Evaluation of Growth, Yield, and Water Productivity of Paddy Rice with Water-Saving Irrigation and Optimization of Nitrogen Fertilization

Abstract

Rice production in Tanzania, with 67% of its territory considered semi-dry and having average annual rainfall of 300 mm, must be increased to feed an ever-growing population. Water for irrigation and low soil fertility are among the main challenges. One way to decrease water consumption in paddy fields is to change the irrigation regime for rice production, replacing continuous flooding with alternate wetting and drying. In order to assess the impact of different irrigation regimes and nitrogen fertilizer applications on growth, yield, and water productivity of rice, a greenhouse pot experiment with soil from lowland rice ecology was conducted at Sokoine University of Agriculture, Tanzania during the 2019 cropping season. The experiment was split-plot based on randomized complete block design with 12 treatments and 3 replications. Water regimes were the main factors comparing continuous flooding (CF) and alternate wetting and drying (AWD) with nitrogen fertilizer levels as the subfactor, comparing absolute control (no fertilizer) with 0 (P and K fertilizers), 60, 90, 120, and 150 kg Nha−1. Alternate wetting and drying (AWD) significantly improved water productivity by 8.3% over CF (p < 0.05). Water productivity (WP) ranged from 0.6 to 1.5 kg of rice per m3 of water. Average water use ranged from 36 to 82 L per season, and water saving was up to 34.3%. Alternate wetting and drying significantly improved yields (p < 0.05) by 13.3%, and the yield ranged from 21.8 to 118.2 g pot−1. The combination of AWD water management and 60 kg N ha−1 nitrogen fertilization application was found to be the optimal management, however there was no significant difference between 60 and 90 kg N ha−1, in which case 60 kg N ha−1 is recommended because it lowers costs and raises net income. Nitrogen levels significantly affected water productivity, water use, and number of irrigations. Nitrogen levels had significant effect (p < 0.05) on plant height, number of tillers, flag leaf area, chlorophyll content, total tillers, number of productive tillers, panicle weight, panicle length, 1000-grain weight, straw yield, grain yield, and grain harvest index. The results showed that less water can be used to produce more crops under alternative wetting and drying irrigation practices. The results are important for water-scarce areas, providing useful information to policy makers, farmers, agricultural departments, and water management boards in devising future climate-smart adaptation and mitigation strategies.

Rice Yield and Nitrogen Use Efficiency With System of Rice Intensification and Conventional Management Practices in Mkindo Irrigation Scheme, Tanzania

“…Nitrogen is involved in cell division and elongation of various internodes, especially basal internodes of rice stems, which lead to increase in plat height (Mazumder et al, 2019;Zhang et al, 2020;Mboyerwa et al, 2021). Transplanting young seedlings under SRI reduces transplant shock because of lesser leaf area during the initial growth stages, which stimulate increased cell division causing more stem elongation resulting in increased plant height as reported by Vijayakumar et al (2006).…”

Lowering nitrogen rates under the system of rice intensification enhanced rice productivity and nitrogen use efficiency in irrigated lowland rice

“…The number of tillers recorded under SRI was higher than that under CP. This is due to nitrogen application, which played role in cell division and elongation of various basal internodes of rice stems leading to increased plat height ( Mboyerwa et al., 2021 ; Zhang et al., 2020 ; Mazumder et al., 2019 ). The increase in number of tillers could be associated with the wide spacing (less competition for the growth resources), aeration due to wetting and drying cycles, and root volume that has enhanced nutrients use and yield increase.…”

Effects of nitrogenous fertilizers on rice yield under continuous flooding and alternate wetting and drying conditions

“…When the application of USG was compared with PU, a non-significant interaction effect on the harvest index of BRRI dhan28 and BRRI dhan29 was found by Bhuiyan et al (2016) and the grain harvest index ranged from 0.40 to 0.52 in BRRI dhan28 and 0.42 to 0.54 in BRRI dhan29. Similarly, Mboyerwa et al (2021) revealed that the harvest index was significantly affected by N levels, which ranged from 0.45 to 0.53, but irrigation methods had little influence (p > 0.05).…”