基于Mask R-CNN的玉米苗与株芯检测方法

【目的】研究基于改进Mask R-CNN的玉米苗冠层分割算法,满足精准作业中对靶施肥的识别要求,提高化肥的使用效率,减少环境污染。【方法】采集田间玉米苗图片并增强数据,生成田间数据集;使用ResNeXt50/101-FPN作为特征提取网络对分割算法进行训练,并与原始ResNet50/101-FPN的训练精度结果作对比;采用不同光照强度及有伴生杂草的玉米苗图片对比验证冠层识别算法效果。【结果】在不同光照强度下,无伴生杂草的目标平均识别精度高于95.5%,分割精度达98.1%;在有伴生杂草与玉米苗有交叉重合情况下,目标平均识别精度高于94.7%,分割精度达97.9%。检测一帧图像的平均时间为0.11 s。【结论】Mask R-CNN的玉米苗及株芯检测算法有更高的准确率和分割精度,更能适应不同光照强度及有伴生杂草的苗草交叉重合情况的目标检测。     

Attributes affecting residual benefits of N<Subscript>2</Subscript>-fixing mungbean and groundnut cultivars

Legumes grown for grain may or may not contribute net N benefits to soil and succeeding crops. An experiment was conducted to assess N₂ fixation attributes of six mungbean cultivars and two groundnut cultivars (Tainan 9 and Non-nod), which determine their residual benefit to the subsequent maize. Nodule number and dry weight of mungbeans peaked early (at 45 days) and declined thereafter strongly. In groundnut nodulation peaked later and declined only by 50% towards the final harvest. The N₂-fixing groundnut produced higher total dry matter yield than mungbeans; however, mungbeans produced higher seed yields. Dry matter harvest index and nitrogen harvest index (NHI) were higher in mungbeans (average 0.44 and 0.69) than groundnut (0.23 and 0.47, respectively, in Tainan 9). The percentage of nitrogen derived from air (%Ndfa, ¹⁵N isotope dilution) ranged from 54% to 62% in mungbeans, similar to that of groundnut (64%). However, Tainan 9 fixed more N₂ (82 kg N ha^–1) than mungbeans (35–50 kg N ha^–1) and resulted in a positive soil net N balance (+22 kg N ha^–1) while negative values were found for Non-nod groundnut and mungbeans (–3 to –12 kg N ha^–1). Maize grown after groundnut Tainan 9 had the highest total dry weight and total N uptake. This was equivalent to maize grown in fallow plots, which received 60–90 kg N ha^–1, while the respective benefits after mungbeans were 30–60 kg N ha^–1. Maize yield was directly related to the amount of residue N returned. Thus, the combination of high N yield, residue quality, %Ndfa and low NHI proved most beneficial to soil fertility and the succeeding crop.     

氮肥施用对黄土高原中部雨养农业区土壤硝态氮分布与累积的影响

黄土高原中部雨养农业区春小麦氮肥试验表明,氮肥施用量对土壤硝态氮的移动深度没有影响,但显著影响土壤硝态氮的含量与累积。连续施氮3年后第3季春小麦收获时,0～200cm土壤剖面中累积大量的硝态氮,其中48.96%～81.38%的总累积量和60.49%～122%的当年净累积量存在于0～110cm土层中。在确定春小麦适宜施氮量时应考虑到0～110cm土层中残留硝态氮的累积量。不施氮和氮磷比例为1:1时,连续施氮三年后土壤硝态氮总累积量最低,数量几乎相等;第3季春小麦收获后较播种时,土壤硝态氮发生亏缺。施氮量为52.5 kgN hm-2时土壤硝态氮的三年总累积率和第3季春小麦当年的净累积率居各处理之首(146.55%和138.21%)。合理的氮磷配比可有效减少土壤硝态氮的累积,不合理的氮磷配比下,低施氮量也会造成土壤硝态氮的大量累积。     

小麦季磷肥施用对后作玉米的效果及土壤中无机磷形态转化的影响

在河北衡水潮土上进行田间试验,研究小麦/玉米轮作体系下,小麦季施用磷肥对玉米的后效及土壤中无机磷形态转化的影响。结果表明,与高施磷量(187.5 kg hm-2 P2O5)相比,小麦季磷肥施用量减少20%或40%,甚至当年不施磷,对后作玉米籽粒产量、生物量、植株吸磷量均无明显影响。从玉米苗期到成熟期,土壤中各形态无机磷下降幅度表现为Ca2-P最大,其次是Ca8-P,再次为Al-P。随着施磷量的减少,土壤Olsen-P、Ca2-P含量开始呈现下降趋势。与单施无机磷肥150.0 kg hm-2 P2O5相比,用有机肥猪粪磷替代其中20%无机磷肥,显著提高了土壤Olsen-P、Ca2-P和Ca8-P含量。本文结论认为在高肥力的华北地区小麦/玉米一个轮作周期中,小麦季减少磷肥用量,对后作玉米生长和产量尚未产生明显的影响。适当配施猪粪,减少无机磷肥,可以提高土壤中的Olsen-P和Ca2-P含量,较好地维持玉米季土壤中磷素肥力水平。     

松嫩平原羊草,虎尾草群落钠元素分布特征的比较研究

本文分析了松嫩平原羊草（Aneurolepidiumchinense）群落、虎尾草（Chlorisvirgata）群落钠元素在植物体及土壤中的分布特征及季节动态。结果表明，虎尾草体内钠含量明显高于羊草，两种植物地上部钠含量均高个地下部。两群落土壤水溶性、交换性钠含量均为春、秋季较高，夏季较低。表层土壤水溶性钠最高含量分别为5．09和7.61cmol·kg-1，交换性钠含量分别为7.33和13．21cmol·kg-1，垂直分布均为上高下低，虎尾草群落土壤各层的含量均高于羊草群落。羊草、虎尾草体内钠贮量变化均呈单峰型，与生物量呈极显著直线相关。     

地膜在土壤中的残留量对茄子生育和产量的影响

经３年连续试验表明：盆栽试验６～４８ｋｇ／６６７ｍ~２的地膜残留量对茄子株高、茎粗和叶面积基本无影响。对根系增长量的影响大于地上部，随着残留量的增加＂根冠比＂值有上升趋势但未达显著水平。对氮、磷、钾吸收的影响仅在Ｐ_２Ｏ_５上有差别。田间试验表明：残留量在３～９６ｋｇ／６６７ｍ~２范围内不论早期产量、总产量还是采收果数仅差０．９％～１．５％。     

Prediction and measurement of residual stresses in injection molded parts

Residual stresses were predicted by a flow analysis in the mold cavity and residual stress distribution in the injection molded product was measured. Flow field was analyzed by the hybrid FEM/FDM method, using the Hele Shaw approximation. The Modified Cross model was used to determine the dependence of the viscosity on the temperature and the shear rate. The specific volume of the polymer melt which varies with the pressure and temperature fields was calculated by the Tait’s state equation. Flow analysis results such as pressure, temperature, and the location of the liquid-solid interface were used as the input of the stress analysis. In order to calculate more accurate gap-wise temperature field, a coordinate transformation technique was used. The residual stress distribution in the gap-wise direction was predicted in two cases, the free quenching and the constrained quenching, under the assumption that the shrinkage of the injection molded product occurs within the mold cavity and that the solid polymer is elastic. Effects of the initial flow rate, packing pressure, and mold temperature on the residual stress distribution was discussed. Experimental results were also obtained by the layer removal method for molded polypropylene.     

复杂景观区土壤有机质预测模型的尺度效应

为研究复杂景观区土壤有机质预测模型的尺度效应,探讨不同空间尺度数据综合利用的问题,本文运用回归Kriging方法对河南省登封市土壤有机质进行预测,分析了不同空间尺度数据在建模过程中的作用和影响.结果表明:土壤有机质关于高程因子的趋势属于宏观趋势,以大尺度数据拟合该趋势值效果最优;小尺度数据不适合用于拟合土壤有机质的趋势值,但揭示了小尺度残差值的空间变异细节,增强了大尺度残差值的空间结构性,能够有效提高土壤有机质预测精度.因此,景观复杂区土壤有机质预测中,应基于大尺度数据模拟趋势值,大尺度数据和小尺度数据相结合拟合残差值的空间变异函数以预测残差值,最后趋势值加上残差值得到土壤有机质预测值.     

Quantitative analysis of ruminal methanogenic microbial populations in beef cattle divergent in phenotypic residual feed intake（RFI）offered contrasting diets

Background：Methane（CH_4） emissions in cattle are an undesirable end product of rumen methanogenic fermentative activity as they are associated not only with negative environmental impacts but also with reduced host feed efficiency.The aim of this study was to quantify total and specific rumen microbial methanogenic populations in beef cattle divergently selected for residual feed intake（RFI） while offered（i） a low energy high forage（HF） diet followed by（ii） a high energy low forage（LF） diet.Ruminal fluid was collected from 14 high（H）and 14 low（L） RFI animals across both dietary periods.Quantitative real time PCR（qRT-PCR） analysis was conducted to quantify the abundance of total and specific rumen methanogenic microbes.Spearman correlation analysis was used to investigate the association between the relative abundance of methanogens and animal performance,rumen fermentation variables and diet digestibility.Results：Abundance of methanogens,did not differ between RFI phenotypes.However,relative abundance of total and specific methanogen species was affected（P〈 0.05） by diet type,with greater abundance observed while animals were offered the LF compared to the HF diet.Conclusions：These findings suggest that differences in abundance of specific rumen methanogen species may not contribute to variation in CH_4 emissions between efficient and inefficient animals,however dietary manipulation can influence the abundance of total and specific methanogen species.     

柱花草属不同种质钾含量研究

对柱花草属8个种153份种质的钾素含量进行测定,结果表明:圭亚那柱花草钾平均含量为1.19％,其中品129显著高于其它种质;西卡柱花草钾平均含量为0.95％,品121和品122显著高于其它种质;灌木状柱花草钾平均含量为0.87％,品153显著高于其它种质;头状柱花草钾平均含量为1.16％;有钩柱花草钾平均含量为0.90％;马弓形柱花草钾平均含量为1.14％;大头柱花草钾含量为1.22％;矮柱花草钾含量为1.03％.不同种柱花草之间钾含量存在显著差异,大头柱花草、圭亚那柱花草、头状柱花草和马弓形柱花草钾含量显著高于矮柱花草、西卡柱花草、有钩柱花草和灌木状柱花草;矮柱花草钾含量显著高于灌木柱花草和有钩柱花草,西卡柱花草与有钩柱花草和灌木状柱花草之间钾含量差异不显著.