Quantifying Leaf Chlorophyll Concentration of Sorghum from Hyperspectral Data Using Derivative Calculus and Machine Learning

Leaf chlorophyll concentration (LCC) is an important indicator of plant health, vigor, physiological status, productivity, and nutrient deficiencies. Hyperspectral spectroscopy at leaf level has been widely used to estimate LCC accurately and non-destructively. This study utilized leaf-level hyperspectral data with derivative calculus and machine learning to estimate LCC of sorghum. We calculated fractional derivative (FD) orders starting from 0.2 to 2.0 with 0.2 order increments. Additionally, 43 common vegetation indices (VIs) were calculated from leaf spectral reflectance factor to make comparisons with reflectance-based data. Within the modeling pipeline, three feature selection methods were assessed: Pearson’s correlation coefficient (PCC), partial least squares based variable importance in the projection (VIP), and random forest-based mean decrease impurity (MDI). Finally, we used partial least squares regression (PLSR), random forest regression (RFR), support vector regression (SVR), and extreme learning regression (ELR) to estimate the LCC of sorghum. Results showed that: (1) increasing derivative order can show improved model performance until certain order for reflectance-based analysis; however, it is inconclusive to state that a particular order is optimal for estimating LCC of sorghum; (2) VI-based modeling outperformed derivative augmented reflectance factor-based modeling; (3) mean decrease impurity was found effective in selecting sensitive features from large feature space (reflectance-based analysis), whereas simple Pearson’s correlation coefficient worked better with smaller feature space (VI-based analysis); and (4) SVR outperformed all other models within reflectance-based analysis; alternatively, ELR with VIs from original reflectance yielded slightly better results compared to all other models.

Variations in Leaf Chlorophyll Concentration in Croton Plants (Codiaeum variegatum L.) Cultivar Gelatik at a Different Leaf Age

The leaf color of croton plants (Codiaeum variegatum L.) cv. Gelatik varies from green, yellow until red. This study aimed to evaluate the variations of leaf chlorophyll concentration in croton plants cv. Gelatik at a different leaf age. The branches of the stem with 9-10 leaves were three times sampled from croton trees grown in Kalasey Dua Village, Mandolang District, Minahasa Regency. All leaves of each branch were picked sequentially, from the oldest leaf in the lowest position to the youngest leaf in the terminal of the branch. Leaf colors were determined using a color grab program downloaded from the Google Play Store. Each leaf was extracted using 95% ethanol and the chlorophyll concentration was measured using the Nano Usage spectrophotometer-3000 at the wavelengths of 649 and 665 nm. The results of this study indicated that total chlorophyll concentration in croton leaves was 3.01-33.14 mg/L, chlorophyll a concentration was 0.03-3.90 mg/L, and chlorophyll b concentration was 18.77-31 25 mg/L. The chlorophyll concentrations in the old leaf with brown-red color was higher than other leaves with different color.Keywords: croton leaf; chlorophyll concentration; leaf ageKonsentrasi Klorofil Daun pada Tanaman Puring (Codiaeum variegatum L.) Varietas Gelatik dengan Umur Daun yang BerbedaABSTRAKTanaman puring (Codiaeum variegatum L.) varietas gelatik menunjukkan variasi warna daun, yaitu hijau, kuning, dan merah. Penelitian ini bertujuan untuk mengevalusi ada tidaknya variasi konsentrasi klorofil daun pada tanaman puring varietas gelatik dengan umur daun yang berbeda. Pengambilan sampel dilakukan sebanyak tiga kali, yaitu cabang tanaman puring varietas gelatik dengan 9-10 daun yang diambil dari pohon puring di Desa Kalasey Dua, Kecamatan Mandolang, Kabupaten Minahasa. Semua daun puring pada cabang pohon tersebut dipetik secara berurutan, dari daun tertua yang berada di posisi bawah sampai daun termuda di terminal cabang pohon tersebut. Warna daun ditentukan dengan menggunakan program color grab yang di- download dari Google Play Store. Setelah daun diekstrak dengan alkohol 95%, konsentrasi klorofil diukur dengan menggunakan spektrofotometer-3000 nano Usage pada panjang gelombang 649 dan 665 nm. Hasil penelitian ini menunjukkan bahwa konsentrasi klorofil total pada daun puring bervariasi antara 3,01-33,14 mg/L, konsentrasi klorofil a bervariasi antara 0,03-3,90 mg/L dan konsentrasi klorofil b bervariasi antara 18,77-31,25 mg/L. Konsentrasi klorofil pada daun tua yang berwarna coklat-merah cenderung lebih tinggi dibandingkan dengan pada daun dengan warna lain.Kata kunci: Daun puring; konsentrasi klorofil; umur daun

Estimación de la concentración de clorofila y su relación con la concentración de proteína cruda en tres especies del pasto Urochloa en el Piedemonte Llanero, Colombia

To establish the relationship between the intensity of the green color of leaves and their crude protein (CP) concentration in Urochloa brizantha, U. decumbens and U. humidicola pastures in the Piedemonte Llanero, Colombia, the leaf chlorophyll concentration was measured (in SPAD units), classified based on the Munsell color chart and compared with the leaf CP concentration determined by the Kjeldahl method. The regression analysis between chlorophyll and CP concentrations showed coefficients of determination (r2) between 0.76 and 0.88. While collection of additional data will allow colorimetric charts based on the Munsell color chart to be developed which can be used to predict CP levels for each of these species, the relationships generated can be used to develop recommendations to assist farmers in the region in their decisions on use and fertilizing of these pastures.

Assessment of Portable Chlorophyll Meters for Measuring Crop Leaf Chlorophyll Concentration

Accurate measurement of leaf chlorophyll concentration (LChl) in the field using a portable chlorophyll meter (PCM) is crucial to support methodology development for mapping the spatiotemporal variability of crop nitrogen status using remote sensing. Several PCMs have been developed to measure LChl instantaneously and non-destructively in the field, however, their readings are relative quantities that need to be converted into actual LChl values using conversion functions. The aim of this study was to investigate the relationship between actual LChl and PCM readings obtained by three PCMs: SPAD-502, CCM-200, and Dualex-4. Field experiments were conducted in 2016 on four crops: corn (Zea mays L.), soybean (Glycine max L. Merr.), spring wheat (Triticum aestivum L.), and canola (Brassica napus L.), at the Central Experimental Farm of Agriculture and Agri-Food Canada in Ottawa, Ontario, Canada. To evaluate the impact of other factors (leaf internal structure, leaf pigments other than chlorophyll, and the heterogeneity of LChl distribution) on the conversion function, a global sensitivity analysis was conducted using the PROSPECT-D model to simulate PCM readings under different conditions. Results showed that Dualex-4 had a better performance for actual LChl measurement than SPAD-502 and CCM-200, using a general conversion function for all four crops tested. For SPAD-502 and CCM-200, the error in the readings increases with increasing LChl. The sensitivity analysis reveals that deviations from the calibration functions are more induced by non-uniform LChl distribution than leaf architectures. The readings of Dualex-4 can have a better ability to restrict these influences than those of the other two PCMs.

Effect of Spraying with Seaweed Extract on Growth and Yield of Two Varieties of Wheat (Triticum aestivum L.)

A field experiment was conducted in agricultural field in Al-Rumaitha, district 25 km north of Al-Muthanna city, during the agricultural season 2017/2018. The aim was to study the effect of spray of seaweed extract at 0, 1 and 2 g.l-1 on growth and yield of two varieties of wheat (Bhooth 22 and Eebaa 99). The experiment was applied according to split plot design with three replicates. The results showed that the increasing of the concentration of seaweed extract up to 2 g L-1 in spray solution led to increase some growth properties (plant height, leaf chlorophyll concentration, flag leaf area and spike length). In addition seaweed extract up to 2 g.l-1 lead to increase the number of spikes/m2, grain yield, and biological yield gave 31.85%, 39.05% and 39.79% respectively compared to the control treatment, while the concentration of seaweed extract up to 1 g.l-1 lead to increased 1 the number of grains per spike. The results revealed a difference in between the varieties in almost growth and reproductive traits. Bhooth 22 has the highest plant height, leaf chlorophyll concentration, spike length, and number of spikes/ m2, grain yield (5979 kg ha-1) and total biomass yield was and the highest biomass (13571 kg ha-1). The interaction between spraying of seaweed extract and varieties explained a significant effect on leaf chlorophyll concertation and biomass yield.

Relationship between Flag Leaf Characteristics and Main Yield Components in Oat (Avena sativa L.)

The objective of this study was to investigate relationships between leaf area index, leaf chlorophyll concentration, yield components and grain yield in oat (Avena sativa L.). Ten oat varieties were analyzed in field conditions regarding those traits. Flag leaf chlorophyll concentration range between 451.51 and 747.79 units of μmol of chlorophyll per m2. Also, leaf area index range between 13.68 to 32.84 cm2. Significant correlation indices were highlighted between yield components and leaf area index, yield/yield components and chlorophyll concentration of flag leaf.

Effect of Tomato Rootstock on Hybrid and Heirloom Tomato Performance in a Midwest High Tunnel Production System

High tunnels allow vegetable growers to extend the growing season, increase crop production, and improve produce quality. Tomatoes (Solanum lycopersicum L.) are the most widely grown crops in high tunnels; however, tomato production in high tunnels can be challenging. Continuous cropping in high tunnels can increase soil-borne disease pressure and can lead to soil salinity or nutrient depletion issues. Based on preliminary research, we hypothesized that use of the rootstock ‘RST-04-106-T’ would increase yield and quality of heirloom and hybrid tomato scions compared with nongrafted plants. To test this hypothesis, our research objectives were to assess marketable yields, fruit quality and nutritional value, and plant growth of grafted and nongrafted hybrid and heirloom tomatoes in a high tunnel production system. Grafted and nongrafted ‘Cherokee Purple’ (heirloom) and ‘Mountain Fresh Plus’ (hybrid) tomatoes were grown in the same high tunnel for two seasons (7 May–20 Oct. 2015 and 29 April–7 Oct. 2016) at the Horticulture Research Station in Ames, IA. Grafted plants produced significantly more marketable fruit, although marketable and total fruit weight did not increase significantly. Individual fruit size was unaffected by grafting. Across cultivars, mean soluble solids content (SSC) in fruit was 0.3 °Brix lower in grafted plants as compared with the nongrafted control. Grafting did not affect lycopene content of fruit. Grafting increased stem diameter by an average of 0.8 mm, but overall plant biomass was unaffected. The effect of grafting on leaf chlorophyll concentration (SPAD readings) was mixed. In addition, grafting increased leaf chlorophyll concentration in ‘Cherokee Purple’ but decreased it in ‘Mountain Fresh Plus’ plants. Grafting is a valuable tool in tomato production, but the impact of ‘RST-04-106-T’ rootstock use appears to be specific to certain soil types with high incidence of bacterial wilt.