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Abstract [Objectives] This study was conducted to provide a theoretical basis for production and application of chicken manure compost.
[Methods] With dry manure as a material， the variations of the major nutrients during simple composting process of dry chicken manure were studied， in order to get the best fermentation method.
[Results] Chicken manure should not be preserved wet， but should be preserved after air-drying and fermented before use. Necessary moisture， simple sealing treatment and a certain amount of N element were conducive to simple fermentation of chicken manure. The treatments in which the chicken manure was wrapped around and compacted， added with an appropriate amount of water （50%-60%） and naturally fermented， or was wrapped around and compacted and added with an appropriate amount of water （50%-60%） and 0.2% of urea， were more appropriate for the production directly.
[Conclusions] This study provides a theoretical basis for the actual production and application of chicken manure compost.
Key words Chicken manure; Simple composting process; Nutrient element; Changing relationship
Received： August 23， 2020 Accepted： October 26， 2020
Supported by Innovation Project of Hebei Academy of Agriculture and Forestry Sciences （2019-3-4-4， 2020-3-4-6）; the Earmarked Fund for China Agriculture Research System （CARS-28-27）.
Jintao XU （1984-）， male， P. R. China， associate professor， devoted to research about fruit tree cultivation and physiological ecology.
*Corresponding author. E-mail： [email protected].
Applying base fertilizer in autumn in orchards is an indispensable technical measure to ensure high and stable yields of perennial fruit trees in the next year， and to improve fruit quality. It is also the most important and rapid way to increase soil organic matter content. The soil thus has high organic matter content， good soil aeration， and large microbial activity， which is conducive to the absorption and utilization of fertilizer by the root system and the improvement of fruit quality， and vice versa.
The orchard grass （including cash crops） covering technology can increase the organic matter content of the orchard soil to a certain extent， but due to the lack of systematic and in-depth research， a complete scientific theoretical system has not yet been formed to guide production practice[1-3]. In addition， fruit farmers are concerned about the increase in production costs and small orchards do not have the technical conditions for grass mulching， so the area for promotion in production is small. There are no large-scale reports on crushing and composting of branches from fruit tree pruning and returning of corresponding compost to the field， and application of bio-organic fertilizers. The most widely used organic manure in production is still farmyard manure. The delayed effectiveness of organic manure nutrients determines the necessity of maturity. Most of the organic fertilizers in production are not decomposed and are directly applied to the orchard， resulting in low fertilizer efficiency， slow results and easy induction of rot diseases， which is not conducive to the next year’s production of fruit trees. However， the conditions for the scientific decomposing of organic fertilizer are relatively strict[4-10]， and it is difficult for fruit farmers to operate by themselves.
In this study， based on production， combining with conventional production and application of fruit farmers， various experimental treatments were designed on dry chicken manure as a test material to simplify composting steps with relaxing composting conditions， so as to investigate the relationship between the variations of the main nutrients in the simple composting process of chicken manure and provide a theoretical basis for production and application.
Materials and Methods
Experiment material
The experiment was carried out in Zhongwu Pear Orchard， Institute of Changli Fruit Tree， Changli County， Hebei Province. The test material was 12 tons of bagged dried chicken manure from the same batch of Zhangzhuang Village， Changli， Hebei. The nutrient contents are shown in Table 1 （C/N=11.1∶1）. The nitrogen fertilizer tested was urea with 46% nitrogen.
Experimental methods
The experiment adopted a simple stack type composting method， with 6 beds with a length of 2.0 m， a width of 1.5 m， and a depth of 0.2 m. The bottom was covered with a plastic sheet to prevent seepage. Six treatments were set， as shown in Table 2. The manure stack was 1.2 m in height and had a small base and a large trapezoid structure. Each fermentation stack was composed of 2 tons of dry chicken manure.
On July 20， August 20， and September 20， samples were taken from the top of each treatment respectively， with sampling depths of 0-20， 20-40， and 40-60 cm， respectively. The samples were brought back to a cool place and air-dried while sheltered from rain.
Item determination
The total N content of samples was determined by the Kjeldahl method[11]. The available N was determined by the reducing alkaline diffusion method[12]. The total P was determined with reference to the national standard GB9837-88. The available P was determined with reference to the agriculture industrial standard NY/T1121.7-2006 of the People’s Republic of China. The total K was determined with reference to the national standard GB9836-88. The rapidly available K was determined with reference to the agriculture industrial standard NY/T889-2004 of the People’s Republic of China. The organic matter was determined with reference to the national standard GB9834-88. Data processing
All treatments were subjected to three balance determinations， and the results were averaged for an arithmetic average. The data was analyzed using Excle2003 software.
Results and Analysis
Effects of different treatments on N content
Effects of different treatments on total N content
It can be seen from Table 3 that different treatment methods had different effects on the total N content. Compared with treatment A0 （control）， the total N content of treatment A1 increased by -29.79%， indicating that chicken manure should not be preserved in a wet state， and fresh chicken manure should be air-dried for storage and then decomposed before application. Compared with the control A0， the total N content of treatment A2 increased by -7.24%， indicating that there was still some N loss in chicken manure during air-dried storage. Compared with the control， the total N content of treatment A4 increased by 26.84%. Except for 0.2% urea mixed in the treatment process， the impurities in the chicken manure might be decomposed into new measurable N elements during the fermentation process. Compared with the control， the total N content of treatment A5 increased by -19.18%， indicating that simple ventilation treatment during the fermentation process would also cause the loss of N.
Effect of different treatments on the content of available N
Different treatment methods had different effects on the content of available N. It can be seen from Table 3 that the contents of available N in treatments A1， A2， and A3 increased by -30.31%， -1.52%， and -3.96%， respectively， compared with the control A0， indicating that treatment A1 was undesirable in production and would significantly lower the available N content. Treatment A2 lost the least amount， further indicating that air-dried preservation of chicken manure was beneficial to reduce the loss of available N. Treatment A3 lost -3.96% of available N， indicating that plastic cloth wrapping and compacting in the fermentation process greatly reduced the loss of available N， and the loss was 26.35% less than that of treatment A1. Compared with the control， the content of available N in treatment A4 increased by 27.67%， mainly because 0.2% urea was added during the fermentation process， or new available N was produced during the fermentation process. The content of available N in treatment A5 increased by -8% compared with the control， indicating that simple ventilation during the fermentation process would cause the loss of available N. It can also be seen from Table 3 that the range of available N/total N for the six treatments was 9.14%-10.49%， with little amplitude of variation， and might be in a dynamic balance. Fewer applications may have a positive effect on guiding production and fertilization， which needs to be further explored.
Effects of different treatments on slow release N content
It can be seen from Table 3 that， with the exception of treatment A4， the slow release N content of each treatment was lower than that of the control A0 to different degrees， indicating that the slow release N was degraded to different degrees during the fermentation process. Among them， the degradation degrees of A1 and A5 were the largest， 29.74% and 20.31%， respectively， but their total N and available N contents did not increase correspondingly， but correspondingly decreased by 29.79% and 19.18%， respectively. The increase of slow release N content and the increase of total N content in each treatment almost showed a 1∶1 positive correlation， indicating that the degradation of slow release N did not increase the total N content， but showed a certain degree of positive correlation with the increase of the available N content， and reduced the loss in available N （treatment A2， A3， A5）. In addition to part of the loss of nitrogen for microbial decomposition to provide energy， the rest might be discharged into the atmosphere. The significant degradation of slow release N in A1 and A5 indicated that ventilation promoted the degradation of slow release N. Compared with the control， the content of slow release N in A4 did not decrease， but increased， indicating that exogenous available nitrogen （urea） had an inhibitory effect on the degradation of slow release N or there might be some slow release N in the chemical fertilizer. Therefore， the content of available N in organic fertilizer should not be too high during the fermentation process.
It can also be seen from Table 3 that the degradation range of slow release N in the simple fermentation process of chicken manure was not too large （7.82%-29.74%）. Therefore， the slow release components of chicken manure cannot be greatly degraded during the simple fermentation process of chicken manure， so how can we preserve the N element in chicken manure may be the focus of simple fermentation[13-15].
Based on the effects of the above different treatments on N content， the A3 and A4 treatments were more suitable for the treatment of the N element in the simple fermentation of chicken manure. Effects of different treatments on P content
Effects of different treatments on total P content
It can be seen from Table 4 that the effects of different treatment methods A0， A1， and A2 on the total P content were similar to the effects on the total N content， further indicating that chicken manure should not be preserved in a wet state， and air-dried storage could greatly reduce losses （18.1%）. Treatments A1， A3， A4， and A5 continued to reduce the loss of total P content， indicating that heat preservation and ventilation treatment of fermented materials were beneficial to the degradation of P-containing substances by microorganisms to increase total P content and offset partial loss.
Effects of different treatments on the content of available P
It can be seen from Table 4 that， except for A1， the content of quick release P all showed different degrees of increase. Among them， the largest increase was in A4 treatment at 40.29%， indicating that the conversion of slow release to quickly available P had a higher efficiency， and moisture and quickly available N （urea） might promote its conversion. Treatment A3 took the second place， and showed a value of 28.35%， which was higher than treatment A5， indicating that although ventilation could improve the degradation efficiency of slow release P to a certain extent， it could also cause partial loss of rapidly available P. The increase of rapidly available P in treatment A1 was a negative value （-1.28%）， while the decrease of its slow release P reached 64.68%， which might be that its conversion rate was not as good as the loss rate， so chicken manure should not be exposed， which further showed that ventilation could cause loss of rapidly available P.
It can be seen from Table 4 that， unlike the effects of different treatments on the N content， the rapidly available P of different treatments accounted for a larger proportion of the total P （58.61%-97.81%）， with large differences， in which the maximum difference was 39.2%. In treatments A3 and A4， the proportions of rapidly available P in total phosphorus were as high as 97.65% and 97.81%， respectively， and the proportions of slow release P were relatively small， suggesting that the decomposition of slow release P was relatively complete.
Effect of different treatments on the content of slow release P
It can be seen from Table 4 that different treatments had a greater effect on the slow release P content. The slow release P contents of treatments A3 and A4 decreased the most， and the slow release P of treatment A2 decreased the least. Water content might be the biggest factor affecting their slow release P contents. The reduction of slow release P in the ventilation treatment A5 was slightly smaller than that in the exposed treatment A1， but the absolute values of total P and rapidly available P were significantly higher than those in A1 treatment. It can also be seen from Table 4 that the absolute value of the increase in the content of rapidly available P was less than the absolute value of the decrease in the content of slow release P， indicating that there was loss in the conversion process. The difference between the two was the largest in the A1 treatment （7 111.11 mg/kg）， and the smallest in the A2 treatment （1 769.95 mg/kg）， and the values of A3， A4， and A5 decreased in turn， and were 5 931.07， 4 115.2， and 2 837.02 mg/kg， respectively. However， the degradation range of slow release P （62.12%） in A5 was smaller than those in A3 （95.62%） and A4 （95.54%）.
Generally， treatments A3 and A4 were more suitable for the treatment of P element in simple fermentation of chicken manure， and treatment A4 was better.
Effects of different treatments on K content
Effects of different treatments on total K content
It can be seen from Table 5 that the total K contents of different treatments decreased to different degrees. The total K content of A1 treatment decreased the most （-19.45%）， and the total K content of A2 treatment decreased the least （-6.35%）， further indicating that chicken manure should be preserved dry， not wet， and fermentation can be carried out before application.
Effect of different treatments on content of rapidly available K
It can be seen from Table 5 that the contents of rapidly available K in treatments A1 to A5 all showed a positive increase （22.04%-129.45%）. Among them， the rapidly available K contents in treatments A2 and A3 increased the most， followed by treatment A4. It showed that no matter which of the above treatment methods， it could promote the increase of the content of rapidly available K. The increase was related to the treatment method. Treatments A2-A4 could better promote the increase of rapidly available K content.
It can also be seen from Table 5 that the rapidly available K/total K in the treatments A2-A4 varied little （57.01%-61.70%）. This phenomenon was similar to the proportion of rapidly available N in total N， which needs further discussion.
Effect of different treatments on slow release K content
It can be seen from Table 5 that the slow release K content in treatments A1-A5 all showed a negative increase （-23.61%--53.77%）， indicating that slow release K degradation occurred in different ranges during the treatment process， and the amplitudes of variation in treatments A1-A4 were relatively concentrated （-49.70%--53.77%）， indicating that the four treatment methods had a little effect on the degradation of slow release K， and moisture was not the root cause of slow release K degradation. The slow release K in treatment A5 had a smaller degradation amplitude， which might be related to ventilation， which was not conducive to heat preservation. In general， it is considered that treatments A2-A4 were more suitable for the K element in simple fermentation of chicken manure， and treatment A2 was the best treatment， followed by A3 taking the second place.
Effects of different treatments on organic matter content
It can be seen from Table 6 that the reduction of organic matter content in treatment A1 was the largest （-12.89%）， which might be related to its bareness， sufficient water supplement， good ventilation， fast diffusion of gas produced during fermentation （carbon dioxide， biogas）， and fast fermentation. The organic matter contents in treatments A2-A5 showed a continuously decreasing law， which might mean that the degradation of organic matter was becoming more and more complete.
Conclusions and Discussion
The results of the study showed that： chicken manure should not be preserved in a wet state， and it should be preserved after air-drying， and then fermented before application. Necessary moisture， simple sealing treatment and a certain amount of N element were conducive to simple fermentation of chicken manure. Treatments A3 and A4 were more suitable for direct production. The monitoring results of treatments A1 to A6 showed that during the simple fermentation of chicken manure， the temperature of 30 cm deep in the fermentation stack was highest at 55 ℃， so treatment 6 was not reported in this study.
Simple fermentation should be carried out in summer when the temperature is higher， so that there is enough fermentation temperature and time. Short fermentation time and insufficient fermentation temperature will affect fertilizer efficiency and even more affect the application of base fertilizer in autumn. However， the price of compost is greatly affected by the season. Generally， the price is more expensive in summer and cheaper in autumn. Therefore， the relationship between the two must be well handled in production.
C/N of farmyard manure such as chicken manure is generally low. Too low C/N will make microorganisms flourish， and even local anaerobic， emitting unpleasant odor. Meanwhile， a large amount of ammonia is released in the form of gas， which reduces fertilizer efficiency. Too high C/N will make microorganisms unable to multiply fast due to lack of nitrogen and slow the progress of composting. Simple fermentation can be added with straw， sawn wood， etc.， to increase C/N.
Farmyard manure inevitably produces a large amount of carbon dioxide and biogas during the fermentation process， resulting in greenhouse effect. The establishment of a dynamic detection system for the content of carbon dioxide and biogas in the orchard is beneficial to control the burning of straw and pruned branches in field on the one hand， and on the other hand， it can monitor whether the orchard is applied with unripe organic fertilizer， so as to achieve the purpose of a green and environmentally friendly orchard.
References
[1] KOU JC， YANG WQ， HAN MY， et al. Research progress on interplanting grass in orchard in China[J]. Pratacultural Science， 2010， 27（7）： 154-159. （in Chinese）
[2] HUI ZM， LI H， LI YL， et al. Research progress of orchard grass on soil properties[J]. Chinese Agricultural Science Bulletin， 2005， 21（5）： 284-287. （in Chinese）
[3] LYU DG， LI FD， QIN SJ， et al. Effect of mowing on ecological factors of near-surface grassfield in grass covered orchard[J]. Northern Horticulture， 2007（11）： 37-39. （in Chinese）
[4] WEI YS， WANG MJ， WANG JS. Composting technology and progress[J]. Development of Environmental Science， 1999（3）： 11-23. （in Chinese）
[5] YU Q， DONG HM， ZHANG ZK， et al. Research progress on compost technic[J]. Journal of Anhui Agricultural University， 2003， 30（1）： 109-112. （in Chinese）
[6] MA HL， XU XH. The technologies of aerobic compost of animal dung[J]. Journal of Northeast Agricultural University， 2005， 36（4）： 536-540. （in Chinese）
[7] CAO Y’E， YONG HY， ZHANG ZX. Study on fermentation effect of different microbial fermentation inoculants on agricultural organic fertilizer[J]. Northern Horticulture， 2012（1）： 144-147. （in Chinese）
[8] YANG X， LIAN B， ZHU XL， et al. Effects of adding potassium-bearing mineral powder on nitrogen， potassium and potassium contents of chicken manure compost[J]. Earth and Environment， 2012， 40（2）： 286-292. （in Chinese）
[9] YANG Y. Study on the dynamic changes of the material composition of manure decomposing under the action of starter[D]. Xi’an： Northwest Agriculture and Forestry University， 2007：1-12. （in Chinese）
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Editor： Yingzhi GUANG Proofreader： Xinxiu ZHU
[Methods] With dry manure as a material， the variations of the major nutrients during simple composting process of dry chicken manure were studied， in order to get the best fermentation method.
[Results] Chicken manure should not be preserved wet， but should be preserved after air-drying and fermented before use. Necessary moisture， simple sealing treatment and a certain amount of N element were conducive to simple fermentation of chicken manure. The treatments in which the chicken manure was wrapped around and compacted， added with an appropriate amount of water （50%-60%） and naturally fermented， or was wrapped around and compacted and added with an appropriate amount of water （50%-60%） and 0.2% of urea， were more appropriate for the production directly.
[Conclusions] This study provides a theoretical basis for the actual production and application of chicken manure compost.
Key words Chicken manure; Simple composting process; Nutrient element; Changing relationship
Received： August 23， 2020 Accepted： October 26， 2020
Supported by Innovation Project of Hebei Academy of Agriculture and Forestry Sciences （2019-3-4-4， 2020-3-4-6）; the Earmarked Fund for China Agriculture Research System （CARS-28-27）.
Jintao XU （1984-）， male， P. R. China， associate professor， devoted to research about fruit tree cultivation and physiological ecology.
*Corresponding author. E-mail： [email protected].
Applying base fertilizer in autumn in orchards is an indispensable technical measure to ensure high and stable yields of perennial fruit trees in the next year， and to improve fruit quality. It is also the most important and rapid way to increase soil organic matter content. The soil thus has high organic matter content， good soil aeration， and large microbial activity， which is conducive to the absorption and utilization of fertilizer by the root system and the improvement of fruit quality， and vice versa.
The orchard grass （including cash crops） covering technology can increase the organic matter content of the orchard soil to a certain extent， but due to the lack of systematic and in-depth research， a complete scientific theoretical system has not yet been formed to guide production practice[1-3]. In addition， fruit farmers are concerned about the increase in production costs and small orchards do not have the technical conditions for grass mulching， so the area for promotion in production is small. There are no large-scale reports on crushing and composting of branches from fruit tree pruning and returning of corresponding compost to the field， and application of bio-organic fertilizers. The most widely used organic manure in production is still farmyard manure. The delayed effectiveness of organic manure nutrients determines the necessity of maturity. Most of the organic fertilizers in production are not decomposed and are directly applied to the orchard， resulting in low fertilizer efficiency， slow results and easy induction of rot diseases， which is not conducive to the next year’s production of fruit trees. However， the conditions for the scientific decomposing of organic fertilizer are relatively strict[4-10]， and it is difficult for fruit farmers to operate by themselves.
In this study， based on production， combining with conventional production and application of fruit farmers， various experimental treatments were designed on dry chicken manure as a test material to simplify composting steps with relaxing composting conditions， so as to investigate the relationship between the variations of the main nutrients in the simple composting process of chicken manure and provide a theoretical basis for production and application.
Materials and Methods
Experiment material
The experiment was carried out in Zhongwu Pear Orchard， Institute of Changli Fruit Tree， Changli County， Hebei Province. The test material was 12 tons of bagged dried chicken manure from the same batch of Zhangzhuang Village， Changli， Hebei. The nutrient contents are shown in Table 1 （C/N=11.1∶1）. The nitrogen fertilizer tested was urea with 46% nitrogen.
Experimental methods
The experiment adopted a simple stack type composting method， with 6 beds with a length of 2.0 m， a width of 1.5 m， and a depth of 0.2 m. The bottom was covered with a plastic sheet to prevent seepage. Six treatments were set， as shown in Table 2. The manure stack was 1.2 m in height and had a small base and a large trapezoid structure. Each fermentation stack was composed of 2 tons of dry chicken manure.
On July 20， August 20， and September 20， samples were taken from the top of each treatment respectively， with sampling depths of 0-20， 20-40， and 40-60 cm， respectively. The samples were brought back to a cool place and air-dried while sheltered from rain.
Item determination
The total N content of samples was determined by the Kjeldahl method[11]. The available N was determined by the reducing alkaline diffusion method[12]. The total P was determined with reference to the national standard GB9837-88. The available P was determined with reference to the agriculture industrial standard NY/T1121.7-2006 of the People’s Republic of China. The total K was determined with reference to the national standard GB9836-88. The rapidly available K was determined with reference to the agriculture industrial standard NY/T889-2004 of the People’s Republic of China. The organic matter was determined with reference to the national standard GB9834-88. Data processing
All treatments were subjected to three balance determinations， and the results were averaged for an arithmetic average. The data was analyzed using Excle2003 software.
Results and Analysis
Effects of different treatments on N content
Effects of different treatments on total N content
It can be seen from Table 3 that different treatment methods had different effects on the total N content. Compared with treatment A0 （control）， the total N content of treatment A1 increased by -29.79%， indicating that chicken manure should not be preserved in a wet state， and fresh chicken manure should be air-dried for storage and then decomposed before application. Compared with the control A0， the total N content of treatment A2 increased by -7.24%， indicating that there was still some N loss in chicken manure during air-dried storage. Compared with the control， the total N content of treatment A4 increased by 26.84%. Except for 0.2% urea mixed in the treatment process， the impurities in the chicken manure might be decomposed into new measurable N elements during the fermentation process. Compared with the control， the total N content of treatment A5 increased by -19.18%， indicating that simple ventilation treatment during the fermentation process would also cause the loss of N.
Effect of different treatments on the content of available N
Different treatment methods had different effects on the content of available N. It can be seen from Table 3 that the contents of available N in treatments A1， A2， and A3 increased by -30.31%， -1.52%， and -3.96%， respectively， compared with the control A0， indicating that treatment A1 was undesirable in production and would significantly lower the available N content. Treatment A2 lost the least amount， further indicating that air-dried preservation of chicken manure was beneficial to reduce the loss of available N. Treatment A3 lost -3.96% of available N， indicating that plastic cloth wrapping and compacting in the fermentation process greatly reduced the loss of available N， and the loss was 26.35% less than that of treatment A1. Compared with the control， the content of available N in treatment A4 increased by 27.67%， mainly because 0.2% urea was added during the fermentation process， or new available N was produced during the fermentation process. The content of available N in treatment A5 increased by -8% compared with the control， indicating that simple ventilation during the fermentation process would cause the loss of available N. It can also be seen from Table 3 that the range of available N/total N for the six treatments was 9.14%-10.49%， with little amplitude of variation， and might be in a dynamic balance. Fewer applications may have a positive effect on guiding production and fertilization， which needs to be further explored.
Effects of different treatments on slow release N content
It can be seen from Table 3 that， with the exception of treatment A4， the slow release N content of each treatment was lower than that of the control A0 to different degrees， indicating that the slow release N was degraded to different degrees during the fermentation process. Among them， the degradation degrees of A1 and A5 were the largest， 29.74% and 20.31%， respectively， but their total N and available N contents did not increase correspondingly， but correspondingly decreased by 29.79% and 19.18%， respectively. The increase of slow release N content and the increase of total N content in each treatment almost showed a 1∶1 positive correlation， indicating that the degradation of slow release N did not increase the total N content， but showed a certain degree of positive correlation with the increase of the available N content， and reduced the loss in available N （treatment A2， A3， A5）. In addition to part of the loss of nitrogen for microbial decomposition to provide energy， the rest might be discharged into the atmosphere. The significant degradation of slow release N in A1 and A5 indicated that ventilation promoted the degradation of slow release N. Compared with the control， the content of slow release N in A4 did not decrease， but increased， indicating that exogenous available nitrogen （urea） had an inhibitory effect on the degradation of slow release N or there might be some slow release N in the chemical fertilizer. Therefore， the content of available N in organic fertilizer should not be too high during the fermentation process.
It can also be seen from Table 3 that the degradation range of slow release N in the simple fermentation process of chicken manure was not too large （7.82%-29.74%）. Therefore， the slow release components of chicken manure cannot be greatly degraded during the simple fermentation process of chicken manure， so how can we preserve the N element in chicken manure may be the focus of simple fermentation[13-15].
Based on the effects of the above different treatments on N content， the A3 and A4 treatments were more suitable for the treatment of the N element in the simple fermentation of chicken manure. Effects of different treatments on P content
Effects of different treatments on total P content
It can be seen from Table 4 that the effects of different treatment methods A0， A1， and A2 on the total P content were similar to the effects on the total N content， further indicating that chicken manure should not be preserved in a wet state， and air-dried storage could greatly reduce losses （18.1%）. Treatments A1， A3， A4， and A5 continued to reduce the loss of total P content， indicating that heat preservation and ventilation treatment of fermented materials were beneficial to the degradation of P-containing substances by microorganisms to increase total P content and offset partial loss.
Effects of different treatments on the content of available P
It can be seen from Table 4 that， except for A1， the content of quick release P all showed different degrees of increase. Among them， the largest increase was in A4 treatment at 40.29%， indicating that the conversion of slow release to quickly available P had a higher efficiency， and moisture and quickly available N （urea） might promote its conversion. Treatment A3 took the second place， and showed a value of 28.35%， which was higher than treatment A5， indicating that although ventilation could improve the degradation efficiency of slow release P to a certain extent， it could also cause partial loss of rapidly available P. The increase of rapidly available P in treatment A1 was a negative value （-1.28%）， while the decrease of its slow release P reached 64.68%， which might be that its conversion rate was not as good as the loss rate， so chicken manure should not be exposed， which further showed that ventilation could cause loss of rapidly available P.
It can be seen from Table 4 that， unlike the effects of different treatments on the N content， the rapidly available P of different treatments accounted for a larger proportion of the total P （58.61%-97.81%）， with large differences， in which the maximum difference was 39.2%. In treatments A3 and A4， the proportions of rapidly available P in total phosphorus were as high as 97.65% and 97.81%， respectively， and the proportions of slow release P were relatively small， suggesting that the decomposition of slow release P was relatively complete.
Effect of different treatments on the content of slow release P
It can be seen from Table 4 that different treatments had a greater effect on the slow release P content. The slow release P contents of treatments A3 and A4 decreased the most， and the slow release P of treatment A2 decreased the least. Water content might be the biggest factor affecting their slow release P contents. The reduction of slow release P in the ventilation treatment A5 was slightly smaller than that in the exposed treatment A1， but the absolute values of total P and rapidly available P were significantly higher than those in A1 treatment. It can also be seen from Table 4 that the absolute value of the increase in the content of rapidly available P was less than the absolute value of the decrease in the content of slow release P， indicating that there was loss in the conversion process. The difference between the two was the largest in the A1 treatment （7 111.11 mg/kg）， and the smallest in the A2 treatment （1 769.95 mg/kg）， and the values of A3， A4， and A5 decreased in turn， and were 5 931.07， 4 115.2， and 2 837.02 mg/kg， respectively. However， the degradation range of slow release P （62.12%） in A5 was smaller than those in A3 （95.62%） and A4 （95.54%）.
Generally， treatments A3 and A4 were more suitable for the treatment of P element in simple fermentation of chicken manure， and treatment A4 was better.
Effects of different treatments on K content
Effects of different treatments on total K content
It can be seen from Table 5 that the total K contents of different treatments decreased to different degrees. The total K content of A1 treatment decreased the most （-19.45%）， and the total K content of A2 treatment decreased the least （-6.35%）， further indicating that chicken manure should be preserved dry， not wet， and fermentation can be carried out before application.
Effect of different treatments on content of rapidly available K
It can be seen from Table 5 that the contents of rapidly available K in treatments A1 to A5 all showed a positive increase （22.04%-129.45%）. Among them， the rapidly available K contents in treatments A2 and A3 increased the most， followed by treatment A4. It showed that no matter which of the above treatment methods， it could promote the increase of the content of rapidly available K. The increase was related to the treatment method. Treatments A2-A4 could better promote the increase of rapidly available K content.
It can also be seen from Table 5 that the rapidly available K/total K in the treatments A2-A4 varied little （57.01%-61.70%）. This phenomenon was similar to the proportion of rapidly available N in total N， which needs further discussion.
Effect of different treatments on slow release K content
It can be seen from Table 5 that the slow release K content in treatments A1-A5 all showed a negative increase （-23.61%--53.77%）， indicating that slow release K degradation occurred in different ranges during the treatment process， and the amplitudes of variation in treatments A1-A4 were relatively concentrated （-49.70%--53.77%）， indicating that the four treatment methods had a little effect on the degradation of slow release K， and moisture was not the root cause of slow release K degradation. The slow release K in treatment A5 had a smaller degradation amplitude， which might be related to ventilation， which was not conducive to heat preservation. In general， it is considered that treatments A2-A4 were more suitable for the K element in simple fermentation of chicken manure， and treatment A2 was the best treatment， followed by A3 taking the second place.
Effects of different treatments on organic matter content
It can be seen from Table 6 that the reduction of organic matter content in treatment A1 was the largest （-12.89%）， which might be related to its bareness， sufficient water supplement， good ventilation， fast diffusion of gas produced during fermentation （carbon dioxide， biogas）， and fast fermentation. The organic matter contents in treatments A2-A5 showed a continuously decreasing law， which might mean that the degradation of organic matter was becoming more and more complete.
Conclusions and Discussion
The results of the study showed that： chicken manure should not be preserved in a wet state， and it should be preserved after air-drying， and then fermented before application. Necessary moisture， simple sealing treatment and a certain amount of N element were conducive to simple fermentation of chicken manure. Treatments A3 and A4 were more suitable for direct production. The monitoring results of treatments A1 to A6 showed that during the simple fermentation of chicken manure， the temperature of 30 cm deep in the fermentation stack was highest at 55 ℃， so treatment 6 was not reported in this study.
Simple fermentation should be carried out in summer when the temperature is higher， so that there is enough fermentation temperature and time. Short fermentation time and insufficient fermentation temperature will affect fertilizer efficiency and even more affect the application of base fertilizer in autumn. However， the price of compost is greatly affected by the season. Generally， the price is more expensive in summer and cheaper in autumn. Therefore， the relationship between the two must be well handled in production.
C/N of farmyard manure such as chicken manure is generally low. Too low C/N will make microorganisms flourish， and even local anaerobic， emitting unpleasant odor. Meanwhile， a large amount of ammonia is released in the form of gas， which reduces fertilizer efficiency. Too high C/N will make microorganisms unable to multiply fast due to lack of nitrogen and slow the progress of composting. Simple fermentation can be added with straw， sawn wood， etc.， to increase C/N.
Farmyard manure inevitably produces a large amount of carbon dioxide and biogas during the fermentation process， resulting in greenhouse effect. The establishment of a dynamic detection system for the content of carbon dioxide and biogas in the orchard is beneficial to control the burning of straw and pruned branches in field on the one hand， and on the other hand， it can monitor whether the orchard is applied with unripe organic fertilizer， so as to achieve the purpose of a green and environmentally friendly orchard.
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Editor： Yingzhi GUANG Proofreader： Xinxiu ZHU