基于HYDRUS-2D模型的滴灌土壤水氮动态模拟研究

【目的】探究河套灌区滴灌条件下玉米各生育期土壤水氮变化规律及不同灌水量对土壤硝态氮累积量的影响。【方法】通过田间试验,设置高灌水量（D1:76 mm）处理和低灌水量（D2:60 mm）处理,分析土壤含水率和土壤氮素（铵态氮和硝态氮）的动态变化规律,利用HYDRUS-2D模型进行模拟验证与预测。【结果】各处理灌水后土壤含水率呈增加趋势;而土壤铵态氮和硝态氮在灌水施肥后迅速升高,随后下降,D1处理和D2处理不同生育期0～10 cm土层铵态氮量和硝态氮量的平均降幅分别为60.0%～62.0%和40.0%～46.7%。拔节期、抽雄期和灌浆期各土层灌水后D1处理相比D2处理的土壤含水率分别增加了5.9%、8.0%和6.7%,而土壤铵态氮量和硝态氮量随着土层深度的增加而降低。不同生育期硝态氮累积量为拔节期>抽雄期>灌浆期,随着生育期的推进,硝态氮累积量呈降低趋势。土壤含水率及氮素模拟值与实测值的吻合度较高,R2、RMSE和d均介于合理范围内。【结论】玉米生育期120 mm的灌溉定额可有效降低0～60 cm土层的硝态氮累积量,可降低硝态氮在60～100 cm土层的积累量。该研究可为当地灌...     

风沙土不同滴灌水量对玉米根系水分和硝态氮分布的影响

为了探究风沙土内水分和养分分布,合理的利用风沙土资源。采用田间试验,以不同灌溉水量为试验因素,其中灌溉水量设置需水系数0.4(IR1)、0.6(IR2)、0.8(IR3)、1.0(IR4)、1.2(IR5)5个水平,施肥量采用推荐施肥量(纯氮)225 kg/hm~2,通过测定不同灌溉条件下土壤水分和土壤硝态氮含量,研究风沙土玉米膜下滴灌不同灌溉条件对土壤水分和养分分布的影响。在风沙土上增大灌水量不能增加土壤的蓄水量,反可能增加土壤水分分布的不均匀性。水平方向上, 0～20 cm范围内灌水量越大,水分运动距离越远;在垂直方向上0～30 cm土层是土壤水分主要分布层。风沙土中硝态氮含量分布不均匀,有明显的集聚。水平方向上,灌水量越大,硝态氮含量峰值距离滴头位置越远;垂直方向上,硝态氮有明显的表聚现象,灌水量增加有利于提高各层硝态氮含量。土壤含水率与土壤硝态氮除表现为以正相关为主,在垂向分布上相关性较高外,空间分布的相关性并不大,且改变灌水量并不能提高两者相关性。在风沙土地区利用滴灌灌溉玉米时,为了更好地将土壤水分和养分控制在根系分布层内,推荐灌溉制度计算公式中的需水系数取0.8。     

玉米膜孔灌苗期不同灌水量对水氮分布的影响

通过室外田间试验,分析了膜孔灌玉米苗期不同灌水量对土壤水氮分布的影响.灌水量越大,土壤含水率越大,分布范围越广,土壤表层硝态氮含量越小,对深层80～100 cm硝态氮含量影响越大;随灌水量的增加,硝态氮累积峰越靠下,增加了硝态氮的淋失.     

利用电容式传感器连续监测土壤硝态氮质量分数的试验研究

通过室内和田间试验,研究土壤硝态氮质量分数与电容式传感器监测的土壤电导率、含水率和温度的定量关系。在室内以NH4NO3分析纯为溶质,进行了溶液质量浓度0～10g/L的7次土柱试验;在2009年和2010年春玉米生育期内监测了不同滴灌水量条件下土壤电导率、含水率和温度动态变化。结果表明,土壤电导率能较好的反映土壤硝态氮质量分数的变化;土壤硝态氮质量分数与电导率、含水率和温度之间的关系可用二次多项式描述,且3个土壤参数对土壤硝态氮质量分数的影响均达到了极显著水平(P≤0.01);由于回归模型的拟合精度受土壤初始养分盐分质量分数及空间变异等因素的影响,为获得较高的预测精度,应进行田间标定。     

干旱区滴灌均匀系数对土壤水氮分布影响模拟

基于HYDRUS-2D软件建立了棉花膜下滴灌水氮运移模型,利用干旱区棉花膜下滴灌试验数据对模型进行了参数率定和验证。将灌水器流量沿毛管的变化离散为依次逐段减小,并假设土壤水分在各段之间不存在交换,利用验证后的数学模型研究了干旱区不同滴灌均匀系数时土壤水氮分布特征,评估了土壤空间变异对水氮分布均匀性的影响。模拟结果表明,随着灌水的进行,滴灌均匀系数Cu为0.60和0.80时,土壤含水率和NO-3-N质量浓度均匀系数均呈下降趋势,而Cu=0.95时变化较平稳;滴灌均匀系数越低,灌水后土壤含水率和NO-3-N质量浓度均匀系数降低的幅度越大;土壤NO-3-N质量浓度均匀系数的变化范围为0.35~1.00,低于土壤含水率均匀系数。田间试验存在的土壤空间变异在一定程度上增加了土壤水氮分布不均匀性。     

再生水地下滴灌对玉米生育期土壤脲酶活性和硝态氮的影响

为了探讨再生水地下滴灌条件下土壤脲酶活性和硝态氮的关系,通过2a再生水地下滴灌试验,研究了滴灌带埋深和灌水量对玉米生育期0~50cm深度土壤脲酶活性和硝态氮分布的影响。灌水量设置灌溉需水量的70%、100%和130%3个水平,滴灌带埋深设置0、15和30cm 3个水平。结果表明,再生水地下滴灌提高了0~50cm脲酶活性。灌水量和滴灌带埋深均对土壤脲酶活性和硝态氮含量产生了显著影响,硝态氮随灌水量和滴灌带埋深的增大运移深度增加,0~10cm深度脲酶活性以70%灌溉需水量和埋深0cm较高,10~50cm深度脲酶活性以130%灌溉需水量和埋深30cm较高。相关分析表明,硝态氮含量和脲酶活性在玉米生育期内由极显著正相关向负相关转变。     

土壤容重对一维垂直浑水肥液入渗水氮运移特性影响

为了揭示土壤容重对浑水肥液入渗水氮运移特性的影响,通过室内土柱试验,研究不同土壤容重(1.30,1.35,1.40,1.45 g/cm³)累积入渗量、湿润锋运移距离、土壤含水率分布规律以及土壤硝态氮运移特性,采用Philip入渗模型和电容充电经验模型对累积入渗量进行了拟合,建立了累积入渗量、湿润锋运移距离与土壤容重之间的关系.结果表明:在同一入渗时间下,浑水肥液累积入渗量随土壤容重的增大而减小;土壤容重越大,湿润体体积、湿润体内水分及硝态氮分布范围均越小.浑水肥液累积入渗量符合Philip入渗模型和电容充电经验模型;湿润锋运移距离与入渗时间呈显著幂函数关系;供水结束后土壤含水率及硝态氮含量均随着入渗深度的增加而减小;随着土壤水分再分布上层土壤硝态氮逐渐减小,下层逐渐增大,再分布2 d后硝态氮含量在湿润锋附近出现峰值,整个湿润体硝态氮含量分布趋于均匀.研究成果为进一步研究浑水肥液入渗氮素运移提供基础参考.     

滴灌施肥时序对不同质地土壤水氮分布的影响

【目的】探究不同滴灌施肥时序下不同质地土壤水、氮的运移规律和分布特征。【方法】通过室内土槽试验,设置3种土壤质地：砂土、壤土、黏土,分别记为S1、S2、S3,4种施肥时序：仅灌水、1/2N-1/2W（前1/2时间施氮肥）、1/4W-1/2N-1/4W（前1/4时间灌水后在中间1/2时间施氮肥）、3/8W-1/2N-1/8W（前3/8时间灌水后在中间1/2时间施氮肥）,分别记为T1、T2、T3、T4,分析了土壤湿润锋的运移以及水分、硝态氮在土体内的分布特征。【结果】在灌水量和滴头流量均相同的条件下,3种土壤的湿润锋分布特征存在明显差异。湿润锋的最大入渗深度：砂土（29.5 cm）>壤土（21 cm）>黏土（15 cm）。硝态氮在湿润体边缘累积,并且随着施肥次序向前推移,硝态氮向湿润体边缘运移的趋势越来越明显。不同施肥时序下,硝态氮在3种土壤中的分布存在差异。S1T4处理的硝态氮在砂土下层的比例最低;S2T3处理下壤土的硝态氮分布最均匀;S3T2处理可以降低硝态氮在黏土表层堆积。【结论】对于砂土、壤土和黏土,分别采用3/8W-1/2N-1/8W、1/4W-1/2N-1/4W和1...     

施氮对不同质地滴灌棉田土壤硝态氮分布及棉花产量的影响

为了探究施氮对不同质地滴灌棉田硝态氮分布及产量的影响,采用温室土柱模拟的方法,研究了滴灌条件下不同质地土壤硝态氮分布迁移特征,分析了施氮对NO_3-N和棉花产量的影响。结果表明,在灌水量一定的条件下,在砂土、壤土中施氮量分别为256.00、287.34 kg/hm~2时,相应的氮素积累量最大,皮棉产量最高,土壤硝态氮主要集中分布在30~40 cm土层,有利于棉花根系的吸收,且分别比不施氮增产43.87%和44.92%。一定施氮量下,壤土硝态氮分布的均匀性优于砂土,并且根层20~40 cm土层硝态氮量高于砂土,且比砂土平均增产6.16%。砂土、壤土中硝态氮量在各生育期总体呈现"降-增-降"的变化趋势,并且收获前期施纯氮340 kg/hm~2处理60cm土层砂土硝态氮量的第二个峰值较壤土提高15.98%,在生育期末端砂土在深层的氮素积累高于壤土,存在继续向下淋失的风险。     

设施条件下灌水量对膜孔灌土壤水氮运移分布影响研究

通过模拟设施条件下不同灌水量灌施硝酸钾肥液试验,分析测定了灌后不同时间的土壤含水率和硝态氮分布。研究表明,不同灌水量的土壤含水率和硝态氮质量分数随着时间延长逐渐减小,以膜孔中心最大,远离膜孔中心逐渐变小;随着灌水量增大,相同位置的土壤含水率变大,而相同位置的土壤硝态氮质量分数变小;增大灌水量对土壤含水率和硝态氮分布的影响有利于植物对水分和硝态氮的吸收。     

水肥气耦合滴灌提高温室番茄土壤通气性和水氮利用

【目的】探索温室作物水肥气耦合滴灌下掺气量、灌水量和施氮量适宜组合方案,为提高水氮利用效率提供理论依据。【方法】设置施氮量(低氮和常氮)、掺气量(常规滴灌和曝气滴灌)和灌水量(低水量和高水量)3因素2水平随机区组试验,以地下滴灌为供水方式,通过系统监测土壤水分饱和度、氧气扩散速率(ODR)、氧化还原电位(Eh)、矿质氮量及作物水氮利用等指标,研究了水肥气耦合滴灌对温室番茄土壤通气性及水氮利用的影响。【结果】与常规滴灌相比,高水量条件下曝气处理的土壤水分饱和度有所降低,ODR和Eh显著提高。灌水量、施氮量和掺气量影响土壤矿质氮量,曝气滴灌下土壤硝态氮和铵态氮量较常规滴灌平均降低21.4%和15.5%(P<0.05),高水量处理土壤硝态氮和铵态氮量较低水量处理平均降低22.7%和14.7%(P<0.05),常氮处理土壤硝态氮和铵态氮量较低氮处理平均增加29.0%和17.8%(P<0.05)。高水量和常氮条件下番茄灌溉水利用效率较低水量、低氮处理平均降低6.7%和增加40.9%(P<0.05),高水量和常氮条件下番茄氮素吸收利用效率较低水量、低氮处理平均增加13.6%和12.7%(P<0.05),曝气滴灌下番茄灌溉水利用效率和氮素吸收利用效率较常规滴灌平均增加22.9%和12.4%(P<0.05)。【结论】水肥气耦合滴灌可有效改善土壤通气性,提高水氮利用效率,促进番茄生长,实现作物增产。本试验中,常氮曝气高水量处理是温室番茄适宜的水肥气组合方案。     

Spatial and temporal distributions of nitrogen and crop yield as affected by nonuniformity of sprinkler fertigation

Deep percolation and nitrate leaching are important considerations in the design of sprinkler systems. Field experiments were therefore conducted to investigate the influence of nonuniformity of sprinkler irrigation on deep percolation and spatial distributions of nitrogen and crop yield during the growing season of winter wheat at an experiment station in Beijing, China. Three experimental plots of a sandy clay loam soil in the 0–40 cm depth interval and a loamy clay soil below 40 cm were irrigated with a sprinkler irrigation system that had a seasonal averaged Christiansen irrigation uniformity coefficient (CU) varying from 72 to 84%. Except for the fertilizer applied before planting, fertilizer was applied with the sprinkler irrigation system. The corresponding seasonal averaged CU for fertigation varied from 71 to 85%. Daily observation of matrix water potentials in the root zone showed that little deep percolation occurred. Consequently, the effect of sprinkler uniformity on deep percolation was minor during the irrigation season for the soil tested. Intensive gravimetric soil core samplings were conducted several times during the irrigation season in a grid of 5 m × 5 m for each plot to determine the spatial and temporal variation of NH₄-N and NO₃-N contents. Soil NH₄-N and NO₃-N exhibited high spatial variability in depth and time during the irrigation season with CU values ranging from 23 to 97% and the coefficient of variation ranging from 0.04 to 1.06. A higher uniformity of sprinkler fertigation produced a more uniform distribution of NH₄-N, but the distribution of NO₃-N was not related to fertigation. Rather it was related to the spatial variability of NO₃-N before fertigation began. At harvest, the distribution of dry matter above ground, nitrogen uptake, and yield were measured and the results indicated that sprinkler fertigation uniformity had insignificant effects on the parameters mentioned above. Field experimental results obtained from this study suggest that sprinkler irrigation if properly managed can be used as an efficient and environment-friendly method of applying water and fertilizers.     

不同水肥条件下土壤N、P、K分布规律研究

通过田间试验对不同水肥条件下土壤NO3--N、速效磷、速效钾、盐分分布进行研究,结果表明：在滴灌施肥条件下,土壤剖面NO3--N分布主要集中在湿润体边缘,速效磷主要分布在0～30cm范围,速效钾主要分布在0～40cm范围;合理水肥比例可提高红枣对养分的吸收和减少养分在土壤中的积累且影响土壤盐分分布。试验结果为盐渍化土壤水肥一体化管理提供参考。     

Effects of drip irrigation system uniformity and nitrogen applied on deep percolation and nitrate leaching during growing seasons of spring maize in semi-humid region

Drip system uniformity is one of the important factors affecting the deep percolation and nitrate leaching under drip-irrigated crops. Field experiments were conducted during two growing seasons of spring maize (Zea may L.) in 2011 and 2012 in North China Plain to evaluate the influence of drip irrigation system uniformity on deep percolation and nitrate leaching under semi-humid conditions. In the experiments, three Christiansen uniformity coefficients of 59, 80, and 97 % (the equivalent distribution uniformity DU values were 57, 71, and 95 %, respectively) and three levels of nitrogen applied at 0, 120, and 210 kg ha^?1 were tested. The results of the study demonstrated that nitrate leaching was most importantly affected by the nitrogen applied, followed by the initial nitrogen content in the soil and the drip irrigation system uniformity. An increasing amount of nitrogen applied and initial nitrogen content increased the seasonal nitrate leaching significantly, while an improving system uniformity decreased the nitrate leaching. The conventional nitrogen application rate of 210 kg ha^?1 could be reduced, and an extremely low drip uniformity of less than 60 % is not recommended to reduce the risk of deep percolation and nitrate leaching in the semi-humid region of North China Plain.     

滴灌施肥灌溉条件下土壤水氮运移的研究进展

对滴灌施肥灌溉条件下水分和养分运移的研究进展进行了总结。许多研究表明 ,滴灌施肥灌溉条件下土壤水、氮的运移和分布主要受土壤特性、灌水器流量、肥液浓度及灌水量的影响 ,而灌水器周围饱和区半径的确定是影响土壤水分和氮素运移模拟精度的关键因素。关于滴灌施肥灌溉条件下氮素运移的研究较少 ,尤其在施肥灌溉系统运行参数对氮素运移、转化、分布影响的研究方面更为薄弱 ,在今后的研究中应予以加强。     

时域反射仪测定高含盐土壤盐分研究

采用室内试验的方法,通过使用时域反射仪(TDR100)测定不同含盐量及不同含水率土样的电导值,与采用电导率仪测定的土壤溶液电导值及烘干法测得的含水率值进行比较。结果表明,它们之间存在显著的线性关系。并根据测定结果得到标定公式,提出使用TDR测定高含盐量土壤含盐量的方法。试验结果可为河套灌区野外测定土壤含盐量提供参考。     

Tomato nitrogen accumulation and fertilizer use efficiency on a sandy soil, as affected by nitrogen rate and irrigation scheduling

Tomato production systems in Florida are typically intensively managed with high inputs of fertilizer and irrigation and on sandy soils with low inherent water and nutrient retention capacities; potential nutrient leaching losses undermine the sustainability of such systems. The objectives of this 3-year field study were to evaluate the interaction between N-fertilizer rates and irrigation scheduling on crop N and P accumulation, N-fertilizer use efficiency (NUE) and NO₃-N leaching of tomato cultivated in a plastic mulched/drip irrigated production system in sandy soils. Experimental treatments were a factorial combination of three irrigation scheduling regimes and three N-rates (176, 220, and 330 kg ha⁻¹). Irrigation treatments included were: (1) surface drip irrigation (SUR) both the irrigation and fertigation line placed underneath the plastic mulch; (2) subsurface drip irrigation (SDI) where the irrigation drip was placed 0.15 m below the fertigation line which was located on top of the bed; and (3) TIME (conventional control) with the irrigation and fertigation lines placed as in SUR and irrigation applied once a day. Except for the TIME treatment all irrigation treatments were soil moisture sensor (SMS)-based with irrigation occurring at 10% volumetric water content. Five irrigation windows were scheduled daily and events were bypassed if the soil water content exceeded the established threshold. The use of SMS-based irrigation systems significantly reduced irrigation water use, volume percolated, and nitrate leaching. Based on soil electrical conductivity (EC) readings, there was no interaction between irrigation and N-rate treatments on the movement of fertilizer solutes. Total plant N accumulation for SUR and SDI was 12-37% higher than TIME. Plant P accumulation was not affected by either irrigation or N-rate treatments. The nitrogen use efficiency for SUR and SDI was on the order of 37-45%, 56-61%, and 61-68% for 2005, 2006 and 2007, respectively and significantly higher than for the conventional control system (TIME). Moreover, at the intermediate N-rate SUR and SDI systems reduced NO₃-N leaching to 5 and 35 kg ha⁻¹, while at the highest N-rate corresponding values were 7 and 56 kg N ha⁻¹. Use of N application rates above 220 kg ha⁻¹ did not result in fruit and/or shoot biomass nor N accumulation benefits, but substantially increased NO₃-N leaching for the control treatment, as detected by EC monitoring and by the lysimeters. It is concluded that appropriate use of SDI and/or sensor-based irrigation systems can sustain high yields while reducing irrigation application as well as reducing NO₃-N leaching in low water holding capacity soils.     

滴灌施肥下水肥用量对温室土壤硝态氮残留的影响

【目的】通过水肥管理达到减少温室土壤硝态氮残留、维持土壤质量的目的,探求温室土壤硝态氮残留与水肥用量的关系。【方法】在滴灌施肥条件下,以灌水量和氮、磷、钾及有机肥用量为试验因素,根据当地日光温室番茄长季节栽培实际中的水肥用量,设计各试验因子的水肥水平,采用五元二次通用旋转组合设计进行试验。拉秧后测定耕层土壤硝态氮量,建立土壤硝态氮量与水肥因子间的数学模型,据此分析了各单因子效应及二因素的耦合效应。【结果】施氮量对土壤硝态氮残留量影响最大,施磷量、灌水量和施钾量次之,有机肥用量最小。当其他因子为0水平时,土壤硝态氮残留量随氮肥用量的增多而增加,随施磷量呈开口向上的抛物线变化,随灌水量、施钾量以及有机肥用量呈开口向下的抛物线变化。灌水量及氮、磷、钾和有机肥用量对土壤硝态氮残留产生的影响程度随其他因子的水平而变,存在明显交互作用。模型寻优显示:灌水量455.1～471.5 mm,施氮量532.3～586.5 kg/hm2,施磷量420.8～466.4 kg/hm2,施钾量646.1～723.5 kg/hm2,有机肥用量25.6～27.9 t/hm2,耕层土壤硝态氮量可维持在100～150 mg/kg的较低水平。【结论】温室菜地土壤硝态氮残留量相对较大,可以通过优化水肥用量来减少土壤硝态氮的残留,故在滴灌施肥条件下仍需严格控制水肥用量。