Claudia Bonomelli

Nitrogen Application in Irrigated Rice Grown in Mediterranean Conditions: Effects on Grain Yield, Dry Matter Production, Nitrogen Uptake, and Nitrogen Use Efficiency

ABSTRACT Field experiments were conducted in the major rice growing area of Chile to evaluate the effects of nitrogen (N) fertilization and site on grain yield and some yield components, dry matter production, N uptake, and N use efficiency in rice cultivar ‘Diamante’. Two sites (indicated as sites 1 and 2) and six N rates (0, 50, 100, 150, 200, and 300 kg N ha−1) were compared. Nitrogen fertilization increased yield, panicle density, spikelet sterility, dry matter production, and N uptake at maturity. 90% of maximum yield was obtained with 200 kg N ha−1 in site 1 (12,810 kg ha−1) and with 100 kg N ha−1 in site 2 (8,000 kg ha−1). These differences were explained by lower panicle density, and the resulting lower dry matter production and N uptake in site 2. Nitrogen use efficiency for biomass and grain production, and grain yield per unit of grain N decreased with N fertilization. While, agronomic N use efficiency and N harvest index were not affected. All N use efficiency indices were significantly higher in site 1, except grain yield per unit of grain N. The observed variation in N use efficiency indices between sites would reflect site-specific differences in temperature and solar radiation, which in turn, determined yield potentials of each site. On the basis of these results, cultivar ‘Diamante’ would correspond to a high-N use efficiency genotype for grain yield.

EFFECTS OF FOLIAR AND SOIL CALCIUM APPLICATION ON YIELD AND QUALITY OF TABLE GRAPE CV. ‘THOMPSON SEEDLESS’

Table grape quality and firmness are key parameters for Chiles export, given distances from the main markets. As a consequence, calcium (Ca) fertilization has become a standard practice in the country, although its effects have not been fully evaluated. The objectives in this study were to investigate the effects of calcium fertilization on table grape nutrition and quality. A two-year field trial was conducted in central Chile, using grapevines (Vitis vinifera) cv. ‘Thompson seedless’, grown on an overhead trellis system. Calcium (CaCl2) application treatments included foliar, soil, foliar plus soil, and a control without Ca fertilization. Calcium and other nutrients concentration were determined afterwards in soil, leaves, and berries. Also, yield and some fruit quality parameters were evaluated. Calcium application method did not have an effect on soil, leaf or fruit Ca content, neither on yield and berry sugar concentration, with levels being similar to the control treatment. Additionally, in treatments where CaCl2 was applied to soil, chlorides concentration in soil, leaves, and berries were higher. Also, berries were larger, more turgent, with lower dry matter and larger cells. In the second season, in these same treatments, berry firmness at harvest was higher, but this effect disappeared after the storage simulation period. These results question the validity that Ca applications might improve table grape postharvest quality for growing conditions similar to the ones in this experiment. The temporal changes in berry quality parameters were attributed to higher Cl soil content and the associated plant osmoregulatory mechanisms.

Effect of phosphate fertilizer on the soil cadmium content in four types of Chilean soils

Phosphate fertilizers may contain cadmiun (Cd) which may become part of the trophic chains. The objective of this study was to evaluate the effect of phosphate fertilizer on available Cd content in four Chilean soil types, belonging to orders Alfisol, Inceptisol, Ultisol and Andisol. Treatments consisted of control without P fertilizer and P application with commercial triple superphosphate containing 53.2 mg Cd per kg of fertilizer. The dose of phosphate fertilizer applied was enough to reach the level of 30 mg kg -1 P-Olsen. The soils were incubated up to 90 days, at 25 o C and field capacity. The experimental design was completely randomized with three replications, and the experimental unit was a container with 250 g of soil (dry matter). Available Cd was measured at 1, 2, 7, 14, 21, 36, 49, 63, 77, and 90 days after incubation. Application of P at agronomic rate using fertilizer with a high Cd content produced significant effects on available Cd content in the soil types studied, however, incubation time period did not present such effect.

Seasonal pattern of root growth in relation to shoot phenology and soil temperature in sweet cherry trees (Prunus avium): A preliminary study in central Chile

C. Bonomelli, C. Bonilla, E. Acuna, and P. Artacho. 2012. Seasonal pattern of root growth in relation to shoot phenology and soil temperature in sweet cherry trees (Prunus avium): A preliminary study in central Chile. Cien. Inv. Agr. 39(1): 127-136. The period between flowering and harvest in the sweet cherry (Prunus avium L.) is shorter than most fruit trees; thus, competition for assimilate and nutrients occurs early in the season. To properly supply water and nutrients during this critical period, optimal growth and root development are necessary. To characterize the root growth pattern of cherry trees in relation to shoot growth and phenology, a study was conducted on a ‘Bing’ cherry orchard on Gisela 6 rootstock at fourth leaf, located in central Chile (34o70’ S, 70o43’ W). During the 2009-2010 season, the shoot length and fruit diameter were measured on eight trees, and the root length was quantified by installing rhizotrons on two trees. Additionally, a two-tone (black/white) plastic cover was placed in the row over one tree with a rhizotron to analyze the effects of the plastic cover on soil temperature and root growth. The results showed three peaks of root growth during the season. The first peak occurred 43 days after full bloom (DAFB), corresponding to the phenological stages of the fruit turning from green to straw color. This peak occurred at 326 accumulated degree days (ADD) in the soil and 212 ADD in the air. The second peak was observed after harvest at 97 DAFB, when the shoot growth had stopped, and the soil and air had accumulated 932 and 692 degree days, respectively. The third and last peak occurred at 167 DAFB, with 1887 ADD in the soil and 1361 ADD in the air. The plastic cover increased the average soil temperature by approximately 1 °C, thereby increasing the ADD by 105.2 units during the study period. However, this increase was not enough to affect the root growth pattern.

DISTRIBUCIÓN ESPACIAL Y TEMPORAL DE LA PRECIPITACIÓN Y LA HUMEDAD DEL SUELO EN TRES SITIOS FORESTALES DE LA VIII REGIÓN DE CHILE

En Chile existen alrededor de dos millones de hectareas con plantaciones forestales, destacandose la VIII Region, por sus favorables condiciones climaticas. Considerando la importancia que tiene el regimen hidrico sobre estas especies, el objetivo de este estudio fue caracterizar las precipitaciones y humedad del suelo en tres sitios representativos de las condiciones de Secano Costero, Valle Central y Precordillera de la region. Los sitios empleados se ubican entre los 37°00 y 37°45? lat. Sur y 72°00 y 73°10? long. Oeste. Desde septiembre de 1993 y hasta agosto de 1996 se registraron las temperaturas, precipitacion y contenido de humedad del suelo en cada sitio. Los resultados indican que la precipitacion mensual en el sitio de Precordillera no fue estadisticamente distinta a la registrada en los sitios del Secano Costero y Valle Central. La misma situacion se observo con las temperaturas medias. Sin embargo, aunque las temperaturas y precipitaciones fueron iguales en todos los sitios, se encontraron diferencias significativas al comparar los niveles de humedad disponible en el suelo. Los valores registrados en el sitio de Precordillera fueron en promedio 420 y 440% superiores a los observados en el Valle Central y Secano Costero, respectivamente. El elevado contenido de materia organica en el sitio de Precordillera seria la principal causa de este fenomeno. Esta mayor disponibilidad de agua se tradujo en mayores tasas de crecimiento en la plantacion forestal. Los resultados obtenidos demuestran la conveniencia de caracterizar el sitio forestal mediante la humedad disponible en el suelo en vez del agua caida.

Changes in fine-root production, phenology and spatial distribution in response to N application in irrigated sweet cherry trees

Factors regulating fine-root growth are poorly understood, particularly in fruit tree species. In this context, the effects of N addition on the temporal and spatial distribution of fine-root growth and on the fine-root turnover were assessed in irrigated sweet cherry trees. The influence of other exogenous and endogenous factors was also examined. The rhizotron technique was used to measure the length-based fine-root growth in trees fertilized at two N rates (0 and 60 kg ha(-1)), and the above-ground growth, leaf net assimilation, and air and soil variables were simultaneously monitored. N fertilization exerted a basal effect throughout the season, changing the magnitude, temporal patterns and spatial distribution of fine-root production and mortality. Specifically, N addition enhanced the total fine-root production by increasing rates and extending the production period. On average, N-fertilized trees had a length-based production that was 110-180% higher than in control trees, depending on growing season. Mortality was proportional to production, but turnover rates were inconsistently affected. Root production and mortality was homogeneously distributed in the soil profile of N-fertilized trees while control trees had 70-80% of the total fine-root production and mortality concentrated below 50 cm depth. Root mortality rates were associated with soil temperature and water content. In contrast, root production rates were primarily under endogenous control, specifically through source-sink relationships, which in turn were affected by N supply through changes in leaf photosynthetic level. Therefore, exogenous and endogenous factors interacted to control the fine-root dynamics of irrigated sweet cherry trees.

Use of Fura 2 Fluorescent Dyes as Indicator for Studying Calcium Distribution in Several Plant Tissues

Calcium (Ca) is an essential plant nutrient and is important in determining quality of fruits in storage. The analytical method presently known to determine Ca concentration in vegetables measures total Ca, and there is a need to develop methods that can determine the distribution of Ca within vegetable tissues. The objective of this study was to determine the ability of fluorescent probes to visualize Ca location and distribution in vegetable tissues. We examined three protocols using fluorescent dyes developed to detect Ca. The first tested Fura 2 acetoximetil (AM) probe in fresh cuts from grapes at different combinations of temperatures and incubation times. The second protocol was developed with the aim of lowering the natural autofluorescense. In the third protocol, the Fura 2 probe was used in tissues previously fixed in formalin, acetic acid, and alcohol solution (FAA). Tissues were observed under an epifluorescence microscope and, to compare and complement the observations, under a scanning electron microscope (SEM). No sign of fluorescence was observed in fixed and fresh tissue using the Fura 2 AM. In fresh cuts, there was autofluorescent interference, provoked mainly by chlorophyll, but also from the vascular system and tannins. The Fura 2 probe was introduced to vegetable tissues by utilizing a pH of 4.5, and a more intense signal was observed in tissues with greater Ca concentration. This signal was also associated with Ca crystals, which might have had some degree of hydrolysis at low pH. Under a SEM microscope, Ca oxalate crystals were clearly observed in those tissues. Our results show that Fura 2 probe can be used to detect Ca and its distribution in vegetable tissues.

Adaptation and Validation of a Methodology for the Measurement of Calcium Fractions in Fruits

ABSTRACT Calcium (Ca) content of fruit is related to fruit quality. However, total content alone is insufficient to judge fruit quality; calcium partitioning and chemical form are also important. There are multiple validated methods for determining total calcium content. However, methodologies to measure calcium fractions are not widely known and tend to be complex, affecting their accuracy. Here, based on previous work, we aim to adapt and validate a method for the extraction of the various forms of calcium in fruits. The main modification was freezing samples to minimize the loss of sample material in the procedure, reducing the centrifugation time and speed, and the addition of nitric acid (HNO3) to improve digestion and eliminate interference from the matrix. An experiment with table grape berries cv. Thompson seedless in harvest and Postharvest (35 days) was carried out. The results of the total calcium were compared with the conventional methodology of calcination and inductively coupled plasma (ICP) measurement. We detected no and no significant differences between the two tested methods. Electron Microscope - Energy-dispersive X-ray spectroscopy analysis (SEM-EDS) and the presence of calcium oxalates were verified.

Substrate effects on vegetative and reproductive growth of Ornithogalum thyrsoides “Royal Beauty”

ABSTRACT The effect of soil amendment with degraded granite or perlite on plant growth of Ornithogalum thyrsoides was investigated in Central Chile. Bulbs were planted in April in raised soil beds under greenhouse. Three different substrates were compared: control (unamended soil), decomposed granite soil (DG) and soil in proportion 1:2, and perlite and soil in proportion 1:2. Soil nutrient availability in all treatments was considered higher than the plant requirements. The plants in the unamended soil had the greatest flower stem diameter, total fresh weight, and aboveground fresh weight. In terms of stem length, inflorescence length, belowground structures fresh weight, and inflorescence fresh weight, perlite with soil had similar results as unamended soil, but never better. Our results indicate that, under the conditions of this experiment, DG or perlite is not recommended for growing O. thyrsoides, since they did not improve either vegetative or reproductive growth.

Differences in quality parameters and nutrient composition in Fukumoto oranges with and without creasing symptoms

ABSTRACT Creasing is a physiological disorder in oranges fruits that affects rind quality. This disorder has been associated with insufficient or imbalances of nutrients in the fruit. A study was carried out in an orange orchard cv. Fukumoto. At harvest, fruit samples were selected with and without creasing, according to visual symptoms. External and internal fruit quality was evaluated in whole fruit, then dry matter and mineral content and concentration (nitrogen N, potassium K, calcium Ca and magnesium Mg) was analyzed in flavedo, albedo and pulp. Oranges with creasing had larger weight and fruit size, higher water content in the pulp and whole fruit, lower coarse rind grading, thinner peel, higher nitrogen content in the pulp and the whole fruit, higher potassium content in all fruit components and lower calcium content and concentration. Magnesium content, only in flavedo showed significant differences, being higher in fruit without creasing. Fruit size and Ca were key factors related to the expression of creasing disorder, as well as nutrient balance.