Humic Acid Fertilizer Incorporation Increases Rice Radiation Use, Growth, and Yield: A Case Study on the Songnen Plain, China

Humic acid fertilizer (HA) incorporation is a common method for improving crop growth and soil fertility. However, the effects of HA on rice are still unknown. We conducted two-year field experiment to determine radiation use, growth, yield grown with five different rates: 110 kg?ha?1 100% urea (pure nitrogen) (T1); 30% 70% (T2); 50% (T3); (T4), 1500 (T5). The results showed that T2 treatment had lowest values photosynthetic efficiency PSII (Fv/Fm), relative leaf chlorophyll content (SPAD), plant height area index (LAI) in both years, which were similar photosynthetically active (IPAR), use (RUE), yield, biomass. In contrast, highest harvest (HI) value was found treatment. two T4 T5 treatments no significant differences. multivariate statistical based principal component analysis first component, LAI, biomass, height, SPAD, Fv/Fm, IPAR, RUE positive correlation, HI negative correlation. HI, but Fv/Fm IPAR correlation second component. Across treatments, comprehensive scores > T3 T1 T2, 2.13, 1.38, ?0.17, ?0.34, ?3.00, respectively. According each index, better than