Effects of integrating deficit irrigation and carbonate foliar fertilizers into the system of rice intensification on water productivity

Abstract

The use of the system of rice intensification (SRI), deficit irrigation and foliar fertilizer application has proven to be effective in enhancing water productivity (WP) individually. However, information on their combined effects is limited. Therefore, this study evaluated the effects of integrating deficit irrigation and carbonate foliar fertilizer (Lithovit) application into the SRI on WP. This study was conducted under the Mkindo Irrigation Scheme in Mvomero, Morogoro, Tanzania, during the dry and wet seasons (October 2020 to June 2021). The experiment was laid out in a split-plot design with three levels of irrigation for the main plots, which were 100% of the irrigation water requirement (40 mm) imitating the SRI alternate wetting and drying pattern and induced deficit irrigation applied at 80% and 50% of the irrigation water requirement as IR₁₀₀, IR₈₀ and IR₅₀, respectively. In addition, there were five subplot fertilizer treatments: (A) diammonium phosphate (DAP) and urea (normal practice); (B) DAP, urea and 100% of the recommended foliar fertilizer (Lithovit standard); (C) DAP, 50% (Lithovit and urea); (D) Lithovit standard only; and (E) no fertilizer. The combined irrigation and fertilizer treatments tested were IR100A, IR100B, IR100C, IR100D, IR100E, IR80A, IR80B, IR80C, IR80D, IR80E, IR50A, IR50B, IR50C, IR50D and IR50E. The highest and lowest WP were 0.851 kg/m³ and 0.562 kg/m³ for IR₈₀B and IR₈₀E, respectively, for the dry season. For the wet season, the highest and lowest WP were 0.540 kg/m³ and 0.306 kg/m³ for IR₅₀B and IR₅₀E, respectively. WP is attributed to the SRI and Lithovit, which act as long-term reservoirs for carbon dioxide, especially during water stress periods. Thus, integrating deficit irrigation and carbonate foliar fertilizers improves WP in rice cultivation. This study demonstrated that this approach can lead to significant water savings while improving rice yields. This integrated approach can be adapted and optimized based on the specific conditions and requirements of different agroecological contexts.