C. Carranca

Distribution and Remobilization of Nitrogen in Young Non-Bearing Orange Trees Grown Under Mediterranean Conditions

ABSTRACT To evaluate the distribution and source of nitrogen (N) in non-bearing orange trees (Citrus sinensis L. Osbeck cv. ‘Lane Late’ grafted on ‘Carrizo’ citrange), an orchard was established in a Gleyic Podzol (South Portugal). Trees were labelled with 15N-enriched ammonium nitrate. A set of trees was used for monthly leaf sampling while a second set was destructively harvested in November of each year and separated into different plant organs. Five trees also received unlabelled N after one year of labeling to evaluate the re-distribution of N within the plant. Nitrogen concentration in new leaves tended to decrease following the growth flushes of March, June, and August. The N derived from fertilizer (%Ndff) was small in April suggesting the importance of internal N reserves for new development in spring. Fertilizer use efficiency was 6, 20, and 30% in the 1st, 2nd, and 3rd years, respectively. More than half of the 15N absorbed by plants each year was allocated to young organs, but the %Ndff was practically the same for all plant organs in the three years. Of the total N content of trees in November 2001, about 35% derived from fertilizer applied that year, 16% from fertilizer applied the previous year, and the remaining 49% came from other N sources.

Effect of Dissolved Organic Matter on Copper - Zinc Competitive Adsorption by a Sandy Soil at Different pH Values

The effect of dissolved organic carbon from sewage sludge on copper and zinc adsorption and interaction on samples from the surface layer (0 - 10 cm) of a sandy soil (Gleyic Podzol) were studied at two pH levels (4 and 7). This soil presented acidification hazards and sewage sludge with a high content of Cu and Zn was used as a fertilizer. Soil samples were treated by solutions of Cu and Zn as nitrate salts with concentration levels up to 30 mg l−1 in a Ca(NO3)2 background at a constant level (180 mg l−1) of dissolved organic carbon (DOC). Copper and zinc sorption capacity decreased in the presence of DOC. As the pH increased, the decrease in Cu adsorption due to interaction with DOC was more obvious. Conversely, without addition of DOC, Cu and Zn adsorption increased with pH. More Cu than Zn was adsorbed. Soil sorption of these cations was described by equilibrium isotherms that fitted both Langmuir and Freundlich type equations, presenting however a better fit to the Freundlich equation (R2>98%). Adsorption dependence on DOC was more noticeable at pH 7.

Effect of Elevated Carbon Dioxide Concentration on Rice Quality: Proximate Composition, Dietary Fibers, and Free Sugars

ABSTRACT Little is known regarding the impact of elevated carbon dioxide concentration ([CO2]) on the chemical composition of rice grains. A field experiment was conducted with open-top chambers with rice (Oryza sativa L. cv. Ariete) grown at two levels of atmospheric CO2 (375 and 550 μmol/mol), and their effects were monitored on the proximate composition and carbohydrate contents of the grains. Following exposure to elevated [CO2], soluble dietary fiber increased by 136, 82, and 77% in brown rice, white rice, and bran, respectively. Increases of a lower magnitude (8%) were observed for insoluble dietary fiber in the bran and brown rice. For all 10 sugars identified, there was a trend for increasing their content. For example, increases of 135% were recorded for glucose in the white rice. In all rice milling fractions, elevated [CO2] reduced the protein (4–15%) and amylose (6–16%) contents, with no effect on the ash, starch, and gross energy contents. The fat content was increased by elevated [CO2] in th...

ASSESSING THE NITROGEN NUTRITIONAL STATUS OF YOUNG NON-BEARING ‘ROCHA’ PEAR TREES GROWN IN A MEDITERRANEAN REGION BY USING A CHLOROPHYLL METER

To find an alternative tool to chemical analysis for assessing the nitrogen (N) nutritional status, the SPAD-Minolta-502 portable chlorophyll meter was tested in one- to three-years-old ‘Rocha’ pear trees fertilized with 0, 10, 20 and 40 kg N ha−1 year−1. SPAD readings in the third and fourth fully expanded leaves were as responsive to N fertilization as leaves sampled for foliar chemical analysis (medium third of one-year-old shoots), but individual leaves showed heterogeneous chlorophyll patterns. SPAD readings in leaves sampled at 60 and 110 days after full bloom (DAFB) related linearly with leaf N concentration but significant relationships could also be obtained later. Assuming an optimum leaf N concentration of ≥20 g kg−1 dry weight, SPAD readings ≥33 in leaves sampled at 60–110 DAFB corresponded to a good nutritional N status of young pear trees, making this diagnostic technique more practical, non-destructive and inexpensive, compared with chemical leaf analysis.

Influence of pH on Copper - Zinc Competitive Adsorption by a Sandy Soil

Copper and zinc adsorption and interaction were studied at different pH levels in a sandy soil (Gleyic Podzol) to understand heavy metal behaviour in soils with acidification hazards, polluted by the use of sewage sludge with high content of Cu and Zn. Soil samples were treated by solutions of Cu and Zn as nitrate salts with concentration levels up to 30 mg l−1 in a Ca(NO3)2 background. More Cu than Zn was adsorbed, mainly specifically adsorbed. Copper and Zn in the exchange complex varied with soil solution pH. Adsorbed Cu and Zn increased with pH and as pH increased, more Cu than Zn was specifically adsorbed. Soil sorption of these cations was described by equilibrium isotherms that fitted either Freundlich or Langmuir type equations. The competitive Langmuir and extended Freundlich equations predicted for Cu and Zn values are in good agreement with the experimental data. Adsorption dependence on pH was more marked above pH 5 with a sharp increase of the distribution ratio D. Values for pH50, offering a relative measure of the selectivity of the adsorbent for the metal cations, were higher for Zn than for Cu increasing with the amount of heavy metal added to the soil sample.

Effect of Elevated Carbon Dioxide Concentration on Rice Quality: Nutritive Value, Color, Milling, Cooking, and Eating Qualities

ABSTRACT Increase in the atmospheric carbon dioxide concentration ([CO2]) enhanced the concentration of carbohydrates in rice grains, according to results of a previous study. However, its impact on other quality traits is little known. To investigate the effect of CO2 levels (375 and 550 μmol/mol) on rice quality, a field experiment was conducted with open-top chambers. Elevated [CO2] affected several nutritional parameters of the grain. Whereas the concentration of α-linolenic acid increased, that of linoleic and γ-linolenic acids decreased. For example, reductions of 9 and 28% were observed for linoleic acid in the brown rice and for γ-linolenic acid in the husk, respectively. Phytic acid concentration and zinc bioavailability were unaffected. Whereas iron bioavailability decreased in the brown rice (22%), calcium bioavailability increased in the bran and husk (5–11%). The concentrations of essential amino acids were also reduced; for example, the amount of isoleucine in the white rice, tyrosine in the...

Contribution of mineral N to young grapevine in the presence or absence of cover crops

The presence of cover crops in vineyards may decrease the availability of nitrogen (N) derived from fertilizer to grapevines. The present study aimed to evaluate the recovery of urea-15N and growth of young grapevines with and without natural vegetation in plant rows. The study was conducted in southern Brazil on one-year-old Chardonnay grapevines grown in soils with and without cover crops. The grapevines were subjected to the application of 40 kg N ha-1 in the form of urea-15N at 3% 15N atom excess. Dry matter yield, total N and fertilizer N were assessed in grapevines and soil layers. A small amount of N that is applied during the growing season of the grapevines is readily assimilated by the plants. The maintenance of cover crops in young vineyards may favor the maintenance of higher levels of N in the subsurface layers of the soil, contributing to the nutrition of the grapevines in the following growth cycles. The presence of cover crops reduced the importance of nitrogen fertilization in the growth cycle of grapevines because a large part of N absorbed by grapevines was derived from other sources. Nitrogen derived from the fertilizer applied to the soil in the presence or absence of cover crops was mainly concentrated in the newly-formed vegetative grapevine organs (leaves and shoots).

Effect of N fertilisation in a young ‘Lane Late’ orchard fertigated by drip irrigation

The aim of this 2 year study was to investigate, the response of young ‘Lane Late’ trees grafted on ‘Carrizo’ citrange rootstock to N fertilisation in the South of Portugal, using fertigation, in order to establish proper N rates and optimal foliar nutrient levels according to the tree size/age. N rates significantly affected canopy width, volume and density, trunk perimeter, and flowers dry weight and N content. Foliar N content significantly increased with the N rates in the 1st year. In both years N concentration was in the high to excess ranges.

Field symbiotic fixation using 15N : II. Vicia faba L. and Pisum sativum L.

In Portugal, results on the amount of N2-fixed and efficiency of grain legumes-rhizobia symbiosis under field conditions are scarce. A two-years experiment in two Orthic Luvisols of Elvas (ENMP and CV), with uninoculated and inoculated fababeans and peas, was set in randomized blocks, replicated five times. Barley was used as control crop. At sowing, 20 kg N ha−1 as 15(NH4)2SO4 4.8 atom% 15N excess were applied in each microplot. Plants were harvested at physiological maturity. In the 1st year experiment, dry-matter, N yield and fixation in both crops were higher at CV soil, probably due to its higher fertility, namely the higher Mo content. In fababean,% Ndfa varied from 65% at ENMP soil to 90% at CV, corresponding to N2-fixed of 80 and 125 kg N ha−1; as to pea,% Ndfa ranged from 35% at ENMP to >85% at CV, corresponding 22 and 107 kg N2-fixed ha−1. Sites and years statistically affected crops, mainly by the deficient Mo level at ENMP, and drought stress in the 2nd year. Inoculation did not significantly affect fixation of fababean, but significantly affected pea. Values of% Ndfa were >60%, for both crops, at both sites, but due to the hydric stress in the 2nd year, N2-fixed was lower than in the 1st year: an average of 70 kg N ha−1 by fababean, and 37 to 55 kg N ha−1, respectively by uninoculated and inoculated peas at CV. At ENMP, pea poorly fixed N2, and negative values for% Ndfa in the pea straw were found.