氮、钾营养对烤烟品质的影响

通过田间小区试验,研究氮素和钾素对烤烟的品质化学成分的影响,结果表明:(1)总糖含量与烟叶成熟期土壤有效钾(K)含量呈显著的二次曲线相关性,成熟期土壤速效钾含量分界点为113.33mg/kg。(2)总烟碱含量与施氮量、烟叶含氮量(中期或成熟期)呈显著的相关性。(3)蛋白质含量与施氮量、烟叶含氮量(中期或成熟期)、烟叶含钾量(中期或成熟期)有一定的相关性。(4)施木克值与成熟期土壤速效钾含量呈显著的二次曲线相关性,成熟期土壤速效钾分界点为133.33mg/kg。(5)糖/碱比与烤烟生育前期施氮量和土壤碱解氮,与中后期土壤供钾和烟叶含钾量有一定的相关性。     

风沙土酿酒葡萄基地钾素资源特征和有效性研究

应用化学分析、吸附试验和生物诊断方法 ,系统研究了风沙土钾的丰缺状况及钾的有效性和利用率 .结果表明 :钾素含量受质地影响较大 ,缓效钾和速效钾则随质地变粘而增加 ,风沙土中的钾主要以矿物态钾形态存在 .被土壤固定的钾量也随着施钾量的增加上升 ,无论是速效钾含量或固定钾量均与施钾量呈显著水平正相关 .土壤钾素释放过程表明 ,土壤钾素的释放量不仅随土壤物理性粘粒的增加而增加 ,其释放容量和强度也逐渐增加。钾素对于植株鲜重、根长、根数、百粒重、结果枝率等均有明显的影响 ,且可使酿酒葡萄含糖量、酒精和出汁率增加 ,而使总酸度降低     

土壤矿物钾的释放及其在植物营养中的意义

本文对土壤钾的形态、矿物钾释放的影响因素及钾的固定、土壤含钾矿物与土壤供钾能力间关系、矿物钾的植物有效性进行了综述 ,表明土壤钾素从有效性的角度进行划分时 ,不能仅把速效性钾和1mol/L热硝酸提取的缓效性钾列为作物吸钾的主要来源 ,而忽视矿物钾的作用 .     

常规方法准确测定土壤有效钾素变化可能性的探讨

土壤中的有效钾状况通常用1 mol L-1中性醋酸铵提取的速效钾或1 mol L-1硝酸煮沸法提取的缓效钾量来表征。我国农田土壤中近些年来1 mol L-1中性醋酸铵提取的速效钾量呈普遍下降趋势。但土壤中的有效钾素的实际下降值,到目前为止还没有办法通过测土的方法进行准确评估。本文通过室内培养实验,人为改变土壤有效钾量,对常规土壤有效钾测定方法反应土壤有效钾素变化的效果进行了比较和评价。并对硝酸连续提取法准确测定土壤钾素变化的可能性进行了探讨。结果表明,几种提取方式中,以2 mol L-1冷硝酸超声波连续提取10次获得的外源钾变化的回收率最高,达75%~80%。其次是1 mol L-1硝酸100℃水浴法连续提取6次,测钾变化的累计回收率可达75%。如进一步增加提取次数,可能会有限地提高测钾变化的回收率,但随提取次数的增加,提取过程的可操作性和结果的稳定性将显著下降。因而用硝酸作为提取剂,即使是在高温、超声波等方式下,也很难准确测定强固钾能力土壤中有效钾的变化。能够准确测定土壤有效钾素变化的方法必须能将土壤中易发生变化的有效态钾全部提出,并尽量不提取土壤的原生矿物态钾,寻找这一方法将是未来土壤钾素测定工作中值得关注的问题。     

土壤含钾矿物的释钾研究进展

介绍土壤中含钾矿物的类型、结构特点、钾素含量与钾素释放的关系,区分了含钾矿物在土壤中的构成及分布特点,同时对国内外关于含钾矿物钾素释放规律的研究状况,钾素释放的作用机理、动力学特性,以及影响土壤含钾矿物钾素释放的因素做了综述。     

江淮丘陵区水稻钾、氮吸收特性与施钾效应研究

江淮地区水稻田间小区施钾效应试验结果表明,施钾能明显提高水稻产量,改善水稻生育性状,在氮磷肥充足时,钾肥的增产效果极其显著。水稻钾吸收量明显以秸秆吸钾量为主,约为籽粒吸钾量的5倍。N来自土壤的数量为120.30 kg hm-2;K2O来自土壤的数量为72.83kg hm-2。NPK全素施钾处理吸钾总量平均高出NP处理48.79%,籽粒和秸秆分别平均增加9.21%和56.8%;说明钾吸收量增加对秸秆产量贡献明显小于对籽粒产量的贡献。除最高施钾量和不施氮处理外,其余处理均出现不同程度钾素亏缺,说明在不施氮肥或氮肥不足的情况下,水稻对肥料钾的吸收量也相应减少。本试验钾肥(K2O)产投比以NPK2处理最高为2.54。综上所述,本地区同等肥力土壤,水稻钾肥推荐用量为120kg hm-2,根据土壤钾素平衡状况,水稻施钾量可适当增加。     

胡敏酸对钾素耗竭土壤固定外源钾的影响

通过室内恒湿和干湿交替培养试验,研究了钾素受到生物耗竭的耕地棕壤对外源钾的固定特征和施用胡敏酸后对土壤固钾作用的影响。结果表明,在保持土壤处于饱和含水量的恒湿条件下,施用外源钾(K)483. 7mgkg-1,经过一天培养土壤的固钾量和固钾率分别达到265. 8mgkg-1和54. 95%,第3天土壤的固钾量达到最大值,为268. 0mgkg-1,再继续恒湿培养,土壤的固钾量有小幅度降低的趋势。然而,恒湿培养4天以后再经过风干1天,土壤的固钾量呈大幅度升高,固钾率提高30. 31%;在恒湿和干湿交替条件下培养,施用胡敏酸对土壤固钾状况的影响不同:施用胡敏酸不仅没有表现出降低土壤固钾量的作用,反而在第3个干湿交替循环周期结束后提高了土壤的固钾量,但在恒湿条件下施用胡敏酸表现出降低土壤固钾量的作用,与对照之间的差异达到了显著水平。     

不同播期和环境条件对籽粒苋生长及富钾能力的影响

本文通过单因素试验 ,研究了不同环境因素 (温度、CO2 、水分、施肥等 )对籽粒苋生长发育及其富钾能力的影响。研究结果表明 :(1)籽粒苋在籽粒苋生长期内 ,以 7月 12日和 2 2日播种的籽粒苋 (日均温为 2 6.9～ 2 6.2℃ )生长最好 ,相应的植株含钾量也最高。 (2 )当大气中的二氧化碳浓度达到 10 0 0 μl/L时 ,籽粒苋的平均株高、单株平均鲜重和植株平均含钾量 (K2 O)较对照均有显著增加。 (3 )土壤水分条件以田间持水量对籽粒苋生长最为合适 ,低于田间持水量则影响植株对钾的吸收。 (4 )籽粒苋属于在多钾、缺钾土壤上 ,吸钾能力强的植物类型 ,施用钾肥有利于提高籽粒苋植株的含钾量     

外源钾对三种不同土壤钾转化影响的研究

采用盆栽试验,在黄棕壤,砖红壤,黑土三种土壤上种植烟草,研究了外源钾对土壤中钾转化的影响,结果表明:在黄棕壤,黑土上,0.0-0.8 g kg-1施肥范围内,随着施钾量的增加,土壤中速效钾和缓效钾的总增量、作物的含钾量均在增加,尤其是在0.8 g kg-1施肥水平时,二者超出了施肥的增加量,说明施钾促进了其它钾的释放;三种土壤中粘土矿物含量为:黑土>黄棕壤>砖红壤。     

长期定位施肥对棕壤钾素垂直分布状况的影响

通过26年棕壤肥料长期定位试验,研究化肥与有机肥长期定位施用对棕壤钾素垂直分布状况的影响,结果表明,从1979年到2004年不论施钾与否各处理0~20 cm土层土壤中各形态钾素含量均高于20~40 cm土层,长期施肥对土壤钾素的垂直移动影响不大。长期不施钾各处理0~20 cm和20~40 cm土层土壤中各形态钾均表现出明显的下降趋势;有机肥的长期施用能维持棕壤速效性钾的平衡,缓解非交换性钾的下降趋势,促进矿物钾的有效化进程。     

Relationships among soil fertility dynamics and remotely sensed measures across pasture chronosequences in Rondônia, Brazil

This study analyzed the relationships between soil fertility and remotely sensed measures over three pasture chronosequence sites in the state of Rondônia, in the western Brazilian Amazon region. Remotely sensed measures included shade, nonphotosynthetic vegetation (NPV), green vegetation (GV) and soil (derived from spectral mixture analysis), and the normalized difference vegetation index (NDVI). These were correlated against soil fertility parameters such as phosphorus, potassium, calcium, and base saturation. In temporal analysis, it was observed that NPV dominated the spectral responses of pasture canopies and tended to increase with pasture age as well. The increase of NPV appeared to be related to the decline of soil fertility, but soil texture variation also played a role. In the correlation analysis, soil P, known as the most limiting nutrient for pasture productivity, showed the highest correlation with remotely sensed measures, followed by soil K and base saturation. However, this result was not observed at the sites where nutrient availability was very low.     

快速检测果苹类蔬菜有机磷农药残留结果分析

本文对环江肯福环境移民安置示范区所采 88个表层土样及 4个剖面土样有机质 ,全氮 ,全磷 ,全钾 ,水解氮 ,速效磷 ,速效钾 ,pH等指标进行了测定。结果表明该区表层土壤有机质含量较高 ,土壤氮相对丰富 ,钾含量偏低 ,磷严重缺乏 ,pH偏酸性。土壤剖面发育完整 ,在土壤剖面中有机质、氮、速效磷、交换性钾主要聚集在 2 0cm的表层土壤中 ,全磷随深度的增加而降低 ,全钾和 pH值则随土壤深度增加而上升     

Analysis of TerraSAR-X data sensitivity to bare soil moisture, roughness, composition and soil crust

Soils play a key role in shaping the environment and in risk assessment. We characterized the soils of bare agricultural plots using TerraSAR-X (9.5 GHz) data acquired in 2009 and 2010. We analyzed the behavior of the TerraSAR-X signal for two configurations, HH-25° and HH-50°, with regard to several soil conditions: moisture content, surface roughness, soil composition and soil-surface structure (slaking crust).The TerraSAR-X signal was more sensitive to soil moisture at a low (25°) incidence angle than at a high incidence angle (50°). For high soil moisture (> 25%), the TerraSAR-X signal was more sensitive to soil roughness at a high incidence angle (50°) than at a low incidence angle (25°).The high spatial resolution of the TerraSAR-X data (1 m) enabled the soil composition and slaking crust to be analyzed at the within-plot scale based on the radar signal. The two loamy-soil categories that composed our training plots did not differ sufficiently in their percentages of sand and clay to be discriminated by the X-band radar signal.However, the spatial distribution of slaking crust could be detected when soil moisture variation is observed between soil crusted and soil without crust. Indeed, areas covered by slaking crust could have greater soil moisture and consequently a greater backscattering signal than soils without crust.     

Using remotely-sensed estimates of soil moisture to infer soil texture and hydraulic properties across a semi-arid watershed

Near-surface soil moisture is a critical component of land surface energy and water balance studies encompassing a wide range of disciplines. However, the processes of infiltration, runoff, and evapotranspiration in the vadose zone of the soil are not easy to quantify or predict because of the difficulty in accurately representing soil texture and hydraulic properties in land surface models. This study approaches the problem of parameterizing soil properties from a unique perspective based on components originally developed for operational estimation of soil moisture for mobility assessments. Estimates of near-surface soil moisture derived from passive (L-band) microwave remote sensing were acquired on six dates during the Monsoon '90 experiment in southeastern Arizona, and used to calibrate hydraulic properties in an offline land surface model and infer information on the soil conditions of the region. Specifically, a robust parameter estimation tool (PEST) was used to calibrate the Noah land surface model and run at very high spatial resolution across the Walnut Gulch Experimental Watershed. Errors in simulated versus observed soil moisture were minimized by adjusting the soil texture, which in turn controls the hydraulic properties through the use of pedotransfer functions. By estimating within a continuous range of widely applicable soil properties such as sand, silt, and clay percentages rather than applying rigid soil texture classes, lookup tables, or large parameter sets as in previous studies, the physical accuracy and consistency of the resulting soils could then be assessed.In addition, the sensitivity of this calibration method to the number and timing of microwave retrievals is determined in relation to the temporal patterns in precipitation and soil drying. The resultant soil properties were applied to an extended time period demonstrating the improvement in simulated soil moisture over that using default or county-level soil parameters. The methodology is also applied to an independent case at Walnut Gulch using a new soil moisture product from active (C-band) radar imagery with much lower spatial and temporal resolution. Overall, results demonstrate the potential to gain physically meaningful soil information using simple parameter estimation with few but appropriately timed remote sensing retrievals.     

Predicting water content using Gaussian model on soil spectra

This paper presents an approach to estimating soil moisture content through fitting an inverted Gaussian function to the continuum in soil spectra. The soil moisture Gaussian model (SMGM) estimates the water content by the declining reflectance in the near infrared (NIR) and shortwave infrared (SWIR) regions, 1.2-2.5 μm, due to the spreading of the fundamental water absorption at 2.8 μm. Convex hull boundary points were used to isolate the spectral continuum and to fit the inverted Gaussian function. The function extrapolates the continuum to the fundamental water absorption beyond the wavelength limits of common laboratory, field, and airborne instruments. Of the derived functional parameters, both amplitude and area on the shortwave side of the inverted Gaussian curve were highly correlated with soil water content.In this study, laboratory spectra, from 0.4 to 2.5 μm, were measured at sequential moisture levels in soil samples collected in Castilla-La Mancha, Spain and in California, USA. The Gaussian area was determined to be the best indicator of gravimetric water content with the initial modeling of 2592 spectra. The SMGM was validated with a separate set of 849 spectra. The model performance significantly improved for water contents below a critical level of 0.32 g water/g soil. Within this restricted range, the SMGM predicted water contents for all soils with a maximum of 0.027 RMSE for 1901 modeled spectra and 0.026 for 602 validation spectra. The water content estimates were improved slightly by stratifying the model and validation sets by the two locations, reducing the RMSE to 0.023 in Spain and 0.025 in California. Further stratifying the model spectra by landform and soil sodicity improved some predictions substantially, but less consistently. Stratifying the samples locally demonstrated that a priori knowledge of soil surfaces by landforms should be part of an image calibration strategy. The SMGM provides practical water content estimates and has a potential use in correcting the effects of soil moisture in hyperspectral images.     

土壤速效氮磷钾测定进展

本文就过去大约二十年来土壤速效氮磷钾的测定方法的进展做一综述。主要进展表现在硝态氮测定中水杨酸法、试纸法、氮测定中梅森瓶法、磷测定中孔雀绿法的应用及依据不同原理的流动分析方法等方面。     

Potential of ASAR/ENVISAT for the characterization of soil surface parameters over bare agricultural fields

The objective of this investigation is to analyze the sensitivity of ASAR (Advanced Synthetic Aperture Radar) data to soil surface parameters (surface roughness and soil moisture) over bare fields, at various polarizations (HH, HV, and VV) and incidence angles (20°-43°). The relationships between backscattering coefficients and soil parameters were examined by means of 16 ASAR images and several field campaigns. We have found that HH and HV polarizations are more sensitive than VV polarization to surface roughness. The results also show that the radar signal is more sensitive to surface roughness at high incidence angle (43°). However, the dynamics of the radar signal as a function of soil roughness are weak for root mean square (rms) surface heights between 0.5 cm and 3.56 cm (only 3 dB for HH polarization and 43° incidence angle). The estimation of soil moisture is optimal at low and medium incidence angles (20°-37°). The backscattering coefficient is more sensitive to volumetric soil moisture in HH polarization than in HV polarization. In fact, the results show that the depolarization ratio σ_HH⁰/σ_HV⁰ is weakly dependent on the roughness condition, whatever the radar incidence. On the other hand, we observe a linear relationship between the ratio σ_HH⁰/σ_HV⁰ and the soil moisture. The backscattering coefficient ratio between a low and a high incidence angle decreases with the rms surface height, and minimizes the effect of the soil moisture.