SPAD Units Research Articles

English

Worldwide, Mexico represents the first exporter of mango. However, in recent years mango exports have decreased by 29 points due to a change in the preference of the American market; hence, it is essential to diversify the supply of mangoes exports. Measurement of the net photosynthesis response and internal CO2 concentrations can provide data on important parameters of the physiology of a variety; these have been widely used in ecophysiological studies and allow the early evaluation of germplasm. The objective of the study is to do a physiological evaluation of 8 mango varieties (Nam Doc Mai, Rosigold, Mallika, Ivory, Alphonse, Neelum, Fairchild and Kesar) recently introduced to Mexico and 2 recently registered by INIFAP (Ataulfo “Diamante” and Ataulfo “Zafiro”), all with export potential. The work was carried out under 2 conditions (laboratory and greenhouse). For the photosynthesis registry, nursery plants approximately 18 months old were used (net photosynthesis, stomatal conductance, internal CO2 concentration and evapotranspiration, SPAD units and nutrients (NO3-, K+, Ca2+ y Na+). In both conditions (laboratory and nursery), it was found that the cultivars with the highest levels of the physiological variables, photosynthesis, concentration of chlorophyll and nutrients in the leaf were Fairchild, Mallika and Kesar. The cultivars such as Rosygold and Nam Doc Mai and Ivory, in contrast, those with the lowest levels were Ataulfo Zafiro, Ataulfo Diamante, Alphonse and Neelum. The evapotranspiration (Evap), net photosynthesis (PN) and concentration of Intercellular CO2 (Cint) kinetics were used to describe that all the cultivars presented a similar behavior and evidenced differences in the intensity of the same. Key words: Mangifera indica L., chlorophyll, photosynthesis, nutrients.

Effect of Conjunctive use of Inorganic Potassium, Potassium Humate and Triacontanol on Chlorophyll, Carotenoid and Nutrient uptake by Tomato (Solanum lycopersicum L.) in an Alfisol of Telangana State

A field experiment was conducted during kharif, 2011 on sandy clay soil to study the effect of individual and integrated use of inorganic potassium, potassium humate and triacontanol on chlorophyll, carotenoid and nutrient uptake by tomato. The experiment was conducted in randomized block design with sixteen treatments replicated thrice. The soil samples were collected from the experimental site and analysed for their salient characteristics and the plant samples were analysed for chlorophyll, carotenoid, nutrient content and uptake. Tomato (ArkaVikas) responded significantly to potassium application. The leaf chlorophyll and carotenoid content were found significantly higher in treatment receiving 60 kg K2O ha−1 along with foliar application of potassium humate @0.5 L/acre at flowering and triacontanol @ 1μM with the corresponding values of 52.41SPAD units and 0.743 mg g−1 respectively. The nutrient content and uptakes by the crop were found to be significantly influenced by the treatment receiving 60 kg K2O ha−1 along with foliar application of potassium humate and triacontanol which was significantly superior to the recommended dose of K.

Đánh giá khả năng chịu mặn tăng dần của cỏ thức ăn gia súc lông tây (Brachiaria mutica), cỏ Paspalum (Paspalum atratum) và cỏ Setaria (Setaria sphacelata) trong điều kiện thí nghiệm

The study was conducted in the net house to evaluate salt tolerance capacity of Para grass, Paspalum grass and Setaria grass which were grown in hydroponics condition with Hoagland solution. NaCl was added to get five levels of 0, 5, 10, 15 and 20‰, with a weekly increment 5‰ was added into the solution until reached the level of 20‰. The experiment was arranged in a completely randomized design with three replications. The results showed that the NaCl level of 15‰ and 20‰ affected the growth of the three studied species, but did not affect survival rate of Para and Setaria grass. Chlorophyll content (SPAD unit) was increased in Para grass and was remained in African grass, whereas it was reduced in Paspalum grass. Para grass accumulated the highest proline content in leaves tissues. The results indicated that salinity tolerance capacity of Paspalum grass is lower than that of Para grass and African grass; therefore, the later two species were the potential species for fodder production in the coastal area or salt-affected soils in the Mekong Delta.

ROLE OF GROWTH REGULATORS BRS AND CPPU IN GROWTH AND LEAVES MINERAL AND HORMONAL CONTENT OF OLIVE TRANSPLANTS

This study was conducted in the olive orchard, in Habbaniyah city, Anbar province 84 km west of Baghdad during 2018 growing seasons to investigate the influence of brassinolide (BRs) and CPPU spray on 2 year's old trees of “Nebali” olive cultivar. This study included two treatments: three levels of spraying of BRs, 0 (BR0), 1mg L-1 (BR1) and 2mg L-1 (BR2) and four levels of spraying of cytokinins (CPPU), 0 (C0), 2.5mg L-1 (C2.5), 5mg L-1 (C5) and 10mg L-1 (C10) and their interaction. Treatments were replicated three times with two transplants in experimental unit at factorial experiment in a RCBD. The number of trees used was 72 trees. The experimental results showed that BRs spray at 2 mg L-1 gave the highest leaves chlorophyll content of 62.69 SPAD units, leaves dry weight of 29.49 %, highest leaf area of 6.80 cm2, leaf nitrogen content of 1.169 %, highest leaf IAA content of 44.49 ?g g-1 FW and highest leaf GA content of 150.24 ?g g-1 FW. Results also showed that CPPU spray at levels 10 mg L-1 superiority of the control treatment and gave the highest leaves chlorophyll content of 62.89 SPAD units, leaves dry weight of 28.92 %, leaf IAA content of 41.82 ?g g-1 FW and highest leaf GA content of 134.00 ?g g-1 FW .The lowest value of these parameters was found in the control (BR0C0).

Efek Paparan Musik Klasik, Hard Rock dan Murottal Terhadap Pertumbuhan Vegetatif Tanaman Bayam Merah (Alternanthera amoena Voss)

This research was conducted to determine the effect of classical music, hard rock and murottal against to vegetative growing of red spinach plants. The research used a completely randomizes design with 4 treatments and 5 replicates. ANOVA result showed that music exposure had significant effect on plant growth. Murottal exposure gave optimal result on plant height 35,70 cm, leaf area 43,40 cm2, root length 9,40 cm, stomata porous length 23,00 µm, wet weigh 15,59 g, and dry weight of the plant 11,25 g. Exposure to hard rock music gives optimal results on the amount of leaf chlorophyll is worth 34,52 spad unit.

Sunlight transmitted by colored shade nets on photosynthesis and yield of cucumber

ABSTRACT: Black shading nets are widely used in the protected cultivation of vegetables as a technique for controlling light and temperature, while the colored shading nets, with special optical properties to improve the use of solar radiation, appeared recently in the agricultural plastics market. Light quality transmitted by gray, aluminized, pearl, blue, red and black (control) nets with 30% shade was evaluated, as well as its effects on photosynthetic properties and fruits production of cucumber plants. Treatments (shade nets) were established under a randomized complete block design with four repetitions. The red net transmitted 23.7 and 40.3% more photosynthetic photon flux density (400 to 700nm) and red light (600 to 700nm) and the blue net transmitted 36% more blue light (400 to 500nm) in comparison with the respective transmissions of black net. All nets increased the photosynthetic responses: transpiration, stomatal conductance and CO2 assimilation, observed in plants grown under black net. Leaf greenness (41.6 SPAD units) and foliar area (90dm2) increased 22.8 and 38.9% with the red net, while the dry weight of leaf (52.5g) increased 21.9% with pearl net. Pearl, red, aluminized and blue nets showed to be viable alternatives because the production of fruit increased in 71, 48, 46 and 46%, respectively, in comparison with the conventional black net (52t ha-1).

SPAD index in the diagnosis of nitrogen status in cauliflower as a function of nitrogen fertilization

The correct management of fertilization in cauliflower crop can be obtained by synchronizing the plant demand with the N supply during the crop cycle. There is no study indicating that the SPAD index can be used in the eval­uation of nitrogen nutrition of cauliflower. Thus, the objective of this work was to evaluate the nitrogen nutritional status of cauliflower using the SPAD index, and curd yield as a function of nitrogen fertilization. Four rates of N in topdressing (0, 150, 300, and 450 kg ha -1 ) were evaluated in the experimental design of randomized blocks with four replicates. The final harvest of curds occurred from 68 to 76 days after transplanting. The first- and second-year results showed a significant difference. Curd fresh mass showed a quadratic adjustment, with the maximum value of 1,435 and 1,611 g, estimated with the rates of 331 and 307 kg ha -1 N, in the first and second year, respectively. The critical levels for leaf total N content were between 48.4 and 57.8 g kg -1 ; and for SPAD units, between 55.90 and 66.63. The nitrogen nutritional status of cauliflower can be estimated using the SPAD index. The critical level for the SPAD index and leaf N content varied from year to year. Higher production of cauliflower curd fresh mass can be obtained with the application of N rates higher than currently recommended.

Estimating tomato tolerance to heavy metal toxicity: cadmium as study case.

This work aimed to develop a reliable and fast approach to estimate the plant tolerance degree to heavy metal (HM) phytotoxicity. Two independent experiments were carried out using tomato accessions, with contrasting morphological features, that were grown in a hydroponic solution containing different CdCl2 concentrations for 7days. Plant dry weight and chlorophyll content (SPAD units) were evaluated, and tolerance degree to Cd toxicity was estimated according to the tolerance index (TI), which is a new mathematical formula based on plant biomass proposed in this study. Although with different magnitudes, tomato exhibited reductions in their dry weight concurrently with the increasing CdCl2 concentration. By contrast, chlorophyll content presented no standard response, decreasing and even increasing according to CdCl2 concentrations, indicating that only under certain conditions (particularly, at CdCl2 50μM), this parameter can be used to estimate plant tolerance to Cd toxicity. TI was efficiently able to segregate tomato cultivars with similar performance (based on the total dry weight of plants), and such segregation was optimized when the hydroponic solution contained from 25 to 50μM CdCl2. Within this range, data pointed at 35μM CdCl2 as the best concentration to be employed in studies related to the tomato tolerance/sensitivity to Cd toxicity. In conclusion, TI proved to be a reliable estimator of tolerance degree to Cd exposure in genetically distinct tomato accessions. Moreover, TI can be used for this same purpose in plants under other HM-induced stresses.

Sufficiency ranges and crop nutrient removals for peppermint (Mentha X piperita L.) established from field and pot fertilizer experiments

ABSTRACTPeppermint is an important aromatic and medicinal plant used across the world in pharmaceutical, cosmetic and food industries. However, there is a lack of agronomic research on this crop which hinders the implementation of best agricultural practice at farm level. Plant analysis, for instance, cannot be used as a tool to implement a suitable fertilizer recommendation program, since sufficiency ranges and crop nutrient removals have not yet been established. Thus, the main objectives of the present work were to assess the response of peppermint to varying nitrogen (N), phosphorus (P), potassium (K) and boron (B) rates, to establish sufficiency ranges from macro, micronutrients and SPAD-readings and to estimate crop nutrient removals in the aboveground biomass. Field trials and pot experiments were conducted from 2013 to 2015 in a wide range of conditions involving 12 N, P, K or B fertilizer trials and a total of 48 cuts of biomass. Nitrogen fertilization increased dry matter yield of peppermint on the vast majority of sampling dates. In contrast, P, K, or B did not produce a significant effect on dry matter yield in any of the experiments. The sufficiency ranges set for macronutrients N, P, K, Ca and Mg are respectively 32.0 – 42.0, 1.2 – 4.5, 10.0 – 30.0, 7.0 – 23.0, and 4.0 – 10.0 g kg−1. Those for micronutrients B, copper (Cu), iron (Fe), zinc (Zn), and manganese (Mn) are respectively 20 – 200, 5 – 25, 100 – 600, 25 – 300, and 30 – 200 mg kg−1. Sufficiency range for SPAD-readings is 45 – 50 SPAD units. All these ranges were established for the commercial harvesting date. The amounts of N, P, K, calcium (Ca), and magnesium (Mg) removed in aboveground biomass are respectively 22.7, 1.6, 26.4, 16.4 and 4.8 kg Mg−1 of dry biomass.

Effect of irrigation suspension on the growth, water state and production of spinach (Spinacia olerácea L.) plants

Spinach is susceptible to drought conditions, and, because of climate change, it is necessary to optimize water application to crops. Therefore, a test was carried out in a completely randomized design (CRD) with four treatments consisting of the following irrigation suspension durations: T1: 0 d, T2: 4 d, T3: 7 d and T4: 10, with six replicates for a total of 24 experiment units (EU). Each EU consisted of 6 plants, for a total of 120 plants that were transplanted to 2 L pots with a mixture of peat and soil (2:1). The upper part of the substrate was maintained with a higher moisture content in the treatment without irrigation suspension and in the one with irrigation suspended for 4 d. An inversely proportional relationship was observed between the moisture content and the leaf water potential. The treatment without irrigation suspension recorded the highest leaf water potential value during the measurement period. There were no significant differences between the chlorophyll content in the SPAD units or for the leaf area, stomatal conductance and dry mass. The fresh mass presented significant differences and had the highest value in the treatment without suspension of irrigation.

Impact of the erineum strain of Colomerus vitis (Acari: Eriophyidae) on the development of plants of grapevine cultivars of Iran.

The present experiment was aimed at determining the influence of the grape erineum strain of Colomerus vitis (GEM) (Acari: Eriophyidae) on responses of local grapevine cultivars. GEM was applied at five density levels to each of five cultivars, i.e. Shahani, Sahebi Uroomie, Khalili Bovanat, Rishbaba and Sezdang Ghalat (listed from early to late grape ripening). The experiment was performed in a full factorial design (12 replicates each) and effects of the mite on the relative content of leaf chlorophyll, internode and cane length, leaf area and weight, number and size of the erinea, and percentage of leaves with erinea were investigated. Also mite density on leaves and in buds was assessed. Data were analyzed with a two-way ANOVA followed by Tukey's test to separate means among treatment levels and cultivars. The relative content of chlorophyll (expressed in Spad units) in infested leaves was reduced along with an increase in mite density and it was shown to be highly significant at the two higher mite density levels for Khalili Bovanat, Rishbaba and Sezdang Ghalat; Shahani and Sahebi Uroomie leaves appeared to be less affected by mite infestation. The highest mite density treatment displayed a strong correlation with weight (positive correlation) and size (negative correlation) of the leaves of four cultivars; leaves of Sahebi Uroomie appeared to be less affected. The reduced internode length was weak in infested plants. Most infested plants produced shorter canes and their lengths appeared to have a strong negative correlation with the highest mite density in four cultivars; canes of Sahebi Uroomie did not appear affected. At the highest mite density, canes of Khalili Bovanat and Sahebi Uroomie displayed the most and the least shortening effects, respectively. The percentage of leaves with erinea, as well as the number of erinea per leaves and the diameter of erinea increased along with the mite population density. The mite densities in buds (April 2014) and on leaves with erinea (in November 2013) were higher at the highest treatment level in the medium-late (Rishbaba) and late ripening (Sezdang Ghalat) cultivars, than in the early and early-medium ripening ones. Almost all data collected in the current experiment allowed the conclusion that Sahebi Uroomie and Shahani were less affected than the other cultivars (Khalili Bovanat, Rishbaba and Sezdang Ghalat).

Efecto de elicitores de origen natural sobre plantas de tomate sometidas a estrés biótico

Los elicitores son sustancias de diversas fuentes tanto inorgánicos como orgánicos que pueden inducir efectos fisiológicos y cambios como la activación de respuestas defensivas y la acumulación de fitoalexinas en el organismo al cual son aplicados, por lo cual, el objetivo de esta investigación fue conocer el efecto de la aplicación de dos elicitores de origen natural sobre el vigor de plantas y la calidad de frutos de tomate en condiciones de estrés biótico causado por Fusarium oxysporum f. sp. lycopersici (FOL). Los elicitores de origen natural (E1 y E2) se aplicaron a los 7, 15 y 56 ddt (días después del trasplante); la inoculación del FOL se realizó a los 19 ddt, usando una concentración de 1×106 esporas mL-1. El vigor en las plantas consistió en medir: la incidencia y severidad de la enfermedad, unidades SPAD, conductancia estomática durante el desarrollo de las plantas, altura, peso seco total y rendimiento; así como el pH, sólidos solubles, firmeza y el contenido de vitamina C en los frutos. La aplicación de los elicitores disminuyó la severidad de los síntomas de la enfermedad. El elicitor E2 incrementó la altura de las plantas tratadas, la acumulación de biomasa y evitó la reducción en el rendimiento, también disminuyo el contenido de sólidos solubles en los frutos. Se concluye que la aplicación de elicitores de origen natural provenientes de extractos de plantas tuvo un efecto positivo sobre el vigor de las plantas de tomate inoculadas con FOL al incrementar la altura y la acumulación de biomasa total, además de que se modificaron algunas variables de calidad del fruto.
 

Inoculation of oil palm seedlings in Malaysia with white-rot hymenomycetes: Assessment of pathogenicity and vegetative growth

The pathogenicity of white-rot hymenomycetes isolated from oil palm (Elaeis guineensis Jacq.) trunks and their effect on the vegetative growth of oil palm seedlings were investigated under nursery condition. The hymenomycetes were selected based on their potential antagonistic ability against the pathogen Ganoderma boninense from a previous study. Rubber wood blocks (RWB's) pre-colonized with either one of the seven hymenomycetes or the pathogen G. boninense PER 71 were placed in direct contact with the roots of three-month-old oil palm seedlings using a sitting technique. After nine months, the seedlings inoculated with G. boninense were severely infected and the infection had spread throughout the seedlings, causing basal stem rot. By contrast, the fronds and boles of the seedlings inoculated with each of the seven hymenomycetes were symptomless until the end of the 18-months study. The frond length of seedlings inoculated with Trametes lactinea FBW or Clitopilus prunulus ST3 was about 2.7-fold greater than those of seedlings inoculated with G. boninense PER 71. Similarly, after nine months, the chlorophyll content of seedlings inoculated with Lentinus tigrinus FBJ G3 or Pycnoporus sanguineus FBR was approximately 60 or 59 SPAD units, respectively, which was significantly higher than that of seedlings inoculated with G. boninense PER 71. The seedlings inoculated with each of the seven hymenomycetes showed a similar growth pattern in terms of frond count, plant girth, plant height and frond length, at nine months. These findings suggested the non-pathogenic nature of the selected seven white-rot hymenomycetes on oil palm seedlings and their possible use as biological control agents against the BSR pathogen, G. boninense. The findings should be further explored for their biocontrol potential under natural field conditions.

Effect of the organic fertilizer Peat wheat and extracted it in growth and yield of eggplant

A field experment was carried out to study effect of organic manure (wheat residues) and the filtrate extracted from it and the interactionbetween them in the growth and the yield plant eggplant in the field experiment of the spring 2014 season in one of the farms Dujailah area in Wasit province. Add compost in the soil four levels) 0، 10، 20 and 30 tons. ha-1(which weredesignate O1, O2, O3 and O4 respectively, also add Abstract Organic spraying method at rates three) 0, 2 and 4 ml. Liter-1(which was designat S1, S2 and S3 respectively. The experiment was adopted as factorial at Randomized Complete Block Design (R.C.B.D) with three replicates. The differences between means were tested by Duncan's Multiples Range Test ( D.M.R.T) at probability of 0.05.
 The results showed that the addition of compost and spraying the Organic extract has affected significantly in the parameters vegetative growth of plant height, number of branches of the main plant, leaf area, content leavesof chlorophyll, yield parameters(fruit weight, number of fruits. Plant -1, one plant yield, and total yield) compared with treatment without added.Increased influence the greater the amount of fertilizer added. The overlapping factors of the study significantly affected, as it gave the treatment of interactionO3S2 (Add compost level of 30 tons.ha-1+extract Organic concentration of 4 ml. Liter -1), the highest values ​​for all parameters the study has been amounted (94.41 cm plant -1,8.11 branch. plant -1, 447.5 dcm2. plant -1,64.88 SPAD units ,197.3 g. fruit -1,8.63 fruit. plant -1 and 1.703 kg. plant -1 and 36.61 tons. ha-1) respectively, compared to the treatment ofO0 S0 (without fertilization), which gave the lowest rate for those parameters .

MORPHOPHYSIOLOGICAL AND PRODUCTIVE RESPONSES OF SUNFLOWER VARIETIES TO IRRIGATION

ABSTRACT The high luminosity rates and high annual average temperatures of the Brazilian semiarid region, combined with the use of irrigation and adaptability of the sunflower crop to local climate, favor increased achene yield due to acceleration of morphophysiological processes. The objective of this work was to evaluate the morphophysiological and productive characteristics of sunflower varieties grown under drip irrigation in the Sub-Mid São Francisco River Valley. The experiment was conducted in the Experimental Field of the Brazilian Agricultural Research Corporation (Embrapa Semiarid), in Petrolina, State of Pernambuco, Brazil, in a randomized block design, with 21 sunflower varieties and four replications. The variables evaluated were flowering time, plant height, number of live leaves, stem and capitulum diameter, number of lodged and broken plants, stem curvature, relative chlorophyll index, photosynthesis, stomatal conductance, transpiration, average leaf temperature, 1000-achene weight and achene yield of the sunflower varieties. The treatments presented flowering time of 43 to 59 days after sowing, plant height of 1.0 to 1.4 m, capitulum diameter of 0.154 to 0.221 m, chlorophyll content of 30.8 to 33.98 Spad units and 1000-achene weight of 35.61 to 80.30 g. The sunflower varieties V7 and V8 stood out, with achene yields above 2,960 kg ha-1 and low number of lodged and broken plants, indicating a greater adaptability irrigation crops in the Sub-Mid São Francisco River Valley.

THE EFFECT OF THE LIGHT SELECTIVE COVER AND SPRAYING WITH PACLOBUTRAZOL ON THE VEGETATIVE GROWTH OF ANTIRRHINUM MAJUS PLANTS

This study was conducted on Antirrhinum majus plant to investigate the effect of the light selective and colored covers red, yellow and control with spraying by paclobutrazol in three concentrations (0,50 and100 mg.L-1) on some vegetative growth. The factorial experiment was carried out within Randomized Complete Block design using three replicates with six plants for each replicate. Results indicated that there was a significant decrease in the plant characters grown under the red and yellow polyethylene covers in comparison with the plants grown under the control cover. These characters were the plants height, number of the internodes, number of branches, diameter of the crown area, number of leaves, leaf area and the total carbohydrate in the leaves the mean values were: 14.84, 17.31 cm, 7.66, 7.11 internode per plant-1, 8.55, 7.77 branch per plant-1, 15.33, 15.44cm, 112.66, 108.55 leaf per plant-1, 1861.6, 1458.7 cm², 43.74, 51,11 % respectively. Also, there was a significant increase in the ratio of chlorophyll in the leaves which was 40.33 and 39.11Spad unit, respectively. Spraying with paclobutrazol at 50 and 100 mlg.L-1 led to a significant decrease in the plant height 18.46 and 18.80cm and number of leaves 110.33 and 111.55 leaf per plant-1 respectively, whereas there was no significant effect on the other characters of the plants sprayed with both concentrations of paclobutrazol.

EVALUATION OF NITROGEN MONITORING, BUD FERTILITYAND ‘THOMPSON SEEDLESS’ GRAPEVINE PRODUCTION ON DIFFERENT ROOTSTOCKS

ABSTRACT Methods of nitrogen analysis were adopted in leaf tissues in the laboratory, nitrate content in the sap of petioles and chlorophyll relative index (CRI, in SPAD unit), as well as the evaluation of the buds fertility rates, production and qualitative aspects of cluster and berries of ‘Thompson Seedless’ vine, grafted on rootstocks ‘Harmony’, ‘Jales’ ‘Paulsen 1103’ and ‘SO4’. The applied dose of N was 80 kg ha-1, and the experiment was installed in the Submédio do Vale do São Francisco, Brazil. The experiment was performed in a randomized blocks design, with four treatments and five replicates, with the experimental plot represented by five plants. In addition to the analysis of N, cluster length and width (cm) and fresh mass (g), berries length, diameter (mm), volume (mL), mass of fresh matter of berries, soluble solids (SS), titratable acidity (TA), SS/TA ratio, potential bud fertility (productive, vegetative, dead and dark buds in %) and real bud fertility (%). There were differences in nitrogen content in the leaves, nitrate in sap and CRI of ‘Thompson Seedless’ in relation to rootstocks. ‘Thompson Seedless’ expressed better potential for the development of clusters and berries when grafted on ‘Harmony’.

ÍNDICE DE VERDOR DE LISIANTHUS (Eustoma grandiflorum (Raf.) Shinners) EN FUNCIÓN DE LA CONCENTRACIÓN DE 6-BENCILAMINOPURINA

El manejo del color del follaje es de gran importancia en las especies ornamentales. El objetivo de la presente investigación fue evaluar en lisianthus (Eustoma grandiflorum (Raf.) Shinners) en precosecha el índice de verdor en los estratos inferior, medio y superior de la planta, número de botones por tallo floral, diámetro de tallo, altura de planta, área foliar y biomasa en función de aspersiones al follaje de 0.5, 1.0 y 1.5 mM de 6-bencilaminopurina (BAP) y de dos testigos, uno a base de aminoácidos y otro sin tratamiento; y en postcosecha el índice de verdor (unidades SPAD), color de pétalo y vida en florero en función de la dosis de 6-bencilaminopurina suministrada en el agua de riego y asperjándola al follaje. Para lo anterior, durante 2014 y 2015, en Toluca, México se realizaron dos experimentos. El diseño experimental en precosecha fue completamente al azar con cinco repeticiones y cinco tratamientos: 0.5, 1 y 1.5 mM de BAP, un testigo con aminoácidos (2 mL L-1) y un testigo absoluto, mientras que en postcosecha se utilizó un arreglo factorial 2 × 3 en bloques completos al azar con tres repeticiones, siendo los factores de estudio la forma de aplicación (agua de riego y follaje) y dosis de BAP (1, 3 y 5 mM). Los datos se analizaron con análisis de varianza y las medias de los tratamientos se compararon con la prueba de Tukey (0.05). En precosecha, mediante la aplicación de aminoácidos a razón 2 mL L-1 se alcanzó el máximo índice de verdor con 69.62 unidades SPAD, lo que superó en 16.65 % al testigo. En postcosecha, la aplicación de BAP 1 mM mantuvo el índice de verdor constante en cada uno de los muestreos realizados. El color del pétalo fue mayor con BAP 3 mM asperjado al follaje (b* = 23.37), valor que corresponde a morado intenso, y la vida en florero para este tratamiento fue de 15 d, lo que superó significativamente al testigo.

Reliability of different color spaces to estimate nitrogen SPAD values in maize

A method to estimate the leaf nitrogen concentration based on image processing techniques was developed. The images came from maize leaves with known levels of nitrogen, measured with a SPAD meter. In order to establish a correlation between the N concentration and the SPAD measurement, an average value in SPAD units and a representative color value were assigned to every leaf. In fact, the representative color values were computed by creating a weighting average of three representative leaf color groups. Accordingly, a prototype of every group and the pixel's area of each group were used to compute the weighting average. Thereby, these groups were created according to their degree of similarity using the k-means clustering technique, which provides a prototype of every group. In specific, the clustering was performed over images in the L∗a∗b∗ color space. In addition, correlation models to predict SPAD values, using a single color channel and two color channels, from the RGB, HSV and L∗a∗b∗ color spaces were tested. The analysis shows that it is possible to correlate SPAD values and color data with the concentration of N, furthermore, shows that when single color channel correlations were performed, the channels G, b∗ and V provide the better modeling accuracy. Moreover, it was likewise shown that better correlations were obtained when a combination of two color channels, from the same or different color spaces, were applied in the correlation. In particular, the most accurate prediction models were obtained held the pairs of color channels S-V and G-b∗.

Long‐Term Effects of Mineral Nitrogen Fertilizer on Irrigated Maize and Soil Properties

Core Ideas Grain yield, biomass, N uptake, SPAD units, soil N levels and N efficiciencies were affected by the N application rate. Maximum grain yields required 203 kg N ha−1 of available N in the 0‐ to 30‐cm layer soil. Sampling to a depth of 0 to 30 cm provided similar correlations than sampling to 0 to 60 and 0 to 90 cm. Mineral N fertilization increased soil organic C stock. Nitrogen is a key determinant of growth and grain yield (GY) in maize (Zea mays L.) and is therefore economically and environmentally important. We investigated the performance of maize crops in a 12‐yr experiment (2002–2007, 2010–2015) under sprinkler irrigation in a petrocalcic calcixerept soil in northeastern Spain, with controlled mineral N application rates (0, 100, 150, 200, 250, 300, and 400 kg N ha−1 yr−1). The application rate affected maize GY, biomass, N uptake, SPAD units, soil N levels, N efficiencies, and soil organic carbon (SOC). Average maximum GY's (∼15 Mg ha−1) required 203 kg N ha−1 of available N (defined as initial soil NO3− plus N fertilizer) in the 0‐ to 30‐cm horizon, confirming the importance of the soil N content. Nitrate levels in the 0‐ to 30‐cm horizon for maximum yields achieved a R2 value in the plateau fitting model similar to the 0‐ to 60‐ and 0‐ to 90‐cm horizons. The GY's increased at a rate of 192 kg ha−1 yr−1, suggesting a combination of genetic improvement in the hybrids and also an improvement in agronomic management. The 200 kg N ha−1 fertilizer treatment achieved almost the highest GY's (∼14 Mg ha−1) with simultaneous high nitrogen use efficiency (NUE) (0.83 kg kg−1). Mineral N fertilization also increased the stock of SOC in the 0‐ to 30‐cm horizon.