基于土壤电导率时空变异性的管理分区技术研究

A coastal saline field of 10.5 ha was selected as the study site and 122 bulk electrical conductivity （ECb） measurements were performed thrice in situ in the topsoil （0-20 cm） across the field using a hand held device to assess the spatial variability and temporal stability of the distribution of soil electrical conductivity （EC）, to identify the management zones using cluster analysis based on the spatiotemporal variability of soil EC, and to evaluate the probable potential for sitespecific management in coastal regions with conventional statistics and geostatistical techniques. The results indicated high coefficients of variation for topsoil salinity over all the three samplings. The spatial structure of the salinity variability remained relatively stable with time. Kriged contour maps, drawn on the basis of spatial variance structure of the data, showed the spatial trend of the salinity distribution and revealed areas of consistently high or consistently low salinity, while a temporal stability map indicated stable and unstable regions. On the basis of the spatiotemporal characteristics, cluster analysis divided the site into three potential management zones, each with different characteristics that could have an impact on the way the field was managed. On the basis of the clearly defined management zones it was concluded that coastal saline land could be managed in a site-specific way.     

玉米植株冠层遥感技术揭示N缺乏的空间变异特征

To evaluate the temporal patterns in N deficiencies in corn and assess the ability of remote sensing to diagnose N deficiencies during the vegetative growth of corn, three field-scale experiments were conducted with various rates (56, 112, and 168 kg N ha-1), timing (early and late applications) and placement (injected into soil and dribbled on soil surface) of N fertilization in a split-plot design. Relationships between canopy reflectance during the growing season and yield data at the end of growing season were studied for different treatments. Results showed significant variation in both grain yields and canopy reflectance among the three cornfields. The N fertilization made in early June resulted in low canopy reflectance in early July, but the differences disappeared as the season progressed. The effect of N rates on canopy reflectance was not significant in early July but it gradually became detectable in mid-July and thereafter. The fertilizer placement had a significant effect on grain yields only in one field but not on canopy reflectance in all three fields. These observations suggest that the deficiency of N developed under field conditions is a dynamic phenomenon, which adds complexity for accurately defining “N deficiency” and effectively developing management strategies for in-season correction. Remote sensing throughout the season helps collect information about important interactions that have not been given enough attention in the past.     

Application of controlled-release urea increases maize N uptake, environmental benefits and economic returns via optimizing temporal and spatial distributions of soil mineral N

The creation of controlled-release urea (CRU) is a potent substitute for conventional fertilizers in order to preserve the availability of nitrogen (N) in soil, prevent environmental pollution, and move toward green agriculture. The main objectives of this study were to assess the impacts of CRU''s full application on maize production and to clarify the connection between the nutrient release pattern of CRU and maize nutrient uptake. In order to learn more about the effects of CRU application on maize yields, N uptake, mineral N (N_min) dynamics, N balance in soil-crop systems, and economic returns, a series of field experiments were carried out in 2018–2020 in Dalian City, Liaoning Province, China. There were 4 different treatments in the experiments: no N fertilizer input (control, CK); application of common urea at 210 kg ha^-1 (U), the ideal fertilization management level for the study site; application of polyurethane-coated urea at the same N input rate as U (PCU); and application of PCU at a 20% reduction in N input rate (0.8PCU). Our findings showed that using CRU (i.e., PCU and 0.8PCU) may considerably increase maize N absorption, maintain maize yields, and increase N use efficiency (NUE) compared to U. The grain yield showed considerable positive correlations with total N uptake in leaf in U and 0.8PCU, but negative correlations with that in PCU, indicating that PCU caused excessive maize absorption while 0.8PCU could achieve a better yield response to N supply. Besides, PCU was able to maintain N fertilizer in the soil profile 0–20 cm away from the fertilization point, and higher N_min content was observed in the 0–20 cm soil layer at various growth stages, particularly at the middle and late growing stages, optimizing the temporal and spatial distributions of N_min. Additionally, compared to that in U, the apparent N loss rate in PCU was reduced by 36.2%, and applying CRU (PCU and 0.8PCU) increased net profit by 8.5% to 15.2% with less labor and fertilization frequency. It was concluded that using CRU could be an effective N fertilizer management strategy to sustain maize production, improve NUE, and increase economic returns while minimizing environmental risks.     

地中海农业生态系统中土壤自生线虫种群多样性及动态研究

To determine the effect of agricultural management on the dynamics and functional diversity of soil nematode communities in a carrot field at Kibbutz Ramat Hakovesh, Israel, soil samples from 0--10 cm and 10--20 cm depths were collected during the growing season of carrot. Indices were used to compare and assess the response of soil free-living nematode communities to agricultural management. Eighteen nematode families and 20 genera were observed during the growing period, with Cephalobus, Rhabditidae, Aphelenchus, Tylenchus, and Dorylaimus being the dominant genera/families. During the planting, mid-season and post-harvest periods the total number of nematodes at both depths was significantly lower (P < 0.01) in the carrot treatment than in the control plots, while during the harvest period at both depths total nematodes and bacterivores were significantly higher in the treatment plots (P < 0.01). The values of the maturity index (MI) at both depths were found to be significantly lower in the treatment plots than in the control plots during the pre-planting period (P < 0.05). Overall, WI, MI and PPI were found to be more sensitive indicators than other ecological indices for assessing the response of nematode communities to agricultural management in a Mediterranean agroecosystem.     

耕作、残茬及施肥管理对土壤有机质动态变化影响的情景分析

Based on data from 10-year field experiments on residue/fertilizer management in the dryland farming region of northern China, Century model was used to simulate the site-specific ecosystem dynamics through adjustment of the model＇s parameters, and the applicability of the model to propose soil organic carbon （SOC） management temporally and spatially, in cases such as of tillage/residue/fertilization management options, was identified v/a scenario analysis.Results between simulations and actual measurements were in close agreement when appropriate applications of stover,manure and inorganic fertilizer were combined. Simulations of extreme C/N ratios with added organic materials tended to underestimate the measured effects. Scenarios of changed tillage methods, residue practices and fertilization options showed potential to maintain and enhance SOC in the long run, while increasing inorganic N slowed down the SOC turnover rate but did not create a net C sink without any organic C input. The Century model simulation showed a good relationship between annual C inputs to the soil and the rate of C sequestration in the top 20 cm layer and provided quantitative estimations of changes in parameters crucial for sustainable land use and management. Conservation tillage practices for sustainable land use should be integrated with residue management and appreciable organic and inorganic fertilizer application, adapted according to the local residue resource, soil fertility and production conditions. At least 50% residue return into the soil was needed annually for maintenance of SOC balance, and manure amendment was important for enhancement of SOC in small crop-livestock systems in which crop residue land application was limited.     

Field-scale spatial variability of soil calcium in a semi-arid region: Implications for soil erosion and site-specific management

Excess calcium(Ca) in soils of semi-arid and arid regions has negative effects on soil structure and chemical properties, which limits the crop root growth as well as the availability of soil water and nutrients. Quantifying the spatial variability of soil Ca contents may reveal factors influencing soil erosion and provide a basis for site-specific soil and crop management in semi-arid regions. This study sought to assess the spatial variability of soil Ca in relation to topography, hydraulic attributes, and soil types for precision soil and crop management in a 194-ha production field in the Southern High Plains of Texas,USA. Soils at four depth increments(0–2, 0–15, 15–30, and 30–60 cm) were sampled at 232 points in the spring of 2017. The Ca content of each sample was determined with a DP-6000 Delta Premium portable X-ray fluorescence(PXRF) spectrometer. Elevation data was obtained using a real-time kinematic GPS receiver with centimeter-level accuracy. A digital elevation model(DEM) was derived from the elevation data, and topographic and hydraulic attributes were generated from this DEM. A generalized least-squares model was then developed to assess the relationship between soil Ca contents of the four layers and the topographic and hydraulic attributes. Results showed that topographic attributes, especially slope and elevation, had a significant effect on soil Ca content at different depths(P 0.01). In addition, hydraulic attributes, especially flow length and sediment transport index(STI), had a significant effect on the spatial distribution of soil Ca. Spatial variability of soil Ca and its relationships with topographic and hydraulic attributes and soil types indicated that surface soil loss may occur due to water or wind erosion, especially on susceptible soils with high slopes. Therefore, this study suggests that the application of PXRF in assessing soil Ca content can potentially facilitate a new method for soil erosion evaluation in semi-arid lands. The results of this study provide valuable information for site-specific soil conservation and crop management.     

稻米和土壤微量元素的空间变异

Consumption of rice is the main source of micronutrients to human in Asia. A paddy field with unknown anthropogenic contamination in Deqing County, Zhejiang Province, China was selected to characterize the spatial variability and distribution of micronutrients in rice grain and soil. A total of 96 paired soil and rice grain samples were collected at harvest. The micronutrients in the soil samples were extracted by diethylenetriamine pentaacetic acid (DTPA). The mean micronutrient concentrations in rice grain were 3.85 μg Cu g-1, 11.6 μg Fe g-1, 39.7 μg Mn g-1, and 26.0 μg Zn g-1. The mean concentrations were 2.54 μg g-1 for DTPA-Cu, 133.5 μg g-1 for DTPA-Fe, 30.6 μg g-1 for DTPA-Mn, and 0.84 μg g-1 for DTPA-Zn. Semivariograms showed that measured micronutrients in rice grain were moderately dependent, with a range distance of about 110 m. The concentrations of the DTPA-extractable micronutrients all displayed strong spatial dependency, with a range distance of about 60 m. There was some resemblance of spatial structure between soil pH and the grain Cu, Fe, Mn, and Zn. By analogy, similar spatial variation was observed between soil organic matter (SOM) and DTPA-extractable micronutrients in the soil. Kriging estimated maps of the attributes showed the spatial distributions of the variables in the field, which is beneficial for better understanding the spatial variation of micronutrients and for potentially refining agricultural management practices at a field scale.     

中国农业生态系统氮磷钾平衡时空变异研究

Nitrogen, phosphorus, and potassium balances for agroecosystems in China from 1993 to 2001 were calculated at national and provincial levels using statistical data and related parameters, and their spatial and temporal variabilities were analyzed with GIS to estimate the potential impacts of nutrient N, P and K surpluses or deficits to soil, water and air. At the national scale, the N and P balances from 1993 to 2001 showed a surplus, with the nitrogen surplus remaining relatively stable from 1997-2001. Although during this period the P surplus pattern was similar to N, it had smaller values and kept increasing as the use of phosphate fertilizer increased year by year. However, K was deficient from 1993 to 2001 even though from 1999 to 2001 the K deficit decreased. The spatial analysis revealed higher N surpluses in the more developed southeastern provinces and lowest in the western and northern provinces where there was less chemical fertilizer input. The serious K deficit mainly occurred in Shanghai and Beijing municipalities, Jiangsu, Zhejiang and Hubei provinces, and Xinjiang autonomous regions. For the years 1992, 1996 and 2001, N surpluses and K deficits had significant positive spatial correlations with per capita gross domestic product (GDP), per capita gross industrial output value, and per capita net income of rural households. This showed that the level of economic development played an important role on nutrient balances in the agroecosystems.     

结合统计和数字地形数据的可视化方法预测土壤深度

Information about the spatial distribution of soil attributes is indispensable for many land resource management applications; however, the ability of soil maps to supply such information for modern modeling tools is questionable. The objectives of this study were to investigate the possibility of predicting soil depth using some terrain attributes derived from digital elevation models (DEMs) with geographic information systems (GIS) and to suggest an approach to predict other soil attributes. Soil depth was determined at 652 field observations over the Al-Muwaqqar Watershed (70 km²) in Jordan. Terrain attributes derived from 30-m resolution DEMs were utilized to predict soil depth. The results indicated that the use of multiple linear regression models within small watershed subdivisions enabled the prediction of soil depth with a difference of 50 cm for 77% of the field observations. The spatial distribution of the predicted soil depth was visually coincided and had good correlations with the spatial distribution of the classes amalgamating three terrain attributes, slope steepness, slope shape, and compound topographic index. These suggested that the modeling of soil-landscape relationships within small watershed subdivisions using the three terrain attributes was a promising approach to predict other soil attributes.     

小麦生产管理知识模型系统

A knowledge model with temporal and spatial characteristics for the quantitative design of a cultural pattern in wheat production, using systems analysis and dynamic modeling techniques, was developed for wheat management, as a decision-making tool in digital farming. The fundamental relationships and algorithms of wheat growth indices and management criteria to cultivars, ecological environments, and production levels were derived from the existing literature and research data to establish a knowledge model system for quantitative wheat management using Visual C^＋＋. The system designed a cultural management plan for general management guidelines and crop regulation indices for timecourse control criteria during the wheat-growing period. The cultural management plan module included submodels to determine target grain yield and quality, cultivar choice, sowing date, population density, sowing rate, fertilization strategy, and water management, whereas the crop regulation indices module included submodels for suitable development stages, dynamic growth indices, source-sink indices, and nutrient indices. Ewluation of the knowledge model by design studies on the basis of data sets of different eco-sites, cultiwrs, and soil types indicated a favorable performance of the model system in recommending growth indices and management criteria under diverse conditions. Practical application of the knowledge model system in comparative field experiments produced yield gains of 2.4% to 16.5%. Thus, the presented knowledge model system overcame some of the difficulties of the traditional wheat management patterns and expert systems, and laid a foundation for facilitating the digitization of wheat management.     

牧草干物质产量的时空变异及其制图研究

以英国Hillsborough农业研究所附近的一块7.9 hm²的牧草田为研究区，采用地统计方法研究分析连续3年的牧草干物质产量在3个收割季节的空间变异，并研究了第一、二季其空间分布的变异在时间上的稳定性，在此基础上制作了牧草干物质产量分级管理地图。第三季由于天气原因未能收集到2001年的数据而未做时间稳定性研究。结果表明，牧草产量在第一季的空间变异最小且在时间上基本稳定，因此，在第一季，根据牧草干物质产量分级管理地图对该牧草地进行精确管理，特别是精确肥料管理，是可行的；而在第二季，牧草产量的空间分布非常零散，且在时间上表现为不稳定，目前还很难对该牧草地进行精确管理。     

牧草氮素产量的时空变异研究

以英国Hillsborough农业研究所附近的一块7.9hm2的牧草田为研究区,采用地统计方法研究分析连续3年的牧草氮素产量在3个收割季节的空间变异,并研究了第一、二季其空间分布的变异在时间上的稳定性。结果表明,试验区牧草氮素产量在单个田块间存在较大的空间变异,而且这种变异在不同的生长季呈现有规律变化,变量施肥是必要的;牧草氮素产量的空间分布与地形有很大的关系,可以根据地形将试验区分片管理。     

Temporal changes in the spatial distributions of some soil properties on a temperate grassland site

Abstract. Precision Agriculture seeks to match resource application and agronomic practice with soil and crop requirements as they vary in both space and time. Therefore, an understanding of both the temporal and the spatial components of variability is essential before decisions can be made about the feasibility of site-specific management. In the present study, the spatial and the temporal components of variability in certain key soil properties of a grassland field were evaluated to assess the likely feasibility of adopting a site-specific approach to grassland management. A 7.9 ha grassland field was selected for the study and soil samples were taken three times at regular 25 m intervals across the field over a two year period, and chemically analysed. Classical and geostatistical procedures were used to evaluate the spatial variability and the temporal stability of soil property distributions. Soil extractable P and K had the greatest within-field variability and soil pH the least. Soil K distributions were also highly unstable over time and it was concluded that the optimal risk aversion strategy would be to apply uniform dressings of this nutrient to the entire field. In contrast, soil pH, P, Mg and sulphate distributions were not only temporally stable, but were also spatially correlated over reasonably large ranges. It was concluded that these properties might be managed in a site-specific way based on the results of periodic soil testing in three clearly defined management sub-units within the field. Over the two year period, C and N accumulated in the soil at surprisingly high rates on certain parts of the field but not in others.     

基于GIS的土壤盐分时空变异及分区管理研究--以浙江省上虞市海涂围垦区为例

采用传统统计学和地统计相结合的方法，在GIS支持下研究了浙江省上虞市海涂围垦区一块面积为10．5hm^2的棉田在3个不同耕作时期上盐分的时空变异性，在此基础上进行了该棉田的精确分区管理研究。结果表明，海涂围垦区盐碱地土壤表层盐分具有较高的变异性，盐分变异的空问结构在时间上保持了相对稳定。盐分分布的空问趋势图显示该棉田东部地区的盐分含量较高，而北部和西部地区盐分含量相对较低。时间稳定性图显示了盐分在时间上的稳定和不稳定区域。将空间趋势图和时间稳定性图叠加所产生的管理分区图，显示了4个潜在的管理子区。最后棉花产量数据被用来验证所划分的管理子区的适用性。研究表明，根据划分的管理分区，可以对海涂围垦区土壤盐分进行精确的田问管理。     

Contributions from carbon and nitrogen in roots to closing the yield gap between conventional and organic cropping systems

This study investigates the effect of different crop rotation systems on carbon (C) and nitrogen (N) in root biomass as well as on soil organic carbon (SOC ). Soils under spring barley and spring barley/pea mixture were sampled both in organic and conventional crop rotations. The amounts of root biomass and SOC in fine (250–253 μ m), medium (425–250 μ m) and coarse (>425 μ m) soil particulate organic matter (POM ) were determined. Grain dry matter (DM ) and the amount of N in harvested grain were also quantified. Organic systems with varying use of manure and catch crops had lower spring barley grain DM yield compared to those in conventional systems, whereas barley/pea showed no differences. The largest benefits were observed for grain N yields and grain DM yields for spring barley, where grain N yield was positively correlated with root N. The inclusion of catch crops in organic rotations resulted in higher root N and SOC (g C/m²) in fine POM in soils under barley/pea. Our results suggest that manure application and inclusion of catch crops improve crop N supply and reduce the yield gap between conventional and organic rotations. The observed positive correlation between root N and grain N imply that management practices aimed at increasing grain N could also increase root N and thus enhance N supply for subsequent crops.     

乡镇尺度烟田土壤有机质时空变异性研究——以襄城县紫云镇为例

为探明田块尺度烟田土壤有机质(SOM)的时空变异特征,本研究采用地统计学和地理信息系统(GIS)相结合的方法,分析了豫中襄城县紫云镇某个约4 hm2的烟田2013年和2014年4月、7月、10月合计6个时期耕层SOM的时空变异特征。结果表明:该田块各个时期SOM的变异系数差异较小;每年不同时期SOM的平均含量表现为先降后升的变化趋势,7月的含量显著低于4月和10月。各时期SOM空间最大相关距离范围在26~203 m;2013年4月和2014年7月SOM具有中等的空间自相关性,其他时期均表现为强烈的空间自相关性。研究田块SOM的稳定高值区主要分布在西部,稳定低值区主要集中在中部;SOM的时间稳定和较稳定级别区域面积很广,占总面积的90.89%。在时空变异研究的基础上,辅以时间稳定性分析能够更好地量化烟田SOM的时空分布,可为研究区更为精确、高效的施肥和田间管理提供决策依据。     

基于电磁感应仪的黄河三角洲地区土壤盐分时空变异特征

针对黄河下游三角洲土壤盐渍化的空间复杂性与发生反复性,运用磁感式大地电导率仪EM38及其移动测定系统,结合GIS与地统计学方法,对该地区典型地块两个关键季节土壤盐分的时空变异特征进行了分析.结果表明,土壤表观电导率与盐分呈极显著相关性;各时段土壤盐分都表现出多层次空间结构的复合尺度效应,且短程变异构成了土壤盐分空间异质性的最主要部分;土地利用方式差异使得秋季时段土壤盐分呈弱各向异性,地形因素导致春季时段土壤盐分各向异性比在全步长域波动,但在整个研究尺度上仍为各向同性.空间分析表明,结构性因素主导了土壤盐分空间分布格局,随机性因素是加快该分布格局形成的重要因素;春季时段研究区总体表现出积盐趋势,且盐分变动幅度主要集中在10.0g/kg范围内.电磁感应仪与GIS的结合运用为不同尺度土壤调查与质量评价提供了新的途径,并为农业水土资源的决策管理提供指导.     

Home field advantage of cattle manure decomposition affects the apparent nitrogen recovery in production grasslands

Based on evidence from forest ecosystems that litter decomposition is highest in its home habitat, the so-called home field advantage (HFA), we tested whether HFA also occurs in production grasslands, to which solid cattle manure (SCM) was applied. Two dairy farms were selected which differed in type of home-produced SCM (stacked or composted) and soil type (sand or peat). Disappearance patterns of manure dry matter (DM) and nitrogen (N) were monitored from litterbags (4 mm mesh size) during the grass growing season. At the same time, apparent herbage N recovery (ANR) of SCM, applied at two rates (200 and 400 kg N ha⁻¹ yr⁻¹), was measured. On average, manure DM and N disappearances on the home farms were 20 and 14% greater, respectively, than on away farms. Differences in ANR were also very pronounced (on average 14 and 53% higher at home than away for the two respective application rates). The two SCM types were also studied on two neighbouring dairy farms (one on sand and one on peat soil) where no SCM had been applied for many years. Here, manure DM and N disappearances from the litterbags were much lower (P < 0.01). This experiment provides strong evidence for a home field advantage in production grasslands differing in fertilization history, showing that site-specific manure management affects the soil–plant interactions regulating plant N-availability. These findings have to be taken into account when changing fertilization regimes in production grasslands. This is the first report to quantify a HFA from an agricultural ecosystem. HFA values we report here have not been established in any ecosystem thus far.