Effects of soil amendments on soil properties and population quality of rice in cold waterlogged paddy field

Long-term waterlogging with large amounts of reducing toxic substances of cold waterlogged soils and nutrient unavailability has often resulted in deteriorated rice growth, reduced rice resistance to adversities, inhibited root growth/activity and reduced rice yield. To explore feasible means of suppressing the negative effects of cold waterlogged paddy soils, a location experiment consisting an open-ditch drainage was conducted to study the effects of different soil amendments (self-developed desulphurization ash, biomass charcoal; and marketed lime, silicon-calcium fertilizer and humic acid) on soil Eh and respiration intensity, microbial quantity and population structure, and rice yield and yield components. The results showed that different soil amendments enhanced soil available nutrients contents and pH, while they did not significantly affected Eh except desulphurization ash treatment. All soil amendments increased respiration intensity and soil microbes at different growth stages of rice, with a significant (P < 0.05) increase in actinomycete population over CK. The respiration intensity and actinomycete population under biomass charcoal treatment were increased by 67.6% and 127.6% respectively. All soil amendments increased rice leaf SPAD, tiller number, dry matter accumulation, panicle number, grain number per panicle, yield, and root bleeding rate. Desulfurization ash and biomass charcoal treatments presented most obvious effects. At 29 days after heading, the rate of root bleeding under desulfurization ash and biomass charcoal treatments increased by 45.4% and 39.1%, respectively. Also leaf SPAD at 29 days after heading was 27.4% and 22.5% higher under desulfurization ash and biomass charcoal treatments over that under CK respectively. Dry matter accumulation increased by 68.5% and 50.5%, panicle number by 12.1% and 10.7%, and yield by 12.8% and 10.3% at maturity stage under desulfurization ash and biomass charcoal treatments over those under CK, respectively. In conclusion, different soil amendments differently improved soil properties and rice quality. Desulphurization ash and biomass charcoal amendments had the best effects.