Improvement of Growth and Biomass of Rice (<i>Oryza</i> sp., Nerica L14 Variety) by Mineral Fertilization over Two Successive Ratoon Cycles

Rice, one of the world’s main cereal crops, is not only a source of grain, but also of straw. However, global rice production remains insufficient, particularly in West Africa, where extensive farming is hampered by demographic and economic pressures. Intensification systems, including the cultivation of rice ratoon from improved varieties, appear to offer a promising solution. This study, conducted in Ivory Coast, aimed to assess the effects of the mineral fertilization on the growth and biomass production of NERICA L14 rice ratoons across two successive cycles. Fertilizer rates of 100 kg.ha<sup>-1</sup> nitrogen 55 kg.ha<sup>-1</sup> phosphorus, 150 kg.ha<sup>-1</sup> potassium, 33 kg·ha<sup>-1</sup> calcium, 15 kg.ha<sup>-1 </sup>magnesium, and 10 kg.ha<sup>-1</sup> zinc were applied, along with an unfertilized control plot (0 kg.ha<sup>-1</sup>). The experiment was conducted in a randomised complete block design with four replications. Before ratooning, all elementary plots had received a basal application of 200 kg.ha<sup>-1</sup> NPK (10-18-18) and 35 kg.ha<sup>-1</sup> urea (46% N) at tillering and heading stages of the main crop. Observations and measurements were conducted on plant height, tiller density, and straw yield. Successive ratoon cycle exerted a depressive effect on both growth (reductions of up to 31.37% for plant height, and 42.41% for tillering), and straw yield (reduction of up to 65.87%) from one cycle to the next. Applications of nitrogen (73.15 and 65.05 cm for first and second cycles; 611 tillers.m<sup>-2</sup> and 2,898.44 kg.ha<sup>-1 </sup>in total), zinc (70.6 and 61.88 cm; 565 tillers.m<sup>-2</sup> and 2,296.88 kg.ha<sup>-1</sup>) and potassium (71.6 and 59.08 cm; 584 tillers.m<sup>-2</sup> and 2,187.50 kg.ha<sup>-1</sup>) significantly increased these parameters, whereas calcium (66.28 and 50.9 cm; 465 tillers.m<sup>-2</sup> and 1,914.06 kg.ha<sup>-1</sup>) exhibited a neutral to depressive effect across all ratoon cycles. Consequently, nitrogen, zinc, and potassium can be recommended as part of a rational fertilization strategy in ratoon culture, aiming to enhance vegetative growth and straw production of rice in Ivory Coast.