The Effects Of Biochar On Soil Physical And Chemical In Karst Area

Yellow Soil,as the main agricultural soil types in Karst area of Guizhou Province,has the characteristics that easily causes water and soil loss,such as the strong acidity,strong clay,low nutrient,low specific water capacity and so on.It is an important problem for the improvement of yellow soil that the method of improve the pH value,nutrient and soil structure.The research reveals the impacts on the nutrient and structure changes of the yellow soil by single addition of biochar and combination addition of plant and biochar in Karst region,which can help to determine the measures to relieve the low fertility and strong clay of Karst yellow soil and provide the scientific basis for improving the relevant limitation factors of agricultural production in Karst area.The yellow soil for testing was collected in Bozhou County,Guizhou Province in China,Pot experiments with 24 treaments were carried out in the greenhouse,including a bare land control?CK?,only planting of ryegrass?R?,only planting of paspalum?P?,only planting of daylily?D?,only addition of biochar at various rates?B₁,B₃,B₅,B₇,B₉;subscripts indicate%biochar added to soil weight:weight?,and ryegrass planting together with addition of biochar at different rates?RB₁,RB₃,RB₅,RB₇,RB₉?,paspalum planting together with addition of biochar at different rates?PB₁,PB₃,PB₅,PB₇,PB₉?,daylily planting together with addition of biochar at different rates?DB₁,DB₃,DB₅,DB₇,DB₉?.The soil physicochemical properties were tested after 120 days,240 days and 360 days.The results indicated that:?1?The treatments B and RB,PB,DB were the most effective way to increase the content of pH value,all nutrients?p<0.001?.The biochar rate has extremely significant impact on the pH value,nutrients,and C/N of the yellow soil.For the same biochar application time condition,soil nutrient contents increased with the increasing of biochar rate.When the biochar ratio was increased to7%⁹%,the contents of available phosphorous in B treatments were decreased.In the plant with biochar combination mode,soil organic matter content is relatively higher than that in ryegrass,soil nitrogen and potassium content is relatively higher than that in paspalum.Plant types should be chosen base on the soil nutrient content.The biochar application time has significant impact on yellow soil,such as the pH value,nutrients?p<0.05?.In B treatments,the soil pH value and the contents of organic matter,alkaline nitrogen,and rapid available phosphorous in the yellow soil increased with the application time;However,in RB,PB,DB treatments,the mean value of soil pH value firstly decrease and then increased.Meanwhile,the variation tendency of the mean value of soil organic matter,alkaline nitrogen,available phosphorous and available potassium content were on the contrary.?2?The contents of micro-aggregates with the diameter of 1⁰.25 mm and 0.25⁰.05 mm were decreased significantly if only the biochar was applied,the values range from 2.99 to 5.05%and-0.08 to 36.05%,respectively.When the biochar was less than 5%,the content of 1⁰.25mm decreased with the increasing of biochar rate,When the biochar proportion increased to 5%,the content of 1⁰.25mmincreased.There is no marked difference of the B₅,B₇,and B₉.Meanwhile,The value of MWD and GMD were decreased significantly if only the biochar was applied,the state of soil agglomeration state was relatively better than that in B₇ treatment.The contents of micro-aggregates with the diameter of 0.25⁰.05 mm were decreased significantly if adding biochar with plant,meanwhile,1⁰.25mm,0.05⁰.01mm?<0.001mm content increased.It showed that the maximum content of 1⁰.25mm micro-aggregates of different plants is BR₉,BP₇ and BD₇ respectively.The value of MWD and GMD were decreased if adding biochar with plant was applied.In RB,PB,DB treatments,the value of MWD and GMD decreased with the increasing of biochar rate as a whole.However,in RB and PB treatments,the MWD value were not significant in the rate of biochar to 3%⁹%,but in DB treatments,about MWD value,when biochar rate was 5%less than 7%.?3?The contents of particle with the diameter of 1⁰.25 mm were increased significantly if only the biochar was applied,at the same time,0.01⁰.005mm?<0.001mm content decreased.And the particle of 1⁰.25mm and<0.001mm increased and decreased with the increasing of biochar rate,respectively.Thevalues range from-0.03 to 4.43%and 1.45 to 13.54%,respectively.Besides,B treatment can reduce the fractal dimension D value of soil particles,and decreased with the increasing of biochar rate.At the end of the experiment,the D value of soil particles reached the minimum value2.9005 in B₅ treatment,followed by B₇ treatment.Compared with only planting of plant,adding biochar with plant can increase1⁰.25mm particle content and reduce<0.001mm particle content,the variation ranges from 0.21 to 4.96%and0.79 to 20.49%,respectively.It can reduce the D value of soil particles,and decreased with the increasing of biochar rate.The largest fractal dimension of ryegrass was under the condition of 1%and 3%biochar rates while the smallest fractal dimension was under the condition of the biochar rate reached 3%or more.?4?Compared with only addition of biochar and combination addition of plant and biochar,it turned out that the biochar rate increased to 3%,the content of soil organic matter in combination addition of plant and biochar were higher than that in only addition of biochar,while the contents of total phosphorus and total potassium were all less.In addition,the MWD and GMD values of the soil micro-aggregates were larger than those of only addition of biochar,and the D values of the particles were on the contrary.By using the principal component analysis method,the effects of only addition of biochar,only planting plant and adding biochar with plant on the quality of yellow soil were compared.It was found that after a period of time,the order of the three layout measures to improve the quality of yellow soil was as follows:adding biochar with plant>only addition of biochar>only planting plant.Meanwhile,considering the optimum pH value for different plant growth and the situation of soil pH value were increased with the application time,the treatment RB₅,PB₅,DB₇ can be recommended for these both improved the soil nutrient status and texture in Karast area.