Underlying causes of yield spatial variability and potential for precision management in rice systems

Our current understanding of the mechanisms driving spatiotemporal yield variability in rice systems is insufficient for effective management at the sub-field scale. The overall objective of this study was to evaluate the potential of precision management for rice production. The spatiotemporal properties of multiyear yield monitor data from four rice fields, representing varying soil types and locations within the primary rice growing region in California, were quantified and characterized. The role of water management, land-leveling, and the spatial distribution of soil properties in driving yield heterogeneity was explored. Mean yield and coefficient of variation at the sampling points within each field ranged from 9.2 to 12.1 Mg ha^?1 and from 7.1 to 14.5 %, respectively. Using a k-means clustering and randomization method, temporally stable yield patterns were identified in three of the four fields. Redistribution of dissolved organic carbon, nitrogen, potassium and salts by lateral flood water movement was observed across all fields, but was only related to yield variability via exacerbating areas with high soil salinity. The effects of cold water temperature and land-leveling on yield variability were not observed. Soil electrical conductivity and/or plant available phosphorus were identified as the underlying causes of the within-field yield patterns using classification and regression trees. Our results demonstrate that while the high temporal yield variability in some rice fields does not permit precision management, in other fields exhibiting stable yield patterns with identifiable causes, precision management and modified water management may improve the profitability and resource-use efficiency of rice production systems.     

江汉平原典型小区域沟渠底泥氮磷含量及其空间变异

在湖北省江汉平原选择了一个由排灌渠自然围成的典型小区域,对其中农田排灌沟、斗渠和支渠0～10 cm底泥中不同形态氮、磷的含量以及分布特征进行了监测分析。结果表明,在36个沟渠底泥样中,全氮含量为0.7～2.9 g/kg,平均值为1.79 g/kg;可溶性总氮含量为17～166 mg/kg,无机态氮占比为88.1%～94.5%,无机氮又以铵态氮为主,其占比为无机氮的84.7%～90.4%。底泥全磷含量为0.4～1.3 g/kg,平均值为0.60 g/kg,其中,Olsen-磷含量为10.2～131.7 mg/kg,占全磷的2.6%～10.1%;水溶性磷含量占Olsen-磷的0.5%～3.7%。底泥中全氮、可溶性总氮和铵态氮,以及全磷、Olsen-磷和水溶性磷两两间在α=0.01水平均呈极显著正相关。底泥中各形态氮素的平均含量在靠近鱼塘的斗渠中呈现最高值,而磷素则在靠近居民生活区的支渠中呈现最高值。     

小尺度地区植被管理系统的构建——以东莞林科园为例

介绍了组件式GIS技术,在VB环境下嵌入MapObjects组件,开发植被信息管理系统,实现对与植被相关的土壤、水资源和基础地理等信息进行综合管理,实现通用的GIS功能,极大地提高小尺度地区植被管理的效率.     

小流域尺度防护林体系空间配置调整方法

该文在分析防护林体系空间配置的研究现状及存在问题的基础上,提出了防护林体系空间配置调整的要素和步骤,研究了小流域尺度防护林体系空间配置调整的主要思路和技术路线,构建了调整分期内的防护林体系空间配置调整的0--1整数规划模型。该模型选择一组需要进入调整分期的小班,以最大限度地发挥了防护林体系的防护效益为目标,经营成本和改进现有的空间配置为约束,生成可供决策者参考的调整方案。该研究充实了防护林体系空间配置的关于现有状态调整的理论研究,同时对于防护林管理部门的生产实践具有实际指导意义。     

Strategy of statistical model selection for precision farming on-farm experiments

Nitrogen (N) fertilization implies two important issues: N enhances grain yields and quality, but applied in excess, nitrous oxide emissions and nitrate leaching may be induced. To reduce environmental impacts, spatial N variability in agricultural fields can be adapted using crop sensors. In on-farm experiments, sensor-based variable rate N application is compared to uniform N application, which is common agricultural practice. On-farm experiments (OFE) provide special considerations as opposed to on-station trials. In OFE, the experimental units in farmer-managed fields are considerably larger, which raises the question if soil heterogeneity may be fully controlled by the experimental design (random treatment allocation and blocking). Grain yield monitoring systems are used increasingly in OFE and provide spatially correlated data. As a consequence, classical analysis of variance is not a valid option. An alternative four-step strategy of statistical model selection is presented, generalizing the assumptions of classical analysis of variance within the framework of linear mixed models. Soil heterogeneity is preliminary identified in step 1 and finalized in step 2 using covariate combinations (analysis of covariance). Yield data correlations are handled in step 3 using geo-statistical models. The last step estimates treatment effects and derives the statistical inference. Analyses of three OFE revealed that different covariate combinations and geo-statistical models were needed for each trial, which involves higher analytical efforts than for on-station trials. These efforts can be minimized by following the steps provided in this study to find a best model approximation. Nevertheless, model selection in precision farming OFE will always accompany some uncertainty.     

Making GIS a versatile analytical tool for research in precision farming

A field-level geographic information system (FIS) is being developed. The system provides special analytical functions useful for research in precision farming. Spatial data from various sources with different accuracies and resolutions are integrated. Remotely sensed data are used to assist field-data analysis. Region blocking and partitioning are obtained using logic and arithmetic queries and overlays. Spatial patterns are analyzed in spatial and frequency domains in both Cartesian and polar coordinate systems. A discrete model was developed to simulate the time lag inherent to a yield sensor on a combine harvester. Z-transformation was used to numerically remove the lagging effect.     

The role of GIS and GPS in precision farming

Examinations in connection with site-specific farming have been carried out by our institute since 1998. Precision farming is a way of agricultural production, which takes into account the in-field variability, a technology where the application-seeding, nutrient replacement, spraying, etc. has taken place to act on the local circumstances of a given field. The geographic information system (GIS) created by computing background makes possible to generate complex view about our fields and to make valid agrotechnological decisions. Our goal was to compare two systems for marking out further research tasks, because in some cases there have been misunderstandings among the researchers, and the information provided by given companies seems to be complicated for potential users (famers).     

Spatial patterns of soil microbial communities and implications for precision soil management at the field scale

Precision Agriculture - Understanding the spatial patterns of soil microbial communities and influencing factors is a prerequisite for soil health assessments and site-specific management to...     

实时实地精量施氮对烤烟不同部位叶片氮代谢的影响

为了探究基于SPAD仪精量施氮下烤烟不同部位叶片生育期氮代谢的变化规律,以“K326”为试材,设置基于SPAD仪的精量施氮模式(SPAD阈值为43)和农户惯用施氮模式两个处理,测定烤烟氮代谢的关键酶活性及含氮化合物含量.结果表明:基于SPAD仪精量施氮下,烤烟随着叶龄的增加,下、中和上部叶的全氮、可溶性蛋白、游离氨基酸、烟碱含量以及硝酸还原酶和谷氨酰胺合成酶活性分别在生育前期高于农户惯用施氮模式,但在接近成熟期时低于农户惯用施氮模式.说明SPAD仪的精量施氮模式在生育前期可提高烤烟大田生长氮代谢水平,有利于烤烟的生长发育,在生育后期适量降低,利于烤烟氮代谢适时向碳代谢过渡,促进落黄,提高烟叶内在化学品质.     

Active crop sensor to detect variability of nitrogen supply and biomass on sugarcane fields

Nitrogen management has been intensively studied on several crops and recently associated with variable rate on-the-go application based on crop sensors. Such studies are scarce for sugarcane and as a biofuel crop the energy input matters, seeking high positive energy balance production and low carbon emission on the whole production system. This article presents the procedure and shows the first results obtained using a nitrogen and biomass sensor (N-Sensor^™ ALS, Yara International ASA) to indicate the nitrogen application demands of commercial sugarcane fields. Eight commercial fields from one sugar mill in the state of S?o Paulo, Brazil, varying from 15 to 25 ha in size, were monitored. Conditions varied from sandy to heavy soils and the previous harvesting occurred in May and October 2009, including first, second, and third ratoon stages. Each field was scanned with the sensor three times during the season (at 0.2, 0.4, and 0.6 m stem height), followed by tissue sampling for biomass and nitrogen uptake at ten spots inside the area, guided by the different values shown by the sensor. The results showed a high correlation between sensor values and sugarcane biomass and nitrogen uptake, thereby supporting the potential use of this technology to develop algorithms to manage variable rate application of nitrogen for sugarcane.     

红壤丘陵区村级农田土壤养分的空间变异与制图

    以红壤丘陵区桃源县的王家垱村为例,通过GPS定位共取得522个耕层(0～20 cm)土壤样品.运用地理信息系统(GIS)和地统计学相结合的方法,分析了红壤丘陵区村级农田土壤养分的空间变异规律并进行了空间异质性的比较.结果表明:在各向同性下土壤有机碳的变程最大,为261 m;全氮次之,为208 m;全磷最小,为133 m.在村级尺度下有机碳和全氮的分形维数较低分别为1.874和1.886,全磷的分形维数较高为1.939.土壤有机碳和全氮在NE150°方向上呈现出明显的条带状梯度变化,并表现出了极为相似的空间分布格局.地形的梯度变化直接导致了景观格局相应的变化,进而形成了有机碳和全氮的空间格局从高值区到低值区的梯度变化.土壤全磷的空间斑块分布变得更加琐碎并呈现镶嵌的"星空"状分布,而没有表现出明显的条带状分布,在NE150°方向上也没有形成对称的分布格局,这与其自身不易移动的特性有关.从标准化变异函数的曲线可以看出,土壤养分空间结构的变化与分形维数的变化规律一致.     

Mapping the spatial and temporal stability of production in mixed farming systems: an index that integrates crop and pasture productivity to assist in the management of variability

Precision Agriculture - While precision agriculture (PA) technologies are widely used in cropping systems, these technologies have received less attention in mixed farming systems. Little is known...     

GIS-based spatial nitrogen management model for maize: short- and long-term marginal net return maximising nitrogen application rates

Precision Agriculture - Crop growth models including CERES-Maize and CROPGRO-Soybean have been used in the past to evaluate causes of spatial yield variability and to evaluate economic consequences...     

空间数据计算机屏幕矢量化精度研究

研究屏幕分辨率和放大倍数对AutoCAD的空间数据屏幕矢量化精度的影响。结果表明，屏幕缩放方法对矢量化精度有较大影响：放大倍数提高使点位中误差和极限误差均下降；图形放大则提高了定点精度，放大8～10倍以上可以将点位中误差控制在0．08mm以下，即在允许中误差0．2mm的40％以下；放大8～10倍是进行屏幕矢量化的最佳方式；屏幕分辨率对点位中误差的影响较小。认为地理信息系统空间数据的人工干预屏幕数字化定点精度应该受到重视。     

供氮水平对草莓氮素同化的影响

以水培丰香草莓为试材,对不同供氮水平条件下草莓的氮素同化作了研究。结果表明:随着水培液硝酸盐浓度的提高,NO3--N吸收速率和植株中NO3--N含量逐渐提高,但NO3--N浓度为7.5 mmol/L时硝酸还原酶(NR)活性最高。根系中NR活性显著低于叶片,叶片中NR活性最高可达390 nmolNO2/(g.h FW),根系仅为121.3 nmolNO2/(g.h FW),表明NR活性是制约草莓对硝酸盐响应的关键因素。     

The role of communication and co-operation in the adoption of precision farming

Research on Precision Farming (PF) relates the adoption of PF primarily to economic incentives as well as farm attributes, whereas social factors are commonly ignored. Therefore, the present study analyses the importance of farmers’ communication and co-operation strategies in the adoption of PF and their relation to farm attributes. Forty-nine qualitative interviews with stakeholders from the agricultural sector were conducted. The survey was based in Germany where most interviews took place and reflected with findings from the Czech Republic, Denmark and Greece. It is revealed that farms differ in their communication strategies depending on farm size. Joint investment in PF was only reported from some regions. It can be assumed that agricultural contractors will be major driving forces behind the adoption of PF over the next 10 years, especially in areas with smaller-sized farms. Agricultural data processing by service providers is seen as a common issue. Concerns regarding potential data misuse, over-regulation and software compatibility were raised.     

Developing a new Crop Circle active canopy sensor-based precision nitrogen management strategy for winter wheat in North China Plain

Active canopy sensor (ACS)—based precision nitrogen (N) management (PNM) is a promising strategy to improve crop N use efficiency (NUE). The GreenSeeker (GS) sensor with two fixed bands has been applied to improve winter wheat (Triticum aestivum L.) N management in North China Plain (NCP). The Crop Circle (CC) ACS-470 active sensor is user configurable with three wavebands. The objective of this study was to develop a CC ACS-470 sensor-based PNM strategy for winter wheat in NCP and compare it with GS sensor-based N management strategy, soil N_min test-based in-season N management strategy and conventional farmer’s practice. Four site-years of field N rate experiments were conducted from 2009 to 2013 to identify optimum CC vegetation indices for estimating early season winter wheat plant N uptake (PNU) and grain yield in Quzhou Experiment Station of China Agricultural University located in Hebei province of NCP. Another nine on-farm experiments were conducted at three different villages in Quzhou County in 2012/2013 to evaluate the performance of the developed N management strategy. The results indicated that the CC ACS-470 sensor could significantly improve estimation of early season PNU (R² = 0.78) and grain yield (R² = 0.62) of winter wheat over GS sensor (R² = 0.60 and 0.33, respectively). All three in-season N management strategies achieved similar grain yield as compared with farmer’s practice. The three PNM strategies all significantly reduced N application rates and increased N partial factor productivity (PFP) by an average of 61–67 %. It is concluded that the CC sensor can improve estimation of early season winter wheat PNU and grain yield as compared to the GS sensor, but the PNM strategies based on these two sensors perform equally well for improving winter wheat NUE in NCP. More studies are needed to further develop and evaluate these active sensor-based PNM strategies under more diverse on-farm conditions.     

中小企业供应链管理中的采购模式探讨

从中小企业视采购活动为成本中心的传统观念角度,分析了中小企业在竞争中处于劣势地位的原因,表现为企业观念落后,规模小、资金少,以致于从供应商处难以获得价格折扣。从中小企业采购活动的现状与目前已有的理论研究出发,提出解决途径是建立供应链采购模式,从纵向、横向两个方面论述改进方法。具体表现为搭建中小企业信息平台、实施联合采购、库存采购向订单采购转变、建立高效的供应商网络、交易关系向战略合作伙伴关系转变、风险防范。     

GPS定位对贵州喀斯特山区县级尺度土壤养分变异与空间格局研究--以务川县为例

在贵州选取有代表性的喀斯特区县,根据耕地土壤类型,利用GPS定位,采集300个土壤样品,开展喀斯特山区县级农田土壤养分变异与空间格局研究。结果表明:喀斯特山区县级尺度下,耕地总体有机质与氮、磷、钾养分含量变幅大(分别为3.81~82.65 g/kg、21.84~325.94 mg/kg、0.64~89.72 mg/kg、30.80~481.28 mg/kg),酸碱反应覆盖范围宽。两种类型耕地土壤养分差异明显,养分的高量水平与低量水平差异达显著水平。5种土壤养分中,有效磷含量分布呈现出较高的均质性,其余4种养分分布格局较为复杂,表现出较强的空间异质性特征。