基于数字图像分析监测不同氮肥处理下加工番茄生长状况的初步研究

利用数字相机获取田间加工番茄冠层影像,通过图像处理软件准确识别冠层和背景像素,分析了加工番茄不同施氮量下提取的地面覆盖度与生物学参数间的相关关系,其相关系数都达到0.96以上的极显著相关;分析了光谱参数--绿色深度指数（DGCI）与叶片叶绿素含量相关关系,二者表现出r=0.74以上的极显著直线相关。结果表明,利用地面覆盖度可在生长前期监控加工番茄生长量,预测生物学产量和叶面积系数;在果实膨大期预测吸氮量和经济产量。利用光谱参数DGCI可监测加工番茄叶片叶绿素含量。本结果可快速准确监测加工番茄生长发育,为加工番茄生产提供科学依据。     

应用数字图像技术进行水稻氮素营养诊断

【目的】研究田间试验条件下水稻不同生育期冠层图像色彩参数(G、NRI、NGI、NBI、G/R和G/B)及植株氮素营养指标(叶片含氮量、植株全氮含量、生物量、氮素累积量和冠层NDVI值)的时空变化特征,并分析两者间的相关性,确立水稻氮素营养诊断的最佳色彩参数和方程模型,为探明数码相机在水稻上的适宜性及精确诊断水稻氮素营养状况提供理论基础。【方法】于2013年5月9月在湖北省武汉市华中农业大学试验基地(30°28'08'N,114°21'36'E)采用不同施氮处理的田间试验,以籼型两系杂交稻"两优6326"为供试作物,设置4个施氮水平:0、75、150和225 kg/hm2(分别以N0、N75、150和N225表示),3次重复,随机区组排列。分别在水稻分蘖期、拔节期、孕穗期和灌浆期采用数码相机(Nikon-D700,1200万像素)获取水稻冠层图像,应用Adobe photoshop7.0软件直方图程序提取图像的红光值R、绿光值G和蓝光值B,研究数码相机进行水稻氮素营养诊断色彩参数,确定植株氮素营养指标诊断模型。【结果】较对照(N0)相比,分蘖期、拔节期、孕穗期和灌浆期3个施氮处理水稻地上部生物量、叶片含氮量、植株全氮含量、氮素累积量、冠层NDVI值和成熟期产量增幅分别平均为40.7%98.0%、42.4%72.4%、36.2%85.3%、125.5%209.1%、51.3%60.6%和60.1%117.0%,差异显著。水稻不同生育期各冠层数字化指标G、NRI、NGI、NBI、G/R和G/B与上述氮素营养参数相关性差异较大,且以数字图像红光标准化值NRI表现最佳,建议作为应用数码相机进行水稻氮素营养诊断的最佳冠层图像色彩参数指标。进一步分析表明,可以用统一的线性回归方程来描述不同生育期、不同氮素水平下水稻植株氮素营养指标随冠层色彩参数NRI的变化模式。【结论】数码相机进行水稻氮素营养诊断测试结果稳定,具有快速、便捷、非破坏性等优点,冠层色彩参数NRI与水稻氮素营养指标和产量之间均表现出较好的相关性,满足氮素营养无损诊断的需求,对实时、快速监测水稻长势状况及氮素营养丰缺水平具有较高的可行性,有望发展成为新时期作物氮素营养无损诊断技术的潜力。     

基于Greenseeker光谱法的棉花氮素营养诊断研究

利用主动遥感光谱仪(Greenseeker)对新疆2个主栽棉花品种4个施氮量条件下2年生育期间的冠层归一化植被指数(NDVI)值进行测试,研究不同施氮量对棉花冠层NDVI值、植株氮素积累速率和叶片全氮含量的影响以及田间条件下简便、快速、非接触性的作物氮素营养状况诊断方法。结果表明:在棉花生育期内,冠层NDVI值呈单峰曲线变化,峰值出现在出苗后90d左右,以后逐渐降低;NDVI值和棉株氮素积累速率呈正相关关系,决定系数R~2在盛花期达到最大,为0.844.7;NDVI值变化趋势与叶片全氮含量呈正相关,决定系数R~2在盛花期达到0.7980。棉花冠层NDVI值随着施氮量增加而提高,不同氮素处理间NDVI值在盛花期和花铃期达极显著差异;主动遥感光谱仪在棉花生长的盛花期和花铃期可以预测棉花氮素养分状况。     

基于冠层覆盖度的玉米植株临界氮浓度模型构建与产量预测

  【目的】  依据临界氮浓度稀释原理,构建基于冠层覆盖度的覆膜滴灌玉米植株临界氮浓度稀释曲线,并通过氮营养指数和氮累积亏缺量模型对玉米氮营养状况进行诊断和评价,以期达到基于该模型的玉米产量预测。  【方法】  于2019—2020年,在宁夏引黄灌区开展了4个氮肥用量(0、120、240、360 kg/hm2)田间试验,采用滴灌水肥一体化技术,氮肥按照苗期10%、拔节—大喇叭口期45%、抽雄—吐丝期20%和灌浆期25%的比例分8次随水追肥。在玉米关键生育时期测定农学参数和图像参数,分别测定了地上部生物量、植株氮浓度和产量,建立和验证基于冠层覆盖度的玉米植株临界氮浓度经验模型。  【结果】  基于冠层覆盖度的玉米植株临界氮浓度、最大氮浓度和最小氮浓度模型R2分别为0.917、0.843、0.873。临界氮浓度模型检验参数RMSE和n-RMES分别为 0.242和 11.753%。以冠层覆盖度为基础的氮营养指数和氮累积亏缺量推算出玉米最佳施氮处理为240 kg/hm2。不同生育时期氮营养指数、氮累积亏缺量与相对产量的关系极显著,R2均不小于0.922,且大喇叭口期和抽雄期R2值最高。采用独立试验验证表明,在大喇叭口期和抽雄期表现出稳定的模型性能,R2值≥0.944,n-RMSE均≤9.089%。在大喇叭口期和抽雄期,氮营养指数、氮累积亏缺量与相对产量呈极显著相关,能准确地解释受氮素限制和不受氮素限制生长条件下相对产量的变化。  【结论】  基于冠层覆盖度构建的植株临界氮浓度稀释曲线可准确判断和评价玉米拔节期至吐丝期的氮素营养状况,依据氮营养指数、氮累积亏缺量与相对产量所构建的关系模型可对玉米产量进行准确估计,其为玉米生长过程中氮肥的精确管理和产量预测提供了一种简便的新方法。     

应用数字图像进行小麦氮素营养诊断中图像分析方法的研究

简便、快速、经济地诊断作物氮素营养状况是实施氮肥用量调控的关键。利用数码相机对作物冠层进行拍照, 通过图像处理软件获得作物色彩参数, 根据色彩参数与作物氮素营养状况的关系可以对其氮素丰缺进行诊断。针对作物数字图像色彩参数的获取方法, 结合小麦多水平氮肥试验, 采用遥感软件PCI Geomatics的非监督分类功能, 将小麦图像分为土壤、反光叶面和不反光叶面, 与Adobe Photoshop 软件普通图像处理方法对照, 比较分析了小麦图像不同类别叶片的8 种色彩参数与SPAD 值及植株全氮的相关性。结果表明, 返青期小麦反光叶面的G/R 与R/(R+G+B)色彩参数能较好地反映小麦的氮素营养状况; 拔节期不反光叶面和反光叶面的R/(R+G+B)色彩参数与植株全氮相关性较好。利用普通图像处理软件获得色彩参数的方法有待改进, 图像分类后能够提高其色彩参数对作物氮素营养诊断的准确性。     

基于LISS4数据的小麦氮素营养状况反演研究

利用LISS4卫星遥感数据在小麦氮素营养状况监测方面进行了初步研究。根据搭载多光谱传感器LISS4的IRS-P6的过境周期,2006年5月3日在江苏省盐城地区进行同步地面取样测试,通过分析试验点小麦LISS4影像光谱信息与小麦叶面积指数及叶片氮含量的相关关系,发现小麦叶面积指数和叶片氮含量与LISS4影像三个波段反射率及植被指数RVI、NDVI、GNDVI均密切相关,表明利用LISS4遥感影像监测小麦氮素营养状况是可行的。比较不同波段原始反射率和植被指数,在本研究中LISS4影像波段4反射率与小麦氮素营养状况相关最密切。检验结果也表明利用LISS4影像波段4反射率估测小麦氮素营养状况是可行的。研究成果为利用遥感技术大面积监测小麦氮素营养状况和实施精确栽培管理提供了理论依据。     

基于高光谱的冬小麦氮素营养指数估测

为了准确定量诊断氮素状况,为施肥和产量、品质的估测提供参考,该文通过设置不同氮素水平和品种类型的冬小麦田间试验,分析孕穗至灌浆初期不同光谱参数在小麦氮素营养状况监测上的差异,筛选叶片氮素含量和冠层氮素密度反演效果较好的参数,建立其与氮营养指数(NNI,nitrogen nutrition index)的经验模型。研究表明,线性内插法红边位置(REPLI)、修正红边单比指数(mSR705)、比值指数(RI-1dB)、简单比值色素指数(SRPI)、红边指数(VOG)等光谱参数与氮素营养指标具有良好的相关性(r0.85),且不受生育期影响,可用来反演评价冠层氮素营养状况;研究对筛选的光谱参数与各氮素指标进行回归建模,并用独立试验数据对所建模型进行验证,结果显示,REPLI在氮营养指数估测方面表现较好(r=0.93),估测模型精度较高(决定系数R2=0.86,均方根误差RMSE=0.08)。NNI在氮素营养状况诊断方面有一定的优势,通过高光谱反演氮营养指数进行氮素营养状态的定性定量诊断有一定的可行性。     

数字图像诊断技术在冬小麦氮素营养诊断中的应用

本文应用数码相机获取冬小麦冠层图像并对其进行相应色彩参数处理, 结合土壤、植株快速测试技术, 分析了色彩参数与传统氮素营养参数之间的数量关系, 研究了应用数字图像技术进行冬小麦氮素营养诊断的可行性, 建立了应用数字图像技术诊断冬小麦氮素营养状况的图像获取方法, 筛选出了适宜于冬小麦氮素营养诊断的最佳色彩参数以及最佳诊断时期, 建立了冬小麦氮素营养诊断指标体系和推荐施肥方程。研究结果表明, 数字图像技术可以作为冬小麦氮素营养诊断的方法。数字图像获取时, 可将数码相机与冬小麦冠层呈30°~60°角度进行拍摄。在冬小麦拔节期和孕穗期多数冠层图像色彩参数与施氮量、叶片SPAD 值、植株硝酸盐浓度、植株全氮含量、0~90 cm 土壤硝态氮含量之间存在显著或极显著相关关系; 在众多色彩参数中, 拔节期冠层图像绿光标准化值G/(R+G+B)与各项氮素指标的相关性最好, 可作为冬小麦氮素营养诊断的最佳色彩参数指标;拔节期可作为应用数字图像技术进行氮素诊断的关键时期。     

数字图像技术在夏玉米氮素营养诊断中的应用

基于6个不同水平的氮肥田间试验,采用数码相机获取夏玉米6叶期和10叶期的冠层图像,分析了不同供氮水平下夏玉米冠层图像色彩参数指标与施氮量、叶片SPAD值、植株硝酸盐浓度、植株全氮含量、0～90cm土壤硝态氮含量之间的关系。结果表明:在6叶期,玉米冠层数字图像色彩参数指标B/(R+G+B)、G/B、R/B、B/L均与施氮量、叶片SPAD值、植株硝酸盐浓度、植株全氮含量、0～90cm土壤硝态氮含量存在极显著的线性相关关系,其中B/(R+G+B)与各营养参数的相关关系最好,其次是B/L。因此,运用数字图像技术进行玉米的氮素营养诊断是可行的。夏玉米6叶期冠层图像色彩参数指标与上述营养参数间的相关性明显高于10叶期,可作为应用数字图像技术进行氮素营养诊断的关键时期,而蓝光标准化值[B/(R+G+B)]是进行夏玉米氮素营养诊断的最佳冠层图像色彩参数指标。     

水稻吸氮量和干物质积累的模拟试验研究

本文描述了土壤氮和肥料氮素对水稻不同时期生长的影响及水稻对氮素吸收和在各组织器官的分布模式 ,借助水稻生长模型ORYZA - 0 ,通过田间和水槽的氮肥试验结果对水稻模型和氮素动态模块进行了验证。结果表明 ,模型模拟的水稻生物量、产量、叶片吸氮量和地上部吸氮量与实测值呈明显的正相关 ,其相关系数分别为 :生物量r=0.9889;产量r =0.9992 ;叶片吸氮量r =0.9597;地上部吸氮量r =0.9234。模拟生物量、产量和实测的生物及产量的相关性较高 ;而对叶片吸氮量、地上部吸氮量的模拟值与实测值的相关性稍低一些。但总体来看 ,该模型不仅能较准确地模拟水稻生长动态 ,而且可以模拟水稻氮吸收和积累的行为动态     

华北地区冬小麦-夏玉米轮作体系的氮素循环与平衡

对华北地区冬小麦-夏玉米轮作体系农田氮素输入输出的数量特征、平衡状况进行了分析,并评估其优化潜力。研究表明,华北地区冬小麦-夏玉米轮作体系农田每年的氮素输入中,化学氮肥、农家肥、降水、灌溉、非生物固氮和种子带入农田的氮分别为545、68、21、15、15和5kghm-2a-1,氮素年输入总量为669kghm-2a-1;每年的氮素输出中,作物收获带走的氮为311kghm-2a-1,而氨挥发、反硝化和淋洗损失的氮分别为120、16和136kghm-2a-1,氮素年输出总量为583kghm-2a-1;氮素年盈余量为86kghm-2a-1。目前我国华北地区冬小麦-夏玉米轮作体系农田氮素处于大量赢余状态,从而导致氮素大量损失。因此,加强氮肥管理,提高氮肥利用率,加大有机肥施用的力度,是华北地区农田氮素资源管理的长期任务。     

Optimum N concentration in winter wheat grown in the coastal plain region of Virginia

Abstract

Limited information is available on optimum N levels in winter wheat (Triticum aestivum L.), particularly at higher yield levels. Three experiments were conducted in the Coastal Plain region of Virginia where N was applied at rates of 0, 67, 90 and 112 kg/ha to Wheeler, Mc Nair 1003 and Coker 747 soft red winter wheat varieties. Yields ranged from 2.33 to 5.83 Mg/ha in the study. Nitrogen fertilization increased yield up to the 67 kg/ha rate and increased N concentration in the plant tissue up to 67 or 112 kg of N/ha, depending on variety. Optimum N concentration, i.e., N concentration at maximum (100%) yield for Wheeler, Mc Nair 1003 and Coker 747, over the three experiments, was 4.54%, 4.52% and 4.81%, respectively, for entire above‐ground plant samples collected at Feekes growth stage 4 and 4.72%, 4.73% and 4.44% for flag leaf samples collected at Feekes growth stage 10. A N sufficiency range of 4.00–5.00% is suggested for use for the plant parts sampled for both growth stages.     

Immobilization of ammonium and nitrate and their interaction with native N in three Illinois Mollisols

Summary Three Illinois Mollisols were incubated for 2 weeks at 25°C after treatment with different amounts of glucose and/or ¹⁵N-labelled (NH₄)₂SO₄ or ¹⁵N-labelled KNO₃. The objectives were: (1) to compare the immobilization and interaction of NH _inf4 ^sup+ –N and NO _inf3 ^sup- –N with the native soil N, and (2) to study the relationship between immobilization of applied N and the added N interaction. As determined, immobilized N refers to forms not extractable with 2 MKCl (immobilized ¹⁵N+clay-fixed ¹⁵NH _inf4 ^sup+ ). In all cases, both NH _inf4 ^sup+ –N and NO _inf3 ^sup- –N were actively immobilized and transformed into organic forms in the presence of glucose. In the absence of glucose, a higher proportion of NH _inf4 ^sup+ than NO _inf3 ^sup- was recovered in organic forms. Although the three soils differed considerably in the amounts of applied N immobilized, similar trends in N immobilization were observed. A positive added N interaction occurred with all soils, the magnitude increasing with the rate of N addition. In the absence of glucose, higher added N interactions were obtained for NH _inf4 ^sup+ than NO _inf3 ^sup- , whereas there was very little difference between NH _inf4 ^sup+ and NO _inf3 ^sup- in the presence of glucose. The results indicate that under conditions of rapid immobilization (e.g., in the presence of glucose), NH _inf4 ^sup+ and NO _inf3 ^sup- will show comparable interaction with the native soil N, whereas in unamended soil, the extent of this interaction will be greater with NH _inf4 ^sup+ than with NO _inf3 ^sup- . Significant correlations were observed between applied N immobilized and the added N interaction only in one soil having a high initial mineral N content.     

黑垆土有机氮组分对可矿化氮的关系

Mineralizable N and organic N components in different layers (0-15, 15-30, 30-45, 45-60, 60-80 and 80-100 cm) of six soils with different fertilities sampled from Yongshou County, Shaanxi Province, China,were determined by the aerobic incubation method and the Bremner procedure, respectively. Correlation,multiple regression and path analyses were performed to study the relation of minerallzable N to organic N components. Results of correlation and regression analyses showed that the amounts of the N mineralized were parallel to, and significantly correlated with, the total acid hydrolyzahle N, but was not so with the acid-insoluble N. Of the hydrolyzable N, the amino acid N and the ammonia N had a highly consistent significant correlation with the mineralized N, and their partial regression coefficients were significant in the regression equations, showing their importance in contribution to the mineralizable N. The amino sugar N, on the other hand, had a relatively high correlation with the mineralized N, but their partial regression coefficients were not significant in the regression equations. In contrast, the hydrolyzable unknown N had no such relations.Path analysis further indicated that the amino acid N and ammonia N made great direct contributions to the mineralized N, but the contributions of the amino sugar N were very low. These strongly suggested tha tthe mineralized N in the soils tested was mainly from the hydrolyzable N, particularly the amino acid N and ammonia N which are the major sources for its production.     

Comparison of Chemical Methods for Assessing Nitrogen Mineralization in Two Calcareous Soils Treated with Organic Materials

Reliable and quick methods for measuring nitrogen (N)–supplying capacities of soils (NSC) are a prerequisite for using N fertilizers. This study was conducted to develop a routine method for estimation of mineralizable N in two calcareous soils (sandy loam and clay soils) treated with municipal waste compost or sheep manure. The methods used were anaerobic biological N mineralization, mineral N released by 2 M potassium chloride (KCl), ammonium (NH₄ ⁺) N extracted by 1 N sulfuric acid (H₂SO₄), NH₄ ⁺-N extracted by acid potassium permanganate (KMnO₄), and NH₄ ⁺-N released by oxidation of soil organic matter using acidified potassium permanganate. The results showed that oxidizable N extracted by acid permanganate, a simple and rapid measure of soil N availability, was correlated with results of the anaerobic method. Oxidative 0.05 N KMnO₄ was the best method, accounting for 78.4% of variation in NSC. Also, the amount of mineralized N increased with increasing level of organic materials and was greater in clay soil than sandy loam soil.     

Mid-Season Recovery from Nitrogen Stress in Winter Wheat

ABSTRACT

Although spring-applied nitrogen (N) has been shown to be most efficient, the technique of delaying all N applications until mid-season, and the resultant effect on maximum yields, has not been thoroughly evaluated. This experiment was conducted to determine if potential yield reductions from early-season N stress can be corrected using in-season N applications. Data from three experimental sites and two growing seasons (six site-year combinations) were used to evaluate three preplant N rates (0, 45, and 90 kg ha^?1) and a range of in-season topdress N rates. Topdress N amounts were determined using a GreenSeeker hand-held sensor and an algorithm developed at Oklahoma State University. Even when early-season N stress was present (0-N preplant), N-applied topdress at Feekes 5 resulted in maximum or near-maximum yields in four of six site-year combinations when compared with other treatments receiving both preplant and topdress N.     

Apparent availability of nitrogen in composted municipal refuse

The use of composted municipal refuse on agricultural land requires prior knowledge of the interactions among compost, soil, and plants. Research into the availability of N in highly matured municipal refuse compost is particularly important considering the current concern about groundwater contamination by NO _inf3 ^sup- -N. A greenhouse pot bioassay was conducted to determine the percentage of short-term apparent bioavailable N of a highly matured refuse compost and its relative efficiency in supplying inorganic N to the soil-plant system in comparison with NH₄NO₃. Municipal refuse (after 165 days of composting) was applied at rates equivalent to 10, 20, 30, 40, and 50 t ha^-1 to a ferrallitic soil from Tenerife Island (Andeptic Paludult). NH₄NO₃ was applied at rates equivalent to the total N content of the compost treatments. Perennial ryegrass (Lolium perenne L.) was grown in 3-kg pots and the tops were harvested at regular intervals after seedling emergence. The compost increased dry matter yield, soil mineral N, and plant N uptake proportional to the applied rate. These increases were significantly higher than the control at an application rate of 20 t ha^-1. After 6 months the apparent bioavailable N ranged from 16 to 21%. The relative efficiency was 43% after 30 days. This suggests that large inputs of inorganic N into soil can be obtained with high rates of this kind of compost, with a potential for NO _inf3 ^sup- -N contamination. However, applied at moderate rates in our bioassay (<50 t ha^-1), compost showed a low N-supplying capacity to ryegrass, i.e. a small fraction of the mineralized compost N was used by plants in the course of time. This was ascribed to a partial biological immobilization. This pattern of N availability in highly matured municipal refuse compost, positive net mineralization but partial immobilization, is similar to the pattern of N availability in biologically active soils and is therefore extremely interesting for the conservation of N in agro-ecosystems.     

Organic nitrogen compounds extracted from arable and forest soils by electro-ultrafiltration and recovery rates of amino acids

Summary Extraction of synthetic amino acids dissolved in water by means of electro-ultrafiltration (EUF) showed average recovery rates of about 75%. Higher losses were obtained, particularly with cysteine, methionine and NH₄ ⁴; the latter, probably being deprotonated at the cathode, may be lost in form of NH₃. The EUF extracts of three arable and two forest soils were investigated for their N compounds. In the arable soils only about 3% of the total organic N extracted by EUF was free amino acids; about 23%–55% consisted of amino N (hydrolysable N) and the rest was non-hydrolysable N. The two forest soils contained higher amounts of EUF-extractable organic N compared with the arable soils. In the two forest soils the content of free amino-acid N amounted to 8% and 11% of the EUF organic N, and the proportion of hydrolysable N from total EUF-organic N was 41% and 46%. It is suggested that the amino-acid N and the hydrolysable N can be easily mineralized.     

保护地蔬菜轮作体系中两种不同复合肥对产量的影响及其氮素动态特征

Yield and N uptake of tomato (Lycopersicum esculentum Mill.) and pepper (Capsicum annuum L.) crops in five successive rotations receiving two compound fertilizers (12-12-17 and 21-8-11 N-P₂O₅-K₂O) were studied to determine 1) crop responses, 2) dynamics of NO₃-N and NH₄-N in different soil layers, 3) N balance and 4) system-level N efficiencies. Five treatments (2 fertilizers, 2 fertilizer rates and a control), each with three replicates, were arranged in the study. The higher N fertilizer rate, 300 kg N ha^-1 (versus 150 kg N ha^-1), returned higher vegetable fruit yields and total aboveground N uptake with the largest crop responses occurring for the low-N fertilizer (12-12-17) applied at 300 kg N ha^-1 rather than with the high-N fertilizer (21-8-11). Ammonium-N in the top 90 cm of the soil profile declined during the experiment, while nitrate-N remained at a similar level throughout the experiment with the lower rate of fertilizer N. At the higher rate of N fertilizer there was a continuous NO₃-N accumulation of over 800 kg N ha^-1. About 200 kg N ha^-1 was applied with irrigation to each crop using NO₃-contaminated groundwater. In general, about 50% of the total N input was recovered from all treatments. Pepper, relative to tomato, used N more efficiently with smaller N losses, but the crops utilized less than 29% of the fertilizer N over the two and a half-year period. Local agricultural practices maintained high residual soil nutrient status. Thus, optimization of irrigation is required to minimize nitrate leaching and maximize crop N recovery.     

土壤微生物生物氮与植物氮吸收的关系

The contents of the soil microbial biomass nitrogen (SMBN) in the soils sampled from the Loess Plateau of China were determined using chloroform fumigation aerobic incubation method (CFAIM),chloroform fumigation anaerobic incubation method (CFANIM) and chloroform fumigation-extraction method (CFEM). The N taken up by ryegrass on the soils was determined after a galsshouse pot experiment. The flushes of nitrogen (FN) of the soils obtained by the CFAIM and CFANIM were higher than that by the CFEM, and there were significantly positive correlations between the FN obtained by the 3 methods. The N extracted from the fumigated soils by the CFAIM,CFANIM and CFEM were significantly positively correlated with the N uptake by ryegrass. The FN obtained by the 3 methods was also closely positively correlated with the N uptake by ryegrass. The FN obtained by the 3 methods was also closely positively correlated with the plant N uptake. The contributions of the SMBN and mineral N and mineralized N during the incubation period to plant N uptake were evaluated with the multiple regression method. The results showed that the N contained in the soil microbial biomass might play a noticeable role in the N supply of the soils to the plant.