Effects Of Acidic Biochar On Crop Growth,Soil Physicochemical Properties And Soil Microbial Community Under Saline Conditions

Salt stress has become one of the environmental constraints to crop productivity in the arid and semi-arid regions of the world.It is one of the abiotic stresses which inhibits the plant growth,yield and development which ultimately causes reduction in the yield.Salinity deteriorates physical,chemical and biological properties of soil.Salt stress triggers inhibition in plant development and yield by imposing osmotic stress,causing ion toxicity and nutrients imbalance in plants.Salinity stress accelerates negative effects on plant morphological,physiological,biochemical and molecular changes.In such conditions a recent one of the organic amendments has been utilized to control the salinity issue for sustainable agriculture.In the last two decades,biochar has received great attention of the researchers.It is a recent application used for its positive effects of ameliorating the salinity stress in plant growth,soil physical,chemical and biological properties.Biochar is extensively used in agriculture because of its numerous benefits,such as increases water holding capacity,permeability and aeration,soil organic matter,minerals,reclaims the saline soils and enhances crop yield.However,the research studies have reported that the application alkaline biochar has been a common practice to alleviate the negative effects of salinity and improving the soil properties and crop growth.Alkaline biochar has high p H,and high electrical conductivity(EC)which can increase soil p H and EC.Whereas,the biochar having low p H has completed been ignored.Therefore,it was necessary to design experiments to investigate the effects of acidic biochar on plant growth,soil chemical and biological properties under saline condition.The study was consisted of four levels of biochar i.e.,0,15,30 and 45g biochar kg^-1 soil(marked as AB0,AB1,AB2,AB3,respectively)against two salt levels(S1 of 0.5% and S2 of 1%).Two experiments were conducted on the growth of spinach and maize seedlings and soil properties during2019 and 2020 in controlled conditions in order to achieve the desired objectives.Treatments were termed as CK(control=without biochar and salt),AB0,AB1,AB2,AB3 for experiment 1^st and CK,B0S1,B1S1,B2S1 and B0S2,B1S2 and B2S2 for 2^ndexperiment.The main findings are as follows:1.A pot experiments was carried out to investigate the effect of acidic biochar on agronomical,physiological and growth parameters,as well as nutrients concentration in spinach tissues.The results showed that the number of leaves,plant height and plant fresh and dry weights decreased by 58.1,53.1and 82.7 and 81.3%,respectively,in AB3 as compared to CK.Physiological characteristics of spinach plants were negatively affected by addition of biochar.The concentration of total nitrogen(TN)in spinach was observed low at the rate of 45 g kg^-1 biochar+1%salt(AB3)compared to CK.In contrast,total phosphorus(TP)uptake was enhanced by 93.8%in B3S1 compared to CK.Moreover,biochar addition decreased soil p H and increased soil electrical conductivity(EC),TP and TN increased by317.4 and 34.5%,respectively in biochar treated soils.Based on the results,it can be observed that physiological and growth parameters of spinach were significantly decreased with acidic biochar under salinity stress However,acidic biochar significantly improved nutrients concentration in spinach tissues and soil properties.2.Application of an acidic biochar can improve plant growth and soil properties in saline condition.In this study,we investigated the effect of acidic biochar on the growth of maize seedling,nutrients concentration in tissues and contents in saline soil.The Experimental results 30 days after sowing,showed that the plant height,leaves plant^-1,leaf area,and shoot fresh and dry biomass,and root fresh and dry biomass were increased for the B2S2 respectively.Similarly,the highest concentration of TN(10.71 mg g^-1),TP(2.46 mg g^-1),TK(3.97 mg g^-1)and Na(14.07 mg g^-1)in maize shoot were observed for B1S1,B0S2,CK and B0S2 respectively.The highest concentrations of TN(33.62 mg g^-1),TP(33.02 mg g^-1),TK(21.52 mg g^-1)and Na(38.18 mg g^-1)in root were obtained with the treatments B0S1,B0S1,B2S1 and B0S1 respectively.Soil properties such as soil p H,and EC decreased and nutrients concentration increased by the addition of acidic biochar under salinity stress.In general,acidic biochar improved maize growth and mitigated the adverse effect of salt.3.The current study aimed to investigate the effect of acidic biochar on maize seedlings rhizosphere bacterial abundance under salinity.The results revealed that relative abundance of Proteobacteria,Actinobacteria and Chloroflexi increased on phylum level,while Actinomarinales,Alphaprobacteria and Streptomyces enhanced on genus level respectively in B2S1 and B2S2,when compared to CK and non-biochar amended soil under saline conditions.The relative abundance of Actinomarinales was positively correlated with total potassium(TK)and Gematimonadetes negatively correlated with total phosphorus(TP).Biochar addition slightly altered the Ace1,Chao1,and alpha diversity.Principal component analysis(PCA)responded the changes in soil bacterial community were closely associated with biochar when compared to CK and salt treated soils.In conclusion,acidic biochar showed improved soil microbial community under salinity.It was observed from the experiments that acidic biochar under saline conditions have increased plant growth,nutrients concentration and improved chemical and biological properties of soil.Under different biochar treatments,different results specially in terms of plant growth parameters were observed.The growth of spinach was adversely affected with the application of acidic biochar but simultaneously,maize growth was significantly increased with the same biochar.Among the different levels of biochar,the 30 g kg^-1 under 1%salt proved appropriate.Soil properties were improved with the acidic biochar application in the experiments.Hence,we conclude that use of acidic biochar can be potential source for the improvement of maize plant growth mitigate the adverse effect of salt stress as well as improves soil properties.Biochar has extensively been used for multiple purposes in agriculture,including improving soil microbial biomass.