| According to the factors affecting nitrogen in composting,In identifying cow dung as compost material,Under the premise that corn straw is a carbon source conditioner and adsorbent,Choose the ventilation capacity,tipping frequency,moisture content and C/N,which are beneficial to compost maturity and nitrogen retention On the basis of previous studies,the feasibility of calcium superphosphate,ferrous sulfate,potassium persulfate and magnesium hydroxide as nitrogen-fixing agent for cow manure straw composting was verified,Four different composting experiments were carried out(the addition amount was the ratio of chemical substances to dry weight of compost materials),a group :4.4%calcium superphosphate treatment(SP),4.1% ferrous sulfate treatment(LF)and control treatment(CK);b groups :2.5%,3.75% and 5% ferrous sulfate treatment(LF1、LF2 and LF3)and control treatment(CK);c group :0.0375% ferrous sulfate 0.625% potassium persulfate,0.625% ferrous sulfate 1.25% potassium persulfate and 1.25% ferrous sulfate2.5% potassium persulfate treatment(FK1、FK2 and FK3)and control treatment(CK);d group :6.06% calcium superphosphate,6.06% calcium superphosphate 1.01% magnesium hydroxide,7.07% calcium superphosphate 1.17% magnesium hydroxide,8.08% calcium superphosphate 1.34% magnesium hydroxide treatment(SP、ST1 、ST2 and ST3)and control treatment(CK).According to the effect of additives on physical and chemical parameters,maturity,nitrogen loss and composting quality,The analysis concludes that:(1)Four groups of compost were sampled regularly,and the temperature,pH value,conductivity and seed germination index of the composting process were measured and analyzed.All treatments go through heating,heat,cooling and ripening stages,The days of high temperature period(>50℃)were:a group:6,9,5;Group b:15,12,13;Group c:3,5,2,10;Group d:3,5,4,3,3.The high temperature period and high temperature time of ferrous sulfate treatment were lower than that of control treatment under the premise of ripening,The addition of potassium ferrous sulfate,but the high temperature period was prolonged.From the pH values of the four groups,In addition to the compound addition of calcium superphosphate and magnesium hydroxide treatment,All other processed pH values are reduced,Basically under 8.5,It effectively avoids the conversion of ammonia nitrogen into ammonia gas and volatilizes into air,Increase nitrogen loss.d group was treated with calcium superphosphate magnesium hydroxide,pH values were significantly higher than those of control,It is not conducive to nitrogen fixation.At the end of composting,All processed pH values meet the requirements.The conductivity is proportional to the soluble salt content,Therefore,the conductivity of compound additive treatment is generally higher than that of single chemical additive treatment.Final conductivity of 4 groups of compost treatment was less than ms cm-1,4.00 Application into the field does not affect the growth of plants.The seed germination index of each treatment increased gradually with the composting process,Up to 80%maturity before the compost is finished,The plant toxicity of compost products to plants basically disappeared.(2)Comparing the results of ammonia nitrogen,nitrate nitrogen,total nitrogen and carbon-nitrogen ratio of four groups of compost samples,The changes of composting indexes of different additives are basically the same,but slightly different.The content of ammonia nitrogen in 4 groups of compost samples showed first rising and then decreasing and then stabilizing.Ammonia nitrogen content of compost samples in a group was higher,At about 250 mg kg-1 early in the compost,High temperature up to mg kg-1,260-467 Ammonia nitrogen content was lower than 100 mg kg-1,in the other three groups Ammonia-nitrogen content is between 200-400 mg kg-1,Should be compost raw materials placed too long caused.Except for the early stage of b group,the content of nitrate nitrogen was very low,As the temperature of the stack rises first and then drops into maturity,Conversion of ammonia nitrogen to nitrate nitrogen,Nitrate and nitrogen gradually accumulated.The total nitrogen content of four groups of compost increased with the process of composting,The total nitrogen content of all treatments showed a slight decrease in the heating period,Then organic matter degradation and ammonia nitrogen content decreased,To reduce the total nitrogen loss,The concentration of total nitrogen was increased.despite the inconsistent initial carbon-nitrogen ratios for each treatment(16.41-20.02),But it’s all ripe,It shows that the carbon-nitrogen ratio of compost initial material can be lower.From the nitrogen loss control effect,The nitrogen loss rate of each group was very different,21.30%,26.18% and 14.95%,respectively.Within the group,Addition of ferrous sulfate alone has a good nitrogen-preserving effect: the nitrogen loss rate in a group decreased by 19.09%,b group decreased by 9.21-19.65.The addition of calcium superphosphate alone to a and d groups,Adding 4.4% in a group didn’t have nitrogen-preserving effect,d treatment nitrogen loss rate of 6.06% addition in the group decreased by 5.4%.Potassium ferrous sulfate in the treatment of compound additives reduced the nitrogen loss rate by 6.70-8.88.The treatment of calcium superphosphate magnesium hydroxide had no nitrogen retention effect in this study.(3)E4/E6、total organic carbon,humic acid,humic acid,fulvic acid,The humification rate HR、humification index HI、humic acid ratio PHA and humus ratio were used to evaluate the quality of compost products.The E4/E6 values of a group decreased by 20.92%,15.77%and 39.55%respectively compared with the initial period.The E4/E6value reduction of CK treatment in b group is close to that in a group,LF treatment increases the stability of organic matter with the increase of ferrous sulfate addition.The reduction of FK treatment E4/E6 in the c group was independent of the addition amount,The whole is between 5.36 and 32.53.The reduction in SP treatment in d group was 6.50%,ST treatment increases with the addition,The stability of compost products becomes worse.Comparison of total organic carbon in four compost groups,It was found that the organic matter loss was lower when ferrous sulfate and potassium persulfate were added,The total organic carbon loss rate of LF treatment was 6.26%lower than that of CK treatment;The loss reduction of LF and FK treatment in b group was positively correlated with the addition amount,between 1.30%-13.41%and 5.90%-11.82%,respectively;Adding calcium superphosphate and magnesium hydroxide in d group can promote the degradation of organic matter.Humic acid,humic acid and fulvic acid are compost humus,Combined with all the processed data,the addition of ferrous sulfate and potassium persulfate is beneficial to the stability of the total amount of humic acid in compost,However,the different treatments of calcium superphosphate and magnesium hydroxide are difficult to unify,No conclusion can be drawn.After composting,The amount of sensitive acid increased,Reduced fulvic acid,The largest increase of humic acid and the most obvious decrease of fulvic acid were LF2 treatment in b group.The results of comprehensive analysis of humification rate HR、humification index HI、humic acid ratio PHA and humus ratio HA/FA,a group had the highest HR,The processing HI、PHA and HA/FA of b group were the highest.The results show that the treatment of ferrous sulfate is beneficial to the formation of humic acid in compost,The degree of aromatization increased with the time of composting.From the results of LF2 processing of infrared spectroscopy,Composting can degrade macromolecular organic matter,The contents of polysaccharides,aliphatic groups and other components were increased,And produce substances with aromatic structure.(4)Through the analysis of nitrogen conservation mechanism,it is found that the LF treatment of a group accords with the principle of reducing the pH value and controlling the volatilization of ammonia gas.By reducing the degradation of organic matter and the loss rate of dry weight,the total amount of nitrogen is fixed,such as all treatments in b and c groups. |
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