Research On Charateristics Of A Biochar-based Nitrogenous Fertilizer And Its Effects On Soils And Crops

Biochar, as soil amendment and carbon sequestrator, has already become hotspot ininternational scientific communities. However, most biochars applied to most soils led togrowth stunt and yield reduction of crops in one season or more seasons, therefore, theincorporation of biochar with fertilizer is trend to application of biochar to agricultural andforestry soils, yet nitrogenous fertilizer is the first one that has maximum comsumption andrisk of environment in agriculture. In this paper, a biochar-based nitrogenou fertilizer preparedby several compounding processes, and its physical, chemical properties, nutrient releasecharacteristics and effects on soils and crops were evaluated and researched through physical,chemical measurements in lab, and analysis of soil and plant samples from pot experiments ingreenhouse. The resulsts and conclusions are as follows:1. The biochar’s properties and characterization showed that:①Bamboo charcoal1、2and wood charcoals prepared by traditional kiln are lump or granular, which showhoneycomb-like microporous in micro-structure. Sawdust charcoal and apple tree chipscharcoal prepared by pyrolysis process also show mesh and tubular pore structure, whichresults from deformed cells of plants. The biochar’s pore structure is one of the reasons forbiochar having large specific surface area and high adsorption performance, and also thespace for adsorption of biochar for nutrient, water and microbial habitats.②Five kinds ofbiochars are mainly composed of C, O, H. After ashing, the ash contains calcium, magnesium,potassium, sodium and other metal ions.③Five kinds of biochar’s are alkaline with pH valuegreater than7.2. The evaluation of physical and chemical characteristics and nutrient releasacharacteristics of the biochar-based nitrogenous fertilizer showed that:①The biochar-basednitrogen prepared by adsorption process and reactive process possess different nutrientretention mechanism. Bamboo charcoal-based nitrogenous fertilizer and wood charcoal-basednitrogenous fertilizer prepared by adsorption process is the physical adsorption of biochar fornitrogenous fertilizer or nutrients. During its preparation there was no chemical change infunctional groups of biochar; During AB and BA reactive processes for bamboocharcoal-based nitrogenous fertilizer chemical reactions occurred among A, B and biochar and made functional groups of biochar change. Its nutrient retention of the reactive processesis superior to the adsorption process, and nitrogen retention of bamboo charcoal-basednitrogen prepared by AB process is lower than that prepared by BA.②The pH ofbiochar-based nitrogenous fertilizer significantly decreased close to neutral in comparisonwith the original biochar which is due to a strong acid-weak base salt of ammonium nitrate.③Four kinds of biochar-based nitrogenous fertilizers all showed better nutrient slow-releaseperformance. The nutrient slow-release performance of Bamboo charcoal-based nitrogenousfertilizer prepared by reactive process is superior to that of Bamboo charcoal-and woodcharcoal-based nitrogenous fertilizer prepared by adsorption process.④The controlled-release perfornance of Bamboo charcoal-based nitrogenous fertilizer prepared by BA reactiveprocess is superior to that prepared by AB reactive process, which is related to the differencesin their sorption mechanisms respectively.3. The results from research on effects of biochar-based nitrogenous fertilizers on soilproperties showed that:①Biochar and biochar-based nitrogenous fertilizer can improve soilwater holding capacity which increases with the dosage increase, however, reduce when theadded doage of biochar excess over a certain level (in this study,80t/hm2dosage), which isrelated to too much macro-void for soil to store water due to excessive biochar.②Biocharand biochar-based nitrogenous fertilizer can increase water conductivity of heavier texturesoils so that they promote the soil water infiltration, however, they can decrease waterconductivity of lighter texture soil so that they reduce the soil water infiltration. The waterpermeability of the two soils with different texture gradually reduces with the increase ofbiochar and biochar-based nitrogenous fertilizers.③Biochar and biochar-based nitrogenousfertilizer can significantly raise soil organic carbon content. Bamboo charcoal-and woodcharcoal-based nitrogenous fertilizers can significantly improve soil CEC and content ofavailable P, available K and mineral nitrogen, yet the content of soil available nitrogen isreduced with bamboo charcoal and wood charcoal alone respectively.④Both biochar andbiochar-based nitrogenous fertilizer can raise soil pH and reduce bulk density. The pHincrement of soil applied with biochar-based nitrogenous fertilizer is lower than that of soilwith biochar alone, which suggestes that biochar-based nitrogenous fertilizer is more suitablefor calcarous soil.4. The results from research on effects of biochar-based nitrogenous fertilizer on cropsand its nutrient utilization efficiency showed that:①Application of biochar-based nitrogenfertilizer to the loam and sandy soil can significantly promote the growth of wheat and milletand increase yield. However, the millet growth slightly increased and the wheat growthinhibited when bamboo charcoal alone applied to loam, in opposite to sandy soil, biochar promote wheat growth but inhibit the millet growth when wood charcoal applied alonely totwo soil.②In two soils, biochar-based nitrogenous fertilizer can improve nitrogen useefficiency, extend the residual period of fertilizer nutrients in the soil and reduce leaching andother losses.