RESUMO
Introduction: The use of controlled-release nitrogen (N) fertilizers has been shown to improve yield and N-use efficiency (NUE) in mechanical transplanted rice. However, the fertilizer requirements for mechanical direct-seeding rice differ from those for mechanical transplanted rice. The effects of controlled-release fertilizers on yield, NUE, and quality in mechanical direct-seeding rice are still unknown. Methods: Hybrid indica rice varieties Yixiangyou 2115 and Fyou 498 were used as test materials, and slow-mixed N fertilizer (120 kg hm-2) as a base (N1), N1+urea-N (30 kg hm-2) once as a base (N2), N1+urea-N (30 kg hm-2) topdressing at the tillering stage (N3), N1+urea-N (30 kg hm-2) topdressing at the booting stage (N4) four N fertilizer management to study their impact on the yield, NUE and quality of mechanical direct-seeding rice. Results and discussion: Compared with Yixiangyou 2115, Fyou 498 significantly increased photosynthetic potential, population growth rate, root vigor, and N transport rate by 3.34-23.88%. This increase further resulted in a significant improvement in the yield and NUE of urea-N topdressing by 1.73-5.95 kg kg-1. However, Fyou 498 showed a significant decrease in the head rice rate and taste value by 3.34-7.67%. All varieties were treated with N4 that significantly increase photosynthetic potential and population growth rate by 15.41-62.72%, reduce the decay rate of root vigor by 5.01-21.39%, promote the N transport amount in stem-sheaths (leaves) by 13.54-59.96%, and then significantly increase the yields by 4.45-20.98% and NUE of urea-N topdressing by 5.20-45.56 kg kg-1. Moreover, the rice processing and taste values were optimized using this model. Correlation analysis revealed to achieve synergistic enhancement of high-yield, high-quality, and high-NUE in rice, it is crucial to focus on increasing photosynthetic potential, population growth rate, and promoting leaf N transport. Specifically, increasing the contribution rate of N transport in stem-sheaths is the most important. These findings offer an effective N management strategy for 4R nutrient stewardship (right source, right method, right rate and right timing) of mechanical direct-seeding hybrid indica rice.
RESUMO
Freshly generated magnesium hydroxide (FGMH), produced by adding water-soluble magnesium salts to highly alkaline solutions, was used to remove anionic surfactant petroleum sulfonate (PS) from aqueous solutions. Adsorption experiments were carried out to investigate the effects of pH, adsorbent dosage, contact time, PS concentration, and temperature. The results showed that FGMH displayed excellent treatment efficiency for PS in the pH range 12.0-13.0. The maximum PS removal efficiency was reached within 60 s. The best dosage of magnesium chloride was 2.0 g/L. The adsorption capacity of FGMH for PS decreased as the temperature increased from 303 K to 333 K. The adsorption process was exothermic. The removal mechanism of PS by FGMH may be a coagulation-adsorption process involving a combination of flocculation, adsorption, charge neutralization, and netting catch affection. The results of this study showed that FGMH can be effectively used to treat surfactant wastewaters.
