首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 31 毫秒
1.
In a 3-year study, grain yield, nitrogen use efficiency (NUE), and grain protein (GP) were evaluated as a function of rate and timing of nitrogen (N) fertilizer application. Linear models that included preplant N, normalized difference vegetation index (NDVI), cumulative rainfall, and average air temperature from planting to sensing (T-avg) were evaluated to predict NUE and GP in winter wheat. GreenSeeker readings were collected at Feekes (F) 3, 4, 5, and 7 growth stages. Combined with rainfall and/or T-avg, NDVI alone was not correlated with NUE. However, NDVI and rainfall explained 45% (r2 = 0.45) of the variability in GP at F7 growth stage. Preplant N, NDVI, rainfall and growing degree days (GDD) combined explained 76% (r2 = 0.76) of the variability in GP at F3. Mid-season climatic data improved the prediction of GP and should therefore be considered for refining fertilizer recommendations when GP levels are expected to be low.  相似文献   

2.
Four spring wheat genotypes (Triticum aestivum L.) were grown without (N0 = 0 kg N ha?1) and under ample (N1 = 250 kg ha?1) nitrogen (N) fertilizer in field experiments in two seasons. The aim was to assess genotypic variation in N use efficiency (NUE) components and N-related indices during grain filling thus to identify superior wheat genotypes. Leaf chlorophyll (SPAD) readings at crucial growth stages were employed to help differentiate genotypes. Interrelations between yield and N-related indices with SPAD, where also assessed to explain possible pathways of improving NUE early in the growing season. Results showed that genotypic effects on NUE were mostly evident in 2000, a year with drier preanthesis and wetter postanthesis than the normal periods. ‘Toronit’ almost always had the highest biomass yield (BY) and grain yield (GY). Except in 1999 under N0, ‘L94491? showed the highest % grain N concentration (GNC). Genotypes affected SPAD at almost all stages and N fertilization delayed leaf senescence for all genotypes and growth seasons. Correlations between SPAD at different growth stages and GY, N biomass yield at maturity (NBYM) and GNC were significant (P≤ 0.001), positive and strong/very strong (>r = 0.7). N translocation efficiency (NTE) was inversely related to PANU (~r = ? 0.77, P≤ 0.001), suggesting that N after anthesis is being preferentially transported to the ears to meet the N demand of the growing grains. It is concluded that there is still a large potential for increased NUE by improved N recirculation, use of fast and inexpensive crop N monitoring tools and high yielding, N uptake efficient genotypes.

Abbreviations: NUE, Nitrogen use efficiency; SPAD, Minolta SPAD-502 chlorophyll meter, NHI, nitrogen harvest index; HI, Harvest index; NTE, N translocation efficiency from vegetative plant parts to grain; DMTE, dry matter translocation efficiency; CPAY, contribution of pre-anthesis assimilates to yield; PANU, Post-anthesis N uptake, d.a.s., days after sowing, N0, zero (0) kg ha?1 applied N fertilizer, N1, 250 kg ha?1 applied N fertilizer.  相似文献   

3.
Greenhouse production of ornamental kale is popular for fall sales. The objective of this study was to evaluate if nondestructive handheld sensors could be used to quantify nitrogen (N) status in Brassica oleracea ‘Nagoya Red’. Topdressed fertilizer treatments of 0, 2.5, 5, 10, 15, and 20 g of 16-9-12 controlled release fertilizer (CRF) were utilized. Individual plants were scanned from 10 pots per treatment for Normalized Difference Vegetative Index (NDVI) values using a prototype NDVI pocket sensor, the recently released commercial GreenSeeker? handheld, and a Soil-Plant Analyses Development (SPAD) chlorophyll meter at three different rating dates starting 25 d after fertilizer treatment application (DAT). Linear and quadratic trends were observed within sampling dates. All three sensors showed correlations with leaf N depending on sampling time. Results indicated that 10 g CRF would be recommended for potted production.  相似文献   

4.
Optimum grain nitrogen (N) concentration and yield in spring wheat (Triticum aestivum L.) can be problematic without proper N fertilizer management. Sensor-based technologies have been used for application of fertilizers and also to predict yield in wheat, although little has been done in the prediction of grain N. Field studies were conducted in South Dakota in 2006 (Gettysburg, Bath, and Cresbard) and 2007 (Gettysburg, Aurora, Leola, and Artas). There were five N treatments (0, 56, 112, 168, and 224 kg N ha?1) applied pre-plant with a second N application applied foliar at anthesis. Sensor readings were taken at growth stages Feekes 10, anthesis, and postfoliar application using the GreenSeeker Hand Held optical sensor. Grain samples were taken at maturity and analyzed for total N. Using similar information collected in 2003 and 2005, a critical normalized difference vegetation index (NDVI) value was determined using the Cate–Nelson procedure. The critical NDVI value needed to ensure optimum grain N was 0.70. In 2006 and 2007, the plots that received an application of N at anthesis had higher grain N than the plots not receiving N. There was also a significant response between applied N and grain yield. The results show that with further studies, the Greenseeker could be used to apply N to maximize yield and grain N in a precise and accurate manner.  相似文献   

5.
The field study investigated the relationship of Minolta SPAD 502 (SPAD) readings to applied nitrogen (N) fertilizer rate, corn (Zea mays L.) yield, and leaf N concentration. The experiment was conducted on a total of six sites in Illinois during 1991 and 1992. Ten different open pedigree corn hybrids were grown at a final population of 65,000 plants ha‐1. Nitrogen was applied at four rates(0, 90, 180, and 270 kgN ha‐1) as 28% liquid N solution. Significant main effects of environment (E), and hybrid (H), and E x H interaction were detected for all measured parameters. SPAD readings and leaf N concentration at all sampling times (V7, R1, and R4) as well as grain N concentration were affected by N fertilizer rate. Maximum mean grain yield and maximum grain N concentration were obtained at 110 and 195 kg N ha‐1, respectively. At all sampling times the correlation of SPAD readings to N fertilizer rate were low but significant (R=0.22 at V7 and R1, R=0.11 at R4). SPAD correlation to corresponding leaf N concentration improved over time. The Pearson correlation was R=0.33 at V7 and increased to R=0.78 at R4. The SPAD meter did a good job at providing a measure of the relative greenness of living leaves at a specific point in time. Chlorophyll readings can therefore be useful in detecting N deficiencies in growing crops. But, the SPAD meter cannot be used to make accurate predictions of how much fertilizer N will be needed by a crop during the future growing season. We conclude then that the SPAD meter will be most useful as a diagnostic aid rather than a tool for N management in corn.  相似文献   

6.
There is still a lack of knowledge about the physiological traits of spring triticale (x Triticosecale Wittm.) and their relationship with grain yield and protein content under the conditions of the environmental Zone Nemoral 2. The objective of this study was to determine the relationships among the physiological indices, grain yield and protein content as affected by nitrogen (N) rates. The correlation among leaf area index (LAI), chlorophyll index (SPAD), canopy greenness index (CGI), leaf area duration (LAD) and grain yield as well as direct and indirect effects of those traits on the yield were investigated using a path analysis. Grain yield, protein content and physiological indices were significantly (P?≤?.01) affected by N fertilization. N90 level was the best compromise for the yield and physiological indices. The interaction of all physiological indices influenced the grain yield by 27–39%, protein by 42–44%. SPAD and LAI had greater influence on grain yield and grain protein than CGI and LAD. SPAD had positive direct dominant (the highest) effect on the yield only at BBCH 59 and BBCH 69 (50% of the tested cases). LAI was responsible for 19–39% of the correlation between yield and physiological indices. The physiological indices can be used for spring triticale growth modelling and agronomic management for improved productivity and grain quality. SPAD and LAI values, established at BBCH 45–69, can be used for grain yield prediction and those estimated at BBCH 69 can be used for grain protein prediction.

Abbreviations BBCH: Biologische Bundesantalt, Bundessortenamt und Chemische Industrie (decimal system for a uniform coding of phenologically similar growth stages of all mono- and dicotyledonous plant species); CGI: canopy greenness index; GS: growth stage; LAD: leaf area duration; LAI: leaf area index; SPAD: chlorophyll index (soil plant analysis development)  相似文献   

7.
Field experiments were conducted for two consecutive years on basmati rice (Oryza sativa L.) during summer and rainy seasons (April–November) of 2009 and 2010 in a sandy clay-loam soil (typic Ustochrept) at the research farm of Indian Agricultural Research Institute, New Delhi. The aim of this study was to determine the influence of zinc fertilizer sources [ethylenediamenetetraacetic acid (EDTA)-chelated zinc (Zn; 12% Zn), zinc sulfate heptahydrate (ZnSO4.7H2O; 21% Zn), zinc sulfate monohydrate (ZnSO4.H2O; 33% Zn), zinc oxide (ZnO; 82% Zn), and ZnSO4.7H2O + ZnO (50% + 50%)] and summer green manuring crops [Sesbania aculeata, Crotalaria juncea and Vigna unguiculata] on productivity, Zn-uptake and economics of basmati rice. Among the summer green manuring crops, Sesbania aculeata accumulated highest amount of total dry matter, 5.46 and 5.77 t ha?1 during 2009 and 2010, respectively. Incorporation of Sesbania aculeata also led to a significant increase in grain, straw and biological yields, Zn content and uptake and economics of succeeding basmati rice. With the incorporation of Sesbania aculeata, grain and straw yields of basmati rice was 4.89, 5.56 and 9.04, 10.21 t?1 ha during 2009 and 2010, respectively. Among the Zn fertilizer sources, EDTA-chelated Zn (12% Zn) was found to be the best with respect to grain, straw, and biological yields, Zn content and uptake and economics. Application of EDTA-chelated Zn (12% Zn) recorded the highest basmati rice grain (5.15 and 5.76 t ha?1) and straw yields (9.30 and 10.48 t ha?1) compared to control (no Zn application), which produced 4.09 and 4.75 t ha?1 of grain and 8.13 and 9.39 t ha?1 of straw yields, respectively, during 2009 and 2010. Highest Zn concentration in grain and straw and its uptake was recorded with Sesbania aculeata incorporation compared with Crotalaria juncea, Vigna unguiculata and summer fallow. Highest total Zn uptake in basmati rice was recorded with EDTA-chelated Zn (12% Zn) application, followed by ZnSO4.7H2O (21% Zn), ZnSO4.H2O (33% Zn), ZnSO4.7H2O + ZnO (50% + 50%), ZnO (82% Zn), and control (no Zn application). Sesbania aculeata incorporation and EDTA-chelated Zn (12% Zn) treatments were found a better combination with respect to basmati rice productivity. The best economical returns were obtained with Sesbania aculeata incorporation and ZnSO4.7H2O (21% Zn) combination. Thus, adequate Zn fertilization along with green manure crop incorporation can lead to higher productivity of basmati rice.  相似文献   

8.
冬小麦叶片氮含量与叶片光合作用和营养状况密切相关,直接影响植株生长发育,而茎秆中的氮含量与茎秆中纤维素、半纤维素和木质素的比例和含量密切相关,直接影响茎秆质量及植株的抗倒伏能力。然而,有关对冬小麦茎秆氮含量估算研究较为有限,限制了从氮含量角度判断茎秆质量及对倒伏的预测能力。为精准估算冬小麦不同器官（叶片、茎秆）氮含量,该研究通过2年田间试验,获取冬小麦4个关键生育期（拔节期、抽穗期、开花期、灌浆期）和3种施氮水平条件下（N1、N2和N3）的冠层光谱反射率、叶片、茎秆氮含量及叶片SPAD (soil and plant analyzer development, SPAD)值。分析了不同生育期和施氮水平条件下高光谱植被指数对叶片和茎秆氮含量的敏感性,并结合5种常用的机器学习算法：随机森林回归（random forest regression,RFR）、支持向量回归（support vector regression,SVR）、偏最小二乘回归（partial least squares regression,PLSR）、高斯过程回归（gaussian process regression,GPR）、深度神经网络回归（deep neural networks,DNN）构建冬小麦叶片和茎秆氮含量估算模型。结果表明：高光谱植被指数对叶片和茎秆氮含量的敏感性受到生育期和施氮水平的影响。在灌浆期,最佳植被指数双峰冠层植被指数 DCNI（double-peak canopy nitrogen index）对叶片氮含量的敏感性最高,R2为0.866。对茎秆氮含量,在抽穗期的敏感性最高,最佳植被指数归一化叶绿素比值指数 NPQI（normalized phaeophytinization index）与氮含量相关系数R2＝0.677。施氮水平的提升增加了光谱植被指数对茎秆氮含量的敏感性。结合SPAD值的机器学习算法提升了氮含量的估算精度,对叶片氮含量,在不同生育期和施氮水平条件下估算精度提升了1%～7%,其中在全生育期的归一化均方根误差NRMSE从0.254提升到0.214,抽穗期的NRMSE提升最大,从0.201提升到0.128。对茎秆氮含量,全生育期的NRMSE从0.443提升到0.400,抽穗期的NRMSE提升最大,从0.323提升到0.268。在全生育期,结合SPAD值的DNN模型对叶片（R2=0.782、NRMSE=0.214）和茎秆（R2=0.802、NRMSE=0.400）氮含量的估算精度最佳。研究说明,SPAD值与光谱植被指数结合有利于提升冬小麦不同生育期和施氮水平条件下叶片和茎秆氮含量的估算精度。  相似文献   

9.
基于SPAD-502与GreenSeeker的冬小麦氮营养诊断研究   总被引：9，自引：3，他引：9  
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。  相似文献   

10.
Present analyses to calculate nitrogen fertilizer recommendations are time consuming and costly. Therefore, a field study determining the efficiency of SPAD and NDVI meters to calculate soil N deficiency and guide fertilizer application timing and rate was completed. Reduced vs. conventional tillage at various N application rates was studied. Regardless of tillage system, both NDVI and SPAD were able to detect N deficiency at early growth stages, however, SPAD measurements better reflected plant N status regarding N application rates. A modified Michaelis-Menten model was used to illustrate the relationship between N rates and grain yield, as well as grain N content and leaf N content, and both showed acceptable goodness of fit. Grain yield under reduced tillage was significantly higher than that of conventional tillage. The combination of leaf nitrogen, SPAD, and NDVI data may become a tool to manage corn field nitrogen status and predict grain yield.  相似文献   

11.
Wheat cultivars (‘AC Barrie’, ‘Brook Field’, ‘Hoffman’, and ‘Norwell’) with different protein concentrations were compared under four nitrogen (N) levels (0, 50, 100 and 150 kg ha?1) in an environment-controlled greenhouse, and the same experiment with an additional N level (200 kg N ha?1) was repeated in the field in 2007. In the greenhouse experiment, application of 100 kg N ha?1 resulted in significantly greater grain yield due mainly to higher number of grains per spike and heavier mean grain weight; in the field study, the 150 kg N ha?1 treatment produced the greatest yield (P<0.01) primarily due to more number of grains per spike. Crude grain protein percentage was increased significantly with each increment of N up to the highest level; however, protein yield (kg ha?1) increased significantly with fertilizer up to 150 kg N ha?1. Leaf chlorophyll contents were increased linearly with increment of N levels up to 150 kg ha?1 both in the greenhouse and field trials while leaf area indices continued to increase up to the highest application rate (200 kg N ha?1). Canopy reflectance, expressed as normalized difference vegetation index (NDVI), attained maximum value with 150 kg N ha?1 in the field experiment. Among the varieties tested, “Hoffman” out-yielded other three varieties due to heavier grain weight. Although highest grain and/or plant crude protein content were recorded in ‘AC Barrie’, it was the variety ‘Hoffman’ that produced the highest total protein (kg ha?1) with largest NDVI and leaf area index (LAI) values.  相似文献   

12.
A field study conducted for two years (2006 and 2007) at the Research Farm of the Indian Agricultural Research Institute, New Delhi, India showed that zinc (Zn) fertilization increased yield attributes, grain and straw yield, enhanced Zn concentrations and its uptake and improved kernel quality before and after cooking in basmati rice ‘Pusa Sugandh 5’. A 2% Zn-coating with zinc sulfate (ZnSO4·7H2O) was found to be the best but a 2% Zn-coating with zinc oxide (ZnO) was very close to it in terms of grain and straw yield and Zn concentrations in basmati rice grain and straw under Zn stress conditions. Partial factor productivity (PFP) of applied Zn varied from 984–3,387 kg grain kg Zn?1, agronomic efficiency (AE) varied from 212–311 kg grain kg?1 Zn (applied) and physiological efficiency (PE) of Zn varied from 6,384–17,077 kg grain kg?1 Zn (absorbed). Thus, adequate Zn fertilization of basmati rice can lead to higher grain yield and Zn-denser grains with improved cooking quality in basmati rices under Zn stress soil conditions.  相似文献   

13.
Methods for determining midseason nitrogen (N) rates in corn have used the parameter normalized difference vegetation index (NDVI) and, in some cases, plant height. The objective of this study was to analyze the relationship of stalk diameter along with predictors of yield, including NDVI and plant height with grain yield. Five site-years of data were analyzed, where several rows of corn plants were selected, and yield from plants within the row was recorded individually. Measurements of stalk diameter, plant height, and NDVI were taken from growth stages V8–VT. Using a value of stalk diameter × plant height gave the best correlation with grain yield (r2 = 0.34, 0.55, 0.67; V8, V10, V12, growth stages respectively). This work showed that stalk diameter × plant height was positively correlated with by-plant corn grain yields, and this parameter could be used for refining midseason fertilizer N rates for growth stages V8–V12.  相似文献   

14.
The GreenSeeker? optical sensor is used as a management decision aid in many crops across the world. This sensor measures the normalized difference vegetative index (NDVI). It has been observed that when the by-plot coefficients of variation (CV) from the GreenSeeker? sensor NDVI readings in winter wheat (Triticum aestivum L.) was incorporated into the midseason calculation of the response index (RI), RI at harvest was better predicted than with NDVI alone. This study further evaluated the use of CV's collected from both small 1.48 m2 and large 17.0 m2 areas. Trials consisted of 3 seeding rates by 4 nitrogen rates. Results from this study showed that CV from NDVI readings and plant population were negatively correlated. Improved prediction of RI by utilizing CV was not found. It was however observed that when CV's were less than 5.0 and NDVI values were greater than 0.80 the RI was less than 1.2.  相似文献   

15.
Recent development in canopy optical‐sensing technology provides the opportunity to apply fertilizer variably at the field scale according to spatial variation in plant growth. A field experiment was conducted in Ottawa, Canada, for two consecutive years to determine the effect of fertilizer nitrogen (N) input at variable‐ vs. uniform‐application strategies at the V6–V8 growth stage, on soil mineral N, canopy reflectance, and grain yield of maize (Zea mays L.). The variable N rates were calculated using an algorithm derived from readings of average normalized difference vegetation index (NDVI) of about 0.8 m × 4.6 m, and N fertilizer was then applied to individual patches of the same size of NDVI readings (0.8 m × 4.6 m) within a plot (2184 m2). Canopy reflectance, expressed as NDVI, was monitored with a hand‐held spectrometer, twice weekly before tasseling and once a week thereafter until physiological maturity. Soil mineral N (0–30 cm depth) was analyzed at the V6 and VT growth stages. Our data show that both variable and uniform‐application strategies for N side‐dressings based on canopy‐reflectance mapping data required less amount of N fertilizer (with an average rate of 80 kg N ha–1 as side‐dressing in addition to 30 kg N ha–1 applied at planting), and produced grain yields similar to and higher nitrogen‐use efficiency (NUE) than the preplant fully fertilized (180 kg N ha–1) treatment. No difference was observed in either grain yield or NUE between the variable‐ and uniform‐application strategies. Compared to unfertilized or fully fertilized treatments, the enhancements in grain yield and NUE of the variable‐rate strategy originated from the later N input as side‐dressing rather than the variation in N rates. The variable‐rate strategy resulted in less spatial variations in soil mineral N at the VT growth stage and greater spatial variations in grain yield at harvest than the uniform‐rate strategy. Both variable‐ and uniform‐application strategies reduced spatial variations in soil mineral N at the VT stage and grain yield compared to the unfertilized treatment. The variable‐rate strategy resulted in more sampling points with high soil mineral N than the uniform‐rate strategy at the VT stage.  相似文献   

16.
Identifying the optimum resolution where differences in corn (Zea mays L.) grain yields are detectable could theoretically improve nitrogen (N) management, thereby resulting in economic and environmental benefits for producers and the public at large. The objective of this study was to determine the optimum resolution for prediction of corn grain yield using indirect sensor measurements. Corn rows, 15–30 m long, were randomly selected at three locations where the exact location of each plant was determined. In 2005 and 2006, four of eight rows at each location were fertilized with 150 kg N ha?1 as urea ammonium nitrate (28% N). A GreenSeeker? optical sensor was used to determine average Normalized Difference Vegetation Index (NDVI) across a range of plants and over fixed distances (20, 40, 45.7, 60, 80, 91.4, 100, 120, 140, 160, 180, 200, 220, and 240 cm). Individual corn plants were harvested and grain yield was determined. Correlation of corn grain yield versus NDVI was evaluated over both increasing distances and increasing number of corn plants. Then, the squared correlation coefficients (rcc 2) from each plot (used as data) were fitted to a linear plateau model for each resolution treatment (fixed distance and number of corn plants). The linear-plateau model coefficient of determination (rlp 2) was maximized when averaged over every four plants in 2004 and 2006, and over 11 plants in 2005. Likewise, rlp 2 was maximized at a fixed distance of 95, 141, and 87 cm in 2004, 2005, and 2006, respectively. Averaged over sites and years, results from this study suggest that in order to treat spatial variability at the correct scale, the linear fixed distances should likely be <87 cm or <4 plants as an optimum resolution for detecting early-season differences in yield potential and making management decisions based on this resolution.  相似文献   

17.
The permanent bed planting system for wheat (Triticum aestivum L.) production has recently received additional attention. Studies using hard red spring wheat (cultivar Nahuatl F2000) were conducted at two locations in central Mexico. The studies included the installation of three furrow diking treatments, two granular N timing treatments and three foliar N rates applied at the end of anthesis. The objective was to evaluate the effect of these factors on wheat grain yield, yield components and grain N in a wheat–maize (Zea maize L.) rotation with residues of both crops left as stubble. Results indicated that diking in alternate furrows increased both grain yield and the final number of spikes per m2. The split application of N fertilizer enhanced the number of spikes per m2 and grain N uptake, but the effect on grain yield was inconsistent. Similarly, grain protein increased with the foliar application of 6 kg N ha?1, depending upon the maximum temperature within the 10 days following anthesis. The normalized difference vegetative index (NDVI) readings collected at four growth stages were generally higher for the split N application than for the basal N application at planting. Grain N uptake was associated to NDVI readings collected after anthesis.  相似文献   

18.
Current methods of determining nitrogen (N) fertilization rates in winter wheat (Triticum aestivum L.) are based on farmer projected yield goals and fixed N removal rates per unit of grain produced. This work reports on an alternative method of determining fertilizer N rates using estimates of early-season plant N uptake and potential yield determined from in-season spectral measurements collected between January and April. Reflectance measurements under daytime lighting in the red and near infrared regions of the spectra were used to compute the normalized difference vegetation index (NDVI). Using a modified daytime lighting reflectance sensor, early-season plant N uptake between Feekes physiological growth stages 4 (leaf sheaths lengthen) through 6 (first node of stem visible) was found to be highly correlated with NDVI. Further analyses showed that dividing the NDVI sensor measurements between Feekes growth stages 4 and 6, by the days from planting to sensing date was highly correlated with final grain yield. This in-season estimate of yield (INSEY) was subsequently used to compute the potential N that could be removed in the grain. In-season N fertilization needs were then considered to be equal to the amount of predicted grain N uptake (potential yield times grain N) minus predicted early-season plant N uptake (at the time of sensing), divided by an efficiency factor of 0.70. This method of determining in-season fertilizer need has been shown to decrease large area N rates while also increasing wheat grain yields when each 1m2 area was sensed and treated independently.  相似文献   

19.
A field study was conducted to evaluate the nitrogen status and yield of spinach grown in soils amended with prunings of Leucaena leucocephala, (applied at a rate of 3, 5, 7 or 11 t ha?1). A ‘no fertilizer’ 0 nitrogen (N) and 150 kg N ha?1 (recommended) were the control treatments. SPAD readings were recorded for the top six leaves. Nitrogen sufficiency indices were used to indicate the N status of plants. Application of L. leucocephala prunings increased spinach yields (8.98–13.86 t DM ha?1) relative to the 0N treatment (1.35 t DM ha?1) and yields increased with increasing rate of pruning application. SPAD readings showed a linear increase with the increase in applied prunings. There was preferential distribution of N to upper leaves. The relationship between shoot N concentration and SPAD readings was linear and strongest for the top three leaves (r2 = 0.84–0.92). The results indicate the potential of chlorophyll meter readings in assessing N status of leafy vegetables grown on soils amended with different levels of legume tree prunings.  相似文献   

20.
The nitrogen (N) requirement of hybrid rice is generally greater than in conventional rice varieties. Recommendations for N monitoring at regular intervals of 7–10 days through leaf greenness are available, but farmers are accustomed to apply fertilizer N at selected growth stages only. An inexpensive leaf color chart (LCC) and nondestructive chlorophyll meters were evaluated for site-specific N management strategy in world’s first aromatic rice hybrid PRH-10 at the Indian Agricultural Research Institute, New Delhi. Two field experiments were conducted on PRH-10 with four levels of N (0, 70, 140, and 210 kg ha?1) during June–October of 2010 and 2011 to determine the LCC, soil–plant analysis development (SPAD), and Fieldscout CM 1000 (CM 1000) values for achieving economic optimum grain yield at three critical growth stages (tillering, panicle initiation, and flowering). Quadratic regression between N levels and grain yield were used to determine economic optimum grain yield (6427 kg ha?1 in 2010 and 6399 kg ha?1 in 2011) corresponding to optimum economical dose of 151 kg N ha?1 (2010) and 144 kg N ha?1 (2011). Nitrogen concentration in fully expanded youngest leaf correlated significantly (P < 0.01) and positively with LCC score, SPAD value, CM 1000 value, and total chlorophyll concentration at tillering, panicle initiation, and flowering for both years. The critical LCC score, SPAD, CM 1000 values, chlorophyll concentration, and leaf N concentration obtained were at tillering 4.4, 42.3, 285, and 2.16 mg g?1 fresh weight and 3.29%; at panicle initiation 4.4, 43.0, 276, and 2.16 mg g?1 fresh weight and 3.02%; and at flowering 4.5, 41.7, 270, and 2.05 mg g?1 fresh weight and 2.83%, respectively. Corrective N application should be done when observed leaf N indicator values at a particular growth stage reach or go below the critical values.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号