[Objectives]To explore the effects of single application of chemical fertilizers on soil carbon fixation capacity and soil fertility under plastic film mulching conditions in eastern Qinghai,and to provide a theoretic...[Objectives]To explore the effects of single application of chemical fertilizers on soil carbon fixation capacity and soil fertility under plastic film mulching conditions in eastern Qinghai,and to provide a theoretical basis for realizing the sustainable development of film mulching planting method in this area.[Methods]The effects of single application of chemical fertilizer cultivation mode under film mulching conditions on the soil organic carbon(SOC),labile organic carbon(LOC),carbon management index(CMI),extractable humus carbon(CHE),humic acid carbon(CHA),and fulvic acid carbon(CFA)in the cultivated layer(0-20 cm)were studied through three consecutive years of field experiments on dryland maize farmland in the eastern Qinghai.[Results]Under the film mulching condition,the SOC,LOC and CMI of the single application of chemical fertilizer cultivation mode were lower than that of the open field control.CHE,CHA and CFA increased with the increase of planting years,but the degree of increase was generally less than that of the open field control.With the increase of planting years,by 2020,the soil LOC/SOC value of film mulching decreased by 4.97%compared with before the start of the experiment,while the open field control increased by 1.11%;the organic carbon oxidation stability coefficient(KOS)of the film mulching was higher than that of the open field control;the soil CHA/CFA value and PQ value were higher than that of the open field control.[Conclusions]Under the condition of single application of chemical fertilizers,the continuous film mulching cultivation mode reduces the soil carbon fixation capacity,and soil organic carbon tends to be stable,which is not conducive to biological utilization and could reduce the soil fertility and degrade the soil quality,causing adverse effects on the stability of crop yield and sustainable production in the long run.展开更多
Elite maize hybrid Guidan0810 was selected as material, and the effects of fertilizing level and planting densities on yield and nitrogen utilization were dis- cussed in the study. In field experiments as per double-c...Elite maize hybrid Guidan0810 was selected as material, and the effects of fertilizing level and planting densities on yield and nitrogen utilization were dis- cussed in the study. In field experiments as per double-cropping system, 4 main plots （fertilization levels） and 6 subplots （planting densities） were set in a split plot design. The results suggested that yield had close relationship with fertilization levels and planting densities. Different fertilization levels and planting densities significantly affected yield. With the increase of nitrogen fertilization, nitrogen use efficiency, nitrogen agronomic efficiency and nitrogen physiological efficiency declined. Under the same fertilization level, nitrogen use efficiency, nitrogen agronomic efficiency and nitrogen physiological efficiency grew a little with the increase of planting density, so nitrogen efficiency could be improved by regulating planting density. The results also showed that A2 （including N 225.0 kg/hm2, P205 75.0 kg/hm^2, K20 187.5 kg/hm^2） matching to B3 （52 500 plants/hm^2） or B4（60 000 plants/hm^2） was a better design, which could obtain a higher yield in the range of 7 913.2-8 207.8 kg/hm2, respectively.展开更多
[Objective] The reason of the high level of agricultural fertilization was studied from economics angle.[Method] Farmers fertilization input model was developed.The time series data from 1990 to 2004 in Jiangsu Provin...[Objective] The reason of the high level of agricultural fertilization was studied from economics angle.[Method] Farmers fertilization input model was developed.The time series data from 1990 to 2004 in Jiangsu Province was applied for analysis.[Result] The fertilizer price,labor price and agricultural products price can explain 93% of the changes of farmers＇ fertilization level.The influence of farmers＇ education level was insignificant.The dysfunction of the agricultural technology promotion system had certain influence on farmers＇ fertilizing behavior.[Conclusion] The high level of fertilization was partially because of shortage of scientific fertilizing technology and more importantly was the substitution effect caused by the rising in wages of labor in relative to price of chemical fertilizations and the derivation effect caused by the increase in the prices of agricultural products.展开更多
We aimed to investigate the effects of phosphate treatment on growth dynamics of wheat in wheat/corn intercropping system in southwest hil y area. [Method] Five phosphate fertilization levels were designed for wheat a...We aimed to investigate the effects of phosphate treatment on growth dynamics of wheat in wheat/corn intercropping system in southwest hil y area. [Method] Five phosphate fertilization levels were designed for wheat and corn respectively to investigate the effects of phosphate fertilization level on wheat/corn intercropping system by field block experiment. [Result] The number of til ers, plant height and yield component of wheat trended to increase with the increase of phos-phate fertilization amount and al reached the peak for phosphate fertilization amount of 135 kg/hm2. However, the number of til ers, plant height and yield component of wheat al decreased significantly with the further increase of phosphate fertilization amount. [Conclusion] Phosphate fertilization contributed to the wheat growth in a certain degree. However, excessive phosphate fertilization would affect final yield.展开更多
Using fertility data from national surveys and population censuses for China,Japan and South Korea,this study analyzes the levels and trends of mean age at childbearing(MAC)in the three countries from 1990 to 2015.Aft...Using fertility data from national surveys and population censuses for China,Japan and South Korea,this study analyzes the levels and trends of mean age at childbearing(MAC)in the three countries from 1990 to 2015.After using the decomposition technique to isolate the effects of parity composition and childbearing schedule in each of the three countries,the article presents a quantitative examination of the factors that underlie dynamic changes and cross-national differences of MACs.Results indicate that the MAC of China experienced a decrease between 1990 and 1995,followed by sustained growth afterwards.The increase of MAC in China has been driven by the postponement of childbearing and changes in parity composition,with the former playing a larger role.The mechanisms underlying the patterns since 2010 deserve special attention.Compared with Japan and South Korea,China has had relatively lower MAC during the last 25 years;the three countries demonstrate different patterns in terms of the roles of parity composition and birth timing.The accuracy of MAC in identifying the timing of period fertility and the policy implications of timing on upturning fertility level are discussed.展开更多
The objectives of this study were to apply statistical techniques to discriminate fertilization treatments of Eremanthus erythropappus（DC.） Mac Leish.through autoregressive modeling, and to develop individual tree m...The objectives of this study were to apply statistical techniques to discriminate fertilization treatments of Eremanthus erythropappus（DC.） Mac Leish.through autoregressive modeling, and to develop individual tree models for diameter and crown area（CA） projection to define management strategies for candeia plantations subjected to different fertilization treatments. This is an important tree species originating from the Brazilian Atlantic Rain forest and Savannah biomes, intensively used in the cosmetic industry. Nonetheless, to date, research has not addressed the management of natural stands or plantations of the species. Our experiment was located in Baependi, Minas Gerais, Brazil, and comprised of four randomized blocks and 13 treatments. The treatments consisted of 12 different regimes of fertilization plus a control. Each sample plot was composed of 50 plants plus two border plants in a planting spacing of 2.5 9 2.0 m and undergoing pruning at 5 and 6 years of age. Starting in the second year, total tree height（H） and circumference（at 1.30 m from the ground or breast height, CBH） were measured every 6 months. Starting in the fifth year CA was measured. Tree growth varied by fertilization strategy.Differences were detected by using an autoregressive approach, considering that standard statistical methods were not powerful enough to detect significant differences.Three growth groups were formed, and maximum growth was obtained for treatment 10（NPK, 8-28-16）. Management guidelines are provided based on individual tree models for different fertilization levels.展开更多
Field experiments were carried out in split plot design during the dry and wet seasons for two years(two seasons each in 2016–2017 and 2017–2018) with two genotypes(SH4 and SUIN053), two plant geometry(30×15 cm...Field experiments were carried out in split plot design during the dry and wet seasons for two years(two seasons each in 2016–2017 and 2017–2018) with two genotypes(SH4 and SUIN053), two plant geometry(30×15 cm and 45×15 cm main plots) and three levels of NPK(20 kg N ha^(–1), 40 kg P ha^(–1) and 40 kg K ha^(–1);20 kg N ha^(–1), 60 kg P ha^(–1) and 60 kg K ha^(–1);20 kg N ha^(–1), 80 kg P ha^(–1) and 80 kg K ha^(–1)) with an objective to study the relationship between fibre yield of sunhmep and thermal indices. The results indicated that the thermal units such as cumulative heat unit(CHU), photo thermal unit(PTU) and helio thermal unit(HTU) were the highest during dry seasons, while relative temperature disparity(RTD) was the highest during wet seasons irrespective of the genotypes, plant geometry and fertilizer levels. The combined analysis of variance showed that the suitability of sunnhemp genotypes for obtaining fibre and seed yields varied with season. The results further indicated that sunnhemp grew during dry seasons with longer photoperiod and higher values of growing degree days(GDD), HTU and PTU resulted in a higher fibre yield, while a higher seed yield and relatively longer, finer and stronger fibres were obtained during wet seasons with higher RTD values. Regression analysis indicated that CHU was positively related to fibre yield, while RTD was positively related to seed yield. CHU beyond 2 000 °C d reduced seed yield and favoured fibre production. In contrary to CHU, RTD values were positively related to seed yield and negatively related to fibre yield. Similarly, HTU had an inverse relationship with fibre yield while PTU had a positive relationship with fibre yield. The genotype SH4 produced a seed yield of 1 361 kg ha^(–1) during wet seasons, which was significantly higher than SUIN053, while a fibre yield of 990 kg ha^(–1)(significantly higher than that of SH4) was obtained for SUIN053 that required less CHU to attain the phenological events during dry seasons. The per unit area yields of seed and fibre with the closer spacing(30 cm×15 cm) by virtue of higher plant density were 17.0 and 14.9% higher than those with the spacing of 45 cm×15 cm, respectively. Higher doses of P and K resulted in higher seed and fibre yields.展开更多
The size distribution of water-stable aggregates and the variability of organic C,N and P contents over aggregate size fractions were studied for orchard,upland,paddy,and grassland soils with high,medium,and low ferti...The size distribution of water-stable aggregates and the variability of organic C,N and P contents over aggregate size fractions were studied for orchard,upland,paddy,and grassland soils with high,medium,and low fertility levels.The results showed that > 5 mm aggregates in the cultivated upland and paddy soils were 44.0% and 32.0%,respectively,less than those in the un-tilled orchard soil.Organic C and soil N in different size aggregate fractions in orchard soil with high fertility were significantly higher than those of other land uses.However,the contents of soil P in different size aggregates were significantly greater in the paddy soil as compared to the other land uses.Soil organic C,N and P contents were higher in larger aggregates than those in smaller ones.The amount of water-stable aggregates was positively correlated to their contribution to soil organic C,N and P.For orchard and grassland soils,the > 5 mm aggregates made the greatest contribution to soil nutrients,while for upland soil,the 0.25-0.053 mm aggregates contributed the most to soil nutrients.Therefore,the land use with minimum disturbance was beneficial for the formation of a better soil structure.The dominant soil aggregates in different land use types determined the distribution of soil nutrients.Utilization efficiency of soil P could be improved by converting other land uses to the paddy soil.展开更多
On the basis of the findings of 227 surveys of Chinese fertility intentions over the years 1980-2011, this paper investigates the longitudinal changes in fertility intentions through cross-temporal meta-analysis. It i...On the basis of the findings of 227 surveys of Chinese fertility intentions over the years 1980-2011, this paper investigates the longitudinal changes in fertility intentions through cross-temporal meta-analysis. It is found that the ideal number of children for the Chinese trended downwards from 1980, but since 2000 the average number has remained basically stable at 1.6 to 1.8. In the 1980s, people＇s fertility levels were higher than their fertility intentions. With economic and educational progress in China, both fertility levels and fertility intentions showed a downward trend, with the former declining faster than the latter. Since 1990, people＇s fertility levels have been lower than their fertility intentions; that is, their actual number of children has been less than their ideal number. This provides an empirical basis for examining the changes in China＇s fertility intentions and fertility levels.展开更多
The anaerobic ammonium oxidizing(anammox) process has been found to play an important role in terrestrial ecosystems in recent years. However,the diversity and abundance of anammox bacteria in nitrogen(N)-rich agricul...The anaerobic ammonium oxidizing(anammox) process has been found to play an important role in terrestrial ecosystems in recent years. However,the diversity and abundance of anammox bacteria in nitrogen(N)-rich agricultural soils under high fertilizer greenhouse conditions are still unclear. Two greenhouse fields with different N fertilizer input levels were chosen, and their soil profiles were studied with molecular technologies, including quantitative polymerase chain reaction assay, a clone library, and phylogenetic analysis based on hzsB(encoding anammox hydrazine synthase β-subunit) gene. Molecular analyses suggested that anammox bacteria were at their highest density at 10–20 cm soil depth, and that the anammox bacterial abundance was significantly lower at high N than at low N. Candidatus Brocadia was the sole anammox bacterial genus throughout the soil depth profiles. The highest diversity of anammox bacteria was found at 30–40 cm soil depth, and different phylotypic clusters of Candidatus Brocadia were associated with specific soil environmental factors, such as nitrates, soil depth, and total N. Correlation analyses and redundancy analyses confirmed that high nitrate content associated with high N fertilizer input had a significant negative influence on the abundance and biodiversity of anammox bacteria. These results imply that excessive use of N fertilizer would affect arid land soil N loss to the atmosphere by the anammox pathway.展开更多
基金Project of Natural Science Foundation of Qinghai Province(2018-ZJ-724)Major Science and Technology Program of Qinghai Province(2019-NK-A11).
文摘[Objectives]To explore the effects of single application of chemical fertilizers on soil carbon fixation capacity and soil fertility under plastic film mulching conditions in eastern Qinghai,and to provide a theoretical basis for realizing the sustainable development of film mulching planting method in this area.[Methods]The effects of single application of chemical fertilizer cultivation mode under film mulching conditions on the soil organic carbon(SOC),labile organic carbon(LOC),carbon management index(CMI),extractable humus carbon(CHE),humic acid carbon(CHA),and fulvic acid carbon(CFA)in the cultivated layer(0-20 cm)were studied through three consecutive years of field experiments on dryland maize farmland in the eastern Qinghai.[Results]Under the film mulching condition,the SOC,LOC and CMI of the single application of chemical fertilizer cultivation mode were lower than that of the open field control.CHE,CHA and CFA increased with the increase of planting years,but the degree of increase was generally less than that of the open field control.With the increase of planting years,by 2020,the soil LOC/SOC value of film mulching decreased by 4.97%compared with before the start of the experiment,while the open field control increased by 1.11%;the organic carbon oxidation stability coefficient(KOS)of the film mulching was higher than that of the open field control;the soil CHA/CFA value and PQ value were higher than that of the open field control.[Conclusions]Under the condition of single application of chemical fertilizers,the continuous film mulching cultivation mode reduces the soil carbon fixation capacity,and soil organic carbon tends to be stable,which is not conducive to biological utilization and could reduce the soil fertility and degrade the soil quality,causing adverse effects on the stability of crop yield and sustainable production in the long run.
文摘Elite maize hybrid Guidan0810 was selected as material, and the effects of fertilizing level and planting densities on yield and nitrogen utilization were dis- cussed in the study. In field experiments as per double-cropping system, 4 main plots （fertilization levels） and 6 subplots （planting densities） were set in a split plot design. The results suggested that yield had close relationship with fertilization levels and planting densities. Different fertilization levels and planting densities significantly affected yield. With the increase of nitrogen fertilization, nitrogen use efficiency, nitrogen agronomic efficiency and nitrogen physiological efficiency declined. Under the same fertilization level, nitrogen use efficiency, nitrogen agronomic efficiency and nitrogen physiological efficiency grew a little with the increase of planting density, so nitrogen efficiency could be improved by regulating planting density. The results also showed that A2 （including N 225.0 kg/hm2, P205 75.0 kg/hm^2, K20 187.5 kg/hm^2） matching to B3 （52 500 plants/hm^2） or B4（60 000 plants/hm^2） was a better design, which could obtain a higher yield in the range of 7 913.2-8 207.8 kg/hm2, respectively.
文摘[Objective] The reason of the high level of agricultural fertilization was studied from economics angle.[Method] Farmers fertilization input model was developed.The time series data from 1990 to 2004 in Jiangsu Province was applied for analysis.[Result] The fertilizer price,labor price and agricultural products price can explain 93% of the changes of farmers＇ fertilization level.The influence of farmers＇ education level was insignificant.The dysfunction of the agricultural technology promotion system had certain influence on farmers＇ fertilizing behavior.[Conclusion] The high level of fertilization was partially because of shortage of scientific fertilizing technology and more importantly was the substitution effect caused by the rising in wages of labor in relative to price of chemical fertilizations and the derivation effect caused by the increase in the prices of agricultural products.
文摘We aimed to investigate the effects of phosphate treatment on growth dynamics of wheat in wheat/corn intercropping system in southwest hil y area. [Method] Five phosphate fertilization levels were designed for wheat and corn respectively to investigate the effects of phosphate fertilization level on wheat/corn intercropping system by field block experiment. [Result] The number of til ers, plant height and yield component of wheat trended to increase with the increase of phos-phate fertilization amount and al reached the peak for phosphate fertilization amount of 135 kg/hm2. However, the number of til ers, plant height and yield component of wheat al decreased significantly with the further increase of phosphate fertilization amount. [Conclusion] Phosphate fertilization contributed to the wheat growth in a certain degree. However, excessive phosphate fertilization would affect final yield.
基金supported by the Project Study on Family Transition in China(16JJD840013)of the Key Research Centers of Minister of Education.
文摘Using fertility data from national surveys and population censuses for China,Japan and South Korea,this study analyzes the levels and trends of mean age at childbearing(MAC)in the three countries from 1990 to 2015.After using the decomposition technique to isolate the effects of parity composition and childbearing schedule in each of the three countries,the article presents a quantitative examination of the factors that underlie dynamic changes and cross-national differences of MACs.Results indicate that the MAC of China experienced a decrease between 1990 and 1995,followed by sustained growth afterwards.The increase of MAC in China has been driven by the postponement of childbearing and changes in parity composition,with the former playing a larger role.The mechanisms underlying the patterns since 2010 deserve special attention.Compared with Japan and South Korea,China has had relatively lower MAC during the last 25 years;the three countries demonstrate different patterns in terms of the roles of parity composition and birth timing.The accuracy of MAC in identifying the timing of period fertility and the policy implications of timing on upturning fertility level are discussed.
基金supported by the Coordenao de Aperfeioamento de Pessoal de Nível Superior(CAPES)the Conselho Nacional de Desenvolvimento Científico e Tecnológico(CNPq)+3 种基金the Fundao de Amparo á Pesquisa do Estado de Minas Gerais(FAPEMIG)the Instituto Estadual de Florestas(IEF)the Instituto Brasileiro do Meio Ambiente e dos Recursos Naturais Renovveis(IBAMA)Ministrio do Meio Ambiente(MMA)and Citróleo
文摘The objectives of this study were to apply statistical techniques to discriminate fertilization treatments of Eremanthus erythropappus（DC.） Mac Leish.through autoregressive modeling, and to develop individual tree models for diameter and crown area（CA） projection to define management strategies for candeia plantations subjected to different fertilization treatments. This is an important tree species originating from the Brazilian Atlantic Rain forest and Savannah biomes, intensively used in the cosmetic industry. Nonetheless, to date, research has not addressed the management of natural stands or plantations of the species. Our experiment was located in Baependi, Minas Gerais, Brazil, and comprised of four randomized blocks and 13 treatments. The treatments consisted of 12 different regimes of fertilization plus a control. Each sample plot was composed of 50 plants plus two border plants in a planting spacing of 2.5 9 2.0 m and undergoing pruning at 5 and 6 years of age. Starting in the second year, total tree height（H） and circumference（at 1.30 m from the ground or breast height, CBH） were measured every 6 months. Starting in the fifth year CA was measured. Tree growth varied by fertilization strategy.Differences were detected by using an autoregressive approach, considering that standard statistical methods were not powerful enough to detect significant differences.Three growth groups were formed, and maximum growth was obtained for treatment 10（NPK, 8-28-16）. Management guidelines are provided based on individual tree models for different fertilization levels.
文摘Field experiments were carried out in split plot design during the dry and wet seasons for two years(two seasons each in 2016–2017 and 2017–2018) with two genotypes(SH4 and SUIN053), two plant geometry(30×15 cm and 45×15 cm main plots) and three levels of NPK(20 kg N ha^(–1), 40 kg P ha^(–1) and 40 kg K ha^(–1);20 kg N ha^(–1), 60 kg P ha^(–1) and 60 kg K ha^(–1);20 kg N ha^(–1), 80 kg P ha^(–1) and 80 kg K ha^(–1)) with an objective to study the relationship between fibre yield of sunhmep and thermal indices. The results indicated that the thermal units such as cumulative heat unit(CHU), photo thermal unit(PTU) and helio thermal unit(HTU) were the highest during dry seasons, while relative temperature disparity(RTD) was the highest during wet seasons irrespective of the genotypes, plant geometry and fertilizer levels. The combined analysis of variance showed that the suitability of sunnhemp genotypes for obtaining fibre and seed yields varied with season. The results further indicated that sunnhemp grew during dry seasons with longer photoperiod and higher values of growing degree days(GDD), HTU and PTU resulted in a higher fibre yield, while a higher seed yield and relatively longer, finer and stronger fibres were obtained during wet seasons with higher RTD values. Regression analysis indicated that CHU was positively related to fibre yield, while RTD was positively related to seed yield. CHU beyond 2 000 °C d reduced seed yield and favoured fibre production. In contrary to CHU, RTD values were positively related to seed yield and negatively related to fibre yield. Similarly, HTU had an inverse relationship with fibre yield while PTU had a positive relationship with fibre yield. The genotype SH4 produced a seed yield of 1 361 kg ha^(–1) during wet seasons, which was significantly higher than SUIN053, while a fibre yield of 990 kg ha^(–1)(significantly higher than that of SH4) was obtained for SUIN053 that required less CHU to attain the phenological events during dry seasons. The per unit area yields of seed and fibre with the closer spacing(30 cm×15 cm) by virtue of higher plant density were 17.0 and 14.9% higher than those with the spacing of 45 cm×15 cm, respectively. Higher doses of P and K resulted in higher seed and fibre yields.
基金Supported by the National Natural Science Foundation of China(No.30971869)
文摘The size distribution of water-stable aggregates and the variability of organic C,N and P contents over aggregate size fractions were studied for orchard,upland,paddy,and grassland soils with high,medium,and low fertility levels.The results showed that > 5 mm aggregates in the cultivated upland and paddy soils were 44.0% and 32.0%,respectively,less than those in the un-tilled orchard soil.Organic C and soil N in different size aggregate fractions in orchard soil with high fertility were significantly higher than those of other land uses.However,the contents of soil P in different size aggregates were significantly greater in the paddy soil as compared to the other land uses.Soil organic C,N and P contents were higher in larger aggregates than those in smaller ones.The amount of water-stable aggregates was positively correlated to their contribution to soil organic C,N and P.For orchard and grassland soils,the > 5 mm aggregates made the greatest contribution to soil nutrients,while for upland soil,the 0.25-0.053 mm aggregates contributed the most to soil nutrients.Therefore,the land use with minimum disturbance was beneficial for the formation of a better soil structure.The dominant soil aggregates in different land use types determined the distribution of soil nutrients.Utilization efficiency of soil P could be improved by converting other land uses to the paddy soil.
基金supported by the Social Research and Database Construction Project of CentralUniversity of Finance and Economicsthe National Social Sciences Fund(Project No.:14CRK011)
文摘On the basis of the findings of 227 surveys of Chinese fertility intentions over the years 1980-2011, this paper investigates the longitudinal changes in fertility intentions through cross-temporal meta-analysis. It is found that the ideal number of children for the Chinese trended downwards from 1980, but since 2000 the average number has remained basically stable at 1.6 to 1.8. In the 1980s, people＇s fertility levels were higher than their fertility intentions. With economic and educational progress in China, both fertility levels and fertility intentions showed a downward trend, with the former declining faster than the latter. Since 1990, people＇s fertility levels have been lower than their fertility intentions; that is, their actual number of children has been less than their ideal number. This provides an empirical basis for examining the changes in China＇s fertility intentions and fertility levels.
基金This study was funded by the National Natural Science Foundation of China(Nos.41401293 and 41771286),the National Science and Technology Pillar Program of China(No.2013BAD11B01),and the National Key Research and Development Program of China(No.2016YFD0200302).The authors thank Professor Peter Bottomley from Oregon State University,USA for language editing of the manuscript.
文摘The anaerobic ammonium oxidizing(anammox) process has been found to play an important role in terrestrial ecosystems in recent years. However,the diversity and abundance of anammox bacteria in nitrogen(N)-rich agricultural soils under high fertilizer greenhouse conditions are still unclear. Two greenhouse fields with different N fertilizer input levels were chosen, and their soil profiles were studied with molecular technologies, including quantitative polymerase chain reaction assay, a clone library, and phylogenetic analysis based on hzsB(encoding anammox hydrazine synthase β-subunit) gene. Molecular analyses suggested that anammox bacteria were at their highest density at 10–20 cm soil depth, and that the anammox bacterial abundance was significantly lower at high N than at low N. Candidatus Brocadia was the sole anammox bacterial genus throughout the soil depth profiles. The highest diversity of anammox bacteria was found at 30–40 cm soil depth, and different phylotypic clusters of Candidatus Brocadia were associated with specific soil environmental factors, such as nitrates, soil depth, and total N. Correlation analyses and redundancy analyses confirmed that high nitrate content associated with high N fertilizer input had a significant negative influence on the abundance and biodiversity of anammox bacteria. These results imply that excessive use of N fertilizer would affect arid land soil N loss to the atmosphere by the anammox pathway.
