| Two key constraints of crop production for sustainable development, on one hand, soilacidification-hardening and a continuing decline in the quality of cultivated land are causedby widespread application of chemical fertilizers, on the other hand, severe damage to the soiland the environment are caused by heavy metal pollution and discarded of agricultural wasteafter burning. Biochar, refers to the rich carbon product through pyrolysis by biomass underhypoxia condition, is able to effectively solve these problems and play an important role inthe agricultural environment.This study focus on the physical and chemical property, effect to crop growth and soilecology, and repair to heavy metal pollution of the biochar which was manufactured frompeanut shells and different corn straw. The main results as follow:1.Different biomass after charring, retained the pore structure of the original biomass,specific surface area enhanced3.7times on average. The pore volume has changedsignificantly, the total pore volume increased4times on average. the micropore volumeincreased3times on average. The amount of carbon fixed increased by6to12.6times, theash content increased by1.3to4.1times. The average pore diameter of different biochar werebetween10-30nm. pH value of biochar varied from7.9to9.8, and its Cation exchangecapacity was9.1-19cmol/kg. The biochar contained nitrogen, phosphorus, potassium, sulfurand other nutrient and mineral element. Biochar which was charred from different biomassare suitable for application on the crop production.2. The effect of biochar on soil physical and chemical properties showed that soil bulkdensity declined, the highest decreasing range was12.94%. Total porosity increased by9%to13%, aeration porosity increased from0.2to2.7times. Soil moisture content, temperature,cation exchange capacity, and available nitrogen and phosphorus were increased. Biocharcould amend soil water, fertilizer, air and heat.3. Effect of biochar on crop growth and development by trial of pot and field showed thatnet photosynthesis ratio, dry matter accumulation, yield and quality of crop were all increased.Rice yield increased by21.89%on average compared with control, treatment of10g biocharadd into1kg dry soil was the highest.The brown rice rate, milled rice rate and head rice ratewere enhanced except the chalky rate and chalkiness degree declined. Pods number, seedsnumber, and grain weight per plant of Soybean were all increased, which led to the increase of yield. The yield increased10.98%on average by biochar treatment of3000kg/hm2and6000kg/hm2compared with control.Impact of biochar addition on the crop growth and development under fertilizer reducedshowed that interaction of biochar and fertilizer could increase leaf net photosynthetic rate,strengthen absorbtion of nitrogen and phosphorus, and improve dry matter accumulation ofsoybean. Biochar addition was used under reduction of the application amount of routinefertilization by15%,30%and60%, increased fertilizer apperent utilizer and yield by327.87%and15.99%compared with equivalent fertilizer with no biochar and by95.09%and10.51%copared with routine fertilization, respectively.Whether biochar application or interaction of biochar and fertilizion could promote plantgrowth and development, and increase yield and quality.4Research on biochar addition into the soil of cadmium(Cd) pollution showed that soilavailable cadmium content has increased in the early growth stage of rice, which couldslightly activate effective cadmium ion. However, effective cadmium ion was decreased withtime prolonged, Biochar had "passivation" effect on the effective cadmium ions and graduallystabilized. Accumulation of Cd content on plant above-ground showed that stem> leaf> grain.The Cd content of grain decreased by33%compared with control at significant level, whichshowed biochar declined the Cd bioavailability. Biochar treatment could increase rice yield by10.66%compare with control. |
