D. L. Bouranis

Designing synthetic polymers as soil conditioners

Abstract This work focuses on synthetic polymeric materials that are designed to function as soil conditioners. A classification of the various polymeric soil conditioners is given and a historical review is attempted. One hundred and three examples are examined, covering the period from 1950 up to today. The routes followed for the preparation of a synthetic polymeric soil conditioner are discussed. In this way, materials and/or properties are tailored for certain applications. Water‐soluble, water‐insoluble (crosslinked or hydrophobic), ionic, or non‐ionic conditioners are examined and pictures of their shapes are given. Finally, a discussion on the combination(s) of materials and/or properties outlines the future trends of this topic. Interpenetrating networks, blends of soil conditioning polymers, polymers combined with slow‐releasing compounds as well as transformable materials are included by examining certain works that are concerned with such materials presenting combined properties that are used ...

Study of a demonstration plant for the co-composting of olive-oil-processing wastewater and solid residue

Abstract The co-composting of the solid residue and wastewaters from the olive-oil production process has been studied as a new method for the treatment of wastewater containing high organic and toxic pollutants. The experimental results for a demonstration plant using solid residue from olive extraction as bulking material and olive-oil-processing effluents as continuously fed wastewater are reported. Composting temperature was controlled between 45 and 65°C by air supply and the wastewater addition was fed mainly in order to keep the moisture in the range of 45 to 60% and secondly to replace the carbon substrate. During 23 days of operation in the thermophilic region, the system was fed with 263 m 3 wastewater in total, which means an average rate of 11.4 m 3 /day wastewater or 2.9 kg wastewater per kg solid residue. The total bioenergy production was estimated to be about 90 000 000 kcal. Then followed a 3 months stabilization period in the mesophilic region until the final product reached ambient temperature.

Seasonal dynamics of mineral nutrients and carbohydrates by walnut tree leaves

Abstract The dry weight accumulation per leaf as well as the concentration per gram of dry weight and the accumulation of nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), iron (Fe), manganese (Mn), zinc (Zn), and copper (Cu) were determined in walnut tree leaves (Juglans regia L.) during a complete life cycle. Additionally, the dynamics of plant nutrient concentration in leaf petiole sap and carbohydrate accumulation in leaves were studied in relation to the main life cycle events of the walnut tree. Total N, P, K, Cu, and Zn concentrations decreased, whereas that of Ca, Mg, and Mn increased during the season. Iron concentration fluctuated around a mean value. Total N, P, K, Mg, and Cu concentrations detected in younger mature leaves were at the sufficient level, whereas Ca, Fe, Mn, and Zn concentrations were at higher levels as compared to those previously reported. All the detected nutrient accumulations increased abruptly during leaf ontogeny and leaf maturation until a maximu...

Patterns of mineral nutrient fluctuations in soybean leaves in relation to their position

Abstract Dry weight accumulation in blades for the trifoliolate leaf as well as the concentration per gram of dry weight and accumulation of nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), iron (Fe), manganese (Mn), zinc (Zn), and copper (Cu) were determined during the vegetative and reproductive phases at different leaf positions of soybean [Glycine max (L) Merrill, var. Halle] grown in the field without fertilization. The leaf blades at each position were sampled three times at seven day intervals. Mature (middle) leaves showed a higher rate of dry weight accumulation particularly during the vegetative stage in comparison to the older (lower) and younger (upper) leaves. These differences increased with the progress of plant growth. The minimization to zero of the rate of dry weight accumulation in blades after the development of pods is differentiated in leaves of different age. The N, P, and K concentration in leaf blades increase and those of Ca and Mg decrease from older (l...

Some characteristics of a new organic soil conditioner from the co‐composting of olive oil processing wastewater and solid residue

Abstract The effectiveness of a new organic soil conditioner from the co‐composting of olive oil processing wastewater and solid residue was examined through the evaluation of some of its physical and chemical characteristics. The concentration of 25% w/w of this material into the conditioner‐soil mixtures appears to be the maximum level for the cultivation of tomato plants. The plants grown on this conditioner‐soil mixture were 1.52±8.5% times larger than those grown on a sandy loam soil. The pure conditioner cannot be used as a substrate for the growth of tomato plants. The water‐holding capacity of the conditioner was almost two times higher than that of the pure soil and remained almost stable for temperatures between 8–40°C. The apparent density of the conditioner was 0.5 times smaller than that of the pure soil. With increased application rate of the conditioner to the soil, there was a decrease in the pH, an increase in the specific conductivity, and an increase in the ammonium‐nitrogen (NH4‐N) and...

Effect of preharvest application of calcium on the postharvest physiology of apricot fruit

Abstract The effect of preharvest calcium (Ca) foliar application on ethylene (C2H4) production, respiratory rate, soluble polyuronides, and fruit firmness of ‘Bebekou’ apricot fruits was determined. The study was carried out in two experimental years, 1991 and 1992. Calcium was applied 21, 17, and 13 days before harvest for 1991 at the concentration of 0.5% calcium chloride (CaCl2) each time and 16 and 12 days before harvest for 1992 at the concentrations of 0.8 and 0.7% CaCl2, respectively. Calcium treatment resulted in a 30–76% increase in the Ca content of fruit flesh. Treated fruits had significantly lower C2H4 production rates than control during (i) four (1991) or five days (1992) at 21°C out of the 7‐day period examined immediately after harvest, and (ii) one (1991) or two days (1992) at 21°C out of the seven‐day period examined immediately after a 3rd‐ (1991) or 4th‐week (1992) storage period at 0°C. After harvest, Ca‐treated fruits displayed one day delay to reach the peak rate of C2H4 productio...

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

Abstract 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.

FLOWER ANALYSIS FOR PROGNOSIS OF NUTRITIONAL DYNAMICS OF ALMOND TREE

The nutritional fluctuations of almond tree leaves and fruits during their development have been studied to relate the fluctuated nutrient concentrations of these tissues to the nutritional status of flowers. Comparative monitoring for two years in an experimental orchard of almond trees (cv Texas) under integrated production management showed that the analysis of almond tree flowers could be used for the forecast of the elemental dynamics of leaves and fruits of this tree. The values proposed to interpret the elemental analysis of the flowers, under the conditions of this study are: nitrogen (N)=2.8% (± 0.5), phosphorus (P)=0.55% (± 0.10), potassium (K)=2.3% (± 0.2), calcium (Ca)=1.25% (± 0.25), magnesium (Mg)=0.45% (± 0.07), iron (Fe)= 125 ppm (± 25), copper (Cu)=40 ppm (± 8), zinc (Zn)=65 ppm (± 10), and manganese (Mn)=26 ppm (± 4).

Seasonal dynamics of mineral nutrients by walnut tree reproductive organs

Abstract The dry weight accumulation per male and female flower as well as the concentration per gram of dry weight and the accumulation of nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), iron (Fe), manganese (Mn), zinc (Zn), and copper (Cu) were determined in walnut tree (Juglans regia L.) catkins and female flowers at the stage of flower bud and during the flower development. Catkin emergence was accompanied by a very fast hydration of the tissues. After the catkin matured, the fresh and dry weights were reduced. The female flower development period was accompanied by the dry and fresh weight increase. Total N, P, K, Fe, Mn, Cu and Zn concentrations in catkin buds were detected at lower levels, Mg in equal levels, and Ca at higher levels as compared to the nutrient concentrations in young growing leaves. The estimated values of the ratio NCmfb/NCygl were: total N = 0.54, P = 0.83, K = 0.56, Ca = 1.5, Mg = 1.0, Fe = 0.46, Mn = 0.71, Cu = 0.85, and Zn = 0.60. Nutrient concentrat...

DYNAMICS OF NITROGEN AND PHOSPHORUS PARTITION IN FOUR OLIVE TREE CULTIVARS DURING BUD DIFFERENTIATION

Variations of nitrogen and phosphorus levels in reproductive shoots and their leaves of self-rooting olive (Olea europaea) cultivars ‘Amfissis’ (A), ‘Kalamon’ (K), ‘Manzanillo’ (M), and ‘Chalkidikis’ (C) were monitored from the end of harvest until the emergence of the inflorescences. This 90-days period was divided into three sub-periods: before (pre-BD), during (BD), and after (post-BD) bud differentiation. The nitrogen (N)-content in leaves of the reproductive shoots varied between 10–20 mg g−1 and among cultivars the order of decreasing concentration levels was C > K > A > M. The N-content in reproductive shoots varied between 6–14 mg g−1 (K > A > C > M). Patterns of time-course variations are presented. Partitioning of N between leaves and shoots (NL:NS) varied with time, with a ratio between 1.5–2. The fluctuations in the NL:NS ratio over the 90 days showed two distinct phases: during pre-BD either increased (‘Amfissis’ and ‘Chalkidikis’) or remained relatively constant (‘Kalamon’ and ‘Manzanillo’), while during BD and post-BD decreased in all cultivars. The order of decreasing NL:NS ratio among cultivars was K > C > M > A. Phosphorus (P) content in leaves of the reproductive shoots varied between 0.1–2.5 mg g−1, (A > C > K > M). Phosphorus content in reproductive shoots varied between 0.2–1.6 mg g−1, with the highest levels in ‘Amfissis’ compared to the other cultivars. Patterns of P partitioning between leaves and shoots were similar in all cultivars. The PL:PS ratio varied between 0.9–2 (A > C > K > M). The N:P ratio varied between 5:1–20:1 in reproductive shoots and 10:1–35:1 in their leaves, increasing over the examined period. The increase rate of the N:P ratio varied between the three sub-periods, the lowest rate being during BD. The pattern of changes in the N:P ratio was similar in both leaves and shoots and an increase of N:P ratio in leaves was highly correlated with the corresponding increase of N:P in shoots.