Effects of vertical distribution of soil inorganic nitrogen on root growth and subsequent nitrogen uptake by field vegetable crops

Information is needed about root growth and N uptake of crops under different soil conditions to increase nitrogen use efficiency in horticultural production. The purpose of this study was to investigate if differences in vertical distribution of soil nitrogen (N_inorg) affected root growth and N uptake of a variety of horticultural crops. Two field experiments were performed each over 2 years with shallow or deep placement of soil N_inorg obtained by management of cover crops. Vegetable crops of leek, potato, Chinese cabbage, beetroot, summer squash and white cabbage reached root depths of 0.5, 0.7, 1.3, 1.9, 1.9 and more than 2.4 m, respectively, at harvest, and showed rates of root depth penetration from 0.2 to 1.5 mm day^?1 °C^?1. Shallow placement of soil N_inorg resulted in greater N uptake in the shallow‐rooted leek and potato. Deep placement of soil N_inorg resulted in greater rates of root depth penetration in the deep‐rooted Chinese cabbage, summer squash and white cabbage, which increased their depth by 0.2–0.4 m. The root frequency was decreased in shallow soil layers (white cabbage) and increased in deep soil layers (Chinese cabbage, summer squash and white cabbage). The influence of vertical distribution of soil N_inorg on root distribution and capacity for depletion of soil N_inorg was much less than the effect of inherent differences between species. Thus, knowledge about differences in root growth between species should be used when designing crop rotations with high N use efficiency.     

不同保护性耕作模式对冬小麦产量及土壤理化性状的影响

在大田条件下设4个处理:传统耕作(CT)、还田免耕(NT1)、整秆覆盖免耕(NT2)、还田深松免耕(NTS),研究了保护性耕作模式对冬小麦产量及土壤理化性状的影响。结果表明,小麦返青后,保护性耕作0~20 cm土壤容重低于传统处理,有机质含量、速效氮、速效钾和速效磷含量高于传统处理,但20~40 cm土壤养分各项指标除NTS表现与0~20 cm相同趋势外,NT1和NT2有减小趋势。保护性耕作最终提高了小麦穗粒数和千粒重,但降低了公顷穗数,比传统耕作减少240万/hm2,产量表现:NTS>CT>NT2>NT1。表明,土壤深松技术与秸秆还田相结合,能有效改善和提高土壤耕层和耕层以下土壤理化性状,发挥保护性耕作的增产潜力。     

Sediment flow behavior in agro-watersheds of the purple soil region in China under different storm types and spatial scales

Conservation tillage has proved to be an effective option to reduce erosion and particulate phosphorus (PP) losses from fields to watercourses. However, it usually leads to the higher losses of P in dissolved reactive (DRP) form if P accumulates into the uppermost soil layer.In this study we investigated the influence of CaCO₃-rich boardmill sludge (BMS, applied 7 years ago) on soil properties and percolate quality with soil samples as well as undisturbed soil columns taken from a long-term conservation-tilled clay field experiment. A short-term laboratory experiment was undertaken to evaluate whether newly added BMS (FS) can be used to improve the quality of percolate waters by reducing turbidity, PP and DRP.The hypothesis was that BMS reduces the risk of dissolved reactive phosphorus (DRP) leaching from conservation-tilled soil. BMS served as a liming agent and counteracted the no-till-induced acidification and accumulation of DRP in the surface soil layer. Surface soil pH was on average 0.3 units higher and soil Ca 500 mg kg⁻¹ higher in the BMS-treated plots than in the plots without BMS. The ability of BMS to enhance the availability of P for plants may prevent the surface accumulation of P in NT cultivation. At the same time, BMS-induced increase in Ca and EC of the surface soil suppress the diffuse double layer by reducing P desorption and leaching risk.In the laboratory experiment, FS reduced percolate turbidity by 80% and PP and DRP concentrations by 62% and 50%, respectively. FS probably improved stability of soil aggregates in the laboratory experiment, obviously through enhanced microbial activity. The covering effect and infiltration of water through the 0–5 cm soil layer seemed to be crucial factors in reducing P losses.BMS proved to be a promising material for the applications to the conservation-tilled fields. The effect of BMS on microbes and immobilization of nutrients, should, however, be studied further in fields under a wider diversity of conditions.     

深松浅旋对半干旱区退化紫花苜蓿人工草地改良效果研究

针对半干旱区退化紫花苜蓿人工草地饲草产量低、品质差问题,试验采用单因素随机区组设计,研究了不同深松浅旋程度：深松30 cm+浅旋5 cm（S₁Q₁）,深松30 cm+浅旋10 cm（S₁Q₂）,深松40 cm+浅旋5 cm（S₂Q₁）,深松40 cm+浅旋10 cm（S₂Q₂）,深松50 cm+浅旋5 cm（S₃Q₁）,深松50 cm+浅旋10 cm（S₃Q₂）以及不做处理（CK）对半干旱区退化紫花苜蓿草地土壤理化性质、生产性能及饲草品质的影响,并利用主成分分析（PCA）方法评价其改良效果。3年试验结果表明,深松浅旋能够不同程度降低紫花苜蓿草地土壤容重,增加土壤孔隙度,显著提高紫花苜蓿株高、分枝数和叶茎比。其中,S₂Q₁处理可降低0~40 cm土层土壤容重,S₂Q₂处理可提高紫花苜蓿分枝数、干草产量和粗蛋白含量,降低中性洗涤纤维、酸性洗涤纤维含量。经PCA综合分析,紫花苜蓿干草产量、叶茎比和粗蛋白贡献率较大,牧草相对饲喂价值和中性洗涤纤维贡献率较小;深松浅旋S₂Q₂处理能够获得较高的紫花苜蓿干草产量（6505.44 kg·hm^-2）和粗蛋白含量（20.74%）;综合性状排名由高到低依次为S₂Q₂,S₁Q₂,S₂Q₁,S₃Q₂,S₁Q₁,S₃Q₁,CK。由此说明,深松40 cm+浅旋10 cm对半干旱区退化紫花苜蓿草地改良效果最优。     

毛竹扩鞭成林新竹生长效果研究

对毛竹林周边扩鞭成林试验表明，不同扩鞭成林措施对扩展区域内新竹的数量和质量指标均有一定的影响，其中，不同措施对新竹株数、扩展范围的影响极显著，对退笋率、胸径的影响显著，对新竹高的影响不显著。施肥措施的新竹扩展范围大、退笋率低；深翻垦复措施的新竹株数多；复合措施的效果更好。随着坡位的降低，毛竹扩鞭成林的新竹数量指标和质量指标均呈变好的趋势。研究结果可为毛竹扩鞭成林提供参考。     

旋转编码器在回转体回转角度测量中的应用

针对回转体回转角度测量的实际情况，研制了新型回转体回转角度测量仪。该测量仪是以光、机、电为一体的旋转编码器作为传感器，测量回转体的回转角度。这种测量输出的信号为数字信号，克服了零漂、测量准确度低等缺点，提高了测量的准确度和可靠性。     

提高减速箱中橡胶油封-金属转轴密封性能的方法

减速箱橡胶油封漏油是一个尚未解决的一个棘手问题 .从摩擦学的角度分析 ,漏油的原因主要是油封与转轴接触部位不符合摩擦学的要求 ,造成此处的摩擦系数过高 ,油封磨损过快 .介绍了几种降低橡胶油封与转轴之间摩擦系数的方法     

Effects of strip wise tillage in combination with liming on chemical and physical properties of acidic spruce forest soils after clear cutting

We investigated the initial effects of strip wise soil loosening (0–35 cm depth) on soil chemical and physical parameters by using a deeply working rotary cultivator in combination with liming and mixing of the dolomite with the soil material of acidic forests. The investigations took place 8 months after the treatment. pH values and contents of exchangeable Ca and Mg increased significantly at the tilled depth whereas the content of exchangeable Al and easily soluble P decreased. The rate of mineralisation increased at this depth which was shown by a loss of Corg, Ntot and short-term loss of NO₃-N. The treatment led to a mobilisation of Mn at the tilled depth. However, the content of exchangeable Pb decreased due to an increased pH value. Below the tillage depth of 35 cm only partly significant changes of exchangeable Mn and NO₃-N were found. The total porosity and bulk density at 10–15 and 40–45 cm depths were not significantly different from those in the control plot, but the rate of infiltration increased significantly.     

基于彩色空间距离优化的秸秆覆盖率检测算法研究

秸秆覆盖率是保护性耕作重要的评价指标之一。针对田间秸秆形态各异、细碎秸秆难以识别的难题,基于机器视觉技术,提出了一种基于K-means和彩色空间距离灰度化方法相结合的田间秸秆覆盖率检测算法。采用彩色空间距离方法对秸秆图像进行预处理,基于K-means算法实现秸秆和土壤背景的分类识别,使用数学形态学腐蚀和膨胀方法对识别后的图像进行处理,降低细碎秸秆对覆盖率的影响,最后计算秸秆图像的覆盖率。2022年10月,通过田间试验对北京小汤山国家精准农业研究示范基地采集的220幅玉米秸秆图像进行了算法验证。试验结果表明,对低秸秆覆盖率(0～30%)图像,识别准确率达到90%;对中等秸秆覆盖率(30%～60%)图像,识别准确率达到88%;对高秸秆覆盖率(60%以上)图像,识别准确率达到86%;整体秸秆覆盖率分等定级准确度达到98.18%。本研究设计的基于K-means和彩色空间距离灰度化方法相结合的田间秸秆覆盖率检测算法为保护性耕作评价提供了快速检测方法和手段。     

深松对苏打盐碱化旱田改良与利用的影响

通过对不同深度深松对经过微咸水淋洗改良的中度和轻度苏打盐碱化旱田的土壤体积质量(容重)、含盐量和pH等理化性状及作物产量等相关性状的影响研究,结果表明:深松措施能够有效地降低经过淋洗改良的中度和轻度苏打盐碱化旱田的土壤体积质量、含盐量和pH,明显改善其土壤理化形状,有效地促进作物根系发育,显著提高作物产量。深松措施可作为苏打盐碱土改良与持续利用的有效耕作方式加以实施;深松方法以效果极为显著且具有可操作性的原垄垄沟深松40cm,中耕时垄沟深松30cm为佳。