Response Of Silicon Availability And Rice Growth To Soil Acidification And Phosphorus Addition In Reddish Paddy Soil

The mobility and availability of phosphorus（P）and silicon（Si）and their interactions in soils are sensitive to soil pH.Although Si fertilizer application can increase P availability in soils,the responses of Si mobility and availability to soil P enrichment are not well understood.Reddish paddy soil is a typical agricultural farming soil in China,It is widely distributed,and has a long history of agricultural utilization,The problem of soil P accumulation is more prominent in some areas.This study intended to investigate the effects of artificial soil acidification and P addition on Si sorption characteristics and availability in soil using adsorption experiment;and to study the effects of soil acidity and P levels on soil Si forms,rice yields and Si absorption through rice pot experiments;combined adsorption experiments,Soil incubation experiment and pot experiment to study the response of reddish paddy soil Si availability and rice growth to soil acidification and P addition from the perspective of P promoting the availability of soil Si,providing a comprehensive evaluation of the agronomic and environmental effects of soil P enrichment a new perspective to further promote nutrient management in paddy soil has important scientific and practical significance.The main study results of the research are as follows:（1）When the soil pH is in the range of 3.5～6.5,The phosphorus had a greater affinity to soil minerals than Si,and the presence of P can displace part of the Si that was adsorbed by the soil.At the same pH,the soil had the higher P adsorption and the lower Si absorption.In addition,P addition could reduce the amount of Si absorption in the soil（The reduction range was between 22%and 88%）,but the competitive effect of P on Si adsorption was weakened at the lower pH.Therefore,the competitive adsorption effect between Si and P was affected by the soil pH value.（2）Based on incubation experiment,the results showed that at the same phosphorus level,the highest pH value（CK）had the lowest content of CaCl₂（soluble Si）and the highest content of Acetic acid sodium acetate at pH 4.0（adsorb Si）.At the same time,the adsorption experiment showed that the Si adsorption capacity of CK treatment was the largest under the same P addition level.The results of pot experiment showed that under the same P application level,the Si extracted by CaCl₂ decreased with the increase of pH,and the Si extracted by acetic acid sodium acetate at pH 4.0 decreased with the increase of pH.In addition,there was a significant positive correlation（p<0.001）between the content of Si extracted by CaCl₂ and the Modified Freundlich equation fitting parameter C₀（Si concentration at equilibrium of exchange system）,while there was a significant positive correlation（p=0.033）between the content of Si extracted by acetic acid sodium acetate at pH 4.0 and the Modified Freundlich equation fitting parameter a（adsorption capacity constant）.（3）Chemical continuous extraction method was used to extracted Si on the incubation soils and pot soils.It was showed that the exchangeable Si increased gradually with the increase of pH,while the organic Si and Fe/Mn-oxide Si decreased gradually with the increase of pH.These results indicated that with the increase of pH,some organic Si and Fe/Mn-oxide Si may be released and transformed into more effective exchangeable Si.（4）The results showed that the Si of plant contain and uptake increased with the decrease of pH and the increase of P addition,and there was a significant positive correlation with the content of CaCl₂-extractable-Si,indicating that soil acidification and P addition were beneficial to the activation of soil Si,which further improved the Si utilization of rice.However,severe soil acidification（e.g.,pH<4.0）may be not favorable for plants growing and thus limiting Si uptake by plants,subsequently resulting in accelerated Si loss from the soil.