| Potassium is one of the large essential nutrients for plant growth,Appropriate application of potash fertilizer is an important way to ensure crop yield and quality.For the shortage of soluble potassium resources in China,alternative measure should be taken,which was related to national food security.Potassium fertilizer produced by the insoluble potassium-containing minerals play a certain role in promoting crop growth.To explore application technology of potassium silicon fertilizer substitute of chemical potash fertilizer,pot expeiment was conducted.Plant biomass,potassium concentration and soil potassium content were invastigated.The effects of different potassium fertilizer types,different potassium silicon fertilizers application rates,different forms of potassium fertilizer ratio on the crop growth,potassium uptake and potash use efficiency in the two cropping systems were studied.And the method of potassium silicon fertilizer application was determined,with the optimum application rate of potassium silicon fertilizer and the reasonable ratio of potassium silicon fertilizer and potassium sulfate identified.On the basis of this,the effects of potassium silicon fertilizer on the growth of rice on heavy metal contaminated soil and the uptake of heavy metals in different parts were studied.The mechanism of potassium silicon fertilizer and silicon calcium fertilizer to reduce the content of heavy metals in paddy soils was analyzed to determin the effects of potassium silicon fertilizer and silicon calcium fertilizer on soil heavy metal.The results provide the theoretical basis for rational application of potassium silicon fertilizer and improving heavy metal contaminated soil.The main findings are as follows:(1)Potassium silicon fertilizer application increased the biomass of the two seasons of crops significantly at same potassium(K2O)supply level.Compared with the non-potassium treatment,the yield of the two crops after potassium silicon fertilizer application increased by 61.2% and 37.8%,while there was no difference with comminuted kaolin powder application treatment.The application of potassium silicon fertilizer increased the potassium content of rape and rice stem significantly.The potassium use efficiency of rape and rice were 50.7% and 26.0% respectively.Soil potassium content increased notably after potassium silicon fertilizer applied in previous season.(2)Under the condition of this study,the optimum application amount of potassium silicon fertilizer was 0.15-0.225 g/kg.The biomass of rape increased with the increase of potassium silicon fertilizer.When the amount of fertilizer reached 2.25 g / pot,the highest yield of rape was 70.6%,which was significantly higher than other treatments.The biomass of the rice increased with the increase of fertilizer application rate.When the fertilizer amount was 3.00 g / pot,the biomass was the largest and the maximum yield was 57.0%.After the two-season crop was planted,the partial nutrient balance was less than 1 when the fertilizer was 3.00 g K2 O / pot,and the soil potassium was in surplus state.(3)The yield of potassium silicon fertilizer with 25%~50% water-soluble potassium of the two crops was the highest.Baiomass and potassium accumulation increased under different forms of potassium fertilizer ratio.Compared with no potassium treatment,the yield of potassium silicon fertilizer with 50% water-soluble potassiumincreased by 61.5% and 50.7% of rape and rice,higher than other treatments.The total potassium accumulation of both rape and rice was highest of potassium silicon fertilizer with 50% water-soluble potassium,and potassium use efficiency of the crops were 58.0% and 52.0%,and actual utilization rate were 98.3% and 58.4%,respectively.The application of potash fertilizer significantly increased soil available potassium and slow K content after the first season.(4)The application of potassium silicon fertilizer significantly reduced the accumulation of Pb and Cd in the shoots of rice,and the accumulation of Pb and Cd in the shoots of rice was further decreased with the increase of potassium and silicon fertilizer.Pb and Cd accumulation in stems,leaves and grains of rice was decreased significantly after the addition of citrate acid-soluble potassium fertilizer.Compared with treatment of K2SO4,the Pb and Cd accumulation in stems,leaves and grains of rice was decreased by 34.2%?49.0%?18.6% and 28.2%?42.4%?24.4%,respectively.With the increase of K fertilizer application,Pb and Cd accumulation in aboveground decreased significantly.However,there was no significant differences on Pb and Cd accumulation in roots among different treatment.After rice cultivation,soil available Pb and Cd content decreased,but no differences on soil available Pb and Cd content was observed between K2SO4 treatments and citrate acid-soluble potassium fertilizer treatments.In conclusion,citrate acid-soluble potassium fertilizer meets the needs of K in rice,also reduce the uptake of heavy metals of rice in aboveground.(5)The application of silicon calcium fertilizer significantly increased the yield of rice and significantly inhibited the uptake and accumulation of heavy metals in rice.Compared with CK treatment,the rice yield increased by 51.9%.Compared with heavy metal treatment,the Pb contents in stems,leaves and grains of rice of heavy metal combind with silicon-calcium fertilizer decreased by 50.9%,56.3% and 24.3%,the Cd in stems and grains of rice contents decreased by 31.6% and 60.4%.Silicon-calcium fertilizer application increased Si contents in each part of rice.The reason for the reduction of Pb/Cd contents in rice may be Si deposition.Si contents and heavy metals contents in each part of rice present the obvious negative correlation.After the rice cultivated,Pb and Cd contents in soil decreased,Pb and Cd contents of different forms in soil has no differences between check treatment and silicon-calcium fertilizer treatment.There is no promoting effect of transformation of different forms of heavy metals in soil after the application of silicon-calcium fertilizer. |
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