Soil Plant Analysis Development Index Research Articles

Iron oxide‐humic acid coprecipitates as iron source for cucumber plants

AbstractIn soil, iron (Fe) solubility depends on complex interactions between Fe minerals and organic matter, but very little is known about plant availability of Fe present in Fe oxides associated with humic substances. For this purpose, this study investigates the effect of Fe mineral crystallinity in the presence of humic acids (HA) on Fe availability to plants. Four Fe–HA mineral coprecipitates were prepared, either in the presence or absence of oxygen, i.e., two goethite (G)‐HA samples containing large amounts of Fe as nanocrystalline goethite and ferrihydrite mixed phases, and two magnetite (M)‐HA samples containing crystalline magnetite. Bioavailability studies were conducted in hydroponic systems on cucumber plants (Cucumis sativus L.) grown under Fe deficient conditions and supplied with the Fe–HA coprecipitates containing goethite or magnetite. Results showed that plants grown in the presence of Fe–HA coprecipitates exhibited a complete recovery from Fe deficiency, albeit less efficiently than plants resupplied with Fe‐chelate fertilizer used as control (Fe‐diethylene triamine penta acetic acid, Fe‐DTPA). However, the supply with either G‐ or M–HA coprecipitates produced different effects on plants: G–HA‐treated plants showed a higher Fe content in leaves, while M–HA‐treated plants displayed a higher leaf biomass and SPAD (Soil–Plant Analysis Development) index recovery, as compared to Fe‐DTPA. The distribution of macronutrients in the leaves, as imaged by micro X‐ray fluorescence (µXRF) spectroscopy, was different in G–HA and M–HA‐treated plants. In particular, plants supplied with the poorly crystalline G–HA coprecipitate with a lower Fe/HA ratio showed features more similar to those of fully recovered plants (supplied with Fe‐DTPA). These results highlight the importance of mineral crystallinity of Fe–HA coprecipitates on Fe bioavailability and Fe uptake in hydroponic experiments. In addition, the present data demonstrate that cucumber plants can efficiently mobilize Fe, even from goethite and ferrihydrite mixed phases and magnetite, which are usually considered unavailable for plant nutrition.

Biostimulant Application with a Tropical Plant Extract Enhances Corchorus olitorius Adaptation to Sub-Optimal Nutrient Regimens by Improving Physiological Parameters

The emerging role of plant biostimulants in enhancing nutrient efficiency is important for maintaining soil fertility under sub-optimal nutrient regimens. We aimed to elucidate the morpho-physiological and biochemical effects as well as mineral composition changes of greenhouse jute (Corchorus olitorius L.) treated with a commercial vegetal-derived biostimulant from a tropical plant extract (PE; Auxym®, Italpollina, Rivoli Veronese, Italy). Plants were sprayed in weekly intervals with a solution containing 2 mL·L−1 PE. Jute plants were supplied with three nutrient solution concentrations: full-, half-, and quarter-strength. Decreasing macronutrient concentrations in the nutrient solution (NS), especially at quarter-strength, triggered a decrease in several morphological (plant height, leaf number, and dry biomass) and physiological (net CO2 assimilation rate (ACO2) and SPAD (Soil Plant Analysis Development) index) parameters. PE application triggered specific ameliorative effects in terms of fresh yield at both half- and quarter-strength nutrient solution (15.5% and 29.5%, respectively). This was associated with an enhancement in ACO2, SPAD index, and especially the nutritional status (high nitrate, K, and Mg contents, and low Na content). The foliar application of PE, strongly increased chlorophyll b content, enhancing jute plant adaptation to fluctuating light and therefore the efficiency of photosynthesis, positively affecting starch, soluble proteins, and total amino acids content but only when jute plants were irrigated with full-strength NS, compared to the respective control treatment. At lower nutrient strength, PE reprogrammed the nitrogen distribution, allowing its remobilization from glutamate, which was quantitatively the major amino acid under lower nutrient strength, but not from chlorophylls, thus maintaining efficient photosynthesis. We confirmed that PE Auxym® acts in a balanced manner on the main metabolic pathways of the plant, regulating the uptake and transport of mineral nutrients and protein synthesis, increasing the accumulation of essential amino acids under full nutritive solutions, and re-distributing nitrogen from amino acids to allow leaf growth and expansion even under sub-optimal nutrient conditions. Overall, the use of natural plant biostimulants may be a potential solution in low-input conditions, where environmental constraints and restricted use of fertilizers may affect potential crop productivity.

Optimizing the Nitrogen Management Strategy for Winter Wheat in the North China Plain Using Rapid Soil and Plant Nitrogen Measurements

ABSTRACTExcessive nitrogen (N) fertilizer with improper split-application in small-scale farming is widespread for reducing N use efficiency and polluting the environment. The objective of this study was to develop a strategy for providing winter wheat with twice-topdressing N by quickly measuring the soil and plant N status. During the period 2009–2011, a field experiment was conducted for winter wheat cultivar Zhongmai-175 in the North China Plain. The mineral N (Nmin) pool at a soil depth of 0–90 cm and topdressing N twice, as total N supply, was gradually increased from 0 to 420 kg N ha–1 to mimic the farmers´ practices. Measurements with the Soil Plant Analysis Development (SPAD) meter were taken on the uppermost fully expanded leaf, and the SPAD index was expressed relative to SPAD readings of sufficiently fertilized plants. Grain yield exhibited linear-plus-plateau responses to total N supply with a significant difference between years, the r2 ranged from 0.73 to 0.94. With a basal N application of 30 kg ha–1, the soil Nmin at 0–90 cm supplemented by twice-topdressing N (1:1 ratio) at Zadoks growth stage (ZGS) 22–23 in early spring and ZGS 47–52 was required at 150–165 kg N ha–1 to achieve a maximum grain yield of 3.9–5.3 t ha–1. The SPAD index exhibited a strong exponential response to N supply irrespective of plant growth stage and year (r2 = 0.95–0.97); the value of 0.94 was critical in denoting N deficiency from sufficiency status. The N topdressing at ZGS 47–52 could be precisely modified/estimated by the equation y = 161.7–218x5.16, where x is the SPAD index. Since SPAD readings varied significantly from year to year, our study suggests that it might be difficult to precisely manage field N for winter wheat.

The response of winter oilseed rape to diverse foliar fertilization

In this experiment, the response of winter oilseed rape cv. SY Alister F1 to diverse foliar fertilization was evaluated. Foliar fertilization with the preparation Insol 5 was applied at the following dates: control (without a foliar fertilizer); autumn; autumn + spring; autumn + twice spring; spring and twice spring. Each variant in which autumn foliar fertilization was carried out contributed to a significant increase in plant density before harvest. In turn, each variant with spring foliar fertilization significantly increased the number of pods per plant compared to the control. Variants with autumn + spring, autumn + twice-spring, and twice-spring foliar fertilization influenced the increase in the soil-plant analysis development index (SPAD), thousand seed weight and protein and fat yield. The leaf area index was the highest after foliar fertilization applied in autumn + in spring or autumn + twice in spring. Foliar fertilization affected a significant increase in seed yield compared to the control. The content of protein and magnesium in seeds was the highest after the fertilizer application in autumn + twice in spring or twice in spring.

Índice de área foliar e SPAD durante o ciclo da soja em função da densidade de plantas e sua relação com a produtividade de grãos

A densidade de semeadura na cultura da soja provoca diversas modificações morfofisiológicas nas plantas, podendo alterar o crescimento e a produtividade de grãos. Objetivou-se avaliar o efeito de densidades de plantas de soja sobre o índice de área foliar (IAF) e índice SPAD (Soil Plant Analysis Development) durante o ciclo de desenvolvimento da cultura, correlacionando esses dados com a produtividade de grãos. O experimento foi conduzido na safra 2015/16, na área experimental da Embrapa Soja, Londrina, PR, em delineamento experimental de blocos completos casualizados, com cinco repetições. Foram avaliadas as densidades de 120, 230, 340 e 380 mil plantas aptas ha-1, em espaçamento de 0,45 m entre fileiras, utilizando a cultivar BRS 359 RR, que apresenta tipo de crescimento indeterminado e arquitetura compacta de plantas. Constatou-se que o aumento da densidade de plantas de soja incrementa o IAF até o estádio R3, mas, após essa fase, o IAF não varia entre as densidades. A densidade de plantas de soja não altera o índice SPAD até o estádio R5.4. Durante o crescimento vegetativo não há correlação entre o IAF e o índice SPAD com a produtividade de grãos, porém na fase de enchimento de grãos há correlações positivas entre essas variáveis.

Effects of conifer wood biochar as a substrate component on ornamental performance, photosynthetic activity, and mineral composition of potted Rosa rugosa

ABSTRACTA greenhouse experiment was conducted to assess the performance of biochar obtained from pyrolysis of conifer wood as a substrate component for growing potted Rosa rugosa plants. Rose plants were grown with different mixtures of sphagnum peat and biochar (100% peat, 75% peat–25% biochar, 50% peat–50% biochar, 25% peat–75% biochar; v:v). Increasing the biochar content from 25% to 75% increased the air content, bulk density, electrical conductivity, and K and Na concentration in the substrates. The addition of 25% biochar to the substrate showed promising potential for R. rugosa when compared with 100% peat given the similar growth performance, water-use efficiency, and ornamental quality (number of flowers and leaf colour). The Ca and Na concentrations in leaves and roots as well as the Mg content in roots increased as the biochar percentage in the substrate increased, whereas an opposite trend was observed for P and K concentrations. The best performance and ornamental quality of R. rugosa grown with 100% peat and 75% peat–25% biochar compared with 50 and 75% biochar treatments were attributed to a higher degree of photosynthesis, Soil Plant Analysis Development index, and pigment content. Overall, adding 25% of conifer wood biochar as a substrate component could be applied for economic purposes without detrimental effects on the yield and quality of potted roses.

Development of Passiflora cincinnata Mast. submitted to different levels of nitrogen and potassium

The present study aimed to evaluate the morphological characteristics of passion fruit (Passiflora cincinnata Mast.) under different levels of nitrogen and potassium, and interactions between these nutrients. The experimental design was randomized blocks, with a 4 x 4 factorial arrangement of treatments, three replications per treatment and 48 experimental plots and the experimental unit was composed of one plant. Factors were four doses of N (0, 75, 150 and 300 mg of N dm-3 of soil, applied as urea, 45 % N), and four doses of K (0, 150, 300 and 600 mg of K dm-3 of soil, applied as potassium chloride, 60 % K2O). After 60 days of transplanting the seedlings to pots, stem diameter, leaf number, SPAD (Soil Plant Analysis Development) index, leaf area, dry weight of shoot and root were evaluated. The interaction effect between levels of N and K was observed when the dry weight of shoot, stem diameter and SPAD index was assessed. The greatest growth rate of Passiflora cincinnata Mast. was obtained at doses of 180 to 300 mg of N dm-3 of soil. Potassium rates used in this study reduced the potential for accumulation of dry mass of the shoots.

Germination and initial development of Brachiaria brizantha and Brachiaria decumbens on exposure to cadmium, lead and copper

Abstract: The objective was to evaluate the germination and initial development of three cultivars of Brachiaria brizantha and Brachiaria decumbens in the presence of trace elements of Cd, Pb and Cu and quantify the Cd and Cu contents in plant tissue of these species. First, seed germination occurred in towel paper containing cadmium, lead, copper and the control. We calculated the percentage of germination, germination speed index, vigor index and seedling length. Later, the seeds were germinated in soil pots contaminated with Cd and Cu, where the Soil-Plant Analysis Development index (SPAD index) was evaluated, as well as dry matter of shoot and root, and the Cd and Cu metal content in plant tissue was quantified. B. decumbens showed sensitivity to the elements studied, with decreases in all parameters. Cu was the element that caused more toxic effects on germination and early seedling development of the species studied. In contaminated soil, the species studied showed no differences in dry matter production of shoots, but the exposure to Cd and Cu caused reductions in SPAD index in all species. The highest Cd and Cu contents were found in the roots.

RELAÇÃO ENTRE O TEOR ABSOLUTO E RELATIVO DE CLOROFILA EM FOLHAS DE VIMEIRO

http://dx.doi.org/10.5902/1980509821122Os métodos tradicionais para a quantificação de clorofilas implicam na destruição das folhas, além de serem demorados e dispendiosos. Uma alternativa aos métodos destrutivos é o uso de medidores portáteis, dentre eles o SPAD 502, que mede a intensidade da cor verde das folhas, resultando no índice SPAD (Soil Plant Analysis Development). No entanto, o índice SPAD deve ser ajustado para o teor de clorofilas, conforme a espécie de interesse. O objetivo do presente trabalho foi calibrar o índice SPAD para a quantificação de clorofilas em folhas de plantas de vime (Salix viminalis). Folhas desta espécie, com tonalidade variando de verde-amarelada (clorótica) a verde-escura, foram avaliadas individualmente com o SPAD-502, seguido de quantificações destrutivas dos teores de clorofilas a, b e totais, expressos em unidade de área e massa fresca foliar. Houve elevado coeficiente de determinação (R²) entre os valores de índice SPAD e os teores de clorofila a, b e totais nas folhas, expressos em µg cm-2 de área foliar (R² de 0,86; 0,88 e 0,93, respectivamente) e entre os valores de índice SPAD e os teores de clorofilas b e totais, expressos em µg g-2 de massa fresca (R² 0,79 e 0,81, respectivamente). Os resultados mostram que existe viabilidade no uso do clorofilômetro SPAD 502, como alternativa aos métodos destrutivos, para a quantificação de clorofilas (em unidade de área; µg cm-2) em folhas de vimeiro.

Effect of nitrogen fertilization and genotype on the yield and yield components of winter wheat

Summary The effect of N fertilization on the yield, yield components, harvest index (HI), and chlorophyll content (SPAD (soil plant analysis development) index) of winter wheat cultivars was investigated in a long-term experiment in Hungary between 2006/2007 and 2008/2009. Maximal grain yield was reached at 80 and 160 kg · ha–1 N treatments, the higher N rate did not lead to a further yield increase in any of the years. A substantial year effect was observed for the yield and yield components. A negative correlation was found between grain number and thousand-kernel weight (TKW). Mv Verbunkos gave among the varieties the highest grain yield, grain number per spike, and SPAD value. There was a significant (P<0.001) positive correlation between the yield and the number of grains per square meter (r=0.85) and between the yield and the SPAD index (r=0.59). A significant (P<0.01) negative correlation was detected between the yield and the TKW (r=–0.44) and a positive correlation between the yield and the HI (r=0.51). Regression analysis revealed a significant linear relationship between the yield and the yield components (number of grains per square meter and TKW) at the various N levels.

Growth, Quality Index, and Mineral Composition of Five Ornamental Cabbage Cultivars Grown Under Different Nitrogen Fertilization Rates

The fertilizer nitrogen (N) inputs to some potted plants such as ornamental cabbage (Brassica oleracea L. var. acephala D.C.) are frequently higher than the actual demand. Optimization of N fertilization rate and selecting N-efficient cultivars are important approaches to increase the nitrogen use efficiency (NUE) and to reduce environmental pollution from nitrate leaching. The aim of this study was to assess the effect of increasing levels of nitrate (0.5, 2.5, 5, 10, or 20 mm of NO3−) in the nutrient solution on plant growth, quality, soil plant analysis development (SPAD) index, chlorophyll fluorescence, leaf pigments, mineral composition, and NUE in five ornamental cabbage cultivars (Coral Prince, Coral Queen, Glamour Red, Northern Lights Red, and White Peacock), grown in closed subirrigation system. ‘Glamour Red’ and ‘Northern Lights Red’ needed 3.3 and 2.9 mm of NO3− in the supplied nutrient solution, respectively, to produce 50% of predicted maximum shoot dry weight (SDW), whereas the vigorous cultivars Coral Prince, Coral Queen, and White Peacock needed 5.5, 4.7, and 4.3 mm of NO3−, respectively. Total leaf area (LA), SDW, SPAD index, N, Ca, and Mg concentrations increased linearly and quadratically in response to an increase of the nitrate concentration in the nutrient solution. Irrespective of cultivars, fertilizing above 10 mm NO3− produced high-quality plants (quality index of 5) and resulted in sufficiently high tissue concentrations of N, P, K, Ca, Mg, and Fe.

Tamanho da amostra foliar para avaliação do estado nutricional e índice SPAD de capim-elefante irrigado para corte

A quantificação de unidades amostrais que irão compor a amostra promoverá a otimização da mão de obra, além de diminuir erros inerentes à recomendação e avaliação do estado nutricional. A coleta de folhas de forrageiras para a diagnose do estado nutricional é uma etapa importante para subsidiar a adubação, sendo o tamanho da amostra imprescindível para representar adequadamente a população de plantas a ser manejada. Assim, objetivou-se dimensionar o número de amostras de folhas para a diagnose do estado nutricional de capim-elefante irrigado para corte, bem como o índice de clorofila SPAD (Soil Plant Analysis Development). A avaliação foi realizada em capineira de capim-elefante, var. Cameroon, com irrigação fixa de baixa aspersão, em área localizada em Sobral-CE, em solo Neossolo fluvico. Coletaram-se 40 amostras simples, em zigue-zague, de maneira aleatória, escolhendo-se folhas recém-expandidas. As variáveis mensuradas foram os teores foliares de macro (N, P, K, Ca, Mg e S) e micronutrientes (B, Cu, Fe, Mn e Zn) e o índice indireto de clorofila, com auxílio de um clorofilômetro. Considerando aceitável um erro amostral de 10%, a coleta de amostras simples de 16 e 80 plantas, respectivamente, para macro e micronutrientes em capim-elefante seria adequada. Para a medida indireta da clorofila, 8 amostras são necessárias para obter um erro de 10%.

Symbiotic nitrogen-fixing bacterial populations trapped from soils under agroforestry systems in the Western Amazon

Cowpea (Vigna unguiculata) is an important grain-producing legume that can forego nitrogen fertilization by establishing an efficient symbiosis with nitrogen-fixing bacteria. Although inoculating strains have already been selected for this species, little is known about the genotypic and symbiotic diversity of native rhizobia. Recently, Bradyrhizobium has been shown to be the genus most frequently trapped by cowpea in agricultural soils of the Amazon region. We investigated the genetic and symbiotic diversity of 148 bacterial strains with different phenotypic and cultural properties isolated from the nodules of the trap species cowpea, which was inoculated with samples from soils under agroforestry systems from the western Amazon. Sixty non-nodulating strains indicated a high frequency of endophytic strains in the nodules. The 88 authenticated strains had varying symbiotic efficiency. The SPAD (Soil Plant Analysis Development) index (indirect measurement of chlorophyll content) was more efficient at evaluating the contribution of symbiotic N2-fixation than shoot dry matter under axenic conditions. Cowpea-nodulating bacteria exhibited a high level of genetic diversity, with 68 genotypes identified by BOX-PCR. Sequencing of the 16S rRNA gene showed a predominance of the genus Bradyrhizobium, which accounted for 70 % of all strains sequenced. Other genera identified were Rhizobium, Ochrobactrum, Paenibacillus, Bosea, Bacillus, Enterobacter, and Stenotrophomonas. These results support the promiscuity of cowpea and demonstrate the high genetic and symbiotic diversity of rhizobia in soils under agroforestry systems, with some strains exhibiting potential for use as inoculants. The predominance of Bradyrhizobium in land uses with different plant communities and soil characteristics reflects the adaptation of this genus to the Amazon region.

Efficacy of Micronutrient Chelate Treatments in Commercial Crop of Strawberry on Sand Culture

Strawberry production is usually carried out in Spain on sand substrate under fertigation. Micronutrient chelates are frequently applied as ethylenediaminetetraacetic acid (EDTA) chelates; EDTA is a recalcitrant chelating agent so the concern about the environmental fate of EDTA applied in agriculture has risen. In this work, the efficacy of iron, manganese, zinc, and copper in two alternative chelating agents has been evaluated: the biodegradable N-(1,2-dicarboxyethyl)-D,L-aspartic acid (IDHA) and a combination of the regioisomers ethylenediamine-N,N´-bis(2-hydroxyphenylacetic) acid (o,o-EDDHA) and ethylenediamine-N-(2-hydroxyphenylacetic)-N´-(4-hydroxyphenylacetic) acid (o,p-EDDHA) (called EDDHA mix). Doses were split according to the stability of the chelates in three or six weekly applications. Experiment started 2 January 2010. Leaf samples were taken 6, 12, and 17 weeks after the first application. Foliar analysis, in comparison with chlorophyll indices based on Soil Plant Analysis Development (SPAD) measurement, was used to evaluate chelate efficacy. No differences between treatments were found for the SPAD index, but the SPAD increment was greater for the IDHA treatment during the whole assay. However, foliar analysis was the most adequate method for evaluating differences among the three chelates. The treatment based on EDDHA mix and the IDHA chelates showed greater Fe content in leaves in the first and last periods respectively. The EDDHA mix and EDTA were better alternatives for Zn nutrition than IDHA. Manganese content in leaf was sufficient and not affected by the treatment used. Copper content in leaf showed similar results for all treatments. The Fe/Mn molar ratio showed results similar to those obtained for Fe contents in leaf. The IDHA and EDDHA mix treatments produced similar quality parameters in fruits as EDTA. As conclusion, IDHA and EDDHA mix could be good alternatives for recalcitrant EDTA to apply micronutrient chelates in strawberry plants in fertigation.

Attributes of irrigated rice as affected by soil sodicity and potassic fertilizer application

Soils of the coastal plains of Rio Grande do Sul, Brazil, are affected by salinization, which can hamper the establishment and development of crops in general, including rice. The application of high doses of KCl may aggravate the crop damage, due to the high saline content of this fertilizer. This study aimed to evaluate the effect of K fertilizer management on some properties of rice plant, grown in soils with different sodicity levels, and determine which attribute is best related to yield. The field study was conducted in four Albaqualfs with exchangeable Na percentages of 5.6, 9.0, 21 and 32 %. The management of KCl fertilizer consisted of the application of 90 kg ha-1 K2O broadcast, 90 kg ha-1 K2O in the row and 45 kg ha-1 K2O in the row + 45 kg ha-1 K2O at panicle initiation (PI). Plant density, dry matter evolution, height, SPAD (Soil Plant Analysis Development value indicating relative chlorophyll contents) index, tiller mass, 1,000-grain weight, panicle length and grain yield were evaluated. The plant density was damaged by application of K fertilizer in the row, especially at full dose (90 kg ha-1), at three sodicity levels, resulting in loss in biomass accumulation in later stages, affecting the crop yield, even at the lowest level of soil sodicity (5.6 %). All properties were correlated with yield; the highest positive correlation was found with plant density and shoot dry matter at full flowering, and a negative correlation with panicle length.

Severidade de doenças e manutenção da área foliar verde em função da aplicação de micronutrientes e fungicidas em trigo

Na safra agrícola de 2007 foi instalado um experimento com a cultura do trigo com o objetivo de avaliar a influência do zinco, manganês e molibdênio aplicados juntamente com fungicidas sobre a severidade de doenças e duração da área foliar verde. As aplicações dos fungicidas foram realizadas no final do emborrachamento e no florescimento, e a de micronutrientes, somente no florescimento. Foram analisados os teores de micronutrientes nas folhas, severidade das doenças causadas por Drechslera tritici-repentis eSeptoria tritici, índice SPAD (Soil Plant Analysis Development), peso hectolítrico, peso de mil grãos, tamanho de espigas, e rendimento de grãos. O uso do epoxiconazol + piraclostrobina proporcionou o melhor controle de D. tritici-repentis e de S. tritici. Produtos com epoxiconazol e piraclostrobina atuaram na fisiologia da planta, incrementando os teores de micronutrientes nos tecidos e prolongando o tempo que o trigo permaneceu com área foliar fotossinteticamente ativa. Epoxiconazol + piraclostrobina, piraclostrobina e epoxiconazol pulverizados associados ou não a micronutrientes, propiciaram aumento do peso hectolítrico, peso de mil grãos e rendimento, quando comparados à testemunha.

Rice Resistance to Brown Spot Mediated by Nitrogen and Potassium

This study was undertaken to investigate the effects of both nitrogen (N) and potassium (K) rates on rice resistance to brown spot, caused by the fungus Bipolaris oryzae. Rice plants (cultivar `Metica 1') were grown in soil corrected with 0, 25, 50, 75 and 100 mg of N/kg (as NH 4 NO 3 ) of soil as well as with 25, 50, 75, 125 and 150 mg of K/kg (as KCl) of soil. Thirty-three-day-old plants were inoculated with a suspension of Bipolaris oryzae conidia and the incubation period (IP), number of lesions (NL) per cm 2 of leaf area and disease severity was evaluated. Disease severity was scored at 24, 48, 72, 96, 120 and 144 h after inoculation and data were used to obtain the area under brown spot progress curve (AUBSPC). Soil plant analysis development (SPAD) index, plant dry weight and concentration of N and K in leaf tissues were also determined for both non-inoculated (NI) and inoculated (IN) plants. Concentration of N in leaf tissue increased as the N rates in the soil increased. Concentration of K in leaf tissue increased sharply as the K rates in the soil increased for both NI and IN plants. Concentration of K in leaf tissue was not affected by N rates. The IP increased as the N rates increased, but was somewhat less impacted by increasing K rates. The NL decreased as the N rates increased. The NL dramatically declined at the highest K rates. The AUBSPC dramatically declined as the N and K rates in the soil increased. SPAD index values increased as the N and K rates in the soil increased for both NI and IN plants. Plant dry weight increased as the N and K rates in the soil increased for both NI and IN plants. Results from this study suggest that combining high N and K rates may contribute to reducing the intensity of brown spot in rice while improving plant development.

Replacing the nitrogen nutrition index by the chlorophyll meter to assess wheat N status

The performance of cultivars is strongly linked to the growing conditions that vary according to both controlled and uncontrolled experimental factors. Specifically, there is a need to control the efficiency of N use by wheat, Triticum aestivum L., to minimize nitrogen losses and deficiency. The nitrogen nutrition index (NNI) is a precise indicator of nitrogen status but it does not suit the users’ practical constraints because it requires time-consuming measurements and destructive plant sampling at a precise growth stage. Here we tested the soil plant analysis development (SPAD) chlorophyll meter as an alternative to the nitrogen nutrition index (NNI). The chlorophyll meter is a more convenient, leaf clip-on device that determines the relative amount of chlorophyll present in plant leaves. We first identified which leaf should be used; we then compared SPAD and NNI data from various experiments. We also followed SPAD measurements around flowering time to determine a common time span of measurements for all the cultivars of a trial presenting a wide range of earliness. Our results show a non-cultivar-dependent, exponential relationship between the SPAD index and NNI at flowering, with a r2 equal to 0.89. This result implies that the SPAD chlorophyll meter can be used as an alternative to NNI to measure N status in wheat. We also showed that SPAD measurements can be taken before flowering, e.g. during heading, to characterize nitrogen status at flowering. This result provides an organizational leeway to experimenters who can then follow more precisely the N status of their trials. Thus the SPAD index is a good substitute for NNI because it is convenient to use.

Critical values of nitrogen indices in tomato plants grown in soil and nutrient solution determined by different statistical procedures

The objective of this study was to establish critical values of the N indices, namely soil-plant analysis development (SPAD), petiole sap N-NO3 and organic N in the tomato leaf adjacent to the first cluster (LAC), under soil and nutrient solution conditions, determined by different statistical approaches. Two experiments were conducted in randomized complete block design with four repli-cations. Tomato plants were grown in soil, in 3 L pot, with five N rates (0, 100, 200, 400 and 800 mg kg-1) and in solution at N rates of 0, 4, 8, 12 and 16 mmol L-1. Experiments in nutrient solution and soil were finished at thirty seven and forty two days after transplanting, respectively. At those times, SPAD index and petiole sap N-NO3 were evaluated in the LAC. Then, plants were harvested, separated in leaves and stem, dried at 70ºC, ground and weighted. The organic N was determined in LAC dry matter. Three statistical procedures were used to calculate critical N values. There were accentuated discrepancies for critical values of N indices obtained with plants grown in soil and nutrient solution as well as for different statistical procedures. Critical values of nitrogen indices at all situations are presented.