Quzhou County Research Articles

Quantifying spatial variability of indigenous nitrogen supply for precision nitrogen management in small scale farming

Understanding spatial variability of indigenous nitrogen (N) supply (INS) is important to the implementation of precision N management (PNM) strategies in small scale agricultural fields of the North China Plain (NCP). This study was conducted to determine: (1) field-to-field and within-field variability in INS; (2) the potential savings in N fertilizers using PNM technologies; and (3) winter wheat (Triticum aestivum L.) N status variability at the Feekes 6 stage and the potential of using a chlorophyll meter (CM) and a GreenSeeker active crop canopy sensor for estimating in-season N requirements. Seven farmer’s fields in Quzhou County of Hebei Province were selected for this study, but no fertilizers were applied to these fields. The results indicated that INS varied significantly both within individual fields and across different fields, ranging from 33.4 to 268.4 kg ha−1, with an average of 142.6 kg ha−1 and a CV of 34%. The spatial dependence of INS, however, was not strong. Site-specific optimum N rates varied from 0 to 355 kg ha−1 across the seven fields, with an average of 173 kg ha−1 and a CV of 46%. Field-specific N management could save an average of 128 kg N ha−1 compared to typical farmer practices. Both CM and GreenSeeker sensor readings were significantly related to crop N status and demand across different farmer’s fields, showing a good potential for in-season site-specific N management in small scale farming systems. More studies are needed to further evaluate these sensing technology-based PNM strategies in additional farmer fields in the NCP.

Ground beetles (Coleoptera: Carabidae) in the intensively cultivated agricultural landscape of Northern China – implications for biodiversity conservation

Abstract. 1. In the intensively cultivated major crop production areas of China, large knowledge gaps still prevail with regard to the current status of biodiversity in general, and especially in relation to agriculture management and planting patterns. Effective measures for species conservation are hence widely lacking.2. The diversity of ground beetle (Coleoptera: Carabidae) assemblages was compared between intensively managed wheat/maize fields, cotton monocultures, lawns, orchards and semi‐natural woodland located in Quzhou county, a typical, intensively managed agricultural region in the North China Plain.3. Although significant differences were found in species composition between different habitats, diversity of ground beetles in non‐cropping sites was not significantly higher than in intensively managed wheat/maize double‐cropping fields, while cotton monocultures had a significant lower carabid diversity. A combination of intensively managed wheat/maize double‐cropping fields with orchards appears to preserve substantial proportions of ground beetle diversity.4. To conserve the full spectrum of beetle species currently observed in the agricultural landscape of the North China Plain, the creation of both diverse habitats and a diversity of cropping systems are important, which includes a strengthening of less intensive farming practices.

Modelling impacts of alternative farming management practices on greenhouse gas emissions from a winter wheat–maize rotation system in China

Agricultural production plays an important role in affecting atmospheric greenhouse gas concentrations. Field measurements were conducted in Quzhou County, Hebei Province in the North China Plains to quantify carbon dioxide (CO 2) and nitrous oxide (N 2O) emissions from a winter wheat–maize rotation field, a common cropping system across the Chinese agricultural regions. The observed flux data in conjunction with the local climate, soil and management information were utilized to test a process-based model, Denitrification–Decomposition or DNDC, for its applicability for the cropping system. The validated DNDC was then used for predicting impacts of three management alternatives (i.e., no-till, increased crop residue incorporation and reduced fertilizer application rate) on CO 2 and N 2O emissions from the target field. Results from the simulations indicated that (1) CO 2 emissions were significantly affected by temperature, initial SOC, tillage method, and quantity and quality of the organic matter added in the soils; (2) increases in temperature, initial SOC, total fertilizer N input, and manure amendment substantially increased N 2O emissions; and (3) temperature, initial SOC, tillage, and quantity and quality of the organic matter added in the soil all had significant effects on global warming. Finally, five 50-year scenarios were simulated with DNDC to predict their long-term impacts on crop yield, soil C dynamics, nitrate leaching losses, and N 2O emissions. The modelled results suggested that implementation of manure amendment or crop residue incorporation instead of increased fertilizer application rates would more efficiently mitigate GHG emissions from the tested agro-ecosystem. The multi-impacts provided a sound basis for comprehensive assessments on the management alternatives.

Harmony coefficient of regional agro-ecosystem assessment at both local-and national –scales—A case study of Quzhou County,Hebei Province

本文构建了区域农业系统协调度评价理论和指标体系,研究了区域农业系统协调度状况,分析了区域农业系统发展存在的问题,并提出了区域农业协调发展建设性建议.选取1995～2003年资料,从自尺度和国家尺度对河北省曲周县区域农业系统进行了协调度计算分析.研究结果表明:在自尺度上,曲周县区域农业系统及社会子系统以失调为主,生态子系统中期协调,前后期失调,经济子系统后期协调,前期失调;在国家尺度上,曲周县区域农业系统及其子系统均失调.表明在国家尺度上,区域农业系统与子系统的协调度较自尺度普遍降低,反映了曲周县农业系统在经济发展、社会发展和生态环境保护3方面国家尺度下处于较低水平,应加快促进系统的协调发展.

Changes of soil organic carbon in an intensively cultivated agricultural region: A denitrification–decomposition (DNDC) modelling approach

Regional modelling of soil organic carbon (SOC) dynamics is important for predicting large-scale patterns in carbon cycling and for assessing potential responses of soil carbon pools to land-use change. However, data uncertainties related to both spatial heterogeneity and small-scale differences in farming practice related to cropping systems affect the accuracy of regional models. A case study is presented from Quzhou County in the North China Plain, an area characterized by highly intensive farming. For this county, the DNDC model was validated using sampling data from 68 sites around the county under generalized farm practices. Unique modelling units based on soil type, soil texture and crop type were created and then used to model the spatial change of SOC under different farming practices. Considering the main factors affecting SOC sequestration, the results indicate that the DNDC model delivers acceptable modelling results at county level. The results show that there is a great potential for SOC sequestration in Quzhou County in its central, southern and eastern parts. Changes in farming practices show a strong effect on carbon sequestration. A very efficient and environmental friendly sequestration of SOC pools could be achieved even by decreasing nitrogen fertilizer inputs, when the amount of straw returned to the field is greatly increased.

Factors affecting soil quality changes in the North China Plain: A case study of Quzhou County

At the end of the 1970s there were 3,300,000 ha of salt-affected land in the North China Plain. After the successful removal of the salt in the 1980s, the land has gradually been used for increasing intensive forms of agriculture. The Household Responsibility System (HRS) was adopted in Chinese rural areas at the time of the economic reform of the early 1980s. Farm households became the basic decision-making units that could directly control soil quality. This paper describes the change in soil fertility after 20 years of intensive agriculture and the driving factors of soil fertility change. Quzhou County was selected as it is representative for the North China Plain. The soil fertility status and nutrient flows of the salt-affected land for 1980–1981 and 1999 in Quzhou County were evaluated. Over 20 years, the total nitrogen (N), the extractable phosphorus (P) and the soil organic matter (SOM) in salt-affected land increased by 127%, 601% and 51% respectively; but exchangeable potassium decreased by 31%. The N, P, K and SOM balance in 1980–1981 was −15, −2, −29 and −24 kg ha −1 y −1, but in 1999 the N and P balance had changed to 24 kg ha −1 y −1 and 25 kg ha −1 y −1 as a result of the widespread use of N and P fertilizer. With the rapid increase in crop production and the sparse use of K fertilizer, the K balance continues to be negative. Straw production increased along with crop yields and there was a development of stock breeding. Together with better straw restitution practices, the SOM balance increased to a positive 613 kg ha −1 y −1. The analysis of farm household land-use and inputs indicated that there were significant differences in behaviour between almost totally off-farm households and other household types. These differences were in the choice of land-use type, the use of fertilizers and crop residue management. However, there was no significant relationship between socio-economic factors and fertilizer inputs. Current nutrient management is not optimal. Therefore, it is important to establish a better system for bottom-up knowledge collection and transfer of scientific information to farmers.

Diversity of carabids (Coleoptera, Carabidae) in the desalinized agricultural landscape of Quzhou county, China

Abstract Diversity and species composition of carabid beetles were investigated at Quzhou county in the North China Plain. The study area was originally affected by high salinity and desalinized in three stages in 1973, 1978 and 1982. At sites desalinized in 1982, carabids were sampled at field margins as well as inside fields to investigate the role of field margins as refuge habitats. Furthermore, samples were taken from field margins desalinized in 1973 and 1978, respectively, to explore long-term developments of carabid assemblages following desalinization. At margins, soil salinity, N contents and the number of plant species as well as the height of dominant plants were recorded and their correlation with the species composition of carabids explored. Overall carabid diversity at Quzhou was low compared to areas not affected by high salinity. Field margins yielded significantly higher numbers of both species and individuals, whereas assemblages within the field had a low diversity and a homogeneous species composition. Carabid diversity slightly increased in relation to decreased soil salt contents and time elapsed since desalinization. These results may be explained by field margins serving as refuge to many carabid species and by an overall low species pool of carabids in Quzhou due to former high salinity, current high levels of fertilizer and pesticide applications, and by a comparatively low colonization rate of carabids to the area. As different carabid species varied strongly in their reaction to environmental parameters, the preservation of a diverse set of habitats will best protect the current diversity of these beetles in the agricultural landscape of Quzhou.

Spatial variability of shallow groundwater level, electrical conductivity and nitrate concentration, and risk assessment of nitrate contamination in North China Plain

In recent years, nitrate (NO 3) contamination of groundwater has become a growing concern for people in rural areas in North China Plain (NCP) where groundwater is used as drinking water. The objective of this study was to evaluate groundwater resource level, to determine groundwater quality and to assess the risk of NO 3 pollution in groundwater in Quzhou County in the NCP. Ordinary Kriging (OK) method was used to analyze the spatial variability of shallow groundwater level, groundwater electrical conductivity (EC) and NO 3–N concentrations, and Indictor Kriging (IK) method was used to analyze the data with NO 3–N concentrations equal or greater than the groundwater NO 3 pollution threshold (20 mg L − 1). The results indicated that groundwater level averaged 9.81 m, a level 6 m lower than in 1990. The spatial correlation distances for groundwater level, EC and NO 3–N concentration were 21.93, 2.19 and 3.55 km, respectively. The contour map showed that shallow groundwater level areas extended from north to south across the County. Groundwater EC was above 3 dS m − 1 in the most part of the northern county. Groundwater NO 3 pollution (NO 3–N ≥ 20 mg L − 1) mainly occurred in the County Seat areas due to wastewater irrigation and excessive fertilizer leaching from agricultural fields. At Henantuang town, besides suburban of the County Seat, groundwater was also contaminated by NO 3 shown by the map generated using the IK method, which was not reflected in the map generated using the OK method. The map generated using the OK method could not reflect correctly the groundwater NO 3 pollution status. The IK method is useful to assess the risk of NO 3 pollution by giving the conditional probability of NO 3 concentration exceeding the threshold value. It is suggested that risk assessment of NO 3 pollution is useful for better managing groundwater resource, preventing soil salinization and minimizing NO 3 pollution in groundwater.

Carabid community and its fluctuation in farmland of salinity transforming area in the North China Plain: a case study in Quzhou County, Hebei Province

Carabid community and its fluctuation in farmland of salinity transforming area in the North China Plain: a case study in Quzhou County, Hebei Province

Monitoring and prognosis of regional water and salt

A system designed for monitoring and prognosis of regional water and salt (PWS), was developed to consist of a monitoring system, a group of models and an information system. PWS was developed and tested using a 253 km 2 portion of a monitored area of 487 km 2 established for observation of the surface water flow and quality, groundwater table and quality, soil water and salt regime in Quzhou county, Hebei Province. Predictive models for groundwater table location and quality were developed using basic principles of hydrodynamics and solved using finite element methods. A regional soil water model was developed based on a water balance approach, while a regional soil salinity models was developed by combining salt balance and expert identification methods. Submodels were integrated and applied seasonally, with satisfactory prediction results for the regional scale. The percentage of mean relative error for groundwater depth (m) and quality (g/l), water storage (mm) and salt storage (kg/m 2) in the 0–1 m soil layer were 14.8, 13.1, 14.1 and 25.4%, respectively. The information system component of PWS, defined as PWSIS, was composed of four parts: the subsystems database, vector management, a system model, and information output. The predicted outputs were expressed as either tables or contour maps of groundwater table or depth and quality, grade maps of soil water and salt storage or drought/waterlogging and salinity status. Some key problems, such as how to expand the point data to a plane and how to determine the boundary of each grade on the map, were solved using “the point-to-plane expanding algorithm” and GIS techniques of digitizing and overlaying the grid maps concerned.