Nitrogen requirement of wide-spaced row crops in the presence of starter fertilizer

Abstract. There is a need to develop sustainable nitrogen (N) management systems that minimize environmental losses by maximizing the use efficiency of applied fertilizers, particularly with wide-row annual crops that are often poor at utilizing N. A key approach is to match nitrogen supply with crop demand using improved methods of fertilizer application and timing. One technique is to target liquid 'starter' fertilizers close to the seed, or around the roots of transplants, and to omit or reduce conventional broadcast applications. This paper examines the effects of starter fertilizer combined with various rates of seedbed and/or top-dressed N on the growth and yield of bulb onion ( Allium cepa L.), crisp lettuce ( Lactuca sativa L.), forage maize ( Zea mays Bonaf.) and sugarbeet ( Beta vulgaris L.). Starter fertilizer improved early growth and, in combination with reduced rates of supplementary N, gave yields comparable with higher rates of base N with each crop, except sugarbeet. The use of top-dressed N was as effective as base N in supplementing starter fertilizer and had the benefit that it allowed a top-dressing requirement to be estimated accurately using a simple nitrogen balance equation. These results, taken with earlier work, show that starter fertilizers offer clear opportunities for reducing N inputs, while maintaining yield and quality of these crops.     

Mechanisms of cuticular uptake of xenobiotics into living plants: evaluation of a logistic-kinetic penetration model

The objective of this study was to determine whether a logistic-kinetic penetration model could be applied to whole plant uptake. Uptake over 24 h was determined for three model compounds, applied in the presence and absence of surfactants, into the leaves of two plant species. Data for two time intervals were used in the model to predict uptake at intermediate intervals and compared with experimental results. Overall, the model fit the whole plant uptake data well. The study confirmed that an increase (or decrease) in active ingredient (ai) concentration or an increase in contact area will have no effect on the penetration rate factor, q, within the normal working concentration range. This enabled uptake to be predicted at different times for concentrations of ai not already studied, having first derived q for one concentration of the formulation of interest and having 24 h (maximum) uptake results for all formulations and concentrations of interest. The advantages of the models and equations described are that few variables are required, and they are simple to measure.     

Field tests of a linear gradient system for exposure of row crops to S02 and HF

An exposure system for exposing plants to gradients of gaseous air pollutants in the field was tested using sulfur dioxide SO₂ and hydrogen fluoride (HF). Well defined linear gradients of SO₂ concentration and HF flux were easily produced and were repeatable from exposure to exposure. The gradients were altered by wind speed and direction, but in tightly closed canopies, the alterations were minor. This system has many advantages: a graded series of exposures can be conducted in a small area, plants may be grown using accepted cultural practices, the cost of the apparatus is low, and more than one pollutant can be used, either concurrently or countercurrently. Disadvantages include the requirement for an intensive air monitoring network and an unnatural vertical pollutant profile in the canopy. The gradient system should be used as a supplement to open-top chambers, and not as a replacement for them.     

A simple cloud-based energy balance model to estimate dew

Two energy balance (EB) analyses, based on two different methods to estimate the downward long wave radiation, were used to model dew duration. Model I utilized cloud cover and cloud altitude to calculate sky temperatures whereas model II was based only on cloud cover to estimate sky apparent emissivity. The models were validated with hourly data from on-site weather station instrumentation for nights with and without occurrence of dew and cloud data from airport weather records, and compared with an empirical model, the CART/SLD model. The accuracy of predicting hourly dew occurrence with the EB models was greater than with the CART/SLD model. EB models I and II correctly predicted dew occurrence in 91 and 88% of hours, respectively, compared with 75% for the CART/SLD model. The majority of CART/SLD errors were due to late estimation of dew onset. It is proposed that an EB model can be used more effectively than the current CART/SLD model without a need for increased environmental observations in most localities.     

A simple model for phosphorus uptake kinetics of wheat seedlings

A simple model to compare and predict phosphorus (P) uptake behavior of plants may be useful to agronomists. A predictive equation based on Michaelis‐Menten kinetics was developed for this purpose. Kinetic parameters for use in the model were determined in an experiment using two cultivars of winter wheat grown for 21 days in 14 soil treatments, including seven P levels, each in fumigated and unfumigated soil. In another experiment, the same wheat cultivars were grown for 7, 14, or 21 days at one soil P level in both fumigated and unfiimigated soil. Using parameter values developed in the first experiment with multiple P levels and one time period, the model closely (R²=0.966, P<0.001) predicted P uptake in the second experiment with one P level over multiple time periods. The model could be a useful agronomic tool because of its simplicity and because no data need be collected from artificial growing conditions.     

A simple mixed model for trend analysis in wildlife populations

This article is concerned with a test for time trend in ecological surveys conducted at multiple sites across several years. The test is useful for studying long-term trends in wildlife populations. We propose a modification of a mixed model—recently suggested by Van Leeuwen, Murray, and Urquhart—which leads to invariance to translation in the origin of the time covariate. The modified model is easily fitted using standard software. Using simulation, the performance of the procedure for un balanced data is shown to be satisfactory. Data on the population density of Thomson’s gazelles (Gazella thomsoni Günther) are used as an example.     

Greenhouse crops: A review

Concerns over increasing production costs and decline in crop revenues have prompted the greenhouse industry to reevaluate criteria used to select crops for greenhouse systems. In the past, crop selection was primarily based on profitability and the strategy was to manipulate the environment to tailor it to the requirements of the crop. As greenhouses are currently evolving from high energy‐consuming to cost‐efficient systems, an emerging strategy is to manipulate the crop to meet the characteristics of the greenhouse environment. To ensure efficient crop manipulation, however, an in‐depth understanding is needed of the inherent ability of crops to adapt and render economic yields under suboptimal conditions. This paper reviews key features of selected greenhouse crops, assesses the impact of changing environment on crop performance, and examines potential avenues for crop manipulation.     

Stage of development affects penetration of calcium chloride into apple fruits

Using young fruits or fruit segments, rates of penetration of ⁴⁵CaCl₂ across apple fruit cuticles (Malus x domestica) were studied during fruit development in two consecutive years (’?Golden Delicious’ in 2000, ’?Cox Orange Pippin’ and ’?Boskoop’ in 2001). The aqueous donor solutions contained 5 g l^—1 CaCl₂ and 0.2 g l^—1 Glucopon 215 CSUP as wetter. A droplet (5 μl) was applied to each fruit disc and allowed to dry within 1 h. Amounts penetrated were estimated immediately after droplet drying (0 h) and after 6 and 24 h penetration, respectively. Temperature during penetration was 20 ?C and 100 % humidity was maintained throughout the experiment, once the droplet had dried. Rates of penetration were greatly affected by the stage of fruit development. With all varieties tested, highest rates were measured during the early stages of fruit development (before June drop) when approx. 100 % of the CaCl₂ applied penetrated within 24 h. After June drop, when trichomes had vanished and most stomata developed into lenticels, penetration rates decreased rapidly and large variability among the samples developed. This pattern was similar with all three varieties. The involvement of trichomes, stomata, and lenticels as preferential sites of penetration of calcium chloride across the apple fruit cuticles is discussed. Using a model calculation, it is argued that ten or more spray applications are needed to significantly increase calcium contents of apples. This has two causes: Only a small fraction of the spray liquid is intercepted by the fruits, and penetration can be rather slow.     

2FHF-4.56型宽行距作物基肥对行分层深施机设计与试验

针对当前西北干旱地区宽行距作物种植过程中施肥方式不科学,传统撒施肥料用量大、利用率低,该研究结合作物种植农艺特点,提出在作物行方向进行基肥分层深施措施,并研制了基肥对行分层深施机,对仿形单体进行设计,分析了仿形单体的运动学和力学特性,确定了仿形单体质量和仿形弹簧型号。同时研制了一种基于雄性蜣螂头部角状突起的仿生开沟铲,得到仿生开沟铲刃轮廓曲线拟合方程,确定了仿生开沟铲结构及工作参数。通过土槽试验优化了仿生开沟铲前刃角,得出前刃角最佳角度为65°,此时仿生铲相对传统铲的开沟阻力减小42.6%,对土壤的扰动明显减小。样机田间试验表明,分层施肥作业对行精度偏差平均值为2.7 cm,6组施肥铲浅层肥料深度平均值为12.44 cm,浅层施肥深度一致性变异系数为6.12%;深层肥料深度平均值为20.49 cm,深层施肥深度一致性变异系数为4.98%。施肥模式对比试验表明,对行分层施肥的植株长势更好,棉果枝数和单株铃数更多,根系发育更为良好,肥料减施25%,同时棉花平均每公顷增产8.9%,玉米平均每公顷增产8.6%,研究结果表明,对行分层深施肥具有较好的减肥增效作用,对推进棉花生产科学施肥具有重大价值和现实意义。     

两年期多熟制西瓜、花生主体栽培模式研究

利用开封沙区光热水肥资源,通过不同作物间的合理配置,提高资源利用效率。简介了早熟西瓜、无籽西瓜、蔬菜、花生等主要作物栽培模式的布局、介入方式及栽培技术,并对预期的经济效益进行了客观评估,该区传统的小麦花生轮作制2年生产投入0.867万元/hm^2,收入1.926万元/hm^2,净赢利1.059万元/hm^2,而采用该模式栽培2年生产投入1.374万元/hm^2,收入5.31万元/hm^2,净赢利3.936万元/hm^2,比传统模式经济效益提高271.7％。     

播种单体对地下压力测量方法和数学模型

对播种下压力实时测量是精准控制的基础,为了提高现有测量方法的通用性、准确性和稳定性,该研究在对播种下压力和播种深度关系模型分析基础上,采用轴销传感器播种下压力测量方法,进行了传感器力学分析和设计选型方法研究,并针对不同播深设定下单一测量模型误差大的问题,建立了融合播种深度因素的播种下压力测量修正模型,模型决定系数(R²)为0.991 6,均方根误差(root mean square error,RMSE)为28.88 N,验证试验表明,不同播深设定下,模型预测误差绝对值最大为44.13 N,最大相对预测误差为3.28%,提高了播种下压力测量模型通用性和准确性。播种下压力田间动态变化分析试验结果表明,在4～8km/h车速下,播种下压力振荡主频幅值随车速增加而减小,且免耕处理下主频幅值和功率谱密度(powerspectraldensity,PSD)峰值均大于旋耕处理。不同车速和耕作方式下,播种下压力振荡主频变化较小,主要集中在0～1 Hz,为后续信号稳定输出的滤波处理提供依据。该研究结果可为播种下压力的精准控制奠定基础。     

Agricultural zinc fluxes into soils and crops of central Iran at regional scale

Mass flux assessment can provide information that is essential for a sustainable management of elements in agricultural soils. In this article, we present an assessment of regional-scale averages of zinc (Zn) fluxes into agricultural soils and crops of central Iran for the period 1997–2011, using available databases such as regional agricultural statistics. The basic units of the balances were 15 townships of the provinces Qom, Isfahan and Fars. Averaged over the entire study region, the net Zn input into arable soil resulting from all fertilizer inputs – Zn removal with harvested crops was 1515 g ha^?1 yr^?1 across the entire region, with a range of 438–3009 g ha^?1 yr^?1 among townships. Estimated average Zn inputs with manure, mineral fertilizers, sewage sludge and compost were 1254, 531, 19 and 7 g ha^?1 yr^?1, respectively. The input-to-output ratio of these fluxes ranged from 1.8 to 12.9 among townships and averaged 6.1 for the entire study area. Considering that outputs other than with crop harvests are minor, Zn stocks are rapidly building up in the soils of the study region. Uncertainties in the manure and crop removal data were the main sources of estimation uncertainty in this study.     

基于改进ShuffleNet V2的轻量化农作物害虫识别模型

及时准确地识别害虫是有效防治的重要前提。针对现有基于卷积神经网络的害虫识别模型实时性差、识别率低、结构复杂不易部署等问题,提出基于改进ShuffleNet V2的农作物害虫识别模型。首先,在ShuffleNet V2中引入多尺度特征融合模块LMFF（Lightweight Multi-scale Feature Fusion）,加强模型对不同尺度害虫的特征提取能力;其次,在ECA（Efficient Channel Attention）注意力机制中增加并行路径,并通过可学习参数自适应更新不同路径的权重,提出AECA（Adaptive and Efficient Channel Attention）注意力机制,将AECA注意力机制嵌入到ShuffleNet V2中,提高模型的跨通道交互能力;然后,使用SiLU（Sigmoid Weighted Liner Unit）替换ReLU激活函数,增强模型的泛化能力;最后,通过调整输出通道数和核心模块的堆叠次数重新设计ShuffleNet V2的整体架构,降低模型的计算量和参数量,从而提出轻量化的农作物害虫识别模型SNPF（ShuffleNet for Pest Field）。试验结果表明,SNPF模型在自建害虫数据集上的平均识别准确率和F1分数为79.49%和78.54%,较改进前分别提高了4.00个百分点和3.09个百分点,而参数量和浮点运算量为3.74 M和0.48 G,较改进前分别下降了30.60%和18.60%。SNPF模型对单张害虫图像的平均推理时间为11.9 ms,与ResNet 50、GoogLeNet、EfficientNet B1等模型相比,SNPF模型的识别精度更高,并且识别时间分别减少了57.04%、50.21%和40.50%。该研究提出的SNPF模型能够较好地识别农作物害虫、并且具有识别速度快和轻量化的特点,可以为农作物害虫的防治提供帮助。     

基于可形变VGG-16模型的田间作物害虫检测方法

由于田间害虫种类多,大小、形态、姿态、颜色和位置变化多样,且田间害虫的周围环境比较复杂,使传统田间害虫检测方法的性能不高,而现有基于卷积神经网络的作物害虫检测方法采用固定的几何结构模块,不能有效应用于田间多变的害虫检测。该研究在VGG-16模型的基础上构建了一种可形变VGG-16模型（Deformable VGG-16,DVGG-16）,并应用于田间作物害虫检测。在DVGG-16模型中,引入可形变卷积后能够适应不同形状、状态和尺寸等几何形变的害虫图像,提高了对形变图像的特征表达能力,然后利用1个全局平均池化层替代VGG-16模型中的3个全连接层,以加快模型的训练。通过DVGG-16模型与VGG-16模型对比试验发现,DVGG-16模型提升了对田间害虫图像的形状、大小等几何形变的适应能力,在不改变图像空间分辨率的情况下,实现了对不规则田间害虫图像的特征提取,在实际田间害虫图像数据库上的检测准确率为91.14%。试验结果表明,DVGG-16模型提升了VGG-16模型对害虫多样性图像的特征表达能力,具有一定的图像形变适应能力,能够较准确地检测到田间形状变化多样的害虫,可为田间复杂环境下作物害虫检测系统提供技术支持。     

基于作物病害胁迫声发射的精准施药

作物病害胁迫声发射技术是当前植保信息化研究的重要内容。该文在分析作物病害胁迫的程度与声发射、环境因子之间的关系的基础上,设计了基于作物病害胁迫声发射机理的精准施药模糊控制模型,提出了适用于现场环境的精准施药自学习模糊算法。并利用MATLAB 对系统模型进行了仿真。结果表明,该模型可方便地控制系统的施药量变化,并能达到较满意的控制效果。该研究为作物精准施药的智能控制提供了一种新的控制思路及方法。     

Extended probability model for dry matter and nutrient accumulation by crops

Accumulation of dry matter and plant nutrients by crops over the growing season is important to resource management for agricultural production and for meeting environmental standards. It is becoming more common in agricultural and environmental management to use mathematical models to describe such systems. In this article, an extended probability model was used to characterize accumulation of dry matter and plant nutrient uptake, both of which exhibited sigmoid behavior with time. Data from field studies included corn (Zea mays L.), tobacco (Nicotiana tabacum), and soybean (Glycine max). For the case of corn, it was shown that maximum total plant dry matter at maturity agreed very closely for the three sites. The ratio of the paramters mean time to standard deviation of the distribution was very similar for dry matter and plant nutrient accumulations, with an average of 3.6 for Wooster, OH and 3.5 for Clayton, NC. The ratio was 4.3 for water reuse at Tallahassee, FL. For tobacco, the ratio was also very similar for dry matter and plant nitrogen (N) and potassium (K), and was 3.2 at Raleigh, NC. The ratio was 2.9 for leaf area of soybeans grown at Gainesville, FL. Data for dry matter and plant nutrient accumulation followed the sigmoid shape of the model rather well. The model also produced the “hump”; often observed in plant nutrient concentration during early stages of growth. The probability model suggests that for the crops studied, growth rate followed a gaussian distribution over the season, at least to first approximation.     

用动态图层融合与纹理-灰度梯度能量模型的果树行识别

为解决果园机器视觉导航中果树行识别易受果园复杂环境干扰的问题,该研究提出一种采用动态选取融合因子对彩色图像与深度图像进行图层融合并采用纹理-灰度梯度能量模型进行图像分割的果树行视觉识别算法。首先,通过搭建立体视觉系统获取果园彩色图像与对应的深度图像,并基于饱和度（S）通道图像的灰度值选取动态融合因子,实现对果园彩色图像与深度图像的图层融合;然后,分别计算融合图像的纹理特征图像与灰度梯度特征图像,并建立纹理-灰度梯度结合的能量模型,基于模型能量最小原则进行树干与背景的分割;最后,以树干与地面交点为果树行特征点进果树行直线拟合,完成果树行角度的识别。并对上述算法分别进行果树行识别试验与移动作业平台视觉对行导航试验。果树行识别试验结果表明,该研究算法果树行角度识别平均偏差为2.81°,与基于纹理、灰度梯度特征的果树行识别算法相比识别平均偏差分别降低2.37°和1.25°。移动作业平台视觉导航试验结果表明,在作业平台速度为0.6 m/s时,对行行驶最大偏差为12.2 cm,平均偏差为5.94 cm。该研究提出的视觉导航算法可以满足果园移动作业平台视觉对行导航需求,研究成果将为基于机器视觉的果园自动导航系统的研究与优化奠定基础。     

A simple dose-effect model of lake acidity in Québec (Canada)

A simple dose-effect model expressing the relationships between lake acidity, weighted mean annual sulfate concentration in wet deposition, Ca, Mg and true color (as an index of organic anion concentration) is presented. The agreement between observed and estimated pH for more than a 1000 lakes is high according to the Pearson coefficients of correlation (0.81 to 0.90) and the standard error of estimation (0.22 to 0.27 pH unit). Results obtained with this model show that an airborne sulfate target loading of 20 kg ha^?1 yr^?1 would be too high to adequately protect sensitive lake ecosystems. A target loading of 15 kg ha^?1 yr^?1 in wet deposition would be best suited for the protection of the greater portion of sensitive lakes. However, a target loading of 10 kg ha^?1 yr^?1 would be required to protect the most sensitive lake ecosystems.     

风送喷雾雾滴冠层穿透模型构建及应用

研究雾滴在树冠内的分布规律,对优化喷雾参数,提高喷雾效果有重要意义。该文以叶密度、出口风速和取样深度为试验变量,用试验法研究了树冠内雾滴穿透比例分布规律;试验结果表明:雾滴穿透比例随叶密度、取样深度的增加而减小,随喷雾机出口风速的增大而增大,其中取样深度对穿透比例影响最为显著。在此基础上,结合试验数据与统计学方法,构建了雾滴穿透比例二次指数数学模型,并确定了模型的待定系数,其模型精度R2高于0.95,经检验模型有一定的合理性和可靠性。基于此模型,计算了雾滴冠后飘移率,与实测值相比,平均相对误差为16.73%。进一步对雾滴冠后飘移率影响因素、双面喷雾机理、喷雾参数优化进行了分析,拓展了模型应用,对模型局限性和进一步优化模型的后续研究设想展开了说明。研究对风送喷雾雾滴分布规律研究具有一定的参考价值。