| Soil salinization is a common problem in the world.It not only affects the sustainable development of agriculture,but also does serious harm to the ecological environment.China also has a large number of saline soils,some of which are mainly distributed in the arid inland areas of Northwest China.The main obstacle factors of salinized soil are high soil salinity,salt damage,poor soil physical structure and low soil available nutrients,which are unfavorable to plant growth and nutrient absorption.There are many engineering,physical,chemical,biological and other measures to improve saline soil.Among them,the use of some new materials is one of the effective ways to improve saline soil by reducing soil salt damage,promoting plant nutrient absorption and improving plant salt resistance.To this end,the paper takes biochar as the matrix,and takes wood vinegar and rhamnolipid as the modified substances to prepare wood vinegar modified biochar and rhamnolipid modified biochar.Through the pot experiment of Chinese cabbage,taking saline soil as the research object,the paper adds wood vinegar modified biochar（W50%,W25%,W10%,W5%）,rhamnolipid modified biochar（R15%,R10%,R5%）and unmodified pure biochar（0%）according to two application levels（1%,2%）,The effects of modified biochar on the p H of saline soil,water-soluble base ions,a large number of trace elements and nutrients in soil,the biomass of Chinese cabbage,and the absorption of nitrogen,phosphorus,potassium,iron,manganese,copper and zinc by Chinese cabbage were studied.The following important results were obtained:（1）The effects of modified biochar on the p H value and the composition of water-soluble base ions in saline soil were studied.The application of modified biochar had no significant effect on soil p H and improved soil conductivity.For soil salt and base ions,the effect on improving soil water-soluble potassium ions is obvious,but it has little effect on the content of other water-soluble cations(Na+,Ca2+,Mg2+);Wood vinegar modified biochar improved the soil Ca2+/Na+ratio and K+/Na+ratio,especially the soil K+/Na+ratio;Rhamnolipid modified biochar also had a certain effect on the increase of soil Ca2+/Na+ratio and K+/Na+ratio.Rhamnolipid modified biochar R15%had a better effect on the increase of soil Ca2+/Na+ratio at the level of 1%,and rhamnolipid modified biochar R15%had a better effect on the increase of soil K+/Na+ratio at the level of 2%.（2）The effects of modified biochar on the contents of organic carbon and major elements in saline soil were studied.The contents of soil organic carbon,soil total nitrogen and soil available potassium increased significantly after the application of modified biochar.The contents of soil organic carbon and total nitrogen increased with the increase of biochar application（2%compared with 1%）;Adding a certain proportion of wood vinegar（W10%）or rhamnolipid（R10%）at the level of 2%significantly increased the content of soil ammonium nitrogen,while adding a certain proportion of wood vinegar（W5%and W50%）or rhamnolipid（R15%）at the level of 2%significantly increased the content of soil nitrate nitrogen;The effect of increasing the content of available phosphorus is small,and it will even reduce the content of available phosphorus in soil;It has obvious effect on improving soil available potassium.Under a certain proportion of wood vinegar or rhamnolipid,the content of soil available potassium can be further increased;There was no significant effect on soil catalase activity.（3）The effect of modified biochar on the content of trace elements in saline soil was studied.Under the condition of applying 2%modified biochar,the content of soil available iron and soil available manganese increased gradually with the increase of the proportion of wood vinegar,and the content of soil available copper and soil available zinc changed little;The content of available iron,available manganese,available copper and available manganese in the soil of each treatment had little change with the addition of rhamnolipid,and r15%treatment significantly increased the content of available zinc in the soil.Under the condition of applying 1%modified biochar,high concentration of wood vinegar modified biochar（w50%）significantly increased the contents of available iron and available manganese in soil;A certain concentration of rhamnolipid modified biochar（r10%）could increase the content of available copper in soil,and r5%could also increase the content of available zinc in soil.（4）The effects of modified biochar on the biomass of Chinese cabbage and the absorption of a large number of nutrients by Chinese cabbage were studied.The application of modified biochar increased the biomass of Pakchoi.At the level of 2%,the effects of w50%and r10%were relatively greater,and at the level of 1%,the effects of w25%and r10%were relatively greater.The application of modified biochar also increased the absorption of nitrogen,phosphorus and potassium by pakchoi.For the absorption of nitrogen by pakchoi,the effect of 0%treatment was relatively greater at the level of 2%,and the effect of w25%treatment and r10%treatment was relatively greater at the level of 1%;As for the phosphorus absorption of pakchoi,w50%treatment had a relatively large effect at the level of 2%,and w25%treatment and r10%treatment had a relatively large effect at the level of 1%;As for the potassium absorption of pakchoi,w50%and r5%treatments had a relatively large effect at the level of 2%,and w25%and r10%treatments had a relatively large effect at the level of 1%.（5）The effect of modified biochar on the absorption of Fe,Mn,Cu and Zn in Chinese cabbage was studied.The application of modified biochar improved the absorption of Fe,Mn,Cu and Zn in Chinese cabbage.As for the absorption of iron,manganese and zinc in Pakchoi,the absorption of iron,manganese and zinc in Pakchoi treated with w50%wood vinegar modified biochar was the highest at the level of 2%wood vinegar modified biochar;As for the copper absorption of pakchoi,at the level of 1%rhamnolipid modified biochar,the treatment with r10%rhamnolipid modified biochar had the highest copper absorption.（6）The effect of modified biochar on salt resistance of Chinese cabbage was studied.The application of modified biochar improved the salt resistance of Chinese cabbage.The application of modified biochar could reduce the content of malondialdehyde,increase the content of soluble protein and increase the activity of SOD.Under the condition of applying2%modified biochar,the content of malondialdehyde was reduced by w50%,w5%and r15%;W25%,w5%and r5%treatments increased the content of soluble protein,and the content of soluble protein in r5%treatment increased by 32.33%compared with the control;Treatment w10%and r15%increased SOD activity,among which treatment r15%increased SOD activity by 10.49%compared with the control.Under the condition of applying 1%modified biochar,the content of malondialdehyde was reduced by w50%,w25%,r15%and r10%;The soluble protein content was increased by r15%and r5%;Treatment with r15%increased SOD activity.To sum up,the application of wood vinegar modified biochar and rhamnolipid modified biochar,which were developed by combining wood vinegar,rhamnolipid and biochar in a certain proportion,to saline soil increased the ca2+/na+ratio and k+/na+ratio of soil solution,increased the contents of soil organic carbon,soil ammonium nitrogen,nitrate nitrogen,available potassium,available iron and manganese and other trace elements,and increased the yield of Chinese cabbage and the absorption of nutrients,The salt resistance of pakchoi was improved.Wood vinegar and rhamnolipid modified biochar are green and environmentally friendly improved materials,which have broad application prospects for saline soil improvement. |
