Soil failure associated with crack propagation for an agricultural tillage tool

Tillage loosens soil to depths of 75–150 mm (3–6 in.). As the soil is tilled, the failure path precedes the motion of the tillage tool. Previous studies have examined soil forces acting on a tine by predicting different soil failure patterns. This paper quantifies the rate and the path of the cracks associated with soil failure front. The propagation of the soil failure path by observing the temporal profile of the leading edge of the failure crack with respect to the tool motion was examined. Crack propagations were analysed for sweep operating at 4 km h⁻¹ speed, and two operating depths of 75 and 100 mm using high-speed digital videography. Higher depth of operation showed distinct phases for crack development and propagation. Short and intermittent soil crack propagation with lower propagation growth rates was observed for shallow depth of operation. Crack growth rate has been observed to have a sinusoidal relation with time.     

Use of caesium-137 data for validation of spatially distributed erosion models: the implications of tillage erosion

Validation of spatially distributed models using spatially distributed data represents a vital element in the development process; however, it is rarely undertaken. To a large extent, this reflects the problems associated with assembling erosion rate data, at appropriate temporal and spatial scales and with a suitable spatial resolution, for comparison with model results. The caesium-137 (¹³⁷Cs) technique would appear to offer considerable potential for meeting this need for data, at least for longer timescales. Nevertheless, initial attempts to use ¹³⁷Cs for model validation did not prove successful. This lack of success may be explained by the important role of tillage erosion in redistributing soil within agricultural fields and, therefore, contributing to the ¹³⁷Cs-derived soil redistribution rates. This paper examines the implications of tillage erosion for the use of ¹³⁷Cs in erosion model validation and presents an outline methodology for the use of ¹³⁷Cs in model validation. This methodology acknowledges and addresses the constraints imposed by the need to: (1) separate water and tillage erosion contributions to total soil redistribution as represented in ¹³⁷Cs derived rates; (2) account for lateral mixing of ¹³⁷Cs within fields as a result of tillage translocation; (3) simulate long-term water erosion rates using the model under evaluation if ¹³⁷Cs-derived water erosion rates are to be used in model validation. The methodology is dependent on accurate simulation of tillage erosion and tillage translocation. Therefore, as greater understanding of tillage erosion is obtained, the potential for the use of ¹³⁷Cs in water erosion model validation will increase. Caesium-137 measurements remain one of the few sources of spatially distributed erosion information and, therefore, their potential value should be exploited to the full.     

测量土壤含水率的频域方法改进

For many years a soil water content sensor with low cost, reliability and sufficient accuracy has been desirable. Thus, an improved measurement method based on the frequency domain （FD） principle for determining soil water content was considered. Unlike other measurement principles, a new measurable index, η, which was independent of the output impedance and the amplitude of the oscillator while relying on the electrical impedance of a multi-pin probe, was proposed. Moreover, a model for processing the impedance of the multi-pin soil probe was developed, and several important electrical parameters for establishing their operating ranges applicable to this probe were evaluated. In order to confirm the theoretical analysis, an experiment was conducted with a 4-pin probe. Using the developed model, the relationship between the proposed index η and soil volumetric water content was shown to be linear （R^2 = 0.9921）. Thus, as the measurable index, η seemed satisfactory.     

Slurry-application implement tine modification of soil hydraulic properties under different soil water content conditions for silt–clay loam soils

Tillage action associated with liquid slurry application systems/management practices can modify soil infiltration properties. The degree or nature of such modification will depend largely on the type of tillage implement used, and the soil conditions at time of tillage activity. The specific objective of this study is to evaluate differences in soil infiltration properties, as measured using pressure infiltrometers and Guelph permeameters, resulting from the immediate tine action of two commonly used slurry application tillage implements (Kongskilde Vibro-Flex (S-tine) and the AerWay SSD (rolling aerator-type tine)) over a variety of silt–clay loam soil water content conditions. The results indicated that there were consistent negative correlations between field saturated hydraulic conductivity and soil water content for all tine-disturbed and undisturbed soil treatments. For Kongskilde, field-saturated hydraulic conductivity was, on average, lower in tine-influenced furrow bottoms, relative to those measured in undisturbed conditions at similar depths for most water content conditions. Generally, the Kongskilde tine-action reduced macropore-based infiltration in the bottom of the furrow for most soil conditions, albeit, this effect was most pronounced at the higher soil water contents. For AerWay, the tine-disturbed soils had generally higher field saturated hydraulic conductivities than undisturbed soil treatments over the observed water content range. This effect was manifested to a greater degree at higher, relative to lower observed water contents.     

新疆农业产值的空间化表达与分析

为使以行政单元为单位的农业产值合理分配到地理单元上,以新疆各县农业用地面积及河流长度为自变量建立多元回归模型,采用面积权重的方法进行农业产值的空间化,实现新疆农业产值1 km?1 km格网模拟。对新疆2012年农业产值的分析表明:1)农业产值与耕地、林地、草地面积及河流长度密切相关。2)农业产值的多元回归模拟效果比较满意,预测值与实际值拟合度达到0.82。3)空间模拟表明,新疆农业产值整体水平较低,大部分地区不足5 000元·km-2;农业产值空间分布整体上呈现带状分布和片状分布相结合的特征,块状高值区主要分布在伊犁地区、塔城地区、天山北坡等,南疆地区普遍较低;带状农业产值高值区主要沿塔里木河上中游、孔雀河流域、叶尔羌河流域,伊犁河谷等分布。同时离道路越近,农业产值越高。4)河流与农业产值的空间分布关系说明水资源是干旱区农业发展的制约因素。5)影响模拟精度的因素有自然地理条件、人文因素、地域差异以及土地利用类型内部生产力差异等。与以往研究相比,本研究结合了干旱区的实际情况,重点突出了水资源对干旱区农业的贡献,这对今后研究具有一定的参考价值。     

农作区净灌溉需水量模拟及不确定性分析

净灌溉需水量是估算农业灌溉用水量的参考依据。该文以西北干旱内陆区石羊河流域上中下游的古浪县,凉州区,民勤县为研究对象,在分析农业净灌溉需水量宏观驱动力因子(1959-2005)的基础上,以关键因子作为输入项,区域农业净灌溉量为输出项,分别建立农业净灌溉需水量的多元线性回归模型、人工神经网络BP模型以及人工神经网络集成模型。并对不同模型的模拟效果进行比较;通过对时间序列的离散化蒙特卡洛(MC)设计,采用不确定性评价指数(d-factor)对3种模型模拟的不确定性进行分析。结果表明:与多元线性回归模型和神经网络BP模型相比,神经网络集成模型具有较高的模拟精度,并能合理地指示影响因素与净灌溉需水量的不确定性变化。     

An approach for draft prediction of combination tillage implements in sandy clay loam soil

A methodology to predict the draft requirements of combination tillage implements in any soil and operating conditions was developed. This methodology required the draft requirements of individual tillage implements in undisturbed soil condition and draft utilization ratio of the rear passive set of combination tillage implement, which is defined as the ratio of the drafts of the rear passive set operating in combination and individually. Laboratory experiments were conducted to measure the draft requirements of a reference tillage tool (single disk), three scale-model individual (moldboard plow, cultivator and disk gang) and two combination (moldboard plow with disk gang and cultivator with disk gang) tillage implements at different depths (5, 7.5 and 10 cm), speeds (1.2, 2.2, 3.2 and 4.2 km/h), wet bulk densities (in the range of 1.27–1.85 g/cm³) and cone index penetration resistance values (in the range of 445–1450 kPa) in soil bin filled with sandy clay loam soil. The average draft utilization ratio of the reference tillage tool obtained were analyzed by both orthogonal and multiple regression techniques to develop the regression equation considering soil properties, operating and tool parameters. The developed draft equation based on the above mentioned methodology was verified with the data obtained for the draft of scale-model and prototype combination tillage implements in the laboratory and field conditions, respectively. It was found that the developed equation predicted the draft of both combination tillage implements within an average absolute variation of 18.0 and 13.5%, respectively.     

利用冻胀能的农产品冷藏设备防结冰表面优化设计

农产品冷藏设备换热表面上的结冰堆积造成能源消耗,并影响了农产品的储藏品质。该文基于水结冰相变过程中的膨胀应力及不同冰点的溶液相变时差对结冰界面稳定性的影响现象,采用带有不同尺寸的凹坑且表面粘附双向拉伸聚丙烯薄膜(biaxially oriented polypropylene,BOPP)的6061铝合金为冻粘基体,探究凹坑直径、凹坑深度及凹坑内的不同质量分数的乙醇溶液对结冰附着强度的影响规律。对试验结果进行方差分析,建立了评价指标与各影响因素的数学回归模型,确定防结冰表面对结冰附着强度影响的主次顺序为凹坑深度、乙醇溶液质量分数、凹坑直径,结合响应面分析得到对结冰附着强降低率具有显著作用的工艺参数组合为:质量分数为8.05%的乙醇溶液和直径23.172 mm、深度4.349 mm的凹坑时,表面结冰附着强度的降低率达到了92.72%。利用水冻结成冰的过程中,释放的冻结膨胀能,破坏冰与材料之间接触界面的稳定性,降低了结冰附着强度,提高冷藏设备表面的主动除冰特性,为后期基于相变膨胀进行防\除冰方法的开发提供新思路及试验依据。     

现代农业园区系统结构与特点分析

现代农业园区的建设与发展已成为各地依靠科技进步调整农业产业结构，引导农民增收致富的有效途径。在实地考察和统计调查的基础上，分析现代农业园区的内涵、类型、系统结构、基本功能和特征，以促进现代农业园区的规范管理和健康发展。     

灰色模型与回归模型在农用地基准地价评估中的比较分析

农用地基准地价评估对于建立一套完整的农用地价格体系和顺利开展土地资产合理配置、土地整理等农村土地管理工作具有十分重要的意义。以辽宁省凌源市农用地为研究对象,以农用地定级成果为基础,建立农用地纯收益预测的灰色模型和回归模型,并运用两种模型结合收益还原法对农用地基准地价进行实证评估分析。结果表明：与回归模型相比,灰色模型更加有效的减小了不同自然地理条件和土地利用方式等因素所导致的不同年份纯收益变化对于农用地基准地价的影响,因此,灰色模型在农用地基准地价计算中具有更加突出的优势。     

An evaluation of controlled traffic with reduced tillage for irrigated cotton on a Vertisol

Where Vertisols are used for the mechanised production of irrigated cotton, the main pre-planting tillage options are ‘direct listing’ (a ‘controlled traffic-reduced tillage’ treatment with retained ridges), deep ripping (0.45 m deep) and chisel ploughing (0.25 m deep). An experiment was established, on a commercial scale under furrow irrigation, to compare the effects of these treatments on the physical properties (aeration, strength and water content) of a frequently irrigated Vertisol over 3 years. The growth and profitability of three cotton crops and one wheat crop were monitored during this period. The soil was well structured when the experiment commenced. Soil measurements showed that whilst the deep ripped treatment had lower resistance to penetration than the direct listed treatment, it provided a less favourable environment for root growth than the direct listed soil due to prolonged waterlogging after irrigation. An excess of water entered the ripped profile under the prevailing irrigation regime. All treatments had a sodic subsoil that was poorly drained. The chisel ploughed treatment generally behaved in a fashion that was intermediate between the direct listed and deep ripped treatments. The direct listed treatment resulted in higher cotton lint yields and lower land preparation costs, in comparison with deep ripping. Profitability increases were of the order of 11% when the lint value was 1.78 Australian dollars kg⁻¹. The deep ripped soil had more stored water than the other treatments throughout each irrigation cycle, but this potential advantage could not be expressed in terms of better crop yield and improved water use efficiency. A supplementary experiment is needed to evaluate the three tillage options where irrigation water is applied less frequently.     

农用喷头雾化粒径测试方法比较及分布函数拟合

农药雾滴粒径是影响农药在靶标上的沉积量和分布均匀性的主要因素,测试方法和仪器很多。该文使用激光粒子图像分析测试系统(particle/droplet image analysis,PDIA)、Sympatec HELOS Vario激光衍射粒度分析仪和Spraytec实时喷雾粒度分析仪3种常用的雾滴粒径分析仪对ST喷头进行雾滴粒径测试,结果表明3种仪器测得的雾滴体积中径(VMD,volume median diameter)绝对结果有差异,但是与已有的喷头雾滴细度界限值相比,该文所用的不同仪器测量结果对相同喷头的定级相同。鉴于此,选用Spraytec对Lechler公司生产的IDK、TR和ST 3种类型、2个国标流量代号(02和03)的6种型号喷头在喷雾扇面内的VMD进行测试,基于最小二乘法对测试结果进一步分析拟合,得到VMD在喷雾扇面内分布规律的函数形式。回归拟合函数以位置信息(喷雾高度,水平位置)为自变量、VMD为因变量,经回归效果检验可知各函数F统计量皆大于其F临界值(α=0.05),且相关指数都大于0.8,表明该文中所得的拟合函数可以较准确地描述雾滴粒径分布规律,并较精确地预测出扇面中非测试点的雾滴粒径。这些拟合函数为进一步研究喷杆各喷头喷雾扇面叠合后的雾滴粒径分布提供了基础。     

Predicting species occurrence using information-theoretic approaches and significance testing: An example of dormouse distribution in Cumbria, UK

Predicting the occurrence of species is an essential part of conservation biology. The range of techniques used to do this has increased in recent years. This has included wider use of information-theoretic approaches; particularly Akaike’s information criteria (AIC). AIC is often used with regression modelling when predicting species distribution. The traditional method of model selection in regression modelling, stepwise significance testing, is also still widely used. This paper compares the two approaches, using the occurrence of the dormouse (Muscardinus avellanarius) in Cumbria, UK as an example. The dormouse is a protected species whose abundance and range have declined nationally. Knowledge of its occurrence in Cumbria is required in order to increase measures for its conservation in the area. The paper uses the habitat features woodland size, altitude, soil type, tree species present, temperature and rainfall as potential predictors. As only presence data was available for dormice in Cumbria, pseudo-absences were generated to allow logistic regression modelling. The use of pseudo-absences was justified using a false record permutation test. Cross-validation allowed the ability of models to predict the data to be assessed. This was judged using ROC plots. The size of the wood, temperature and whether the soil was wet or dry were the best predictors of dormouse incidence in Cumbria. The two approaches produced different models; those from the information-theoretic approach had a better ability to fit the data. The information-theoretic approach also had the advantage of enabling model averaging and provided greater understanding of the system.     

Comparison of multivariate models and variable selection algorithms for rapid analysis of the chemical composition of field crops

This study evaluates the use of visible and near-infrared spectroscopy for rapid prediction of total carbon, total nitrogen, and total phosphorus concentrations in field crop samples. Two multivariate models (partial least squares regression and support vector machine regression) were compared. In addition, four spectral variable selection algorithms (competitive adaptive reweighted sampling, genetic algorithm, uninformative variable elimination, and variable importance for projection) were applied with support vector machine regression to determine the most accurate predictions. The results showed that support vector machine regression performed better than partial least squares regression for predicting the three chemical compositions. The combination of competitive adaptive reweighted sampling and support vector machine regression outperformed the other models for the predictions of total carbon and total nitrogen with high coefficients of determination of 0.91 and 0.90, respectively. For the determination of total phosphorus, the prediction accuracy of competitive adaptive reweighted sampling was comparable with the best result obtained from genetic algorithm with the coefficients of determination of 0.73 and 0.77, respectively. In conclusion, the support vector machine regression combined with competitive adaptive reweighted sampling has great potential to accurately determine the chemical composition of field crops using the visible and near-infrared spectroscopy.     

农产品产地加工与储藏工程技术分类

生鲜牛肉的含水率对其牛肉的加工、储藏、贸易与食用质量有重要影响,为了提高牛肉的经济价值和食用品质,需要研究牛肉含水率的无损检测技术。以取自不同超市的内蒙小黄牛和鲁西黄牛背最长肌为研究对象,有效样本86个,其中,75%的样本作为校正集,25%的样本作为验证集。采集牛肉新鲜切口处400～1170 nm波长范围内的漫反射光谱,用国标方法测定牛肉含水率。经过多元散射校正（multiplicative scatter correction, MSC）、变量标准化（standard normalized variate, SNV）和直接正交信号校正（direct orthogonal signal correction, DOSC）等方法预处理,在400～1170 nm范围内分别建立多元线性回归（multiple linear regression, MLR）模型、主成分回归（principal component Regression, PCR）模型和偏最小二乘回归（partial least squares regression, PLSR）模型。结果表明使用MSC预处理方法建立的模型预测效果最佳,其中用PLSR建模结果最好,校正集的相关系数和校正标准差分别是0.92和0.0069,验证集的相关系数和验证标准差分别是0.92和0.0047,外部验证的相关系数和验证标准差分别是0.85和0.0054。结果表明,可见/近红外光谱结合MSC预处理方法建立的PLSR模型,可以对牛肉含水率进行准确的快速无损评价,为生鲜牛肉含水率快速无损检测技术的应用提供理论参考。     

An improved model for forces on narrow soil cutting tines

The existing models for predicting forces on narrow soil cutting tines are based on different assumptions and give different results of calculated values. A new mathematical model for predicting forces on narrow soil cutting tines has been developed including a more realistic geometry of soil wedge, compared to previous mechanical models. The new model takes into account variability of the inclination angles of bottom failure surface in the side segments. Also included is the calculation of inertial forces for differential side segments based on the spatial position of the velocity triangle, which gives different absolute velocity for particular segments. The forward rupture distance depends on critical depth and the side rupture distance is given by a regression equation. Draft prediction is based on the complex set of forces, including the critical depth and two-dimensional failure zone together with inertial forces in the three-dimensional zone. The unknown values of the critical depth together with the rupture angle have been calculated by the minimisation of the total force acting on the tool. In order to check the extended model, experiments were performed in a soil bin and the results were compared with those calculated from the new model as well as from existing models. Absolute values of difference between calculated and observed values, related to measured values, taken as an error of different theoretical models, amounted to 11.7% for our model, and 17.1–34.9% for existing models. Statistical analysis of measured and calculated forces showed that for 58 degrees of freedom and a confidence level =0.05, the t-test value amounted to 0.795 and the significance level was 0.430. It means that the H0 hypothesis cannot be rejected and the developed model predicts the forces satisfactorily. The main result of our model is the possibility of more exact prediction of the resistance of narrow tines, by introducing a variability of the inclination angles of bottom failure surface in side segments of different deflections from the direction of a tine motion, which was not taken into consideration in the existing models.     

农业机械化发展关键影响因素的辨识与分析

农业机械化发展受到系统内外许多因素制约,确定农业机械化发展的关键影响因素成为研究的重要环节。利用DEMATEL方法,从各因素之间的相互影响关系出发,建立直接影响矩阵并求出综合影响矩阵,通过计算各因素的影响度、被影响度、中心度,考察因素综合影响关系,确定了农业机械化发展的关键影响因素并对其进行系统分析,提出了新时期农业机械化发展的建议。