourage further research on UDP in this environment. Yield response curves were derived for N fertilizer applications from the experimental data from the two experiment sites. The Taungoo site yield response curve for N was thought to be more applicable to the general soil fertility levels of rice farms in central Myanmar. This paper presents the first results from these experiments which will be expanded on as the full dataset including soil and plant analysis is obtained