Research On Effects Of Applying Different Amendments On Soil Nitrogen Retention And Crop Growth

Nitrogen fertilizers were widely used in agricultural production,but most of them were lost in the actual process.In order to reduce the loss of fertilizers,pot experiments,a soil leaching experiment combined with field experiments were carried out in this study to explore the effects of applying biochar,urease inhibitors(NBPT)and sulfur on soil nitrogen retention,soil properties and the crop growth.The main conclusions are as follows:1.The application of sludge biochar had a certain holding effect on soil nitrogen.The reasons are: sludge biochar could cause an increase in soil ammonia volatilization because of its high alkaline and would increase soil pH after applied.For all the treatments: fertilizer;fertilizer+1% biochar;fertilizer +3% biochar,fertilizer +5% biochar and reduce 1/3 Fertilizer +3% biochar,the cumulative ammonia volatilization accounted for 23.13%,25.87%,30.39%,37.03% and 32.74% of the applied N,respectively.Biochar applied at 1%,3% and 5%,the cumulative ammonia volatilization was increased by 11.8%,31.36% and 60.06%,respectively compared with the fertilizer treatment.The increase in ammonia volatilization was dependent on the amount of biochar.The soil column experiment showed that biochar could reduce the leaching of soil nitrogen.In the treatments with 1%,3% and 5% biochar,the cumulative leaching loss of nitrate nitrogen was decreased by 14.45%,25.02% and 19.66%,respectively,while the cumulative leaching loss of ammonium nitrogen was decreased by 12.02%,15.75% and 19.48%,respectively compared with the fertilizer treatment.2.Sludge biochar could increase soil total nitrogen,cation exchange capacity and organic matter content.When applied at 3%,the improvement effect was most obvious.In addition,biochar can promote the growth of wheat,for the treatment of 3% biochar,the wheat has the highest plant height.Even under the condition of reducing 1/3 of the Urea with the biochar added at 3%,the plant height of wheat is still 57.03% higher than that of fertilizer treatment.3.The urease inhibitors could reduce soil ammonia volatilization,the cumulative ammonia volatilization was 25.34% lower than the conventional fertilization,and the combined use of sludge biochar and urease inhibitors could weaken the impact of biochar.The amendments could also increase soil total nitrogen content.The soil total nitrogen content in the urease inhibitor + biochar treatment is 1.70 g/kg,12.58% higher than the fertilizer treatment of 1.51 g/kg.In addition,the use of amendments could also increase the biomass and total nitrogen content of maize crops,especially when combined biochar with urease inhibitors.The biomass and total nitrogen content of maize were increased by 14.85% and 19.28%,respectively compared with the fertilizer treatment.The sulfur could adjust soil pH.After three months of application,the soil pH was reduced by about 0.3 units compared with the fertilizer treatment.4.Field experiments showed that sludge biochar could reduce the leaching of soil nitrate.For the treatment without biochar,the soil nitrate nitrogen content was gradually increased with the increase of depth from the beginning of 20-40 cm soil layer.While in the biochar treatment,the soil nitrate nitrogen content was higher in the 0-20 and 20-40 cm soil layer.5.The neutral wood biochar could reduce the loss of soil ammonia volatilization,and the cumulative ammonia volatilization was reduced by 10.64% compared with the fertilizer treatment.When combined the wood biochar with urease inhibitor,cumulative ammonia volatilization could be reduced by 36.17% compared with the fertilizer treatment.