The Effect Of Rice Genotype And Fertilization Strategies On Phytolith Carbon Sink

The phytolith-occluded carbon(PhytOC)is a vital mechanism for terrestrial biogeochemical carbon sequestration.After decomposition of plant residuals,phytolith with PhytOC occluded release into soil.Because of the protection of phytolith,PhytOC can be saved in soil for a long time,which plays an important role in both biogeochemical coupling of carbon and silicon,and global climate change.Argo-ecosystem is an important part of terrestrial ecosystem,while rice and wheat are two major important crops in argo-ecosystems.They have strong silicon-uptake ability and large planting area,which leads to an immense potential of phytolith carbon sequenstration.Thus,investigating into the regulatory mechanisms of phytolith carbon sink in rice-wheat rotation ecosystems appears to be particularly important.For this,we selected four rice genotypes differing in silicon uptake to investigate the influence of silicon-absorbing ability on the content,distribution and carbon sequestration characteristics of phytolith in rice in a pot experiment.Meanwhile,we explored the effect of long-term fertilization on phytolith contents in rice and wheat and its carbon sequestration characteristics.In this study,we investigated the response of phytolith carbon sink potential to silicon absorption and fertilization in rice and wheat system,which can provide theoretical basis for illuminating the mechanism of phytolith carbon sequestration in argo-ecosystem.The main results obtained are presented as follows:(1)The contents of SiO2 and phytolith were,in the rice mutants tested,highest in leaf,followed by sheath and stem,but were the highest in sheath,followed by leaf and stem in the wide types of rice tested.The contents of PhytOC and PhytOC per gram of dry biomass were the highest in the leaves of the four rice genotypes tested.The PhytOC contents showed the following trend:leaf>stem>sheat.The PhytOC per gram of dry biomass showed the following trend:leaf>sheath>stem.(2)Compared with the mutants,the contents of SiO2 and phytolith,dry biomasses and PhytOC per gram of dry biomass of rice were higher in the wild types of rice.Although the PhytOC contents were lower in the wild types,the PhytOC storages were higher eventually.The trend of PhytOC storages per pot was as follows:Lsi2 wild type(377.39 mg)>Lsi2 wild type(311.35 mg)>Lsi2 mutant(151.45 mg)>Lsil mutant(52.96 mg).(3)The long-term application of inorganic fertilizer reduced the contents of phytolith,PhytOC per gram of dry biomass,phytolith flux and rate,and PhytOC flux and rate in rice.Compared to the NPK treatment,partial substitution of chemical fertilizer with pig manure organic fertilizer(NPKM),straw(NPKS)and pig manure plus straw(NPKMS)had higher contents of phytolith,PhytOC,PhytOC per gram of dry biomass,phytolith flux and rate,and PhytOC flux and rate.The phytolith flux was the highest in NPKM treatment(87.31 kg CO2/ha/yr),which was 63.97 kg CO2/ha/yr more than that of CK and 65.59 kg CO2/ha/yr more than that of NPK treatment.The phytolith carbon sink of rice in different fertilization treatments showed the following trend:NPKM(2.37×106 T CO2/yr)>NPKMS(1.75×106 T CO2/yr)>NPKS(0.72×106 T CO2/yr)>CK(0.63×106 T CO2/yr)>NPK(0.59×106 T CO2/yr).(4)Compared to the CK treatment,long-term application of inorganic fertilizer reduced the contents of phytolith,PhytOC,and PhytOC per gram of dry biomass in wheat,but increased the contents of aboveground net primary productivity(ANPP),phytolith flux and rate,and PhytOC flux and rate.Compared to the NPK treatment,partial substitution of chemical fertilizer with pig manure organic fertilizer(NPKM),straw(NPKS)and pig manure plus straw(NPKMS)increased the contents of phytolith,PhytOC,PhytOC per gram of dry biomass,ANPP,phytolith flux and rate,and PhytOC flux and rate.The phytolith flux was the highest in NPKM treatment(7.67 kg CO2/ha/yr),which increased by 308%and 124%in comparison to CK and NPK treatments.