中国生态农业学报(中英文)

Review on greenhouse gas emission and reduction in wheat-maize double cropping system in the North China Plain

WANG Yuying, LI Xiaoxin, DONG Wenxu, ZHANG Yuming, QIN Shuping, HU Chunsheng

2018, 26(2): 167-174. doi: 10.13930/j.cnki.cjea.171117

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Abstract:
The winter-wheat and summer-maize double cropping system in the North China Plain (NCP) is the classic intensive crop production pattern with high water demand and nitrogen fertilizer inputs. The carbon (C) emission quantities are higher than the carbon sequestration quantities in the cropping system. C was being lost from the intensive wheat-maize double cropping system in the NCP at a rate of 77 g(C)·m^-2·a^-1 when harvest removals are considered, even though crop residue C is input into the soil since 30 years ago. High nitrogen (N) fertilizer application rate[>400 g(N)·hm^-2·a^-1] results in the increase of C emissions directly. Yield-scaled N₂O emission is lowest at N application rate of 136 g(N)·hm^-2·a^-1. And it is found that maximal crop yield is achieved at a N application rate of 317 g(N)·hm^-2·a^-1, which is 20% less than current practice. More than 90% of the annual cumulative greenhouse gas (GHG) fluxes originated at soil depths shallower than 90 cm. The subsoil (>90 cm) is not a major source or sink of GHG, but it acts as a 'reservoir'. Considering the synthetic greenhouse effect, some measures of greenhouse gas reductions were put forward in papers such as reductions of fertilizer input and water supply and improving farming system (tillage reduction or zero tillage). Furthermore C reduction needs to be in step with C sequestration. In the future, studies on greenhouse gas emissions in NCP require to be further strengthened in the following aspects:1) in-situ continuous online monitoring of canopy scale greenhouse gases, and using stable isotope techniques to track their sources and proportions; 2) in soil profile, using stable isotope techniques to study the sources and proportions of greenhouse gases, and exploring the responding mechanism between greenhouse gas production/consumption in soil profile and their emissions at soil surface is fairly crucial; 3) using models to estimate greenhouse gas emissions of soil-atmosphere continuum.

The effect of rice plant traits on methane emissions from paddy fields: A review

JIANG Yu, GUAN Dahai, ZHANG Weijian

2018, 26(2): 175-181. doi: 10.13930/j.cnki.cjea.171155

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Abstract:
Rice is the most important stable food in China and rice paddies constitute a major source of methane (CH₄) emission. Rice plant traits not only play an important role in rice yield, but also significantly affect CH₄ emission from paddy fields. However, there have been wide gaps in the understanding of the effects of rice plant traits on CH₄ emissions from paddy fields. Thus research status and progress on the impact of rice plant on CH₄ emissions were reviewed in terms of plant morphological and physiological characteristics (especially photosynthetic characteristics), plant-environment interactions, etc. The effects of aboveground plant traits (e.g. tiller, plant height and leaf area) on CH₄ emissions from paddy fields have remained inconclusive. The belowground system plays a key role in CH₄ emission. Optimizing photosynthate allocation can reduce CH₄ emission in continuously flooded paddy fields. High biomass rice plants can increase CH₄ emission in low C paddy soils, but reduce CH₄ emission in high C paddy soils. Based on the summary of the effects and the underlying mechanisms reported in existing studies, further efforts were needed, such as assessment of the effects of root morphological and physiological characteristics and plant-environment interactions on CH₄ production, oxidation and emission. There was also the need to pay more attention on the underlying mechanisms that combines microcosmic and field experiments and other new research methods. Meanwhile, the interaction and underlying mechanisms of carbon and nitrogen in plant-soil systems needed further exploration in future studies. A good understanding of the impact of rice plants on CH₄ emissions can provide the theoretical basis for rice cultivar breeding and innovative rice cropping with less greenhouse gas emissions and high yields.

Advance in soil dinitrogen emission

ZHANG Zhijun, QIN Shuping, YUAN Haijing, ZHANG Yuming, HU Chunsheng

2018, 26(2): 182-189. doi: 10.13930/j.cnki.cjea.171070

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Abstract:
The amount of applied nitrogen fertilizer has increased dramatically since the invention of the industrial ammonia synthesis in the early 20th century. In some countries or regions, the amount of nitrogen fertilizer input has exceeded crop nitrogen demand. This has led to a large amount of nitrogen losses to the environment, causing environmental pollution such as ammonia volatilization, nitrous oxide emission and groundwater contamination. Soil microbes can transform active nitrogen into inert dinitrogen and consequently remove superfluous nitrogen from soil via denitrification and anammox. Direct and precise measurement of soil denitrification has been a continuous challenge due to high background concentration of atmospheric dinitrogen, which has hindered progress in research on soil dinitrogen emissions. This paper reviewed the main pathways of soil dinitrogen emission[denitrification, dissimilatory nitrate reduction to ammonium (DNRA) and co-denitrification] and their contributions to soil dinitrogen emission. It also covered the methods of soil dinitrogen flux determination (acetylene inhibition technique, ¹⁵N tracing method, N₂/Ar membrane-inlet mass spectrometry, helium environment method and natural abundance ¹⁵N₂O isotopic method) and their advantages, disadvantages. The key factors regulating soil dinitrogen emission (oxygen, dissolved organic carbon, nitrate, microbial community structure and functional gene expression) and the related mechanisms were also summarized. In conclusion, it was essential to develop new methods for in situ dinitrogen flux determination in undisturbed soils. More studies were needed to quantify soil dinitrogen flux in typical ecosystems (such as dryland, farmland, forest, grassland and wetland), clarify microbial mechanism involved, and simulate and predict the responses of soil dinitrogen emission to global change.

The mechanisms of HONO emissions from soil: A review

WU Dianming, XIA Yuling, HOU Lijun, LIU Min

2018, 26(2): 190-194. doi: 10.13930/j.cnki.cjea.171061

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Abstract:
Nitrous acid (HONO) significantly contributes to atmospheric hydroxyl radical (OH·) and also influences atmospheric oxidation capacity and air quality. Comparison of HONO concentrations measured in a field campaign and by modeling showed a large unknown HONO source during daytime. Studies have shown that the unknown HONO source can be attributed to soil emissions, a major source of atmospheric HONO. The mechanisms may be taking the form of chemical equilibrium between soil nitrite and H⁺, reactive uptake and displacement by soil, emissions by ammonia-oxidizing bacteria (AOB) and other micro-organisms, or surface reaction between hydroxylamine and H₂O. Therefore, HONO flux from soils is controlled by soil nitrite concentration, pH, AOB abundance, soil minerals, soil moisture and C/N ratio. The mechanism of HONO emissions from soil has remained a point of hot discussion and few results have been reported from China. Here, we introduced the background of HONO emissions from soil, reviewed studies on the mechanisms of HONO emissions from soil and the related driving factors. This review was a relevant support for research on reducing nitrogen loss, enhancing nitrogen use efficiency, and evaluating the effects of nitrogen fertilization on environmental and urban air quality.

High-frequency dynamic observation of N₂O emission flux from cropland in the North China Plain

LI Fadong, DU Kun, ZHANG Qiuying, GU Congke, LENG Peifang, QIAO Yunfeng, ZHU Nong, HAO Shuai, HUANG Yongbin, SHI Shengjin

2018, 26(2): 195-202. doi: 10.13930/j.cnki.cjea.171209

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Abstract:
Nitrous oxide (N₂O) is one of the primary greenhouse gases, which depletes ozone sphere and results in strong greenhouse effects. Nowadays, a series of studies on greenhouse gases emissions of vegetation-soil-atmosphere system has been carried out domestic and overseas with the measurement method of static chamber/gas chromatograph, in which gas sampling time is concentrated in a fixed period during daytime rather than around the clock. Moreover, its' sampling frequency is usually longer than one minute inducing difficulty to implement a real-time, high-frequency and continuous determination of greenhouse gas emissions in situ for a long time. As an important source of N₂O emission, farmland ecosystem is a human-disturbed system with fast N recycle and large N₂O emission. To improve N₂O emission observation methods and provide a reference for N₂O change study in the North China Plain, we chose a typical farmland ecosystem, a maize field at the Yucheng Comprehensive Experiment Station, Chinese Academy of Sciences, and monitored N₂O concentration change with a new monitor instrument TGA200A (Trace Gas Analyzer 200A) to achieve a automatically real-time monitoring of N₂O emission for day and night. The TGA200A was equipped with a laser launch tube simultaneously controlled by current and temperature and some related measuring devices. When sample and reference gases (with a known concentration) entered the analyzer synchronously, the target gas concentration was determined by through scanning and comparing the linear absorption wavelengths of laser energy between sample and reference gases. The monitoring was from the middle of June 2017 to September 2017. The results showed, firstly, the N₂O emission was higher in night from 0:00 to 6:00 and 18:00 to 24:00 (0.618-1.171 mg·m^-3) than in daytime from 6:00 to 18:00 (0.526-1.145 mg·m^-3) in fine weather. N₂O emission was facilitated under higher atmospheric temperature in daytime, but the emission peak appeared in 15:00 to 17:00 indicating a significant hysteresis of temperature effect. Secondly, in rainy day, maize field N₂O emissions were increased by 0.033 mg·m^-3 in 3 hours with a proper rainfall and presented an accumulative effect. But if the rain was too heavy for a long time, the N₂O emission would be reduced. Thirdly, N₂O emission was affected by strong wind, but this conclusion needed more verification because such result was not regular. This study demonstrated the data determined by the TGA200A was useful and reliable for study on dynamic change of N₂O emission in different weathers. TGA200A was available in an automatically and real-time monitor of N₂O emission for day and night with different environment elements (temperature, rain, wind) and made it possible to reduce human costs and errors in greenhouse gas flux observation.

Effects of fertilization regimes on N₂O and NO emissions from agro-ecosystem of purplish soil

XIAO Qianying, HUANG Yousheng, HU Tingxu, ZHU Bo

2018, 26(2): 203-213. doi: 10.13930/j.cnki.cjea.171158

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Abstract:
Nitrous oxide (N₂O) and nitric oxide (NO) emissions from agro-ecosystem of purplish soil were measured (starting from October 2003) in a long-term purplish soil fertilization platform (established in 2002) using closed static-chamber and gas chromatography systems. Single synthetic nitrogen fertilizer (N), pig manure (OM), regular synthetic nitrogen, phosphorus and potassium fertilizer (NPK), pig manure combined with synthetic NPK fertilizer (OMNPK) and returned crop residues combined with synthetic NPK fertilizer (RSDNPK) under the same total nitrogen rate were set, and N₂O and NO emissions from croplands of purplish soil were monitored under these fertilization regimes. No fertilizer treatment (CK) was used as control in the calculations of the emission coefficients. The results showed large fluctuations in emission rates of N₂O and NO, with N₂O and NO peak emissions at the early stage of fertilization. N₂O emission was enhanced by heavy rainfall, but rainfall had no significant effect on NO emission. For the whole wheat-maize rotation period, cumulative annual emissions of N₂O in N, OM, NPK, OMNPK and RSDNPK treatments were 1.40, 4.60, 0.95, 2.16 and 1.41 kg(N)·hm^-2; and with emission coefficients of 0.41%, 1.56%, 0.25%, 0.69% and 0.42%, respectively. The cumulative emissions of NO in N, OM, NPK, OMNPK and RSDNPK treatments were 0.57, 0.40, 0.39, 0.46 and 0.17 kg(N)·hm^-2; and with emission coefficients of 0.21%, 0.15%, 0.15%, 0.17% and 0.07%, respectively. Fertilizer application regimes significantly (P < 0.05) influenced cumulative N₂O and NO emissions. Compared with conventional NPK fertilizer, pig manure amendment stimulated N₂O and NO emissions, with increases of 384% and 3% for OM and 127% and 18% for OMNPK, respectively. Returned crop residues combined with regular synthetic NPK fertilizer decreased NO emission by 56%. The application of pig manure (OM) increased N₂O and NO emissions, whereas returned crop residues plus regular synthetic NPK fertilizer (RSDNPK) decreased NO emission. The research also showed that both soil temperature and moisture conditions significantly influenced N₂O and NO emissions during wheat season (P < 0.01), but not during maize season (P> 0.05). However, soil inorganic nitrogen content was the main limiting factor for N₂O and NO emissions during the whole wheat-maize rotation year (P < 0.01). Returned crop residues plus regular NPK fertilizer was recommended as the optimal fertilization regime for simultaneous mitigation of N₂O and NO emissions.

Impact of conversion from forestland to cropland on soil N₂O emission from purplish soil

REN Xiao, LIU Hongbing, ZHU Bo

2018, 26(2): 214-221. doi: 10.13930/j.cnki.cjea.171156

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Abstract:
Land use change is one of the main reasons for changes of greenhouse gases concentration in the atmosphere. However, the impacts of land use change process, such as conversion process from forestland to cropland, on soil N₂O emission is still lack of a systematic study. In this study, forestland was converted into cropland in the hilly area of the Central Sichuan Basin in mid July 2016, and then planted as winter wheat-summer maize rotation from October 26, 2016 to September 15, 2017. Static chamber-gas chromatographic technique were used to compare the characteristics of N₂O emission from croplands, converted from forest land with tillage without fertilizer (CL-T) and with tillage and fertilizer (CL-TF), and forestland (CK). The results showed that during the experimental period, the soil N₂O emission fluxes of CL-T and CL-TF both significantly increased compared to CK (P < 0.01), and there was an obvious emission peak at the beginning of land use conversion from forestland to cropland. The mean N₂O emission fluxes in the wheat season and maize season were 2.52 μg(N)·m^-2·h^-1 and 4.60 μg(N)·m^-2·h^-1 under CK, 3.55 μg(N)·m^-2·h^-1 and 11.63 μg(N)·m^-2·h^-1 under CL-T, 6.26 μg(N)·m^-2·h^-1 and 22.16 μg(N)·m^-2·h^-1 under CL-TF, respectively. N₂O emission peak flux was significantly higher in maize season than in wheat season. The annual accumulative soil N₂O emissions were 0.271 kg(N)·hm^-2, 0.515 kg(N)·hm^-2 and 0.957 kg(N)·hm^-2 under CK, CL-T and CL-TF, respectively. Compared to CK, CL-T and CL-TF increased the annual accumulative soil N₂O emissions by 89.8% and 253.0%, respectively. This indicated that land use conversion from forestland to cropland significantly induced the increase of N₂O emission in purplish soil. Tillage changed soil structure and significantly increased soil inorganic nitrogen content (P < 0.05), then fertilizer application increased soil inorganic nitrogen content sharply by a large quantity, which resulted in pulsive N₂O emission. While soil temperature (5 cm) and soil moisture (WFPS) were not changed significantly (P> 0.05), and planting did not change N₂O emission significantly in short time during the process of land use conversion. It was suggested that the fundamental mechanism of stimulating N₂O emission caused by land use conversion from forestland to cropland might be derived from the increase of mineralization rate of soil organic nitrogen. However, the effect of land use conversion on soil nitrogen transformation and the mechanism of changing of soil N₂O emission need to be further studied.

A review of the factors influencing soil organic carbon stability

XU Jiahui, SUN Ying, GAO Lei, CUI Xiaoyang

2018, 26(2): 222-230. doi: 10.13930/j.cnki.cjea.170627

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Abstract:
Increasing soil carbon sequestration is an effective measure to deal with global climate change. As an important carbon sink, soil organic carbon (SOC) is a critical medium for carbon sequestration. In recent decades, the molecular structure of SOC has been identified as the most important element in predicting SOC cycle. However, new studies have proven that the recalcitrance of the molecular structure of organic carbon limits the determination of SOC stability in the soil. Also the interaction between SOC and the surrounding environment significantly limits the possibility of degradation of SOC. Soil micro-organisms influence SOC cycle not only through decomposing, but also through microbial products which are the primarily components of SOC. Abiotic factors including inorganic soil particles, inorganic soil environment and nutrient conditions directly or indirectly control SOC dynamics. Among these factors, adsorption to soil minerals and occlusion within soil aggregates have been determined to strong support the long-term stability of SOC. The role of minerals in SOC adsorption and stability depends on the mineralogy and chemical property of SOC. Soil aggregates not only physically protect SOC from mi-crobial and enzymatic attack, but also promote the adsorption of SOC to minerals. On the contrary, organic mineral complex can also combine with other inorganic or organic materials to form aggregates so that SOC adsorbed to minerals can be further occluded by aggregation. Therefore, SOC adsorption to minerals and occlusion within aggregates complement each other. Moreover, inorganic environment (e.g., temperature and moisture) also acts on SOC dynamics. Put together, we suggest that the persistence of SOC was mainly due to complex interactions between SOC and the surrounding environment, including micro-organism, reactive mineral surfaces, soil aggregates, temperature, water and nutrient. Meanwhile the biochemical property of SOC also depends on environment conditions. However, whether the inherent quality of SOC or its surrounding environment is an ecosystem property; and each property affects and interacts with each other. Therefore, the persistence of SOC is a specific property of ecosystem that integrates each property.

Responses of soil nitrogen mineralization during growing season to vegetation and slope position on the northern Loess Plateau of China

LIU Jiao, FU Xiaoli, LI Xuezhang, JIA Xiaoxu, SHAO Ming'an, WEI Xiaorong

2018, 26(2): 231-241. doi: 10.13930/j.cnki.cjea.170626

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Abstract:
Nitrogen (N) mineralization is critical for nitrogen cycle in terrestrial ecosystems and significantly influences the availability of soil N. In this paper, we studied the changes in soil mineral N and N mineralization rates in slope lands in the northern Loess Plateau region in relation to vegetation types, sampling sites and slope positions during vegetation growing season. The objectives of the study were to determine the dynamics of N mineralization during growing season and the influencing factors. Slope lands with Chinese pine (Pinus tabulaeformis) and korshinsk peashrub (Caragana korshinskii) were selected in the Liudaogou catchment and an in situ mineralization method was used to measure soil N mineralization for the period from April through October. The measurements were conducted in upper, middle and lower positions of the slope with under-and non-under-canopy at the 0-10 cm and 10-20 cm soil depths. Soil mineral N in the growing season was dominated by ammonium, which accounted for 61% and 70% of total mineral N at the 0-10 cm and 10-20 cm soil depths, respectively. The proportion of ammonium to total mineral N increased during the growing season. Soil ammonium in the upper and middle slope positions was significantly higher than that in the lower slope position for Chinese pine, but not affected by slope positions for korshinsk peashrub. Furthermore, soil ammonium was not affected by sampling site in both Chinese pine and korshinsk peashrub plantations. Soil nitrate and total mineral N were affected by vegetation type and sampling site, rather than by slope position. Under-canopy soil nitrate was similar to that of non-under-canopy in Chinese pine vegetation, but it was greater than that for non-under-canopy in porshinsk peashrub vegetation. Soil N mineralization during growing season resulted mainly from nitrification at the 0-10 cm soil depth, but also influenced by both nitrification and ammonification at the 10-20 cm soil depth. Ammonification rate was significantly high during the early growing season and low during the mid growing season. Moreover, ammonification rate was affected by slope position, vegetation type and sampling site. Nitrification and net N mineralization rates in under-canopy soils were similar to those in non-under-canopy soils in Chinese pine vegetation, but it was greater than that in non-under-canopy soils in korshinsk peashrub vegetation. Additionally, when compared with other slope positions, lower slope position had highest nitrification and net mineralization rates of soil N in under-canopy conditions, but it was the lowest in lower slope position in both Chinese pine and korshinsk peashrub plantations. The results suggested that korshinsk peashrub enhanced nitrification and mineralization of N in soils in under-canopy conditions, while the effects of Chinese pine on soil mineral N and N mineralization were not related to sampling site.

Characteristics and effects on crop production of heat resources changes in Heilongjiang Province

DU Chunying, GONG Lijuan, ZHANG Zhiguo, ZHAO Huiying, WU Shuang, TIAN Baoxing, ZHAO Fang

2018, 26(2): 242-252. doi: 10.13930/j.cnki.cjea.170621

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Abstract:
Under the global warming background, heat resources variation has significant impact on production environment, growth and development, cropping system and cultivation zone of corps in the clod region.To explore variations in cultivation zones, growing seasons and yields of major crops (rice, maize and soybean) under climate change of Heilongjiang Province, China, we analyzed the characteristics of tempo-spatial changes and abrupt changes by using accumulated anomaly method, Mann-Kendall trends test and Empirical Orthogonal Function (EOF) of heat resources indices, including accumulated temperature above 10℃ and 0℃ and frost-free periods in 67 meteorological stations from 1971 to 2014 in Heilongjiang Province.We also calculated regression coefficients between heat resources indices and development stages of crops to investigate the influence of heat resources change on crop development.The differences in crop cultivate zones and yields between before and after abrupt change year were also discussed according to accumulated temperature above 10℃ and actual and meteorological yields.The results showed that the accumulated temperatures above 10℃ and 0℃ increased significantly at rates of 86.7℃·d·((10a)^-1 and 80.5℃·d·((10a)^-1, respectively, from 1971 to 2014.The annual frost-free period increased at a rate of 3.8 d·(10a)^-1.There were abrupt changes in the accumulated temperatures above 10℃ and the annual average frost-free period in 1993.The accumulated temperature above 10℃ increased 226.1℃·d averagely, and the frost-free period prolonged 9.2 d averagely after the abrupt change year.The abrupt change promoted the initial dates and postponed the ending dates of the temperatures above 10℃, 0℃ and the frost-free period.From 1971 to 2014, the increasing rates of accumulated temperatures above 10℃ and 0℃ were greater in the west than in the east.The annual frost-free period was longer in mid-west than in northeast.The area with greater change of heat resource was also sensitive area of agricultural heat resources change.With the increase of heat resources, the suitable growth period of crops prolonged.The planting areas of rice, maize northward and westward expended.The center of soybean cultivation area northward moved.The planting areas with original especial-early-maturing and early-maturing crops varieties became the areas suitable for middle-maturing and middle-late-maturing varieties of crops.In general, the increased heat resources provided more yield increasing potential of rice, maize and soybean in Heilongjiang Province.

Simulation of water flow and shallow groundwater recharge in coarse-textured soils on the Loess Plateau, China

GE Jiamin, FAN Jun, WANG Sheng

2018, 26(2): 253-262. doi: 10.13930/j.cnki.cjea.170495

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Abstract:
The Loess Plateau suffers serious soil and water loss, resulting in a fragile ecological condition with intense water resources deficit. Groundwater is crucial not only to guarantee regional social and economic development, but also to maintain ecosystem balance. However, the process of groundwater transformation and recharge on the Loess Plateau is still not entirely clear. The objective of this study was to investigate water movement in deep soil profile and test the possibilities of precipitation recharge of shallow groundwater in the water-wind erosion crisscross region on the Loess Plateau. Considering the limitations in current equipment and techniques for deep soil profile moisture observation, the HYDRUS-1D model was used to calculate solute soil hydraulic parameters and simulate deep profile (0-1 500 cm) soil water movement. The datasets used in the simulation included meteorological data and soil water content in the 0-600 cm soil layer in a willow field plot with aeolian sandy soil in the Liudaogou catchment in Shenmu City of Shaanxi Province, China for the period 2013-2016. The upper boundary condition was set as atmosphere boundary conditions with inputs of rainfall and potential transpiration (T_p) and potential evaporation (E_p) partitioned from crop evapotranspiration (ET₀) by using measured leaf area index (LAI) in different growing periods. The lower boundary condition was set as free drainage. The optimized hydraulic parameters were derived from a repeated inverse solution process and used to simulate soil water movement in the 0-1 500 cm soil layer. Then the depth of soil water infiltration and the possibility of shallow groundwater recharge were analyzed. The results showed a slight soil water content deficit in the 0-600 cm soil layer at both the end and start of growing season in 2014 (439 mm, normal precipitation year) and 2015 (371 mm, dry year). However, there was surplus soil water content at the end of growing season, compared with the start of growing season in 2013 and 2016 (both were wet years with 669 mm and 704 mm precipitations), and rainfall infiltration exceeded observed 600 cm depth. From the simulation results, soil water content of deep soil profile did not significantly change in 2014 and 2015 with slight and slow water movement into the deeper soil layer, while rainfall infiltration depth reached 1 100 cm in 2013 and 1 200 cm in 2016. This exceeded rooting zone at the end of 2013 and 2016, which raised the possibilities of rainfall recharge of shallow groundwater in the study area. For the 4-year simulation period, average soil evaporation was 14.87 cm·a^-1 and average plant transpiration was 33.70 cm·a^-1, soil water contents were mainly consumed in the form of transpiration. Due to high infiltration rate of the coarse-textured soil in wet years, a large proportion of rainfall was transformed into shallow groundwater. Dry and wet years alternated on the Loess Plateau with intensive rainfall variations. Rainfall infiltration in wet years was one important way of shallow groundwater recharge in the region.

Multi-scale spatial autocorrelation analysis of cultivated land quality in China's southern hillside areas: A case study of Lichuan County, Jiangxi Province

ZHANG Han, ZHAO Xiaomin, OUYANG Zhencheng, GUO Xi, LI Weifeng, KUANG Lihua, YE Yingcong, HUANG Cong, WANG Xiaoyan

2018, 26(2): 263-273. doi: 10.13930/j.cnki.cjea.170513

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Abstract:
Cultivated lands are among the most fundamental resources for national food security and sustainable social development. Scientific analysis of the spatial distribution patterns and evolutionary characteristics of cultivated land quality is significant for the protection and layout optimization of cultivated lands. Analysis of the spatial distribution of cultivated land quality at different scales is the basis of cultivated land quality improvement and strengthening of cultivated land protection. This paper was based on cultivated land quality monitoring experimental unit in Lichuan County in Jiangxi Province and then used weighted average, variation coefficient, and spatial autocorrelation to analyze spatial disparity characteristics of cultivated land quality. Multi-scale spatial autocorrelation analysis of cultivated land quality research is a hot research area. The innovation in this paper was the introduction of natural land grade index, use of the grade index and economic grade index as the space variable to separately explore and discuss the degree of spatial correlation and spatial disparity of cultivated land quality at county-scale, township-scale and village-scale in GIS environment. The results of the research showed that:1) Cultivated land quality index was high in the south and north and low in the west and east in Lichuan County. When the threshold distance was 400 m, there was a significant spatial autocorrelation in cultivated land quality. The Moran's I value of natural land grade index was highest, followed by economical land grade index, and land use grade index was the lowest. The Moran's I value of cultivated land quality from county to township and then to village scales decreased systematically. Multi-scale spatial autocorrelation analysis of cultivated land quality exhibited a significant aggregation of spatial distribution in Lichuan County. 2) It was found that different types of cultivated land quality indexes had remarkably different spatial correlations at different spatial scales. For the influence degree of spatial scale, land use grade index was greatly affected by spatial scale, followed by natural land index, and the economic land grade index was the weakest. For the coefficient of variation of cultivated land quality index, fluctuation in Moran's I value for cultivated land at village-scale was far greater than that at township scale. While at the same spatial scale, the coefficient of variation of natural land index was strongest, followed by economic land index and then land use index. 3) The results based on local indicators of spatial association (LISA) showed that positive spatial autocorrelation of cultivated land quality, included the high-high type and the low-low type, emerged as the shape of the cluster and in the form of group, while the negative spatial autocorrelation contained the high-low type and low-high type was fragmented in space. The results of the study showed that spatial disparity in cultivated land quality was sensitive to spatial scale. Therefore, for cultivated land quality improvement and protection, there was the need to pay more attention to spatial disparity of cultivated land quality at town scale and village scale. Also based on the difference in spatial correlation degree among the natural conditions, utilization conditions and economic benefits, it was possible to explore cultivated land quality improvement and protection measures that met actual ground situations in the study area. The results of the study provided the needed references for the construction of high-standard basic farmlands, land reclamation, regional cultivated land quality monitoring, cultivated land protection, partitioning and management of cultivated lands, cultivated land quality improvement and spatial optimization of cultivated land quality.

Spatial variation in phosphorus accumulation and the driving factors in cultivated lands in Fujian Province

ZHAN Qiuli, ZHANG Liming, ZHOU Biqing, WU Shunjin, XING Shihe

2018, 26(2): 274-283. doi: 10.13930/j.cnki.cjea.170767

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Abstract:
Phosphorus is one of the largest nutrient elements needed for plant growth. Under the intensive production conditions, most farmland soils in China have had phosphorus enrichment problem, mainly due to excessive application of phosphate fertilizers, strong fixation and inefficient use of phosphorus. The enrichment of phosphorus in cropland soils is one of the important causes of non-point pollution, which has also restricted sustainable agricultural development in China. In this study, the 1:250 000 spatial database on farmland soil types and the available phosphorus data on tillage layer soil samples of cultivated land (1 676 samples in 1982 and 200 322 samples in 2008) in Fujian Province were used to determine the spatial variation in the degree of phosphorus enrichment and the related driving factors in cultivated lands for the past 26 years. To do so, an integrated GIS with grey correlation analysis model was used. The aim of the study was to clarify the enrichment characteristics of soil available phosphorus, and its spatial variability and driving factors. The results showed that soil available phosphorus had been abundant in Fujian Province in the past 26 years. In addition, soil available phosphorus enrichment area reached 1 216 777 hm², accounting for 92.81% of the total area of cultivated land in the province. The yearly average enrichment amount and rate of available phosphorus were 24.38 mg·kg^-1 and 10.01%, respectively, which showed obvious spatial variations. While cropland soils in Xiamen (which is in southern subtropics) had the largest degree of available phosphorus enrichment, those in Nanping (which is in mid-subtropics) showed the lowest degree of available phosphorus enrichment in Fujian Province. The soil types with high available phosphorus enrichment included purplish soils, fluvo-aquic soils, paddy soils and latosolic red soils. Then the soils with less available phosphorus enrichment included coastal solonchaks and calcareous soils. Soil subtypes with larger degrees of available phosphorus enrichment included submerged paddy soils and bleached paddy soils, while those with lower levels of available phosphorus enrichment included brown calcareous soils and coastal solonchaks. In general, enrichment of available phosphorus in tillage layer of cultivated land soil had happened in large area with wide distribution range and significant spatial variation in Fujian Province. Grey correlation analysis showed that soil available phosphorus enrichment and its spatial variation were mainly affected by annual application rate of phosphate fertilizer, soil pH, mean temperature and soil clay content, which were with grey correlation coefficients higher than 0.722. However, the effect of soil sand content, precipitation and soil organic matter content on phosphorus enrichment in cultivated soils in study areas was relatively weaker. Their gray correlation coefficients were less than 0.720. Based on the degree of phosphorus enrichment and spatial variation, inorganic phosphate fertilizer application should be controlled strictly to deal with the phosphorus enrichment in cultivated soils in Fujian Province. At the same time, there was the need to optimize fertilization management by increasing organic fertilizer and reducing chemical fertilizer use.

Soil quality evaluation in typical coastal reclamation zones based on weighted Topsis method

SUN Beiting, GAO Chao, ZHANG Yan

2018, 26(2): 284-293. doi: 10.13930/j.cnki.cjea.170711

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Abstract:
Tidal flat is an important reserve of cultivated land resource in China. There is high spatial heterogeneity, properties and environment changes of soil in the transformation from wetland to agricultural soil. In order to evaluate the effect of soil quality under different reclamation durations and multiple land use in a typical coastal area in Cixi County, Zhejiang Province, 276 soil/sediment samples from farmland, vegetable land, orchard, forestland, aquafarm, wasteland and tidal flat reclaimed for 0 to 50 years were collected and analyzed. Considering the spatial heterogeneity, principal component analysis was used in combination with norm value, then minimum data set (MDS) with seven indexes was put forward. This included organic matter (OM), calcium oxide (CaO), sulfur (S), bromine (Br), boron (B), plumbum (Pb) and cadmium (Cd) under six reclamation duration and seven utility patterns. About 29.2% of the index accounted for 80.3% of the information. The Topsis method, which combined maximum difference normalization method and variable coefficient fixing weight method, was used to assess the soil quality. Compared with the traditional membership function method, the used method was a much more effective one. Besides, the distance to optimal vector directly was used to explain the obstruction factor, which showed the primary obstacle and was applicable in supervising soil environment and improving soil quality by the local government. The results suggested that the range of soil quality comprehensive indexes for the 276 soil/sediment samples was 44.6-74.1. The trend in the indexes increased sharply in first 20 years and then stabilized in the 20-30 years, and then it again increased sharply for 30-50 years of reclamation. In general, the overall soil quality in the study area was moderate to infertile. The class Ⅰ soil quality was only 7.1% of the samples. More than half of the soil samples belonged to classes Ⅳ or Ⅴ. Based on land use types, soil quality was ranked in the following order:vegetable field > orchard > farmland > forest > aquafarm > tidal flat > wasteland. Paddy field was better than dry land for the same reclamation period, which indicated that basic paddy farmland was much more environmental friendly in Cixi reclamation district. Irrigation-induced decalcification and desalination effectively improved the quality of reclaimed soil. Meanwhile, low OM and high CaO and Cd primarily limited soil quality. Next were salt content as Br, S and B, followed by heavy metal as Pb. Soil content of Cd increased quickly to critical point of pollution, which was easily enriched in paddy and caused diseases. Reasonable use of chemical fertilizers was a key to further promotion of soil quality in reclaimed tidal areas.

Climatic factors and mulching affect soil salinity dynamics in coastal areas

ZHANG Jiao, CUI Shiyou, FENG Zhixiang, WANG Kuishan, ZHAI Caijiao

2018, 26(2): 294-302. doi: 10.13930/j.cnki.cjea.170572

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Abstract:
To clarify the impact of climatic factors on seasonal variations in soil salinity and to explore the effects of vegetation cover and straw mulching on soil desalination and salinity control in coastal areas, a field experiment was conducted in the medium-heavy saline coastal area of Rudong, Jiangsu Province. Four treatments were set in the study-control (bare land, CK), straw mulch (at 15 t·hm^-2, SM), vegetation cover (PC) and PC combined with SM (at 7.5 t·hm^-2, PC+1/2SM). Climatic factors (rainfall and air temperature) and topsoil salinity dynamics were determined for the period from May 2014 to May 2015. The results showed that:1) seasonal variations of soil salinity to some extent occurred in bare lands in coastal areas, with obvious salt accumulation during the period from October to December with the highest EC_1:5 (3.90 dS·m^-1) in October. 2) Correlation analysis showed that change in soil salinity under CK treatment was significantly negatively correlated with 7-day cumulative rainfall before sampling (P < 0.01) and also with 15-day cumulative rainfall before sampling (P < 0.05), but no so obvious significant correlation were found under SM, PC and PC+1/2SM treatments (P> 0.05). Under CK treatment, multi-factor interphase analysis of climatic factors indicated that increase in rainfall promoted soil desalinization (P < 0.01) and increase in air temperature exacerbated soil salt accumulation in surface soil (P < 0.01). Simultaneously, interaction between rainfall and air temperature had a positive effect on soil salt accumulation (P < 0.01). 3) Surface mulching (including PC and SM) significantly altered the effects of climatic factors on seasonal variations in soil salinity. Under PC and PC+1/2SM treatments, the relationship of the change in soil desalinization ratio (Y) with treatment time (X) followed the quadratic functions of Y_PC=0.001X²-0.345X + 54.41 (R²=0.456, P < 0.01) and Y_PC+1/2SM=0.001X²-0.293X + 57.121 (R²=0.526, P < 0.01), respectively. Under SM treatment, the relationship was a Logistic curve with an equation of Y_SM=94.912/(1+e^1.482-0.052X) (R²=0.980, P < 0.001). In addition, soil desalination rate increased rapidly after 29 days of SM treatment (that is June to August) and the trend stabilized as the rate reached 94.91% in 70-80 days after straw mulching. Moreover, large amount of straw mulch (15 t·hm^-2) had a more obvious effect on soil desalination, but also caused more obvious alkalinity problems. To therefore control desalination and salinity, a suitable amount of straw mulching (such as straw cover of 15 t·hm^-2) or suitable amount of straw mulching combined with vegetation cover (such as Sesbania cannabina Pers. and Brassica juncea L. Czern. et Coss.) were recommended in coastal area with seasonal concentrated high rainfall. This promoted soil desalinization and future soil reclamation under warming-wetting climate in coastal areas.

Phytoremediation of single and combined pollution of Cu and Pb by Medicago sativa, Lolium perenne, and Pennisetum alopecuroides

ZHU Jianfei, LI Minghong, XIE Peijun, QIAO Yunlei

2018, 26(2): 303-313. doi: 10.13930/j.cnki.cjea.170363

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Abstract:
With rapid socio-economic development, the problem of heavy metal contamination of soils is increasingly threatening food security and human health. So far, phytoremediation has been the main mode of treatment of soils for heavy metal pollution. To develop pastures suitable for remediation of complex Cu and Pb contaminated soils, a pot experiment consisting of 9 treatments was set up. The control (CK) was not treated with heavy metal salts. Four other treatments had low and high pollutions of single metals including Cu (Cu₁:200 mg·kg^-1 Cu²⁺; Cu₂:400 mg·kg^-1 Cu²⁺), Pb (Pb₁:300 mg·kg^-1 Pb²⁺; Pb₂:800 mg·kg^-1 Pb²⁺). The other four treatments consisted of both Cu and Pb pollutions of Cu₁Pb₁, Cu₁Pb₂, Cu₂Pb₁ and Cu₂Pb₂. The effects of pastures (forages) plantation on the Cu and Pb contaminated soil remediation were determined by comparing the adaptability and enrichment characteristics of alfalfa (Medicago sativa), ryegrass (Lolium perenne) and pennisetum (Pennisetum alopecuroides). The results showed that:1) the aboveground and belowground biomasses of M. sativa were largest under Pb₁ treatment, which were significantly larger than those for the other treatments. The aboveground biomass of L. perenne was largest under Cu₁Pb₁ treatment and belowground biomass of L. perenne largest under Pb₁ treatment. The aboveground biomass of P. alopecuroides was largest under Cu₂Pb₂ treatment and belowground biomass of P. alopecuroides largest under Cu₂ treatment. 2) When the soil was treated solely with Cu, the resistance coefficient of P. alopecuroides was largest among the three pasture species. Then when the soil was treated solely with Pb, the resistance coefficient of M. sativa was largest. For Cu and Pb combined treatment, the resistance coefficient of P. alopecuroides was largest. The order of aboveground biomass, belowground biomass and resistance coefficient of the three pasture plants under high Cu concentration treatments was P. alopecuroides > L. perenne > M. sativa. Then the aboveground biomass, belowground biomass and resistance coefficient of P. alopecuroides were significantly higher than those of L. perenne and M. sativa. 3) Soil contents of Cu and Pb decreased after planting the forage plants. At a certain concentration, soil Cu-Pb promoted the absorption of each other by the pasture plants. 4) The enrichment coefficient of Cu for aboveground biomass of M. sativa was highest under Cu₂Pb₂ treatment, which was 1.61. Then the enrichment coefficient of Cu for belowground biomass of L. perenne was highest under Cu₂Pb₂ treatment, which was 3.80. Only the enrichment coefficient of Pb for aboveground and belowground biomass of L. perenne exceeded 1.0, reaching 1.46. 5) The absorption ability of Pb by L. perenne was stronger and accumulated mainly in belowground biomass. M. sativa had the best comprehensive repair effect of complex Cu-Pb pollution. The transport coefficients of Pb in M. sativa and L. perenne were higher than 1.0 in complex Cu-Pb and single Pb polluted soils, respectively, and were 2.72 and 2.06, which reflected their respective potentials for enrichment of Pb in the soil. Thus L. perenne had a stronger tolerance to Pb pollution and was therefore a better remedy for Pb-polluted soils. M. sativa had a stronger tolerance to Cu and Pb and was therefore a better remedy for soils polluted with single Cu or composite Cu-Pb.

A new book for introduction of agroecology practices in multiple countries

LUO Shiming

2018, 26(2): 314-316. doi: 10.13930/j.cnki.cjea.171176

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Abstract:
The main content of the new book Agroecological Practices for Sustainable Agriculture:Principles, Applications and Making the Transition edited by Alexander Wezel is introduced here. New idea and new methods for agroecology development which are especially suitable as a reference for China are pinpointed. The major advantages and some weaknesses are also addressed.

2018 Vol. 26, No. 2