Effects Of Reducing Nitrogen And Biomass Carbon Application On Water Quality In Field Surface Water And Rice Yields

Rice is one of the most important food crops in China covering more than30×106hm2of thecultivation area and accounting for30%and50%of total grain crop planting area and grain output,respectively. Over-fertilization in paddy field would result in substantial loss of chemical elements suchas N P, K etc and pollution of water system near surrounding paddy field. The current study shows thatrates and types of fertilizers as well as fertilization way are important factors affecting the loss of N andP in the paddy fields. Reducing fertilizer rates and combination organic manure and chemical fertilizercan coordinate the supply of fertilizer and improve nitrogen fertilizer use.A field experiment was conducted in Hengxu Village, Taihuyuan Town, Lin’an City, Zhejiangprovince, China in2013. Eight fertilizer treatments consisted of without fertilization, conventionalfertilization,20%reduction of inorganic fertilizer, organic and inorganic compound fertilizer, areduction of20%biomass carbon+no fertilizer, biomass carbon+conventional fertilization, biomasscarbon+20%reduction of inorganic fertilizers, biomass carbon+20%reduction of organic andinorganic fertilizers. The trial design was replicated three times in a randomized block design. Theeffects of reducing fertilization and biomass carbon on nutrient loss of paddy field surface water andrice yields were conducted for two years by using the rice cultivars as Zheyou. The main results are asfollows:The study on effects of reducing fertilization and biomass carbon on nutrient loss of paddy fieldsurface water showed that the concentrations of total N, dissolved N, ammonium N and dissolved K inthe field surface water with all fertilization treatments except no fertilization reached the highest valueson the second day after fertilization, and tended to be stable. However, their concentrations a week laterwere9.2~15.5%,11.0~38.5%,16.6~42.8%, and30.4~68.0%of the peak values. Total P and dissolved Pconcentrations reached the highest on the third day after fertilization, then declined rapidly, and finallytended to be stable a week later. Their concentrations a week later were29.2%~64.8%and33.5%~59.6%of the peak values. Nitrate N concentrations in the field surface water reached the peak value onthe second day after fertilization, then subsequently decreased, finally fell to the level with no fertilizer.Application of biomass carbon could moderately absorb nutrients of N, P, and K, which resultingreduction of nutrient loss. Addition of suitable amount of organic fertilizer significantly increased P concentration and DOC in the field surface water by24.4%~81.7%, respectively as compared with thetreatment of no inorganic fertilizer. Therefore, combination inorganic fertilizer and organic fertilizer orbiomass carbon can optimize nutrient ratio in the field surface water, which helping to absorption of thenutrients by rice.The study on effects of reducing fertilization and biomass carbon on yield trait and yields of riceshowed that rice yields of different fertilization treatments without biomass carbon ranged5213~5991kg/hm2and there were no significant differences in rice yields between them. However, there weresignificant differences in rice yields between different fertilization treatments with biomass carbon.Compared with the treatment N1+C, the treatments of N2+C and N1+C increased rice yields by24.6%and22.0%, respectively. In addition, there were significant differences in panicle length, plant height,and1000grain weight of rice as well as N and P accumulation in the rice straw and grain between thetreatments of different fertilizer levels.