Leaf SPAD Readings Research Articles

PREVIOUS CROPS AND ORGANIC FERTILIZERS IN LETTUCE: EFFECTS ON YIELDS AND SOIL PROPERTIES

The use of organic amendments in agriculture could sustain crop production and preserve the agroecosystem, due to their importance in the conservation of organic matter in soil. The objective of this research was to evaluate the effects of differing organic fertilizers and of previous crops on lettuce growth, nutritional status and yields. The effects on soil characteristics were further investigated. The research was carried out during two years (2006 and 2007) at Metaponto (MT) in southern Italy, on lettuce crops cultivated after eggplant and melon to avoid their continuous cropping. The effects of application of a mineral fertilizer (MF), and of three treatments with organic fertilizers (commercial stable manure - OM; anaerobic digestate based on wine distillery wastewater - AD; composted municipal solid organic wastes coming from the separate collection - MSW) were studied. Head average weight, leaf area index, nitrate content and SPAD readings during the cropping cycles did not show significant differences among fertilizer treatments. On the contrary, marketable yield and head average weight at the harvest presented significantly different among the three organic fertilizers. The average marketable yield and head average weight of organic fertilizers experimental (AD and MSW treatments) decreased of 16 and 17%, respectively, compared to OM treatment. The previous melon crop influenced positively all analyzed parameters of the lettuce compared with previous eggplant crop. The previous melon crop reached the highest marketable yield with an increase of 59% compared with previous eggplant crop. Compared to the mineral fertilizer, the organic ones significantly increased the extracted fraction of soil organic carbon (6.9, 10.7 and 14.9% for OM, AD and MSW, respectively), without significant changes for the humic and fulvic content.

Use of a Chlorophyll Meter to Diagnose Nitrogen Status of ‘Fuyu’ Persimmon Leaves

A possible relationship between leaf SPAD readings and nitrogen (N) concentrations was evaluated at different growing stages of ‘Fuyu’ persimmon trees under different N regimes in pots and in the field. When 5-year-old trees grown in pots received 0 to 40 g N over the growing season, leaf SPAD reading, N concentration, and specific leaf weight tended to increase with increasing N rate. The correlation between leaf SPAD reading and N concentration was statistically significant from late April to early November (R2 = 0.72 to 0.97). It was noted that the slope of regression line decreased as the season progressed. Similar significant correlations were found from pot-grown 4- to 7-year-old trees grown under various nutrient regimes (R2 = 0.67 to 0.96). Significant correlations were also confirmed with the leaves collected from 31 commercial orchards at different locations. The highest coefficient of determination was observed from the leaves collected at harvest time in both the pot and field experiments. Although the regression equations differed depending on the growing stage of trees, SPAD readings were found useful in estimating leaf N status at a specific time and in quickly judging the need for N application at that time. Seasonal changes of leaf SPAD readings from five well-managed orchards are presented as a reference guide for practical use.

URBAN WASTE COMPOST, MANURE AND NITROGEN FERTILIZER EFFECTS ON THE INITIAL GROWTH OF CORN (ZEA MAYS L.)

Field experiment was conducted in 2008 at the Research Field of Agricultural College of Shiraz University, Shiraz, Iran to investigate the effects of urban waste compost (UWC), manure and chemical fertilizer on the initial growth of corn (Zea mays). Experimental design was split plot factorial with three replications. Main plots were assigned to nitrogen (N) fertilizer (0 and 200 kg N ha-1), and sub plots were factorial application of municipal waste compost (0, 25 and 50 t ha-1) and manure (0, 25 and 50 t ha-1) with all possible combinations. Results showed that increase in urban waste compost and manure increased corn dry matter, height, stem diameter, leaf area, leaf number, SPAD meter readings and leaf N. There was a close relationship between SPAD meter readings and leaf N (R2=0.84). Correlation and path analyses showed that leaf area and SPAD readings are major components which affect corn dry matter at initial growth stage. Results of the present study revealed that organic fertilizer can improve initial growth of corn similar to chemical fertilizer. It can be concluded that manure and compost can be effective nutrient sources for corn production and can be considered as potential alternatives to chemical N fertilizer.

Responses of rice leaf thickness, SPAD readings and chlorophyll a/b ratios to different nitrogen supply rates in paddy field

The objective of this paper was to investigate the influence of different nitrogen (N) application rates to some morphological and physiological features of leaf blades, including leaf thickness, chlorophyll content at different leaf ages and chlorophyll a/b ratios. A paddy field and a cement tank experiments were conducted simultaneously. Rice leaf thickness was measured through a specially developed displacement sensor. Meanwhile, chlorophyll content was estimated using chlorophyll meter (SPAD) and spectrophotometer after ethanol extraction of leaf samples. With the increase of N application, leaf thickness became thinner and chlorophyll a/b ratios decreased. Moreover, the sensitivity of the SPAD readings of the same leaf at different leaf ages to N rates was assessed through coefficients of variation (CV). CV of SPAD readings increased from 8.8% to 21.6% during leaf lifetime, which indicates that SPAD readings became more and more sensitive to nitrogen rates as leaf aged. Therefore, SPAD readings of the lower leaves, which were physiologically older than the upper ones, were more sensitive to nitrogen rates.

Avaliação do estado nutricional azotado de pés-mãe de Eucalyptus globulus Labill. ssp. globulus com recurso a um medidor portátil de clorofila

With the aim of evaluating the use of the portable chlorophyll meter “Minolta SPAD 502” readings (SPAD readings) as an indicator of the nitrogen status of Eucalyptus globulus Labill. ssp. globulus (E. globulus) mother plants, a nitrogen fertilization experiment with this species was performed. Mother plants of two clones (HD 161 and CN5) of E. globulus were grown in an open-air nursery, in 12 L pots. Plants received 5 different nutrient solutions containing 50, 100, 200, 400 e 800 mg N L-1. During 1999, mother plants were subjected to a formative pruning. During 2000 and 2001 the following parameters were evaluated: number of cuttings produced, rooting ability of the cuttings, nitrogen content of the youngest fully expanded leaf, and leaf SPAD readings. Results obtained showed a significant asymptotic relationship between nitrogen availability and SPAD readings and a linear, positive and significant relationship between SPAD readings (y) and nitrogen leaf contents (x, g kg –1): y=23,27+0,75x; r=0.94; n=150. Results also showed a good fitting of quadratic model to the relationship between SPAD readings and the mother plants production (cuttings production and rooting ability of the cuttings). The determination coefficients (78%) were similar to those obtained when the model was adjusted to the relationship between leaf nitrogen and mother plants production (80%). Results indicate that, in this experiment, SPAD readings can be used to evaluate nitrogen status of E. globulus mother plants with a diagnostic “quality” similar to leaf nitrogen contents.

Effect of Saline Water Irrigation on Growth and Physiological Responses of Three Rose Rootstocks

Salt-tolerant landscape plants are needed for arid and semiarid regions where the supply of quality water is limited and soil salinization often occurs. This study evaluated growth, chloride (Cl) and sodium (Na) uptake, relative chlorophyll content, and chlorophyll fluorescence of three rose rootstocks [Rosa ×fortuniana Lindl., R. multiflora Thunb., and R. odorata (Andr.) Sweet] irrigated with saline solutions at 1.6 (control), 3.0, 6.0, or 9.0 dS·m (-1) electrical conductivity in a greenhouse. After 15 weeks, most plants in 9.0 dS·m (-1) treatment died regardless of rootstock. Significant growth reduction was observed in all rootstocks at 6.0 dS·m (-1) compared with the control and 3.0 dS·m (-1), but the reduction in R. ×fortuniana was smaller than in the other two rootstocks. The visual scores of R. multiflora at 3.0 and 6.0 dS·m(-1) were slightly lower than those of the other rootstocks. Rosa odorata had the highest shoot Na concentration followed by R. multiflora; however, R. multiflora had the highest root Na concentration followed by R. odorata. All rootstocks had higher Cl accumulation in all plant parts at elevated salinities, and no substantial differences in Cl concentrations in all plant parts existed among the rootstocks, except for leaf Cl concentration in R. multiflora, which was higher than those in the other two rootstocks. The elevated salinities of irrigation water reduced the relative chlorophyll concentration, measured as leaf SPAD readings, and maximal photochemical efficiency of photosystem II (PSII) and minimal fluorescence (F(0))/maximum fluorescence (F(v)/F(m)), but the largest reduction in F(v)/F(m) was only 2.4%. Based on growth and visual quality, R. ×fortuniana was relatively more salt-tolerant than the other two rootstocks and R. odorata was slightly more salt-tolerant than R. multiflora.

Influência da aplicação de nitrogênio e fungicida no estádio de emborrachamento sobre o desempenho agronômico do arroz irrigado

Limitações ao crescimento e desenvolvimento da planta de arroz provocados por deficiência nutricional, especialmente de nitrogênio e por doenças, afetam a capacidade fotossintética e a produtividade de grãos. O objetivo do trabalho foi avaliar o efeito da aplicação de nitrogênio e de fungicida no estádio de emborrachamento do arroz irrigado por inundação sobre a duração da área foliar fotossintetizante e a produtividade de grãos. O experimento foi desenvolvido no ano agrícola de 2005/2006, em área experimental de várzea do Departamento de Fitotecnia da Universidade Federal de Santa Maria. O delineamento experimental utilizado foi o de blocos ao acaso com quatro repetições. Os tratamentos, arranjados em esquema fatorial, constituíram-se de doses de nitrogênio (50, 100 e 150 kg ha-1), perfazendo o fator A, e práticas de manejo realizadas durante o estádio de emborrachamento (aplicação suplementar de 30 kg ha-1 de nitrogênio, pulverização com fungicida, combinação das duas práticas anteriores e um tratamento testemunha), que compuseram o fator D. As doses de nitrogênio utilizadas promoveram diferenças nas características avaliadas até o emborrachamento (número de colmos m-2, índice de área foliar e leitura SPAD); no entanto, não foi verificada interação entre os fatores estudados para as avaliações procedidas durante o período de enchimento de grãos. As práticas de manejo realizadas no emborrachamento não alteraram a área e a senescência foliar, a produtividade e os seus componentes. A baixa severidade de doenças foliares e o eficiente aproveitamento do nitrogênio, relacionados às condições ambientais favoráveis durante o ciclo da cultura, podem explicar, em parte, a falta de resposta às práticas de manejo utilizadas.

Improvement of nitrogen management in rice paddy fields using chlorophyll meter (SPAD)

Optimum rate and timing application of nitrogen (N) fertilizer are most crucial in achieving high yield in irrigated lowland rice. In order to assess leaf N status, a semidwarf rice cultivar (Khazar) was grown with different N application treatments (0, 40, 80, and 120 kg N ha−1 splited at transplanting, midtillering, and panicle initiation stages) in a sandy soil in Guilan Province, Iran, in 2003. The chlorophyll meter (SPAD 502) readings were recorded and leaf N concentrations were measured on the uppermost fully expanded leaf in rice plants at 10-day internals from 19 days after transplanting to grain maturity. Regression analysis showed that the SPAD readings predicted only 23% of changes in the leaf N concentration based on pooled data of leaf dry weight (N dw) for all growth stages. However, adjusting the SPAD readings for specific leaf weight (SPAD/SLW) improved the estimation of N dw, up to 88%. Specific leaf weight (SLW), SPAD readings, leaf area and weight as independent variables in a multiple regression analysis predicted 96% of the N dw changes, while SPAD readings independently predicted about 80% of leaf N concentration changes on the basis of leaf area (N a). It seems that chlorophyll meter provides a simple, rapid, and nondestructive method to estimate the leaf N concentration based on leaf area, and could be reliably exploited to predict the exact N fertilizer topdressing in rice.

Leaf Responses of Young Iron‐Inefficient Maize Plants to Sulfur Deprivation

Hydroponically‐grown young iron (Fe)‐inefficient maize (Zea mays L.) plants were deprived of the external source of sulfate following an initial period when the sulfur (S)‐supply was sufficient. The effects of sulfate deprivation on leaf dry weight, dry weight to fresh weight ratio, chlorophyll fluorescence, SPAD reading, nitrogen (N) concentration, and Fe concentration of the lower leaves were monitored for 10 days. The patterns of leaf mass, area, chlorophyll content, and SPAD readings were analyzed according to leaf position. Decreased Fe concentration of leaf tissues was observed in all plants after the fourth day of the experiment, suggesting that this cultivar was Fe‐inefficient. An initial effect of short‐term S‐deprivation on leaves of young Fe‐inefficient maize plants was a lower Fe concentration of lower leaves in the second day. The fourth day of S‐deprivation experiment was a critical stage for the lower leaves, characterized by exhaustion of internal sulfate pools. After day 4, S‐deprivation affected both Fe‐ and N‐concentration of lower leaves. Nitrogen‐concentration remained stable and significantly less than that of the control plants and chlorosis became apparent. From the sixth day onwards, the lower leaves were characterized by decreased dry mass, higher dry weight to fresh weight ratio indicating less water content, less chlorophyll content although existing PSII systems were not affected, lower Fe concentration, and lower N concentration. Leaf development ceased, the fifth leaf did not emerge and the fourth one was less developed, the leaf mass to area ratio of the first three leaves was lowered, a progressive delay in the pattern of partitioning of chlorophyll content among leaves was observed, and the distribution of chlorosis intensity within the leaf blade was altered. Thus, after the sixth day the S‐starved plants experienced a complex constraint consisting of S‐depletion, Fe‐deficiency, and induced N‐deficiency.

Compost Amended Media and Irrigation System Influence Containerized Perennial Salvia

Three perennial species, wine sage (Salvia spp. Sell x roenen Schultes `Van Houttei'), blue anise sage (Salvia gauranitica St.-Hil. Ex Benth. `Black and Blue'), and indigo spires salvia (S. longispicata Martius Galeotti × S. farinacea Benth. `Indigo Spires') were transplanted in containers filled with a biosolid-yard waste compost, a commercial peat-based mix, or a mixture of 1 compost: 1 peat-based mix by volume) and grown under ebb-and-flow, drip, or manual irrigation systems. Initial physical, chemical, and elemental analyses of the media indicated that compost alone had higher pH, electrical conductivity (EC), total porosity (TP), bulk density (BD), particle density (PD), N, C, P, Ca, Zn, Cu, Fe, and B; lower initial moisture, Mg and Al; and similar Mn contents than did the 100% peat-based medium. Heavy metal (Cd and Pb) contents of compost did not exceed EPA 503 Rule limits for biosolid usage. After 6 weeks, plants were measured for leaf nutrient content, growth (leaf and stem dry weights, stem lengths), and quality (number of flowers, leaf greenness, and subjective quality ratings). At 6 weeks, plants grown in 50% or 100% compost generally had higher leaf K, P, and Mn; similar N and Ca; and lower Mg, Fe, and Al content than plants grown in the 100% peat-based medium. Plants grown in media amended with compost generally produced similar or slightly smaller plants (stem weight, leaf weight, and stem length) than when grown in peat-based media. Plants irrigated by ebb and flow resulted in higher (`Van Houttei') or similar (`Indigo Spires') dry stem weights than plants irrigated manually or with drip irrigation. Plants grown in compost had leaf SPAD readings (leaf greenness), number of flowers, and visual quality ratings that were generally similar (`Indigo Spires') or slightly reduced (`Van Houttei') than plants grown in peat-based media. However, for each species (except for `Van Houttei' grown in 50% compost using drip irrigation), plants were of marketable quality, regardless of irrigation system or medium. This study suggests that compost may serve as a viable alternative substrate for peat in the production of containerized perennials using ebb-and-flow, manual, or drip irrigation systems.

Using SPAD-502 Values to Assess the Nitrogen Status of Apple Trees

Four apple (Malus domestica Borkh) cultivars (`Fuji', `Spartan', `Fiesta', and `Gala') on Malling 9 (M.9) rootstock were grown in the field with three N rates (5, 20, and 35 g N/tree per year), supplied as Ca(NO3)2, and fertigated daily for 9 weeks. In the second year, leaf SPAD readings (chlorophyll readings obtained with the Minolta-502 SPAD meter) increased over the growing season for all cultivars, and leaf N decreased. Leaf SPAD and leaf N measurements increased in response to N fertigation rate at all sampling times. `Gala' consistently had lower SPAD readings than the other cultivars, and, with the exception of the first sampling time, `Fuji' had higher and `Fiesta' lower leaf N concentrations than other cultivars. There were strong relationships between leaf N concentration and SPAD readings for all cultivars until mid-July (r2 = 0.44 to 0.89), but not later in the growing season. Differences in SPAD readings and leaf N concentration due to cultivar and over time were as great as those due to N treatments, indicating that in the future, determination of critical SPAD values for apple leaves must be standardized for cultivar and sampling time. SPAD readings could be used to assess the need for N early in the growing season in fertigated orchards where rapid changes in nutrition programs can be undertaken readily.

Correlation of leaf chlorophyll readings and stem nitrate concentrations in peppermint

Abstract The SPAD chlorophyll meter appears promising for rapid, on‐farm analysis of crop nitrogen (N) status. Leaf SPAD chlorophyll levels have been correlated with total leaf N concentrations, but it has not been determined how they relate to other widely applied N diagnoses such as petiole or stem nitrate (NO3) analysis. Our objective was to examine the relationship between leaf SPAD readings and stem NO3 levels in peppermint (Mentha piperita L.). Upper canopy SPAD chlorophyll and stem NO3 concentrations were determined weekly during two seasons for peppermint grown with variable N inputs. Leaf SPAD levels exhibited significant linear‐plateau responses with respect to stem NO3, indicating that SPAD readings do not respond to luxury N consumption. The meter is therefore promising for the detection of crop N deficiencies by comparison of production fields to well fertilized plots or strips. Break‐points in the linear‐plateau regressions describe saturation concentrations of stem NO3 with respect to leaf ...