Iron Sources Effects on Growth,Physiological Parameters and Nutrition of Cacao

Productivity and sustainability of cacao (Theobroma cacao L.) in tropical soils are affected by levels of iron. Information is lacking on the cacao response to various sources of iron (Fe). A greenhouse experiment was conducted to evaluate the effects of five iron sources iron sulfate heptahydrate, ferric ethylenediamine-N,N’-bis(2-hydroxyphenylacetic acid), ferric diethylenetriaminepentaacetic acid, ferric ethylenediaminetetraacetic acid, fiesta herbicide (FeSO₄ · 7H₂O, FeEDDHA, FeDTPA, FeEDTA,) at 10 mg Fe kg^?1 soil on growth, photosynthesis, content of photosynthetic pigments and starch and macro- and micronutrient nutrition of cacao. The various iron sources had significant effects on shoot and root dry biomass accumulation, leaf chlorophyll a and b content, carotenoid levels, SPAD index and P_N. These parameters were significantly correlated with concentration, uptake, influx, and transport and use efficiency of Fe. In cacao net photosynthesis, stomatal conductance, internal carbon dioxide (CO₂)_, and transpiration in leaf level responded differently to the sources of Fe. Invariably, macro and micronutrient uptake, influx, transport, and use efficiency showed differential responses to sources of iron but significant effects were only observed for copper (Cu), Fe, manganese (Mn), and zinc (Zn). Overall, FeDTPA, FeEDTA and FeHEDTA could be the best sources of Fe in improving, growth, photosynthesis and macro and micro nutrition of cacao.     

The Effect of Liming on the Availability of Cadmium in Soils and Its Uptake in Cacao (Theobroma c acao L.) In Trinidad & Tobago

ABSTRACT

Cadmium (Cd) is absorbed and bio-accumulated by cacao (Theobroma cacao L.) trees, resulting in unacceptably elevated levels in cocoa beans, necessitating measures to reduce its uptake from soils. A field experiment, lasting 18 months, was carried out to assess the effectiveness of liming on pH, bioavailability of Cd in soils and its uptake in cacao tissues. The treatments were: (a) control (untreated) and (b) lime-treated trees. Results demonstrated a significant (P < 0.05) increase in the soil pH (lime treated) and a natural fluctuation in pH for the control. For the lime-treated trees, bioavailable Cd levels generally stabilized with no significant change (P > 0.05) compared to the significant (P < 0.05) increase showed by control trees. The Cd levels in the leaves of both treatments decreased, however, the rate of decline in leaf Cd concentrations for lime-treated trees (?0.1378) was 3x faster than control (?0.0497) trees demonstrating the effectiveness of liming.     

Prediction of macronutrients in plant leaves using chemometric analysis and wavelength selection

Purpose

Fast and real-time prediction of leaf nutrient concentrations can facilitate decision-making for fertilisation regimes on farms and address issues raised with over-fertilisation. Cacao (Theobroma cacao L.) is an important cash crop and requires nutrient supply to maintain yield. This project aimed to use chemometric analysis and wavelength selection to improve the accuracy of foliar nutrient prediction.

Materials and methods

We used a visible-near infrared (400–1000 nm) hyperspectral imaging (HSI) system to predict foliar calcium (Ca), potassium (K), phosphorus (P) and nitrogen (N) of cacao trees. Images were captured from 95 leaf samples. Partial least square regression (PLSR) models were developed to predict leaf nutrient concentrations and wavelength selection was undertaken.

Results and discussion

Using all wavelengths, Ca (R²_CV?=?0.76, RMSE_CV?=?0.28), K (R²_CV?=?0.35, RMSE_CV?=?0.46), P (R²_CV?=?0.75, RMSE_CV?=?0.019) and N (R²_CV?=?0.73, RMSE_CV?=?0.17) were predicted. Wavelength selection increased the prediction accuracy of Ca (R²_CV?=?0.79, RMSE_CV?=?0.27) and N (R²_CV?=?0.74, RMSE_CV?=?0.16), while did not affect prediction accuracy of foliar K (R²_CV?=?0.35, RMSE_CV?=?0.46) and P (R²_CV?=?0.75, RMSE_CV?=?0.019).

Conclusions

Visible-near infrared HSI has a good potential to predict Ca, P and N concentrations in cacao leaf samples, but K concentrations could not be predicted reliably. Wavelength selection increased the prediction accuracy of foliar Ca and N leading to a reduced number of wavelengths involved in developed models.

     

Influence of nitrogen forms and levels on the growth and nutrition of cacao

Ammonium and nitrate are the major forms of nitrogen (N) present in tropical soils. An experiment was conducted to assess the influence of nitrate and ammonium forms (NO₃^?, NH₄⁺, and mix of NO₃^? + NH₄⁺), and levels (1.5–12.0 mM) of N on the growth and nutrition of cacao (Theobroma cacao L). Growth parameters were significantly influenced by N forms, and nitrogen supplied as NH₄⁺ proved better for the growth of cacao compared with NO₃^? form and mixtures of these two forms. Irrespective of the forms of N, levels of N had no significant effect on plant growth parameters. Nutrient efficiency ratios (NERs) (shoot dry matter produced per unit of nutrient uptake) for macronutrients were sulfur>phosphorus>calcium>magnesium>nitrogen>potassium (S>P>Ca>Mg>N>K) and for micronutrients NERs were in the order of copper>boron>zinc>iron>manganese (Cu>B>Zn>Fe>Mn).     

Fulvic acid in foliar spray is more effective than humic acid via soil in improving coffee seedlings growth

ABSTRACT

Humic (HA) and fulvic (FA) acids improve the nutrient availability and uptake by plants but some aspects of their agronomic use still need to be clarified. The effects of HA soil application and FA foliar application on the growth, Zn and B uptake by coffee seedlings were evaluated. HA was added to an Oxisol at concentrations 0, 10, 25, 50, 75 and 100 mg kg^?1 (C-HA), in both limed (pH 6.2) and overlimed (pH 7.2) conditions. FA (0, 0.2, 0.5 and 1 g L^?1 C-FA) was applied to coffee leaves in three different application modes (M): with 0.3% Zn and 0.6% B supplied via foliar (M₁), 0.6% B and 1.2% Zn supplied via foliar (M₂) and 1.2 mg kg^?1 B and 6 mg kg^?1 Zn supplied via soil (M₃). HA addition in soil significantly (p < 0.05) reduced leaf B and Zn accumulation and coffee growth in both pH conditions. In the M₁ and M₂, FA application significantly (p < 0.05) increased the shoot growth at 0.59 and 0.45 g L^?1 and B accumulation at 0.96 and 0.45 g L^?1 C-FA. Foliar application of C-FA, instead soil application of C-HA, is a suitable practice to improve coffee seedlings growth and nutrition on Oxisol.     

Inoculation of ‘Golden Delicious’ Apple Trees on M9 Rootstock with Azotobacter Improves Nutrient Uptake and Growth Indices

ABSTRACT

Roots of young ‘Golden Delicious’ apple on M9 rootstock were inoculated with four strains of Azotobacter chroococcum, which were isolated from various soils. Effects of these strains in combination with different levels of nitrogen (N) fertilizer and compost on plant growth and nutrient uptake were studied over two seasons. Therefore, a factorial arrangement included four strains of A. chroococcum, two levels of N-fertilizer (0 and 35 mg N kg^?1soil of ammonium nitrate) and two levels of compost (0 and 12 g kg^?1 soil of air-dried vermicompost). Among the four strains, AFA₁₄₆ was the most beneficial strain, as it increased leaf area, leaf potassium (K), magnesium (Mg), iron (Fe), manganese (Mn), zinc (Zn), and boron (B) uptake and root N, phosphorus (P), potassium (K), Mn, and Zn. The combination of AFA₁₄₆ strain, compost and N fertilizer increased leaf uptake of Ca, Mg, Fe, Mn, Zn, and B, and root uptake of P, K, Ca, Mg, Mn, and copper (Cu), and root dry weight.     

The effect of potassium soil amendments,trenching and foliar sprays on the mineral content,growth, yield and fruit quality of sweet cherry (Prunus avium L.) and prune (Prunus domestica L.)

Abstract

Potassium sulfate was applied to established, non‐irrigated, K deficient trees on fine textured soil by banding, placing in augered holes and injecting into the soil. Additional trees received a heavy compost mulch in early fall. Trenches were dug in the fall beside trees to break roots and then were backfilled with K₂SO₄, dolomite lime or a combination of the two. One percent K solutions of KNO₃ or K₂SO₄ were sprayed on trees four times during the growth season.

Sweet cherry trees only responded to compost mulch applications within two years. August midshoot leaf K, leaf N and fruit size were increased within one year however tree growth and yield were not affected. Fruit size and shoot growth were partially dependent on August leaf K level.

August midshoot leaf K of prune trees was increased within one growing season by all treatments except trench plus lime. Trees receiving compost also had increased levels of leaf N, P, Ca, Mn, Fe, Cu and B. Yield and shoot growth were increased only by compost mulch applications. Fruit size was partially dependent on August leaf K levels.     

Prediction of Soil Cadmium Bioavailability to Cacao (Theobroma cacao L.) using Single-Step Extraction Procedures

In this study, complexation extractants ammonium bicarbonate diethylene triamine pentaacetic acid (AB-DTPA), diethylene triamine pentaacetic acid (DTPA), and ethylene diamine tetraacetic acid (EDTA) and mild cation-exchange extractants calcium chloride (CaCl₂) and ammonium nitrate (NH₄NO₃) were used to evaluate the bioavailability of soil cadmium (Cd) to cacao in the field. Among the five extractants, the extractable Cd generally followed the order EDTA > DTPA > AB-DTPA > CaCl₂ > NH₄NO₃. Correlation analysis was done between the extractable Cd in soil and total Cd content of cacao tissues (nibs, shells, leaves, and pods). The Cd extracted by CaCl₂ and NH₄NO₃ was significantly (P < 0.05) correlated with some of the tissues but their Pearson correlation coefficients were weak. In contrast, extractants AB-DTPA, DTPA, and EDTA showed stronger, significant correlations to the Cd concentration in all four tissues. Overall, regression analysis demonstrated that AB-DTPA, DTPA, or EDTA can be used to predict bioavailable Cd in soils for cacao. Of these, AB-DTPA and DTPA both showed the strongest correlations compared to EDTA. However, the ease of preparation and the superior shelf-life of DTPA over AB-DPTA make it the preferred reagent for Cd bioavailability extractions from cacao soils and is currently being used to develop cost-effective soil treatments to reduce bioavailable Cd to cacao plants.     

Boron stress inhibits beet (Beta vulgaris L.) growth through influencing endogenous hormones and oxidative stress response

Objective: This study aimed to evaluate the pleiotropic effects of boron stress on beet (Beta vulgaris L.) growth.

Methods: Beet seedlings were treated with varying concentrations of H₃BO₃ (0.05, 0.5, 2, and 30 mg/L) for 30 d for evaluation of diverse morphological parameters related to shoot and root growth. Transverse sections of beet leaves were observed under a microscope, and the leaf thickness was measured. Photosynthesis in beet was evaluated by measuring the photosynthetic rate, intercellular carbon dioxide concentration, and chlorophyll content; chloroplast morphology was observed by transmission electron microscopy. In addition, the levels of diverse endogenous hormones, as well as oxidative stress parameters, were also analyzed in beet leaves.

Results: We found that boron accumulated in different beet tissues but was observed mainly in mature leaves, followed by young leaves, mature petioles, young petioles, and roots. Boron stress (boron toxicity, 30 mg/L; boron deficiency, 0.05 mg/L) significantly inhibited beet shoot, root growth, and leaf expansion while promoting leaf thickening. Additionally, the levels of indole-3-acetic acid, gibberellin A3, and zeatin in beet leaves decreased significantly under boron stress, whereas the level of abscisic acid increased. Moreover, the levels of superoxide dismutase, peroxidase, catalase, malondialdehyde, and proline in beet leaves increased significantly under boron stress.

Conclusion: Together, our results indicate that boron stress significantly inhibited normal beet growth via the influence of endogenous hormone levels and oxidative stress responses.     

Use of a chlorophyll meter to evaluate the nitrogen status of dryland winter wheat

Abstract

Chlorophyll meter leaf readings were compared to grain yield, leaf N concentration and soil NH₄‐N plus NO₃‐N levels from N rate studies for dryland winter wheat Soil N tests and wheat leaf N concentrations have been taken in the spring at the late tillering stage (Feekes 5) to document a crop N deficiency and to make fertilizer N recommendations. The chlorophyll meter offers another possible technique to estimate crop N status and determine the need for additional N fertilizer. Results with the chlorophyll meter indicate a positive association between chlorophyll meter readings and grain yield, leaf N concentration and soil NH₄‐N plus NO₃‐N. Additional tests are needed to evaluate other factors such as differences among locations, cultivars, soil moisture and profile N status.     

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 SPAD levels peaking at 12,000 mg NO₃‐N/kg in mid to late July and declining later in the season. The SPAD meter may be applied directly to N management by use of reference plots or it may be used as a tool to aid in determination of criteria for other diagnoses such as tissue NO₃.     

Leaf nitrate partitioning and growth response in pumpkin as influenced by nitrogen rate

Abstract

Pumpkin species Cucurbita moschata ‘Dickenson Field’ and C. pepo ‘Connecticut Field’ were grown in the greenhouse in a Plain‐field sand at 8 rates of N applied as Ca(NO₃)_2. Petiole NO₃ concentrations in recently mature and mature leaves were highly responsive to N rate. Wien plants were stressed for N, translocation of petiole NO₃ was primarily to the corresponding blade. The levels as well as the range of NO₃ concentration in the leaf blade were lower than those in the petiole. The NO₃ content in the leaf blade was slower to react to N stress than that in the petiole. Variability in NO₃ concentration among leaf parts was lowest in the petiole and highest in the blade. For each leaf part, variability in NO₃ concentration decreased with leaf age. Critical NO₃‐N concentrations in C. moschata were estimated at 18950 and 3500 ppm in mature petioles and 14700 and 3050 ppm in recently mature petioles at early vegetative and full flower growth stages, respectively.     

ALUMINUM EFFECTS ON GROWTH,PHOTOSYNTHESIS, AND MINERAL NUTRITION OF CACAO GENOTYPES

A solution culture experiment was conducted in a greenhouse with two cacao genotypes (Catongo and Theobahia). Plants were subjected to seven aluminum (Al) concentrations and Al effects on growth, photosynthesis, and mineral content were assessed. Inter-genotypic differences for F_o, F_m and F_v fluorescences, as well as for F_v/F_m, were observed with increasing Al concentrations. There was a decreasing of F_o, F_m, F_v and F_v/F_m for the Catongo. Increasing Al concentration decreased photosynthetic rate, stomatal conductance and leaf transpiration rate, however, inter-genotypic differences in these parameters were not observed. The Al-treatments decreased content of nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg) in different plant parts, with the exception of K content in stems of Theobahia and in leaves of both genotypes. Theobahia showed higher tolerance to Al phytotoxicity, manifested mainly in the higher levels of Al in the growth medium. Inter-genotypic differences were observed in the growth and mineral nutrition.     

Effect of nitrogen source,rate and time of application on fruit yields of the Micmac strawberry

Abstract

Rate and source of nitrogen application significantly increased total yields from Micmac strawberry plants, but only in the first of 3 successive cropping seasons. Early harvest yields of marketable and total fruit from control plots were equal to or higher than those from the nitrogen treatments in all seasons, but these differences were not reflected in significant total yield responses in the 2— and 3— cropping seasons. Early season soil NO₃‐N and NH₄‐N values, in the planting year, reflected nitrogen application but the effect decreased as the season progressed and there was no consistent effect of any subsequent nitrogen treatment on soil or leaf N levels, marketable or total yields. A leaf N range of 1.5–2.0% at full bloom and spring soil NH₄‐N, NO₃‐N and mineralizable N levels of 4, 10 and 25 ppm, respectively, were adequate for optimum yields.     

Soybean pod wall P and K as related to extractable P and K and grain yield

Abstract

It was proposed that the pod wall surrounding the developing soybean seed (growth stage R6) could serve as a diagnostic indicator of crop nutritional status. This was evaluated by summarizing soybean responses (R1 trifoliate and R6 pod wall P and K concentrations, and yield) to various levels of soil P and K availability in ten field experiments. Pod wall P and K concentrations were closely related to available soil P (Bray P₁) and K (MNH₄C₂H₃O₂‐pH 7.0), respectively. The relationship of pod wall P concentration to grain yield was superior to those found when either trifoliate leaf P or available soil P was related to grain yield. Pod wall K was similarly superior to leaf K or available soil K. Though further work is needed to describe changes in pod wall composition during grain‐fill, it appears that pod wall sampling offers an alternative or additional sampling interval in the evaluation of soybean nutrition     

Turbidimetric determination of potassium in leaf tissues with sodium tetraphenylboron

Abstract

A turbidimetric method using sodium tetraphenylboron for the determination of potassium (K) in leaf tissues was investigated. Analysis of K was performed on soybean and coffee leaves. Results were compared with those obtained with flame photometry and a very good correlation was found. Using a spectrophotometer set at 420 nm and a 1.0‐cm optical path cuvette, 1.0 μg/mL of K can be quantified. The method is recommended as an alternative to flame spectrophotometry.     

Growth Patterns of Jojoba Male and Female Leaf Callus with Various Ammonium and Nitrate Sources

Abstract

Male and female leaf discs of Jojoba [Simmondsia chinensis (Link) Schneider] were cultured on Murashige and Skoog (MS) media supplemented with various nitrate:ammonium ratio and phytohormones concentrations. For the optimum callus growth, hormonal concentrations were remained equal for both male and female leaf tissues i.e., 0.4 mg L^?1 2,4‐dichlorophenoxyaceticacid, 1.25 mg L^?1 6‐benzyladenine and 0.5 mgL^?1 kinetin. However, a statistically significant difference was observed when Murashige and Skoog media was supplemented with an additional nitrogen source. In female leaf tissue, maximum fresh and dry weights were recorded in Murashige and Skoog media supplemented with an additional source of NO₃ ^?:NH₄ ⁺ (60 mM) whereas in male leaf tissue this addition was inhibitory. This study suggests that nitrogen requirement may be different for optimum callus growth in both male and female leaf tissues.     

Interactions between Soil,Leaves and Beans Nutrient Status and Dry Biomass of Beans and Pod Husk of Forastero Cacao: An Exploratory Study

ABSTRACT

In cacao crop the understanding of the multiple relationships between bean and pod husk dry biomass and mineral nutrition in the soil-plant system is scarce. The main objective of this work is to verify the linear, bivariate and multivariate correlations between the mineral nutrient concentrations in the soil, leaves and beans of 53 cacao trees with known dry biomass of cacao beans and pod husk, and further graphically identifying the consistency of these information. For this study, soil samples, leaves and fruits (pod husk and beans) were collected from each cacao trees, for the analysis of nitrogen-N, phosphorous-P, potassium-K, calcium-Ca, magnesium-Mg, iron-Fe, manganese-Mn, zinc-Zn and cooper-Cu mineral nutrient concentrations. The interpretation of the results by the exploratory analysis technique linked to the linear correlation analysis proved to be an essential tool to support studies related to mineral nutrition in the soil-plant system. Foliar N concentration were directly related to the high and very high dry biomass classes of cacao beans. Levels of exchangeable Ca and Mg in the soil were inversely correlated with the dry biomass of cacao pod husk (DBCH), in contrast to results with the positive correlations of these nutrients in the leaves and cacao beans data sets. The foliar concentrations of Zn, Mn, Fe and Cu are shown to be more positively associated with DBCH than dry biomass classes of cacao beans. The concentrations of Fe, Mn and Cu in dry cacao beans show such similar pattern of association with dry biomass of pod husk and beans.     

Light Intensity Effects on Growth and Micronutrient Uptake by Tropical Legume Cover Crops

ABSTRACT

Cover crops are important components of a sustainable crop-production system in plantation crops such as cacao (theobroma cacao), coffee (Coffee arabica), oil palm (Elaeis Spp.), and banana (Musa Spp.). Optimal growth of cover crops in plantation agriculture is determined by adaptability of crop species, light intensity reaching their leaf canopies, and their nutrient-use efficiencies, including those of micronutrients. An experiment was conducted in a climatically controlled growth chamber to evaluate the influence of levels of light intensity on growth and micronutrient [boron (B), copper (Cu), iron (Fe), manganese (Mn), and zinc (Zn)] uptake parameters in legume cover crops. Two photosynthetic photon flux density (PPFD, 200 and 400 μmol m^?2 s^?1) light treatments were imposed on nine legume species (joint vetch (Aeschynomene americana), sunhemp (Crotalaria juncea L.), Crotalaria rchroleuca, showy crotalaria (crotalaria spectabilis), hairy indigo (Indigofera hirsute L.), lab-lab (Lablab purpureus), sesbania (Sesbania microcarpa), Brazilian stylo (Stylosanthes guianensis), and cowpea (Vigna unguiculata)). Overall, light intensity significantly affected growth, micronutrient uptake, and use-efficiency ratios; with few exceptions, interactions between cover crop species and PPFD were also significant. Such PPFD × crop species interactions show that the cover crops used in this study differed in growth and nutrient-uptake parameters under the conditions imposed. Sunhemp, cowpea, sesbania, and lab-lab species were superior in producing shoot dry weight and in nutrient accumulation compared with other species at lower as well as at higher PPFD levels. Interspecific differences in nutrient influx and transport were observed. Influx and transport of micronutrients was in the order Mn > B > Fe > Zn > Cu. Overall, growth, nutrient uptake, and use-efficiency ratios were higher at higher PPFD than at lower PPFD. Results of this study indicate that the use of proper crop species at adequate light intensities is an important component of successful cultivation of cover crops in plantation agriculture.     

Nitrogen effect on yield and kernel protein content of sweet corn grown on sandy soils

Abstract

Early spring application of N to Iowa sandy, leachable soils results in reduced sweet corn yields and kernel protein content. Normally, split N applications are used to coincide with crop N demand. Our objectives were to determine if nitrapyrin, a nitrification inhibitor, applied with urea would provide high yields and kernel protein levels when applied at planting.

Nitrogen rate increased yield, ear leaf N concentration, and kernel protein content in 1976 and 1978, with the optimum rate dependent on the year and soil N residual. Urea, with or without nitrapyrin, significantly enhanced yield 13%, early leaf N concentration 17%, and kernel protein content 9% as compared with Ca(NO₃)₂ for both years. High leaching loss of NO₃‐N occurred with the Ca(NO₃)₂ source as compared with urea alone. Kernel protein concentration correlated well with ear leaf N concentration (r = .74) and yield (r = .61). Ear leaf K content was not affected by N rate or source, but Ca(NO₃)₂ enhanced uptake of Ca and Mg as compared with the urea sources. Urea, with nitrapyrin, decreased leaf Mg content in 1978, but not in 1976, as compared with urea alone.