叶绿素仪在夏玉米氮营养诊断中的应用

叶绿素仪(SPAD-502)的出现使通过无损伤的田间速测对作物进行氮营养诊断成为可能。采用简单的试验和研究方法在田间条件下研究了叶绿素仪应用于夏玉米氮营养诊断的可行性。研究结果表明,应用叶绿素仪监测夏玉米氮营养状况的最佳测定部位为最上部完全展开叶的中部,该部位叶绿素仪测定值与作物全氮、施氮量及产量之间均有较好的相关性。由于作物品种对叶绿素测定影响很大,需要通过相对叶绿素仪读数的方法对其进行校正,校正后叶绿素仪对夏玉米追肥推荐中营养状况的预测精度为66.7%。     

基于SPAD-502与GreenSeeker的冬小麦氮营养诊断研究

用GreenSeeker和SPAD-502测定了不同氮素处理的冬小麦冠层NDVI与叶片SPAD值, 分析了它们与叶片全氮、叶绿素含量及产量间的关系。结果表明: 冬小麦抽穗期SPAD值和NDVI值均与叶绿素含量呈极显著正相关; 除抽穗期和返青期外, SPAD值与叶氮含量、叶绿素含量的相关系数在其余各生育期均达到显著或极显著水平; NDVI值与叶氮含量、叶绿素含量在拔节期、乳熟期的相关性同SPAD值一致; SPAD值可以进行叶绿素的诊断, NDVI值可以进行氮的诊断。氮营养诊断时期应该选择拔节期。通过回归建立了基于SPAD值、NDVI值的产量估测模型, 可以通过SPAD值、NDVI值对冬小麦产量进行估算。     

应用叶绿素计诊断烤烟氮素营养状况

为探讨叶绿素计在估测烤烟叶绿素和氮浓度上的应用价值,进行了3个田间试验。即:郑州点2003年设施N.51.0.kg/hm2与4个品种NC89、RG17、85048、541;2004年设5个氮肥用量:N.30.04、0.5、51.0、61.5、75.0.kg/hm2与2个品种中烟101、云烟85;玉溪点于2005年设5个氮肥用量:N.02、7.0、54.5、81.8、109.0.kg/hm2与K326品种的试验。测定了不同试验条件下烤烟叶片的叶绿素计(SPAD-502和CCM-200)值和实际叶绿素浓度、全氮浓度,并进行了三者关系分析。结果表明,应用叶绿素计监测烤烟叶片最佳测定部位为完全展开叶的中部。叶绿素计测定值因年份、地点、氮肥水平、叶位、同一叶片不同的部位而异。叶绿素计值与叶绿素浓度、叶片全氮浓度之间有稳定的极显著相关性。叶绿素计SPAD-502的SPAD值和CCM-200的CCI值与叶绿素浓度之间的决定系数分别为0.8755(P0.001)和0.9499(P0.001)。SPAD计值(SPAD)与全氮浓度(N)之间回归方程为N=0.0265SPAD+0.9601(R2=0.7649,P0.001),经检验该模型具有较好的精确性和普适性,利用叶绿素计进行烤烟氮素营养监测是可行的。     

主要粮食作物基于SPAD的氮素营养诊断方法研究进展

基于叶绿素计测定的SPAD值与植物叶片叶绿素和氮浓度的关系,详细综述了用叶绿素计在玉米、小麦、水稻以及其他作物上进行氮素营养诊断的研究进展.第一,"相对SPAD值"、"氮饱和指数"或"归一化SPAD"等指标能够消除或减小品种、生育期及区域年际间的误差;第二,不同生育期应选择理想指示叶作为诊断目标;第三,不同叶位间的SP...     

应用叶绿素仪诊断冬小麦氮营养状况的研究

利用叶绿素仪SPAD-502进行田间快速测定,并对作物进行氮肥推荐。结果表明,冬小麦应用叶绿素仪监测氮营养状况的测定部位为最上部完全展开叶的中部,该部位叶绿素仪测定值与作物全氮、施氮量及作物产量之间均有较好的相关性。作物品种对叶绿素测定结果影响很大,需要通过相对叶绿素仪读数的方法对其进行校正。     

镉污染水稻土中水稻氮素营养的SPAD诊断

治理和安全利用重金属污染水稻土过程中,氮素营养的快速诊断是制定合理施肥措施的基础。叶绿素测定仪SPAD已广泛应用于非污染耕地土壤中玉米、小麦和棉花等作物的氮素营养诊断,然而针对镉污染条件下的不同类型水稻土,SPAD在诊断水稻氮素营养的适应性方面仍然缺乏系统研究。本研究采集了我国水稻主产区的21种典型水稻土,以德农2000为供试水稻品种,设置无镉污染、轻度镉污染、重度镉污染处理的水稻盆栽试验,研究水稻叶片SPAD值对镉污染水稻土氮素供应诊断和水稻产量预测的能力。结果表明:水稻土类型影响了水稻叶片SPAD值对不同水平镉污染的响应,土壤p H是主控因子,其相对影响的平均值为20%。水稻叶片SPAD值与不同生育期水稻籽粒氮素含量显著正相关,其中拔节期的相关系数最大;同时水稻叶片SPAD值与水稻营养生长期(苗期至拔节期)土壤溶液总氮和铵态氮含量呈显著正相关,且不受镉污染程度和土壤类型的影响。总体上,不同生育期(尤其是拔节期)水稻叶片的SPAD值可以表征镉污染条件下不同类型水稻土氮素养分供应对水稻氮素营养的影响。     

基于SPAD的西瓜氮素营养诊断与推荐施肥技术研究

为解决西瓜生产中存在盲目或过量氮肥施用导致的果实品质下降和氮素利用率低下等突出问题,开展了基于叶绿素仪测定值(SPAD值)的西瓜全生育期氮素营养诊断与推荐施肥技术研究,以期为利用SPAD仪建立田间西瓜氮素营养实时诊断技术、开发西瓜精准氮素养分管理模式提供理论依据。试验于2020—2021年在甘肃河西灌区的张掖市以‘金城5号’西瓜为材料,设置了0、80、160、240、320、400 kg/hm² 6个氮肥水平,通过研究不同施氮水平下西瓜关键生育时期不同叶位及叶片不同位置上的SPAD值、叶绿素含量、全氮含量的变化特征及其与西瓜产量、品质指标的相互关系,建立基于SPAD值进行西瓜氮素营养诊断与推荐施肥的实时氮肥管理(RTNM)模式,并开展RTNM模式的生产性验证。西瓜苗期顶一叶叶尖、伸蔓期顶三叶叶中、膨果期功能叶叶中位置SPAD值与叶片叶绿素、全氮含量相关性最佳,且变异系数小,是较为理想的指示叶或参照叶;通过指示叶SPAD值与西瓜产量、品质指标及施氮量的回归分析,获得西瓜产量超过60000 kg/hm²的SPAD阈值范围为苗期49.1～51.0、...     

硝酸盐反射仪和SPAD法对玉米氮素营养诊断的比较

精准的营养诊断是了解作物氮素营养及推荐施肥的基础。本文在田间滴灌条件下利用SPAD叶绿素仪(SPAD-502 Plus)和硝酸盐反射仪(RQ flex10)两种诊断方法对玉米关键生育时期的氮素营养诊断进行研究,旨在筛选出适宜的诊断方法,并依据诊断值建立滴灌玉米不同生育时期的施肥模型。试验设置0 kg(N)·hm~(-2)(N0)、225 kg(N)·hm~(-2)(N225)、330 kg(N)·hm~(-2)(N330)、435 kg(N)·hm~(-2)(N435)和540 kg(N)·hm~(-2)(N540)5个施氮水平,在不同生育时期测定了玉米叶片SPAD值和叶鞘NO_3~-含量,并分别与施氮量、植株全氮含量、产量进行方程拟合,比较两种诊断方法对玉米氮素营养的响应。研究结果表明:1)玉米叶片SPAD值和叶鞘NO_3~-含量均随施氮量的增加而显著升高,且在拔节期对施氮量的响应最敏感。叶鞘NO_3~-含量对施氮量变化的响应较SPAD值大,其与施氮量及玉米产量的拟合度均高于SPAD值,说明硝酸盐反射仪法对滴灌玉米氮素丰缺的反应更灵敏。2)玉米全氮含量与叶片SPAD值呈显著线性关系,而与叶鞘NO_3~-含量则以线性加平台表示。当叶鞘NO_3~-含量小于186 mg·L~(-1)时,植株全氮与NO_3~-间呈显著线性相关;当叶鞘NO_3~-含量大于186 mg·L~(-1)时,植株全氮随NO_3~-含量增加趋于不变。3)本农作区滴灌玉米最佳经济施氮量为402.5 kg·hm~(-2),对应的玉米产量为17 049 kg·hm~(-2)。玉米拔节期、抽雄吐丝期和灌浆期的临界叶鞘NO_3~-含量分别为729.3 mg·L~(-1)、536 mg·L~(-1)和81.2 mg·L~(-1)。SPAD叶绿素仪和硝酸盐反射仪均可对滴灌玉米进行氮素营养诊断,但硝酸盐速测值能更敏感地反映氮素丰缺状况,基于硝酸盐反射法进行作物氮素营养诊断及推荐施肥具有较好的准确性与适用性。     

主动遥感光谱仪Greenseeker与SPAD对玉米氮素营养诊断的研究

以手持式主动遥感光谱仪Greenseeker和叶绿素仪SPAD对玉米不同氮素水平下各个生育期的NDVI值及叶片SPAD值进行测试,研究不同氮素对玉米群体和个体营养状况的变化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,在一定的范围内随着氮肥用量的增加NDVI值也增加,氮肥施用量为N 300kg/hm2时NDVI值达到最高,NDVI 与氮肥施用量符合线性加平台的关系;玉米不同生育期间NDVI 值变化明显,苗期NDVI值比较低,大喇叭口期NDVI 值达到最高,以后逐渐下降并在抽雄期后趋于稳定。SPAD值与NDVI 值的变化趋势相一致,SPAD值与叶绿素含量成正相关关系,大喇叭口期完全展叶的SPAD 与产量存在正相关关系。手持式主动遥感光谱仪Greenseeker和叶绿素仪SPAD结合能够对玉米的氮素营养状况作营养诊断。     

氮素调控对寒地玉米氮素吸收与叶片SPAD值影响的初探

由于氮肥分配比例和施用时期不当,以及没有确定氮肥追肥时期的量化指标等原因,造成了氮肥利用率较低。试验通过对玉米进行氮素(追肥时期、追肥量)的优化,研究不同叶龄期玉米叶片叶绿素(SPAD值)及氮素积累动态的变化规律,确定玉米追肥时期的叶绿素阈值,对玉米进行调控和优化定量施肥。结果表明,玉米最佳追氮时期为十叶期,在此时期,玉米穗位叶SPAD值虽然逐渐降低,但上位叶在抽雄期达到最大,然后下降。玉米全株氮素积累逐渐增加。在十叶期追氮,高氮处理(150 kg/hm2)玉米的产量最高。     

叶绿素仪在氮肥推荐中的应用研究进展

叶绿素仪(Chlorophyll.meter)是近年来欧美一些国家在推荐施氮中开始使用的一种新型便携式仪器。这种仪器以叶绿素对红光和近红外光的不同吸收特性为原理来测定植物叶片的相对叶绿素含量,通过叶绿素与叶片全氮的关系来反映作物的氮营养状况,进而确定作物是否缺氮。这种新型仪器的使用为简便、快速、准确地进行氮肥推荐提供了一种新的思路。因此,通过研究不同作物,不同种植条件下叶绿素仪测定值与作物叶片全氮、作物产量之间的相关性,确定叶绿素仪测定值的临界水平,以及不同作物的测定部位、样品采集数量及影响测定准确性的因素,使这种技术尽快地应用于田间生产,有助于推动我国推荐施氮技术的进步。     

CALIBRATING CHLOROPHYLL METER (SPAD-502) READING BY SPECIFIC LEAF AREA FOR ESTIMATING LEAF NITROGEN CONCENTRATION IN SWEET SORGHUM

The chlorophyll meter (SPAD-502) is used to estimate nitrogen status of various crops. However, the relationship between SPAD readings and leaf nitrogen concentration (LNC) in sweet sorghum (Sorghum bicolor) has not been fully established. We examined the relationship between SPAD readings and LNC in sweet sorghum in a two-year study; and the effects of leaf thickness on the relationship was also examined. There was a significant relationship between the SPAD reading and LNC at each of two growth stages, but the correlation was weaker when the data for the two growth stages were pooled. This correlation improved when the specific leaf area was introduced as a second independent variable in the multiple regression analysis. This regression equation was applicable to not only different growth stages but also different seasons. The results suggest that the regression equation developed in this study can help in optimizing nitrogen fertilization for sweet sorghum production.     

Microwave‐oven drying of rice leaves for rapid determination of dry weight and nitrogen concentration

Predicting the need for fertilizer‐nitrogen (N) topdressing based on plant N status is an important N management strategy for increasing both grain yield and N‐use efficiency of irrigated rice. Plant N analysis by conventional‐oven drying and micro‐Kjeldahl procedure generally requires several days. Accurate estimation of leaf N content per unit dry weight (Ndw) at different growth stages by the chlorophyll meter requires that meter‐reading values (SPAD values) be adjusted for specific leaf weight (SLW). This study demonstrated that a microwave oven can be used for drying rice leaves for quick estimation of leaf dry weight without significantly influencing the estimation of Ndw by micro‐Kjeldahl procedure. Microwave oven drying of 0.5 g (dry weight) leaf samples required only two minutes. Extended exposure duration up to six minutes did not alter the measured Kjeldahl N concentration. Specific leaf weight determined with microwave‐oven drying improved the prediction of Ndw by SPAD. The chlorophyll meter with SLW adjustment can provide another tool to make rapid, in‐season diagnosis of crop N status.     

Chlorophyll meter estimates leaf area‐based nitrogen concentration of rice

Abstract

The chlorophyll meter (SPAD‐502) can be used to diagnose the nitrogen (N) status of rice (Oryza sativa L) plants to determine the need for fertilizer‐N topdressing. However, accurate estimation of leaf N concentration on a dry weight basis (N_dw) by SPAD requires the adjustment of SPAD values for specific leaf weight (SLW). The objective of this study was to determine if SPAD estimates of leaf N concentration on a leaf area basis (Na) without correcting for SLW. SPAD values were measured from different genotypes at various growth stages with the chlorophyll meter. Leaf N concentration was determined by micro‐Kjeldahl procedure and expressed based on dry weight and leaf area. Specific leaf weight was calculated as the ratio of leaf dry weight to leaf area. At each growth stage, SPAD estimated Na better than Ndw, especially at the middle and later growth stages. When data for all stages were pooled, SPAD values also correlated with Na better than with Ndw (r value of 0.81 versus 0.43). This finding was also true across 80 genotypes. For estimation of N_a by SPAD, therefore, no adjustment of SPAD values for SLW is needed.     

Chlorophyll meter readings in corn as affected by plant spacing

Abstract

Heightened environmental consciousness has increased the perceived need to improve nitrogen (N) use efficiency by crops. Synchronizing fertilizer N availability with maximum crop N uptake has been proposed as a way to improve N‐use efficiency and protect ground water quality. Chlorophyll meters (Minolta SPAD 502) have the potential to conveniently evaluate the N status of corn (Zea mays L.) and help improve N management. A potential problem with the use of chlorophyll meters is the effect of within‐row plant spacing on meter reading variability. Chlorophyll meter readings and leaf N concentration of irrigated corn at anthesis and grain yield at harvest were measured on plants grouped into eight within‐row plant spacing categories. Leaf N concentration was not affected by plant spacings, but chlorophyll meter readings and grain yield per plant increased as plant competition decreased and N fertilizer rate increased. These data indicate that avoiding plants having extreme spacings can greatly increase precision when using chlorophyll meters to evaluate the N status of corn.     

Evaluation of the Dualex for the Assessment of Corn Nitrogen Status

The Dualex is a new leaf-clip instrument that can be used to monitor corn nitrogen (N) status. It is based on the measurement of polyphenolics (Phen), which are secondary metabolites affected by stress factors. The purpose of this study was to compare Dualex to SPAD (chlorophyll meter), the latter having been used for several years in monitoring crop N status. As well, the interest of combining Dualex and SPAD information in Chl/DUAD (ratio of SPAD to Dualex reading on adaxial side), Chl/DUAB (ratio of SPAD to Dualex reading on abaxial side), and Chl/Phen (ratio of SPAD to the sum of DUAD and DUAB) ratios were considered. Significantly positive and negative correlations with corn leaf N concentration were found for SPAD and Dualex, respectively. Successful N status diagnosis could be achieved with either Dualex or SPAD for corn within 21 days after topdressing while the Dualex lost sensitivity at later stages. Dualex measurements could be limited to leaves abaxial side or adaxial side, instead of adaxial + abaxial sides, with no inconvenience. Among all parameters considered, the combined ratios with SPAD (Chl) and Dualex readings, Chl/DUAD, Chl/DUAB, and Chl/Phen were strongly related to applied N dose at all samplings dates, and found the most sensitive and robust through the season.