Remote Sensing Using Canopy and Leaf Reflectance for Estimating Nitrogen Status in Red-blush Pears

Reflectance measurements at leaf and canopy scales were made in a red-blush pear (Pyrus communis) orchard for two growing seasons. Canopy reflectance measurements were obtained using a multispectral camera flown on board an unmanned aerial vehicle (UAV), and leaf reflectance measurements were undertaken in a laboratory using a portable spectrometer. These measurements were used to compute reflectance indices as surrogates for direct leaf nitrogen (N) concentration measurements. The indices were evaluated against laboratory analysis of leaf N concentration. Regression results for leaf %N on canopy-level measurements with the multispectral camera resulted in the highest R2 value [R2 = 0.67; root mean square error (RMSE) = 0.24%N] with a new index, Modified Canopy Chlorophyll Content Index (M3CI)_710 nm. Regression results for leaf %N on leaf-level measurements in-laboratory resulted in the highest R2 value (R2 = 0.65) with two other indices, Normalized Difference Vegetation Index (NDVI) and Normalized Difference Red-edge Index (NDRE)_720 nm. The corresponding RMSE values were 0.26%N. The results indicate that reflectance indices measured at the leaf level, with a controlled light source and calibration, could be used to estimate leaf %N. An analysis of uncertainty indicated that if leaf %N is estimated from leaf-level reflectance values, 10 or more leaves (from the same tree) should be averaged. The results support the use of a UAV-based assessment for canopy %N using the M3CI_710 nm, which could provide spatial information of leaf N concentration across an orchard.

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Optical sensing estimation of leaf nitrogen concentration in maize across a range of water-stress levels

Crop and Pasture Science ◽

10.1071/cp10374 ◽

2011 ◽

Vol 62 (6) ◽

pp. 474 ◽

Cited By ~ 9

Author(s):

Tong-Chao Wang ◽

B. L. Ma ◽

You-Cai Xiong ◽

M. Farrukh Saleem ◽

Feng-Min Li

Keyword(s):

Water Stress ◽

Vegetation Index ◽

Optical Sensing ◽

Leaf Nitrogen ◽

Growth Stages ◽

N Concentration ◽

Leaf N Concentration ◽

Chlorophyll Index ◽

Plant Moisture ◽

Leaf N

Optical sensing techniques offer an instant estimation of leaf nitrogen (N) concentration during the crop growing season. Differences in plant-moisture status, however, can obscure the detection of differences in N levels. This study presents a vegetation index that robustly measures differences in foliar N levels across a range of plant moisture levels. A controlled glasshouse study with maize (Zea mays L.) subjected to both water and N regimes was conducted in Ottawa, Canada. The purpose of the study was to identify spectral waveband(s), or indices derived from different wavebands, such as the normalised difference vegetation index (NDVI), that are capable of detecting variations in leaf N concentration in response to different water and N stresses. The experimental design includes three N rates and three water regimes in a factorial arrangement. Leaf chlorophyll content and spectral reflectance (400–1075 nm) were measured on the uppermost fully expanded leaves at the V6, V9 and V12 growth stages (6th, 9th and 12th leaves fully expanded). N concentrations of the same leaves were determined using destructive sampling. A quantitative relationship between leaf N concentration and the normalised chlorophyll index (normalised to well fertilised and well irrigated plants) was established. Leaf N concentration was also a linear function (R2 = 0.9, P < 0.01) of reflectance index (NDVI550, 760) at the V9 and V12 growth stages. Chlorophyll index increased with N nutrition, but decreased with water stress. Leaf reflectance at wavebands of 550 ± 5 nm and 760 ± 5 nm were able to separate water- and N-stressed plants from normal growing plants with sufficient water and N supply. Our results suggest that NDVI550, 760 and normalised chlorophyll index hold promise for the assessment of leaf N concentration at the leaf level of both normal and water-stressed maize plants.

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Nitrogen use efficiency and critical leaf N concentration of Aloe vera in urea and diammonium phosphate amended soil

Heliyon ◽

10.1016/j.heliyon.2020.e05718 ◽

2020 ◽

Vol 6 (12) ◽

pp. e05718

Author(s):

Md. Akhter Hossain Chowdhury ◽

Taslima Sultana ◽

Md. Arifur Rahman ◽

Tanzin Chowdhury ◽

Christian Ebere Enyoh ◽

...

Keyword(s):

Nitrogen Use Efficiency ◽

Aloe Vera ◽

Diammonium Phosphate ◽

Nitrogen Use ◽

N Concentration ◽

Leaf N Concentration ◽

Use Efficiency ◽

Leaf N ◽

Amended Soil

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Estimating Plant Nitrogen Concentration of Maize Using a Leaf Fluorescence Sensor across Growth Stages

Remote Sensing ◽

10.3390/rs12071139 ◽

2020 ◽

Vol 12 (7) ◽

pp. 1139

Author(s):

Rui Dong ◽

Yuxin Miao ◽

Xinbing Wang ◽

Zhichao Chen ◽

Fei Yuan ◽

...

Keyword(s):

Precision Agriculture ◽

Fluorescence Sensor ◽

Accurate Estimation ◽

Growth Stages ◽

Fluorescence Sensors ◽

N Application ◽

N Concentration ◽

Leaf N Concentration ◽

N Status ◽

Leaf N

Nitrogen (N) is one of the most essential nutrients that can significantly affect crop grain yield and quality. The implementation of proximal and remote sensing technologies in precision agriculture has provided new opportunities for non-destructive and real-time diagnosis of crop N status and precision N management. Notably, leaf fluorescence sensors have shown high potential in the accurate estimation of plant N status. However, most studies using leaf fluorescence sensors have mainly focused on the estimation of leaf N concentration (LNC) rather than plant N concentration (PNC). The objectives of this study were to (1) determine the relationship of maize (Zea mays L.) LNC and PNC, (2) evaluate the main factors influencing the variations of leaf fluorescence sensor parameters, and (3) establish a general model to estimate PNC directly across growth stages. A leaf fluorescence sensor, Dualex 4, was used to test maize leaves with three different positions across four growth stages in two fields with different soil types, planting densities, and N application rates in Northeast China in 2016 and 2017. The results indicated that the total leaf N concentration (TLNC) and PNC had a strong correlation (R2 = 0.91 to 0.98) with the single leaf N concentration (SLNC). The TLNC and PNC were affected by maize growth stage and N application rate but not the soil type. When used in combination with the days after sowing (DAS) parameter, modified Dualex 4 indices showed strong relationships with TLNC and PNC across growth stages. Both modified chlorophyll concentration (mChl) and modified N balance index (mNBI) were reliable predictors of PNC. Good results could be achieved by using information obtained only from the newly fully expanded leaves before the tasseling stage (VT) and the leaves above panicle at the VT stage to estimate PNC. It is concluded that when used together with DAS, the leaf fluorescence sensor (Dualex 4) can be used to reliably estimate maize PNC across growth stages.

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Rootstock influences postharvest anthracnose development in 'Hass' avocado

Australian Journal of Agricultural Research ◽

10.1071/ar01015 ◽

2001 ◽

Vol 52 (10) ◽

pp. 1017 ◽

Cited By ~ 22

Author(s):

S. L. Willingham ◽

K. G. Pegg ◽

A. W. Cooke ◽

L. M. Coates ◽

P. W. B. Langdon ◽

...

Keyword(s):

First Record ◽

Mineral Nutrients ◽

Fruit Flesh ◽

N Concentration ◽

Nursery Stock ◽

Leaf N Concentration ◽

Hass Avocado ◽

Mn Concentration ◽

Leaf N

Rootstock studies conducted on ‘Hass’ avocado found that rootstock had a significant impact on postharvest anthracnose susceptibility. This is the first record of such an effect for avocado. The severity and incidence of anthracnose was significantly lower on ‘Hass’ grafted to ‘Velvick’ Guatemalan seedling rootstock compared with the ‘Duke 6’ Mexican seedling rootstock. Differences in anthracnose susceptibility were related to significant differences in concentrations of antifungal dienes in the leaves and mineral nutrients in the leaves and fruits from trees grafted to different rootstocks. Leaf diene concentrations were up to 1.5 times higher in ‘Hass’ trees on the ‘Velvick’ than the ‘Duke 6’ rootstock. In ungrafted nursery stock trees, diene concentrations were around 3 times higher in ‘Velvick’ than ‘Duke 6’ leaves. The ‘Velvick’/‘Hass’ combination also had a significantly lower leaf N concentration, a significantly higher fruit flesh Mn concentration, and significantly lower and higher leaf N/Ca and Ca+Mg/K ratios, respectively. A significant correlation (r = 0.82) between anthracnose severity and skin N/Ca ratio was also evident.

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Effect of N fertilization rate on soil alkali-hydrolyzable N, subtending leaf N concentration, fiber yield, and quality of cotton

The Crop Journal ◽

10.1016/j.cj.2016.03.006 ◽

2016 ◽

Vol 4 (4) ◽

pp. 323-330 ◽

Cited By ~ 17

Author(s):

Binglin Chen ◽

Hongkun Yang ◽

Weichao Song ◽

Chunyu Liu ◽

Jiao Xu ◽

...

Keyword(s):

Fertilization Rate ◽

N Fertilization ◽

Yield And Quality ◽

Fiber Yield ◽

N Concentration ◽

Leaf N Concentration ◽

Leaf N

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Diagnostic nitrogen concentrations for tomatoes grown in sand culture

Australian Journal of Experimental Agriculture ◽

10.1071/ea9880401 ◽

1988 ◽

Vol 28 (3) ◽

pp. 401 ◽

Cited By ~ 3

Author(s):

DO Huett ◽

G Rose

Keyword(s):

Critical Values ◽

Sand Culture ◽

Nutrient Concentrations ◽

Total N ◽

Nitrate N ◽

N Concentration ◽

Leaf N Concentration ◽

Petiole Sap ◽

N Status ◽

Leaf N

The tomato cv. Flora-Dade was grown in sand culture with 4 nitrogen (N) levels of 1.07-32.14 mmol L-1 applied as nitrate each day in a complete nutrient solution. The youngest fully opened leaf (YFOL) and remaining (bulked) leaves were harvested at regular intervals over the 16-week growth period. Standard laboratory leaf total and nitrate N determinations were conducted in addition to rapid nitrate determinations on YFOL petiole sap. The relationships between plant growth and leaf N concentration, which were significantly affected by N application level, were used to derive diagnostic leaf N concentrations. Critical and adequate concentrations in petiole sap of nitrate-N, leaf nitrate-N and total N for the YFOL and bulked leaf N were determined from the relationship between growth rate relative to maximum at each sampling time and leaf N concentration. YFOL petiole sap nitrate-N concentration, which can be measured rapidly in the field by using commercial test strips, gave the most sensitive guide to plant N status. Critical values of 770-1 120 mg L-I were determined over the 10-week period after transplanting (first mature fruit). YFOL (leaf + petiole) total N concentration was the most consistent indicator of plant N status where critical values of4.45-4.90% were recorded over the 4- 12 week period after transplanting (early harvests at 12 weeks). This test was less sensitive but more precise than the petiole sap nitrate test. The concentrations of N, potassium, phosphorus, calcium and magnesium in YFOL and bulked leaf corresponding to the N treatments producing maximum growth rates are presented, because nutrient supply was close to optimum and the leaf nutrient concentrations can be considered as adequate levels.

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Non-Destructive Monitoring of Maize Nitrogen Concentration Using a Hyperspectral LiDAR: An Evaluation from Leaf-Level to Plant-Level

Remote Sensing ◽

10.3390/rs13245025 ◽

2021 ◽

Vol 13 (24) ◽

pp. 5025

Author(s):

Kaiyi Bi ◽

Zheng Niu ◽

Shunfu Xiao ◽

Jie Bai ◽

Gang Sun ◽

...

Keyword(s):

Precision Agriculture ◽

Spatial Information ◽

Nitrogen Concentration ◽

Point Clouds ◽

Future Research ◽

Least Squares Regression ◽

N Concentration ◽

Leaf Level ◽

Plant Level ◽

Remote Sensing Techniques

Advanced remote sensing techniques for estimating crop nitrogen (N) are crucial for optimizing N fertilizer management. Hyperspectral LiDAR (HSL) data, with both spectral and spatial information of the targets, can extract more plant properties than traditional LiDAR and hyperspectral imaging systems. In this study, we tested the ability of HSL in terms of estimating maize N concentration at the leaf-level by using spectral indices and partial least squares regression (PLSR) methods. Subsequently, the N estimation was scaled up to the plant-level based on HSL point clouds. Biomass, extracted with structural proxies, was utilized to exhibit its supplemental effect on N concentration. The results show that HSL has the ability to extract N concentrations at both the leaf-level and the canopy-level, and PLSR showed better performance (R2 > 0.6) than the single spectral index (R2 > 0.4). In comparison to the stem height and maximum canopy width, the plant height had the strongest ability (R2 = 0.88) to estimate biomass. Future research should utilize larger datasets to test the viability of using HSL to monitor the N concentration of crops, which is beneficial for precision agriculture.

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How Nitrogen Supply Affects Growth and Nitrogen Uptake, Use Efficiency, and Loss from Citrus Seedlings

Journal of the American Society for Horticultural Science ◽

10.21273/jashs.121.1.105 ◽

1996 ◽

Vol 121 (1) ◽

pp. 105-114 ◽

Cited By ~ 14

Author(s):

John D. Lea-Cox ◽

James P. Syvertsen

Keyword(s):

Plant Growth ◽

N Uptake ◽

Single Application ◽

N Application ◽

N Supply ◽

N Concentration ◽

Leaf N Concentration ◽

Use Efficiency ◽

Complete Nutrient Solution ◽

Leaf N

We examined how N supply affected plant growth and N uptake, allocation and leaching losses from a fine sandy soil with four Citrus rootstock species. Seedlings of `Cleopatra' mandarin (Citrus reticulata Blanco) and `Swingle' citrumelo (C. paradisi × P. trifoliata) were grown in a glasshouse in 2.3-liter pots of Candler fine sand and fertilized weekly with a complete nutrient solution containing 200 mg N/liter (20 mg N/week). A single application of 15NH415NO3(17.8% atom excess 15N) was substituted for a normal weekly N application when the seedlings were 22 weeks old (day O). Six replicate plants of each species were harvested at 0.5, 1.5, 3.5, 7, 11, and 30 days after 15N application. In a second experiment, NH4 NO3 was supplied at 18,53, and 105 mg N/week to 14-week-old `Volkamer' lemon (C. volkameriana Ten. & Pasq.) and sour orange (C. aurantium L.) seedlings in a complete nutrient solution for 8 weeks. A single application of 15NH415NO3 (23.0% 15N) was substituted at 22 weeks (day 0), as in the first experiment, and seedlings harvested 3,7, and 31 days after 15N application. Nitrogen uptake and partitioning were similar among species within each rate, but were strongly influenced by total N supply and the N demand by new growth. There was no 15N retranslocation to new tissue at the highest (105 mg N/week) rate, but N supplies below this rate limited plant growth without short-term 15N reallocation from other tissues. Leaf N concentration increased linearly with N supply up to the highest rate, while leaf chlorophyll concentration did not increase above that at 53 mg N/week. Photosynthetic CO2 assimilation was not limited by N in this study; leaf N concentration exceeded 100 mmol·m-2 in all treatments. Thus, differences in net productivity at the higher N rates appeared to be a function of increased leaf area, but not of leaf N concentration. Hence, N use efficiency decreased significantly over the range of N supply, whether expressed either on a gas-exchange or dry weight basis. Mean plant 15N uptake efficiencies after 31 days decreased from 60% to 47% of the 15N applied at the 18,20, and 53 mg N/week rates to less than 33% at the 105 mg N/week rate. Leaching losses increased with N rate, with plant growth rates and the subsequent N requirements of these Citrus species interacting with residual soil N and potential leaching loss.

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Fruit Yield, Size, and Color Responses of Two Greenhouse Cucumber Types to Nitrogen Fertilization in Perlite Soilless Culture

HortTechnology ◽

10.21273/horttech.15.3.0565 ◽

2005 ◽

Vol 15 (3) ◽

pp. 565-571 ◽

Cited By ~ 10

Author(s):

C. Jasso-Chaverria ◽

G.J. Hochmuth ◽

R.C. Hochmuth ◽

S.A. Sargent

Keyword(s):

Nutrient Solution ◽

Fruit Production ◽

N Fertilization ◽

N Concentration ◽

Hue Angle ◽

Greenhouse Cucumber ◽

Leaf N Concentration ◽

Black Plastic ◽

Spring Harvest ◽

Leaf N

Two greenhouse cucumber (Cucumis sativus) cultivars with differing fruit types [European (`Bologna') and Beit-alpha (`Sarig')] were grown during two seasons in a perlite medium in black plastic nursery containers in a passively ventilated greenhouse in northern Florida to evaluate fruiting responses to nitrogen (N) fertilization over the range of 75 to 375 mg·L–1. Fruit production, consisting mostly of fancy fruits, increased quadratically with N concentration in the nutrient solution, leveling off above 225 mg·L–1 for both cucumber cultivars. Fruit length and diameter were not affected by N concentration in the nutrient solution. Leaf N concentration, averaged over three sampling dates, increased linearly with N concentration in the nutrient solution from 46 g·kg–1 with 75 mg·L–1 N to 50 g·kg–1 with 375 mg·L–1 N. Fruit firmness decreased with increasing N concentration and there was little difference in firmness between the two cultivars. Firmness was similar across three measurement dates during the spring harvest season, but increased during the season in the fall. Fruit color responses to N concentration were dependent on the specific combination of experiment, sampling date, and cultivar. For most combinations of experiment, sampling date, and cultivar, cucumber epidermal color was greener (higher hue angle) with increased N concentration. The color was darkest (lowest L* value) and most intense (highest chroma value) with intermediate to higher N concentrations.

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Solar radiation effects on leaf nitrogen and phosphorus stoichiometry of Chinese fir across subtropical China

Forest Ecosystems ◽

10.1186/s40663-021-00344-6 ◽

2021 ◽

Vol 8 (1) ◽

Author(s):

Ran Tong ◽

Yini Cao ◽

Zhihong Zhu ◽

Chenyang Lou ◽

Benzhi Zhou ◽

...

Keyword(s):

Forest Ecosystems ◽

Chinese Fir ◽

Path Coefficient ◽

Soil P ◽

P Concentration ◽

N Concentration ◽

P Content ◽

Leaf N Concentration ◽

Leaf P ◽

Leaf N

Abstract Background Solar radiation (SR) plays critical roles in plant physiological processes and ecosystems functions. However, the exploration of SR influences on the biogeochemical cycles of forest ecosystems is still in a slow progress, and has important implications for the understanding of plant adaption strategy under future environmental changes. Herein, this research was aimed to explore the influences of SR on plant nutrient characteristics, and provided theoretical basis for introducing SR into the establishment of biochemical models of forest ecosystems in the future researches. Methods We measured leaf nitrogen (N) and phosphorus (P) stoichiometry in 19 Chinese fir plantations across subtropical China by a field investigation. The direct and indirect effects of SR, including global radiation (Global R), direct radiation (Direct R) and diffuse radiation (Diffuse R) on the leaf N and P stoichiometry were investigated. Results The linear regression analysis showed that leaf N concentration had no association with SR, while leaf P concentration and N:P ratio were negatively and positively related to SR, respectively. Partial least squares path model (PLS-PM) demonstrated that SR (e.g. Direct R and Diffuse R), as a latent variable, exhibited direct correlations with leaf N and P stoichiometry as well as the indirect correlation mediated by soil P content. The direct associations (path coefficient = − 0.518) were markedly greater than indirect associations (path coefficient = − 0.087). The covariance-based structural equation modeling (CB-SEM) indicated that SR had direct effects on leaf P concentration (path coefficient = − 0.481), and weak effects on leaf N concentration. The high SR level elevated two temperature indexes (mean annual temperature, MAT; ≥ 10 °C annual accumulated temperature, ≥ 10 °C AAT) and one hydrological index (mean annual evapotranspiration, MAE), but lowered the soil P content. MAT, MAE and soil P content could affect the leaf P concentration, which cause the indirect effect of SR on leaf P concentration (path coefficient = 0.004). Soil N content had positive effect on the leaf N concentration, which was positively and negatively regulated by MAP and ≥ 10 °C AAT, respectively. Conclusions These results confirmed that SR had negatively direct and indirect impacts on plant nutrient status of Chinese fir based on a regional investigation, and the direct associations were greater than the indirect associations. Such findings shed light on the guideline of taking SR into account for the establishment of global biogeochemical models of forest ecosystems in the future studies.

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