Determination of soil salinity based on WET measurements using the concept of salinity index

We evaluated the Malicki and Walczak model (MW) and its appropriately modification (MMW) in the prediction of the electrical conductivity of the soil solution (σ_p), utilizing the WET dielectric sensor. In the MMW approach, the prediction of σ_p requires determination of the WET‐based salinity index (X_s) and clay and sand contents of the soil. MMW appears to be more effective than MW in all cases except for the cases of finer soils when σ_p > 3 dS m^?1.     

Performance of the theta probe ML2 in the presence of nonuniform soil water profiles

An attempt is made to investigate the soil permittivity regime which is predicted by ML2 theta probe in cases where a nonuniform soil moisture profile prevails. Our investigation was performed in laboratory columns, under temperature-controlled conditions for a number of different porous media. Five distinct cases, where the moisture regime could be established in a predesigned manner were tested. These are: (a) Air over a water or ethanol layer of changing thickness. (b) Air over a saturated porous material of changing thickness and the same in the reverse order. (c) Dry porous material over the same but saturated porous material of changing thickness and vice versa. (d) Gradual wetting from the top surface of initially dry soils. (e) Initially saturated vertical soil profiles, left to gradually dry by evaporation from both open surfaces (top and bottom).From our experimental investigations it is shown that the bulk dielectric constant predicted by the ML2 probe in nonuniformly wet profiles irrespective of their layer thickness is closely described by the arithmetic averaging scheme. This fact makes the water content predictions from the manufacturer calibration equations for these cases, seriously overestimated. A comparison of the actual water contents with those predicted with the calibration equations of Robinson et al. [Robinson, D.A., Jones, S.B., Blonquist, J.M., Friedman, S.P., 2005. A physical derived water content/permittivity calibration model for coarse–textured layered soils. Soil Sci. Soc. Am. J. 69 (5), 1372–1377] gives very satisfactory results.     

连续负压供水对辣椒种植土壤速效养分及酶活性的影响

为探索负压供水对辣椒土壤速效养分和土壤生物活性的影响,在温室大棚内采用盆栽试验,试验利用负压供水装置,设置-5、-10、-15 k Pa以及人工浇水(CK)4个处理,测定了辣椒各生育期土壤碱解氮、有效磷、速效钾含量,以及土壤过氧化氢酶、脲酶、蔗糖酶和磷酸酶活性指标。结果表明,试验中供水压力控制在-5~-15 k Pa时,辣椒各生育期土壤碱解氮、有效磷、速效钾含量,4种土壤酶活性均显著高于CK,其中,-5k Pa处理对土壤养分及酶活性的提高显著。土壤速效养分含量与酶活性相关分析表明,在负压供水条件下,土壤4种酶活性之间,土壤碱解氮、有效磷、速效钾含量之间,土壤酶与土壤速效养分之间均呈极显著正相关;主成分分析表明,第一主成分对土壤养分供应能力的贡献大,第二主成分反映出过氧化氢酶及蔗糖酶不断分解减少时,有效磷及速效钾权重减少。综上所述,采用负压供水方式,能促进土壤酶活性提高,有利于辣椒土壤养分的转化,当供水压力稳定在-5 k Pa时,提高辣椒土壤养分效果更为显著。     

在盐水浇灌条件下堆肥对土壤性质、小麦生长以及作物营养的影响

A greenhouse experiment was conducted to test and compare the suitability of saline compost and saline irrigation water for nutrient status amendment of a slightly productive sandy clay loam soil,to study the macronutrient utilization and dry matter production of wheat(Triticum aestivum c.v.Gemmiza 7) grown in a modified soil environment and to determine the effects of compost and saline irrigation water on soil productivity.The sandy clay loam soil was treated with compost of five rates(0,24,36,48,and 60 m 3 ha-1,equivalent to 0,3,4.5,and 6 g kg-1 soil,respectively) and irrigation water of four salinity levels(0.50(tap water),4.9,6.3,and 8.7 dS m-1).The results indicated that at harvest,the electrical conductivity(EC) of the soil was significantly(P < 0.05) changed by the compost application as compared to the control.In general,the soil salinity significantly increased with increasing application rates of compost.Soluble salts,K,Cl,HCO 3,Na,Ca,and Mg,were significantly increased by the compost treatment.Soil sodium adsorption ratio(SAR) was significantly affected by the salinity levels of the irrigation water,and showed a slight response to the compost application.The soil organic carbon content was also significantly(P < 0.05) affected by application of compost,with a maximum value of 31.03 g kg-1 recorded at the compost rate of 60 m 3 ha-1 and the irrigation water salinity level of 8.7 dS m-1 and a minimum value of 12.05 g kg 1 observed in the control.The compost application produced remarkable increases in wheat shoot dry matter production.The maximum dry matter production(75.11 g pot-1) occurred with 60 m 3 ha-1 compost and normal irrigation water,with a minimum of 19.83 g pot-1 with no addition of compost and irrigation water at a salinity level of 8.70 dS m-1.Significant increases in wheat shoot contents of K,N,P,Na,and Cl were observed with addition of compost.The relatively high shoot N values may be attributed to increases in N availability in the tested soil caused by the compost application.Similarly,significant increases in the shoot contents of Na and Cl may be ascribed to the increase in soil soluble K and Cl.The increases in shoot P,N,and K contributed to the growth stimulation since P supplied by the compost was probably responsible in saline and alkaline soils where P solubility was very low.     

低盐再生水灌溉对亚热带红壤水力特性及微观结构的影响

低盐再生水是一种回用潜力巨大的替代性水源,为探究其灌溉亚热带红壤的适宜性,该研究以校园生活污水为再生水水源,设置再生水单一灌溉（WW）、再生水与蒸馏水交替灌溉（AWW）两种灌水模式,并以蒸馏水单一灌溉（CK）为对照。通过室外模拟土柱试验,研究了低盐再生水不同灌溉模式下红壤的盐碱度、微观结构及水力特性,并探讨了三者之间的相互作用关系。结果表明：1）低盐再生水灌溉降低了红壤的持水能力和导水能力;2）与CK处理相比,低盐再生水灌溉导致红壤田间持水率和凋萎系数降低,有效水在WW处理下增加6.33%,在AWW处理下减小27.85%;3） 两种低盐再生水灌溉模式下土壤大孔隙均增加,而有效孔隙、微小孔隙在WW处理下分别增加1.3%、5.0%,在AWW处理下分别减小4.3%、1.1%;4）与CK处理相比,低盐再生水灌溉使红壤电导率（Electrical Conductivity,EC）和Na+含量显著提高,而交换性阳离子总量（Cation Exchange Capacity,CEC）显著降低（P<0.05）。再生水两种灌溉模式中,AWW处理下土壤交换性钠百分比（Exchangeable Sodium Percentage,ESP）和钠吸附比（Sodium Adsorption Ratio,SAR）分别显著高于WW处理142.4%、120.3%（P<0.05）,从而引起更强烈的土壤黏粒分散;5）田间持水率、凋萎系数、有效水及有效孔隙和微小孔隙比例均与交换性Na+、ESP、SAR呈显著负相关,与CEC呈显著正相关。综上,低盐再生水灌溉亚热带红壤宜选择单一灌溉模式,且应定期监测土壤SAR和ESP等指标。研究结果可为再生水水质标准和灌溉制度制定提供参考。     

微咸水灌溉下土壤水盐动态及对作物产量的影响

华北平原农业灌溉用水非常紧缺,水资源日益缺乏与粮食需求日益增多之间的矛盾尖锐。充分利用微咸水资源是缓解这一矛盾的重要途径之一。该文以中国农业大学曲周试验站1997－2005年冬小麦和夏玉米微咸水灌溉田间长期定位试验为基础,研究了充分淡水、充分淡咸水、关键期淡水、关键期淡咸水和不灌溉等5个处理下土壤饱和电导率和含盐量的动态变化,探讨了微咸水灌溉对冬小麦和夏玉米产量的影响。结果表明：土壤水盐动态呈受灌溉和降雨影响的短期波动和受季节更替影响的长期波动;在正常降雨年份,使用微咸水进行灌溉是可行的,不会导致土壤的次生盐渍化;微咸水灌溉虽然导致冬小麦和夏玉米产量降低10%～15%,但节约淡水资源60%～75%。如果降雨量达到多年平均水平以及微咸水灌溉制度制订合理,微咸水用于冬小麦/玉米田间灌溉前景广阔。     

Effect of effective microorganism and gypsum amendments on nutrient leaching,pH, electrical conductivity,and Okra growth parameters under coastal saline soil

Nutrients losses through leaching are the main problem facing coastal saline soil. Effective microorganisms (EM) and Gypsum (G) at the application rate of 5%G and 10%G by weight were used as soil amendments. The pot experiment aimed to improve the leaching of nitrate (NO₃), ammonium (NH₄) and total nitrogen (TN) on the coastal saline soil. The EM+ 5%G treatment effectively reduced the content of NO₃ and NH₄ in the leachate by 86.59% and 68.18%, respectively. EM treatment reduced the leaching of NO₃ and NH₄ by 70.86% and 62.12% and EM+ 10%G reduced NO₃ and NH₄ by 11.80% and 50.76%, respectively. Moreover, the content of TN in leachate was reduced up to 13.23%, 5.80%, and 2.67% in response to EM, EM+ 5%G, and EM+ 10%G, respectively, compared to the control. These results indicate that EM combined with G as soil amendments can reduce leaching of nutrients and further support the regulation of a coastal saline soil pH and EC.     

土壤水分和养分时空变异性与作物产量的关系

精确农业使得农田土壤水分和养分的时空变异与产量关系的研究显得尤为重要,这就要求在其研究方法上取得新的进展,以加快精确农业的进程。该文运用传统统计理论和地质统计学理论结合分析了冬小麦苗期、灌浆期的土壤水分和养分变异与产量变异之间的关系。提出用“综合指示率”综合评价土壤的水分和养分状况,并分析了综合指示率的变异与作物产量变异之间的关系。结果表明在67.8 m范围内综合指示率与产量之间存在很强的空间相关性,综合指示率越大,产量越高。Kriging估计的空间分布图也表明综合指示率与产量有较好的对应关系,综合指示率能解释产量变异的58.4%,比多元回归结果提高17.4%。多元逐步回归分析和综合指示率与产量的两变量回归分析结果都表明,同时考虑土壤水分和养分的变异能解释产量变异的33.3%～58.4%,比只考虑土壤养分变异时提高0～5.2%,同时考虑苗期和灌浆期土壤水分和养分变异能解释产量变异的41.0%～58.4%,比只考虑其中1个时期提高4.3%～16.5%。综合指示率为表达农田土壤水分和养分时空变异性及其与作物产量的关系提供了一种思路和方法,其分布图不仅是管理者综合评价土壤水分和养分状况的有利工具,而且把它与产量分布图对比,可以为精确农业的实施提供一定参考。     

滑县土壤养分变化动态研究

滑县第二次土壤普查以来进行四次土壤耕层养分调查的结果表明,耕层土壤养分含量总体呈上升趋势;土壤养分含量的变化由第二次土壤普查时受土壤质地的主导转变为受人为耕作施肥的主导,在土壤—作物系统养分年循环中,土壤氮、磷元素总体上处于盈余状态,土壤钾素总体上处于亏缺状态。增加有机肥和化肥投入,能够提高土壤养分含量,保持地力常新。     

Spatial pattern consistency and repeatability of proximal soil sensor data for digital soil mapping

Data from proximal soil sensors can facilitate digital soil mapping at high spatial resolutions. However, their use for predicting static soil properties, such as texture, is affected by spatio-temporal changes in environmental and measurement conditions. In this research study, seasonal changes in spatial patterns and repeatability of data provided by a platform that simultaneously measures the red (Red) and near infrared (NIR) reflectance, apparent soil electrical conductivity (ECa), temperature, and volumetric moisture content of topsoil (at 3–6 cm depth) were assessed. Test fields are located in Southern Finland with textures dominated by clay and fine sandy till. During single scans, mean relative differences between the data from duplicated measurement points ranged from ~4% to 6% and were the highest for temperature and Red values. The consistency of spatial patterns across seasons (spring and autumn 2021 and 2022) was the highest for ECa values, and the lowest for NIR. ECa and moisture were significant for predicting the clay contents at a cereal grain crop site, whereas temperature was significant at grass ley sites. Errors were generally lower when using spring data compared with autumn data (RMSE ranging from 4.8% to 11.1% for the data from different fields and measurement dates). For the fields, where static soil properties change at small spatial scales, spatially detailed moisture and temperature data support the understanding of seasonal changes in the spatial patterns derived from multi-sensor data, and the corresponding changes in the performance of calibration models.     

去电子处理微咸水矿化度对土壤水盐运移特征的影响

为探究去电子处理微咸水对土壤水盐运移的影响,该文通过室内土柱试验,分析了不同矿化度微咸水(0.14、2、3、4、5 g/L)经去电子处理后土壤水分入渗及盐分分布规律。结果表明:不同矿化度去电子微咸水土壤入渗速率及湿润锋运移速率明显大于未处理微咸水,入渗时间为200 min时,累积入渗量和湿润锋运移深度在矿化度为4 g/L时增加幅度最大。相同矿化度去电子微咸水与未处理微咸水相比,Philip入渗公式吸渗率、Green-Ampt入渗公式饱和导水率及湿润锋处吸力均显著增加。去电子微咸水能够显著提高土壤的持水效率和上层土壤盐分的淋洗效果,矿化度为4 g/L时,相对淋盐率和Na+相对淋洗率最大。该研究表明去电子化处理能够改善土壤水盐运移特性,有利于微咸水安全利用。     

Estimation of soil salinity in semi‐arid land using a geostatistical model

Soil salinity is one of the great problems in arid and semi‐arid environments. The estimation and prediction of spatial soil salinity may be considered as a stochastic process, observed at irregular locations in space. Environmental variables usually show spatial dependence among observations which is an important drawback to traditional statistical methods. Geostatistical techniques that analyse and describe the spatial dependence and quantify the scale and intensity of the spatial variation, provides spatial information for local estimation of soil salinity. In this paper we propose a Gaussian Spatial Linear Mixed Model (GSLMM), which involves a non‐parametric term, accounting for a deterministic trend given by exogenous variables, and a parametric component defining the purely spatial random variation, possibly due to latent spatial processes. We focus here on the analysis of the relationship between soil electrical conductivity as a parameter related directly to soil salinity as well as sodium content (sodicity) to identify spatial variations in these parameters. This kind of methodology is demonstrated as a useful tool for environmental land management. Copyright © 2007 John Wiley & Sons, Ltd.     

再生水灌溉对土壤斥水性的影响

深入探求再生水灌溉条件下不同土壤中水分和溶质的分布及斥水性变化规律,能为再生水灌溉条件下土壤斥水性产生原因及其影响因素的研究提供一定的参考。选用砂土、砂姜黑土、塿土和盐碱土进行土柱再生水灌溉试验,取样测定不同灌水量条件下剖面土壤的潜在斥水性、含水率、Cl-、有机质(organicmatter,OM)含量及电导率(electrical conductivity,EC)等。结果表明:再生水灌溉后,塿土及盐碱土分别出现0～2,1～3级斥水性,砂土及砂姜黑土为0级斥水性,4种土表层表现出较强的斥水性。土壤斥水性随再生水灌水量和灌溉时间的增加而显著增强,并且灌水量越大,斥水性差异性越显著。4种土有机质含量OM与土壤斥水持续时间变化值TR呈正相关关系,Cl-含量、EC值与土壤斥水持续时间变化值TR呈负相关关系。相比较其他3种土而言,砂土更适合再生水灌溉。     

适宜耕作模式提高黄淮海平原冬小麦产量并改善土壤水肥状况

为了探索黄淮海小麦生产适宜的耕作模式,该研究设计长期定位试验（2017年—2022年）对比了简化耕作模式深耕（deep tillage, DT）、轮耕（rotational tillage, RT）和免耕（no-tillage, NT）对冬小麦产量和土壤水肥状况的影响。结果表明：RT处理显著提高了冬小麦苗期0～20 cm土层土壤水分吸收利用情况,冬小麦孕穗期、灌浆期RT处理0～20、>20~40 cm土层土壤含水量显著高于DT、NT处理。RT处理0～20、>20～40 cm土壤全氮、有机质含量和碳氮比含量较DT、NT处理显著提高, 2021—2022年0～20 cm土壤全氮、有机质含量、碳氮比RT处理较DT和NT处理分别显著提高40.45%和31.58%、56.66%和45.34%、11.62%和9.91%。2020—2021年和2021—2022年RT处理冬小麦产量较DT、NT处理分别显著提高20.20%、13.39%和20.35%、18.74%。RT处理显著增加了冬小麦千粒质量,其产量变异系数最低,产量可持续指数最高,说明RT处理有助于增加冬小麦生产力稳定性和可持续性,可以实现黄淮海冬小麦高产稳产。研究可为黄淮海平原冬小麦生产应用一年深耕、两年免耕的轮耕耕作模式提供理论指导与技术支撑。     

基于表观电导率和Hydrus模型同化的土壤盐分估算

精细刻画农田土壤盐分运移过程对盐渍化精准治理具有重要意义。该文以磁感式大地电导率仪EM38测定的土壤表观电导率作为数据源,利用表观电导率与剖面土壤盐分之间的反演模型作为观测算子,将集合卡尔曼滤波(ensemble Kalmanfilter,En KF)同化方法应用于土壤水盐运移过程模型(HYDRUS-1D),进行滨海盐渍农田周年土壤盐分动态的模拟,并分析了同化过程的敏感性。结果表明:与单纯使用HYDRUS模型相比,En KF同化方法对模型观测算子的更新,有效提高剖面土壤盐分模拟精度,且En KF同化值的精度优于En KF同化模拟值,在同化过程中的调整量亦最大;敏感性分析结果显示土壤盐分同化过程对状态变量集合数大小不敏感,对观测数据误差和引入观测数据的深度较为敏感,观测数据误差水平越高、引入观测数据的深度越浅其误差越大。研究表明基于水盐运移模型和土壤表观电导率数据的EnKF同化方法能提高土壤盐分的模拟精度,为利用多源数据和机理模型进行较大尺度生态过程模拟预测提供了有效手段。     

云南省施肥及土壤养分变化分析

为了掌握云南省农业生产中肥料施用量及施肥结构、土壤养分含量状况及其变化,对云南实施测土配方施肥项目的28个县16 000余农户的施肥情况进行调查,并采集土样分析化验,统计结果表明,云南化肥施用氮磷钾的比例由1989年的1∶0.34∶0.09提高到2008年的1∶0.33∶0.20,施肥比例有较大改善,但钾素总量仍不足;耕地土壤有机质含量较第二次土壤普查大幅下降,平均含量为28.14 g·kg-1,较第二次土壤普查下降49.93%;土壤磷含量明显增加,平均值达到22.7 mg·kg-1,比土壤普查增加61.0%.耕地土壤缺乏硼、钼、锌的比例较大,缺水溶态硼比例达78.26%,缺有效钼比例48.34%,缺有效锌比例28.84%.     

长武地区土壤导气率及其与导水率的关系

为了寻求快速、直接、耗资低并且可用于评估野外饱和导水率的量级和其空间变异性的方法,利用PL－300土壤导气率测量仪对长武小麦试验田不同含水率、体积质量、土层、取样方向、根系密度下的导气率,以及室内原状土壤样本（248 cm3）在田间持水率情况下的导气率及饱和导水率进行了研究。发现在不同的影响因素下导气率具有一定的变化规律;含水率接近田间持水率时的土壤导气率和饱和导水率之间存在对数线性关系。土壤导气率与饱和导水率的这种预测关系在早期的试验研究中也有所反映。将本试验结果与Loll、Iverson等人的研究成果进行对比论证,验证了通过测量土壤导气率预测田间饱和导水率的方法是可行的。     

Maize (Zea mays L.) yield and soil properties as affected by no tillage in the black soils of China

A four-year tillage experiment on maize was conducted in the high latitude region of Northeast of China. The main objective of this study was to investigate the effects of different field tillage practices on maize grain yield, soil physical properties, and soil water and temperature dynamics in Northeast of China. The tillage practices included moldboard plow tillage (MOT), rotary tillage (ROT), reduced tillage (RET), combined tillage (COT), and no tillage (NOT). The surface soil water content at depths of 0–20 cm was higher under NOT compared with other tillage practices, but not different at the deeper soil depths in 2011. The soil temperatures under NOT and RET were lower than those under moldboard plow tillage and ROT at depths of 5 and 15 cm, respectively, measured at 9:00 am in 2005. From the hourly dynamics of soil temperature, the differences among the tillage practices mainly appeared during the daytime (from 8:00 am to 7:00 pm). Among all the practices, the average daily soil temperature under ROT was the highest, while that under NOT was the lowest. MOT, ROT, and RET had higher soil accumulative infiltration compared with NOT and COT. The surface soil bulk density under NOT was higher than or equal to that under the other four tillage practices. The maize yields under NOT were the lowest among all the tillage practices for three years straight. Meanwhile, the yields under MOT were the highest, which were about 47%, 61%, and 38% higher than those under NOT. NOT practice is not recommended for use in spring-planted maize under the high latitude humid cool climate Mollisol region in Northeast of China.     

滴灌均匀系数对土壤水分和氮素分布的影响

为了确定滴灌均匀系数的设计与评价标准,在日光温室内研究了滴灌施肥灌溉均匀性和施氮量对土壤水氮分布特性的影响。试验中滴灌均匀系数（Cu）设置0.62、0.80和0.96 3个水平,施氮量设置150和300 kg/hm2 2个水平。土壤含水率和电导率采用沿毛管均匀布置的TDR探头（Hydra Probe）连续监测,并定期取土样测试土壤硝态氮和铵态氮含量。结果表明,在作物生育期内3种滴灌均匀系数处理的土壤含水率一直保持很高的均匀系数,滴灌均匀系数和施氮量对土壤含水率均值及其均匀系数的影响均不显著（α=0.05）。土壤电导率及硝态氮含量的均匀性在很大程度上取决于土壤初始氮素含量的均匀性,其均匀系数低于土壤含水率的均匀系数,滴灌均匀系数的影响也不显著。从获得均匀的土壤水氮分布的角度出发,现行滴灌均匀系数标准尚有降低的空间。