Effects of liquid fertilizer and reduced application rate on rice growth, nutrient uptake, and rice yield during the tillering stage

Background: Liquid fertilizers are increasingly used in modern agriculture due to their high solubility and convenient application. However, the regulatory mechanism of liquid fertilizer on rice morphological construction, photosynthetic characteristics, and nutrient uptake during the tillering period is still unclear, and its impact on the final yield formation also needs to be further explored. Results: In this study, ‘Huanghuazhan’ was selected as the experimental material, and four treatments were set up: HS (standard solid fertilizer application rate), HL (standard liquid fertilizer application rate, identical to the solid fertilizer application rate), HL-10% (10% reduction from the standard liquid fertilizer application rate), and HL-20% (20% reduction from the standard liquid fertilizer application rate) to systematically investigate the effects of liquid fertilizer and reduced application rate on rice during the tillering stage. The results showed that compared with the HS treatment, the HL, HL-10%, and HL-20% treatments significantly increased rice growth parameters, with aboveground dry weight increasing by 174.45%, 83.22%, and 57.67%, respectively. Meanwhile, liquid fertilizer and reduced application rate enhanced photosynthetic capacity and promoted carbohydrate synthesis. In addition, the aboveground N, P, K uptake, root N, P uptake in HL, HL-10%, and HL-20% treatments were all higher than those in the HS treatment. Compared with the HS treatment, the HL, HL-10%, and HL-20% treatments increased agronomic efficiency and partial factor productivity. Specifically, the nitrogen agronomic efficiency significantly increased by 44.44%, 20.03%, 9.23%, respectively. Compared with the HS treatment, the HL, HL-10%, and HL-20% treatments increased rice yield and yield components. For example, yield increased by 50.12%, 20.82%, and 9.67%, respectively, and 1000-grain weight increased by 6.31%, 2.33%, and 0.71%, respectively. Conclusions: In conclusion, the experiment on gradient reduced application of liquid fertilizer showed that, even reduced application rate (HL-10% and HL-20% treatments) treatments still performed better than the HS treatment in terms of morphological construction, photosynthetic characteristics, nutrient uptake during the tillering stage, and yield formation, achieving the goal of "reduced application rate with increased yield."