Effects Of Biochar Addition On The Stoichiometric Characteristics Of Black Soil Vegetable Fields In A Facility

Stoichiometry could illuminate the relationships between the properties of plants growth and the limiting factors by using the stoichiometric relations of elements(formally C,N,P).Regular irrigation and fertilization treatment(WF),regular irrigation and fertilization with biochar addition treatment(WFB)and the reducing irrigation by 20%and reducing chemical fertilizers by 20%with biochar addition(80%W80%FB)in Facilities Black Soil Fields Positioning Experiment conducted in Institute of Horticulture,Heilongjiang Academy of Agricultural Sciences,were selected in present study.Based on the theories and methods in stoichiometry,nutrients contents in soil of different depth and the different part of plants,the relationships between soil nutrients contents and plant nutrients contents,and the stoichiometry characteristics of plants and soil were also studied,which is of great significance for the study on the nutrient limitation.The results are mainly as follows:(1)The contents of soil organic carbon(SOC),soil total nitrogen(STN)and soil total phosphorus(STP)all decreased with the increasing soil depth.Nutrients in the soil located in 0-20 cm was enhanced in the addition of biochar.For WFB,the increases in SOC,STN and STP were 8.90%,3.75%and 2.92%,respectively;and for 80%W80%FB,the increases in SOC,STN and STP were 32.33%,19.58%and 13.87%,respectively.In comparison with WF,SOC,STN and STP in the soil of 20-100 cm in WFB and80%W80%FB all decreased.STN and STP in 60-100 cm changed slightly,but SOC in80-100 cm decreased significantly after the addition of biochar(p<0.05).(2)The stoichiometry study on C,N,P in soil showed that C:N,C:P and N:P all increased in soil of 0-20 cm.C:N,C:P and N:P in WFB were increased by 0.57,1.12 and0.01,respectively;and those in 80%W80%FB were increased by 1.15,3.04 and 0.08,respectively.For the soils of 20-100cm in WFB,no obvious change was found in C:N(p>0.05).C:P and N:P increased by 0.17 and 0.12 in 20-40 cm and in 40-100 cm(p>0.05)and C:N,C:P and N:P all decreased in different extents.In 80%W80%FB,C:P exhibited a continuous increase in 20-60 cm and a slight decrease in 60-100 cm;however,N:P was significantly enhanced(p<0.05).It is notable that N:P in all soils were less than 5.2,indicating that N was the main limiting factor while the addition of biochar can efficiently depress the N limitation.(3)In view of nutrients contents of the different plant parts,WFB significantly increased organic carbon(POC),total nitrogen(PTN)and total phosphorus(PTP)in fruits by 8.48%,13.12%and 51.13%,respectively.For leaves and stems,the POC decreased by 0.74%and 4.33%,PTN increased by 20.09%and 2.29%,and PTP increased by 33.77%and 1.32%.For roots,POC and PTN increased by 1.54%and 1.64,but PTP deceased by9.68%.In 80%W80%FB,POC,PTN and PTP were all enhanced,which were increased by 1.43%,7.60%and 30.32%respectively.For leaves,POC and PTP increased by 0.16%and 40.26%,but PTN decreased by 0.54%.For stems,PTN and PTP both increased by3.80%and 1.32%,but POC decreased 5.52%.For roots,POC,PTN and PTP all decreased by 2.17%,3.09%and 16.13%.The distribution of PTN and PTP in different parts of plants was in the order of fruits>leaves>stems>roots.(4)The stoichiometry characteristics in different parts of plants suggested that WFB and 80%W80%FB both decreased the C:N,C:P and N:P in fruit.80%W80%FB improved the C:N,C:P and N:P in roots.No significant changes were found in the C:N,C:P and N:P in different parts of plants with the addition of biochar,demonstrating the inherent stability in plants.And the addition of biochar can depress the N:P of fruit,leading to the less P limitation.(5)C:N of 0-20 cm soil layer and C:N of fruits and stems were significantly negatively correlated(p<0.05),with correlation coefficients 0.676 and 0.721,respectively;C:P of stems and C:P of 0-40 cm soil were significantly positively correlated(r=0.821-0.832,p<0.01).C:P of stems and that of 40-60 cm soil showed a significantly positive correlation(r=0.797,p<0.05).C:P of roots and that of 0-20 cm soil displayed a significantly positive correlation(r=0.857,p<0.01).The C:P of stems and that of 20-40cm soil exhibited a significantly positive correlation(r=0.755,p<0.05).N:P of leaves and stems and that of 20-40 cm soil displayed a significant correlation(p<0.01),with correlation coefficients 0.820 and 0.887,respectively.N:P of stems and N:P of 40-60 cm soil displayed a significantly positive correlation(r=0.717,p<0.05).(6)In comparison with WF,WFB greatly improved the yield of eggplants by 6.96%and a slight yield decrease in 80%W80%FB was also found,which indicating that biochar could enhance eggplant yield.However,the biomass verified in a narrow range(from60.87-61.24 t/hm~2),suggesting that the biochar would have little effect on the biomass in eggplants in facility vegetable in Northeast China.