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The objective of this work was to determine the effect of nitrogen fertilization on the respiration of the microbial population associated with the rhizosphere of Saccharum officinarum L. The quantities of soil microorganisms as an expression of its quality, allow establishing relationships with its chemical properties, by determining microbial respiration. In a long-term experiment, Umln_6, planted with Saccharum officinarum L., and six levels of nitrogen, planted in Santiago of Cuba province. The microbial respiration was determined through chemical assessments in a closed environment, agricultural yield and the interaction with chemical and meteorological variables of the ecosystem. The data were processed by factorial variance analysis, AMMI model and PCA. The respiratory variable had a differential behavior for the levels of N applied and the phenology of the crop, in addition to the influence of these factors on the chemical properties of the soil that reaches its maximum value with an average dose of N, of 100,6 kg.ha-1. The results indicate that the evaluation of sugarcane-soil microorganism interactions can be useful for better management of nitrogen fertilization. [ABSTRACT FROM AUTHOR]

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Spinach has several relevant properties, great nutritional importance, and an affordable price, being a significant subject in various studies. However, the current literature is scarce regarding the production and nutritional requirements of this crop, with nitrogen being the element mostly required. The objective of this study was to evaluate the effect of nitrogen doses and application timings on the nutrition and productivity of spinach. The experimental design was a randomized block in a 6 x 4 factorial scheme, consisting of the combination of six N doses (0, 30, 60, 90, 120, and 150 kg ha-1) and four application timings (planting (PT), 15, 30, and 45 days after planting (DAP)) of urea nitrogen fertilizer, with four replications. The analyzed variables were chlorophyll content (CF), plant height (AP), fresh mass (MF), dry mass (MS), nitrogen content (TN), and nitrogen accumulation (AN). The data obtained were subjected to analysis of variance (F test), and the means obtained based on the N application timing were compared by Tukey's test at a 5 % probability level. For nitrogen doses, regression analysis was performed. At 15 DAP, the application of 90 kg ha-1 of nitrogen stood out, increasing productivity and obtaining 50.38 kg ha-1 of spinach. However, the productivity achieved in absence of nitrogen topdressing fertilization was satisfactory. Therefore, under conditions like those of the conducted study, it is possible to achieve good productivity and nutrition values without resorting to topdressing nitrogen fertilization, thereby emphasizing the advantage of reduced production costs. [ABSTRACT FROM AUTHOR]

Winter cereals are important in the agricultural production of the semi-arid central Pampas region and among them the most widespread is bread wheat (Triticum aestivum L.). In this area, durum wheat (Triticum durum Desf) is not yet cultivated, although it is a crop with good performance for semi-arid zones. Grain and semolina industrial quality of four genotypes of wheat durum cultivated in the Capital department in the province of La Pampa, Argentina, under different nitrogen availability were analyzed. Field work was carried out with four genotypes: Bonaerense INTA Cariló, Ciccio, Buck Cristal and Concadoro and two levels of nitrogen availability in tillering and flowering. There were significant differences among cultivars in all studied characteristics. Nitrogen fertilization increased in some genotypes grain protein concentration and vitreousness. The percent of vitreousness and the yellow pigment content were low, and in the semolina dough there was a high loss of pigment due to the processing associated with the lipoxigenasa activity. Semolina had a high glutenin/gliadin ratio indicating that it would be strong gluten. These results showed that grain and semolina quality attributes were satisfactory although it is necessary to continue generating industrial quality information, evaluating the response of others cultivars particularly, chosen genotypes that allow the optimization of nitrogen fertilization in La Pampa province. [ABSTRACT FROM AUTHOR]

Copyright of Avances is the property of Instituto de Informacion Cientifica y Tecnologica and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Roca: Revista Científico-Educacional de la Provincia de Granma is the property of Universidad de Granma, Departamento Editorial and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Agro Productividad is the property of Colegio de Postgraduados and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

An experiment was conducted in La Molina, Lima, Peru, with the objective of evaluate the effect of planting densities (62 500 and 69 444 plants ha-1), nitrogen doses (180, 200 and 220 kg ha-1) and nitrogen splitting (two times: stages V3 (50%) and V7 (50%); and three times: stages V3 (20%), V7 (40%) and V12 (40%)), on the agronomic performance of the flint yellow corn hybrid EXP-05. The experiment used a completely random block design, in 2x3x2 factorial arrangement, with four replications. There was not significant effect of the interactions of the evaluated factors on growth and yield components. On the other hand, there was an individual effect of nitrogen doses and planting density on grain yield and stem diameter, respectively. The highest grain yield (10.639 t ha-1) was obtained with 200 kg ha-1 of N and the largest stem diameter (2.42 cm) with the lowest planting density (62 500 plants ha-1). Although the interaction of the evaluated factors was not significant, the highest grain yield (10.939 t ha-1) was obtained with 200 kg ha-1 of N, splitting in two stages which are V3 (50%) and V7 (50%) and using 69 444 plants ha-1. [ABSTRACT FROM AUTHOR]

Copyright of Revista Veterinaria is the property of Universidad Nacional del Nordeste and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The use of management strategies, such as adjustment of grazing intensity and nitrogen fertilization, are fundamental for the success of animal production, in crop-livestock integration systems (IAG). The objective was to evaluate the effects of grazing intensity and nitrogen fertilization on the nutritional value of Italian ragweed pastures (Lolium multiflorum Lam.), individual performance and by area of steers Nelore x Charoláis IAG. A randomized block experimental design with 2 x 2 factorial application and three repetitions was used. The first factor was grass height: High Height 25 cm (AA) and Low Height 10 cm (BA). The second factor was the period of nitrogen fertilization applied at two different times in the system: N applied in the pasture (NP) and N applied in the grains crop (NG), in doses of 200 kg of N ha-1, forming 4 treatments: AANG, AANP, BANG and BANP. The grass height of Italian raigras (Lolium multiflorum Lam.) was regulated by continuous grazing with variable number of animals. With nitrogen fertilization in the pasture, it is possible to handle the Raigras 'Winter star' grasses with an average height of 12.5 cm. The accumulation rate and the total DM production were higher in AANP. Nitrogen fertilization of the pasture resulted in higher crude protein content, less of neutral detergent fiber and acid detergent fiber. With the advance of the grazing period and the pasture phenology, there was a decrease in crude protein and an increase in the neutral and acid detergent fiber. The average daily gain did not present a difference between treatments and was greater than 1.0 kg day-1, the average gain per area was greater in the BANP treatment. [ABSTRACT FROM AUTHOR]

Copyright of Agriscientia is the property of Revista AgriScientia and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The objective was to assess the production and efficiency of the initial growth of Cajanus cajan var. Black and EGV22 with and without nitrogen fertilizing. The plants were planted in plastic bags during summer 2012. Two nitrogen fertilization treatments were applied at 90 d of germination (+ N and - N). The variables were: number of nodules (NN), long of root (LR), weight of nodules (WN), height of plant (HP), dry matter total (DMT), index of area leaf (IAL), area foliar specific (AFS), rate of assimilation (RA), rate relative of growth (RRG) and rate of growth of the crop (RGC). A full-randomized experimental design was used with a factorial arrangement 2 x 2 and regression analysis. Differences were observed (P < 0.05) among varieties for NN, HP, so and RGC, where the highest average HP was obtained by EGV22 variety. For the nitrogen factor, its application decreased (P < 0.05) NN, WN, and HP. It is concluded that Black variety can be used in the production systems since it has great DMT and the best establishment for the environmental conditions of the tropic of Ecuador. [ABSTRACT FROM AUTHOR]

Nitrogen fertilization is essential to raise sugarcane yield in soils deficient in N. The objective of this study was to evaluate the effect of nitrogen application in production and borer attack on sugarcane. The experiment was conducted at Escobar District, State of Paraguarí, Paraguay. Three sugarcane growing seasons were evaluated during 2011-2013. The experimental design was randomized blocks with seven treatments and three repetitions, with annual application of increasing of nitrogen 0, 30, 60, 90, 120, 150 and 180 kg ha-1). At 360 days of each crop cycle, harvest was performed with the following assessments: industrial plant height, number of internodes per plant, infestation intensity index and yield. The nitrogen rate of maximum technical efficiency and maximum economic efficiency was determined. Statistical analysis of variance, means comparison and regression were performed. Nitrogen fertilization did not affect plant height and number of internodes, but increased yield and borer attack. For every kg ha-1 of nitrogen applied 0.25 t ha-1 of yield is added, and 0.27 % of infestation intensity index increase is obtained. The rate of maximum technical efficiency was 157,4 kg N ha-1 for a yield of 73,6 t ha-1, and the rate of maximum economic efficiency was 136.5 kg N ha-1 for a yield of 88,2 t ha-1. [ABSTRACT FROM AUTHOR]

Soil nematode assemblage was studied in a chronosequense (S1, S2 y S3) that included 2008-2009, 2009-2010 and 2010-2011 growing seasons of a pear commercial orchard with different nitrogen fertilizer management: 776, 375 and 80 kg N ha-1, respectively, in a silt loam saline soil (5.2 dS m-1). Nitrogen application in S1 and S2 was split in seven times and in S3 in three times. Soil characteristics, nematode abundance, ecological indices, and fruit yield were evaluated. Organic matter (4.2%), nitrate (29.5 mg kg-1) content and soil pH (7.64) did not change in the chronosequence. Smectite clays, that are one of dominant minerals in the soil, exhibit high buffering capacity and high resistance to change in pH when the nitrogen fertilizer is applied to the soil. Plant-feeding nematodes were the most abundant trophic group (48%) and the families belonging to the herbivores of c-p 2 guild were dominant. Aporcelaimellus represented a 16% of total abundance of nematodes. In S1, the increase in enrichment index (78.6%) was attributed to the high abundance of bacterivores of c-p=1 guild (Ba1) and fungivores of c-p=2 guild (Fu2), where the rate of nitrogen applied was greater, respect to S2 and S3. The numbers of Panagrolaimidae and Rhabditidae increased in S1. Soil nitrate content was not correlated with Ba1 and Fu2 abundance. Neither omnivores and carnivores density nor indices of structure (81.4%), channel (14.2%) and basal (11.1%) were altered by nitrogen application in the growing seasons. The low value of channel index indicated a bacterial decomposition pathway of soil organic matter. The pear fruit yield was similar in the chronosequense. [ABSTRACT FROM AUTHOR]

The objective of this investigation was to evaluate the response of barley production to nitrogenized fertilization (NF) and its impact on the protein content of the grain and the availability of nutrients on the soil. The study was carried out in two sites in Hacienda Valencia, in Pintag, Quito, Ecuador, between March 2014 and February 2015. A variety of INIAP Cañicapa 2003 was used, and the NF was done with normal urea and polymerized (urea + tiophosphate of N-nbutiltriamida). An experimental design of randomized full blocks in four repetitions of divided lots [the urea (normal and polymerized) was used in the main lot and the NF (0, 30, 60, 90, 120, y 150 kg N/ha) in the sub-lot]. 110 kg/ha of seed was used; 50% of the NF was applied three weeks after planting (broadcast) and 50% eight weeks after. The type of urea did not affect the production (p>0,10), although the average was different between two sites (4,33 y 2,08 t/ha for sites 1 and 2, respectively). Excess of rain could have limit the effect on the urea type. On average a cuadratic response to NF was obtined, with an optimum dose of N (DON) of 90 kg N/ha and a production of 3,41 t/ha. This DON was similar to the dose of N recomended for barley in Ecuador. The NF augmented the protein content up to 14,50% (p<0,01) and acidified the ground, because the urea nitrification produces H+. [ABSTRACT FROM AUTHOR]

Nitrogen (N) mineralization during a short anaerobic incubation (NAN) could be used as a soil health indicator. To adjust its use, it is necessary to characterize and understand how it is affected by different management practices. For soils of the Southeast of the Buenos Aires Province we hypothesized that i) higher carbon (C) inputs through crop residues lead to lower NAN variations in the arable soil layer without difference between conventional tillage (CT) and no tillage (NT), and ii) the amount and quality of the preceding crop residue affects the NAN content. The aims of this work were: i) to evaluate the change in time of NAN at 0-20 cm under different crop sequences, CT and NT, and with and without N fertilization (NF), and ii) to analyze the effect of different crop residues on NAN at 0-20 cm. We determined NAN in stored soil samples taken from the 0-5 and 5-20 cm soil layers in two long term tillage system (TS) experiments (CT and NT): Experiment 1 with two levels of NF (with and without N), and Experiment 2: with three crop sequences (corn-corn-wheat, corn-soybean-wheat, soybean-soybean-wheat). Anaerobic N decreased along years under cropping at 0-5, 5-20 y 0-20 cm, under both TL and levels of NF. Only at 0-5 cm decreases were significantly different between TS (CT>NT). At 0-20 cm there were no differences in NAN decreases neither between levels of NF nor among crop sequences. Hence, different C inputs of different biomass productions did not lead to differential changes in NAN along cropping years. Different preceding crops did neither affect NAN contents. Nitrogen fertilization could have produced higher soil organic C mineralization since it decreases the soil system C/N ratio, masking the expected effects of crop residue characteristics on NAN. However, our results contribute to confirm the feasibility of using NAN as a soil health indicator. [ABSTRACT FROM AUTHOR]

Ammonia oxidation to nitrite is a critical step in the nitrogen (N) cycle and is performed by ammonia-oxidizing bacteria (AOB) also called Nitrifying. Agricultural management can affect the AOB community due to the prolonged use of nitrogen fertilizers such as urea which tend to increase soil acidity. After 12 years of urea application, size, activity, AOB composition and chemical variables were investigated. The performed field experiment had a complete randomized block design with three replicates on a typical Argiudol soil located in Marcos Juárez, Southeastern Córdoba, Argentine. The treatments were: A control without N-application; B and C with 95 and 165 kg ha-1 of urea as the N source respectively. Soil samples were collected before sowing and after corn harvest. The AOB community was studied through the most probable number method, shaken soil slurry, polymerase chain reaction and electrophoresis in denaturing gradient gel. Urea fertilization decreased soil pH, increased AOB abundance and diversity but did not significantly affect nitrifying potential. Bacterial community structure was dominated by members of the Group 3 of Nitrosospira in all the treatments. The results showed that the long-term urea fertilization in a typical Argiudol was a substrate source and not a limiting factor for the nitrifying bacteria. The fertilization effect was more evident in the sampling date before corn sowing. [ABSTRACT FROM AUTHOR]

La eficiencia máxima de nitrógeno (N) se alcanza cuando el fertilizante de N se usa con silicio (Si). Por tanto, el objetivo de este estudio fue evaluar los atributos químicos del suelo, el estado nutricional, la producción de tallos y la acumulación de N y Si en el cuarto cultivo de soca de caña (Saccharum sp.), y la influencia de la dosis de N en presencia y ausencia de Si y cal. El estudio se realizó en la granja experimental del campus UNESP-Jaboticabal, estado de São Paulo, Brasil. El diseño experimental fue de bloques completos al azar con un arreglo factorial de 5x2: cinco dosis de N (0, 40, 80, 120 y 160 kg ha-1), y dos materiales correctivos, silicato y cal; con cuatro repeticiones por tratamiento. El suelo se clasificó como Latosol Rojo distrófico y la variedad de caña de azúcar fue RB855156. Durante el experimento se midieron el contenido de N (N-NH4 + y N-NO3 -) y Si en el suelo, el contenido de N y Si en la hoja, la producción de tallos y la acumulación de N y Si en las hojas y tallos. La fertilización con N asociada con silicato y caliza aumentó los niveles de N-NO3 - y Si en el suelo, lo cual mejoró el estado nutricional y la acumulación de N y Si en las hojas y tallos de la caña de azúcar, pero la producción de tallos fue menor al usar silicato, comparado con cal. [ABSTRACT FROM AUTHOR]

El nitrógeno es un nutrimento que incrementa el crecimiento, la duración del área foliar y la fotosíntesis del cultivo, características que permiten al girasol (Helianthus annuus L.) aumentar el rendimiento de semilla por unidad de superficie. El objetivo del presente estudio fue evaluar la tasa de asimilación neta, el rendimiento y sus principales componentes en dos cultivares de girasol (Periquero y Victoria) en función de dos tipos de urea (urea común y urea de liberación lenta) y tres dosis de N (40, 80 y 120 kg N ha-1), en tres localidades del Estado de México (Toluca, Balderas y Chalco). El diseño experimental fue bloques completos al azar con arreglo factorial. Los 36 tratamientos resultaron de las combinaciones de las tres localidades, los dos cultivares, los dos tipos de urea y los tres niveles de nitrógeno. Los datos se analizaron con ANDEVA y las medias de los tratamientos se compararon con la prueba DSH (p⩽0.05). Para conocer la relación entre el rendimiento de semilla y la tasa de asimilación neta se calculó la regresión lineal simple. El análisis de los resultados indicó que en Chalco el girasol rindió (732.0 g m-2) más que Toluca (285.9 g m-2) y Balderas (467.0 g m-2), debido a la mayor tasa de asimilación neta (0.89 g dm-2 d-1); Victoria, con rendimiento promedio de 508.2 g m-2 e índice de cosecha de 0.33, fue superior a Periquero en 5.1 % y 11.76 %, respectivamente. Con urea común se alcanzó una producción promedio de grano de 508 g m-2, superior en 5.2 % al obtenido con urea de liberación lenta. La mejor dosis en este estudio fue 120 kg N ha-1 ya que su rendimiento promedio fue 541.5 g m-2. Se concluye que la tasa de asimilación neta afectó positivamente el rendimiento de semilla, porque la ecuación de regresión y = 217.8 + 308.2 (x) (r2 = 0.69**) significa que por cada unidad de incremento en la tasa de asimilación neta, el rendimiento aumenta 308.2 g m-2. [ABSTRACT FROM AUTHOR]

Diagnosis of soil nitrogen fertility does not usually include the contribution of soil organic pools. Mineralisable nitrogen under anaerobiosis (Nan) and other labile N fractions may be useful to predict the mineralized soil nitrogen pool and to improve the diagnosis of soil nitrogen fertility, although management practices may affect these pools. The aims of our study were to: i) evaluate the effect of long-term nitrogen fertilization and crop sequences on organic nitrogen in the soil particulate fraction (NOP) and Nan, and ii) evaluate the relationship between Nan, total nitrogen (NT) and NOP. In a longterm continuous maize experiment, and two other experiments with different crop sequences and two soil types, NT, NOP and Nan were determined in the bulk soil samples and on macroaggregates in two depths. The sources of variation evaluated in these experiments did not show differences in NT, NOP and Nan contents. In addition, positive relationships were found between Nan and NT contents (R² = 0.65; P < 0.001) and between Nan and NOP (R²= 0.85, P < 0.001), which are attributed to the variation in depths and contrasting sites. Moreover, we found a strong association between Nan in bulk soil sample and Nan in macroaggregates (P < 0.001), evidencing that a high proportion of Nan was allocated in the macroaggregates. The determination of Nan and NOP in soil macroaggregates did not present advantages compared to the evaluation in the bulk soil sample. [ABSTRACT FROM AUTHOR]

Copyright of Revista Luna Azul is the property of Universidad de Caldas and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The objective of this work was to evaluate the effect of inoculating the arbuscular mycorrhizal fungi (AMF) strain Glomus hoi-like on the response of Brachiaria hybridcv. Mulato II (CIAT 36087) to organic and nitrogen fertilization. The experiment was carried out in the Pastures and Forages Station of the Genetic Breeding Enterprise "Niña Bonita" ,located in Artemisa province, on a Lixiviated Red Ferraliticsoil. Rates of 15 and 30 t of cattle dung.ha-1, 30 t of cattle dung.ha-1 combined with 150 kg N.ha-1.year-1, 15 and 30 t ofcattle dung.ha-1 combined with 0, 75 and 100 kg N.ha-1.year-1plus the inoculation of AMF strain Glomus hoi-like, and the corresponding controls without cattle dung or N, to establisheleven treatments, were assessed. These were distributed in arandom block design with four replications. Cattle dung improved the soil chemical properties when increasing its pH,organic matter and available P and K contents, and its effects was observed during the first two years after its application; the highest effects were observed with the application of30 t.ha-1. The inoculation of G. hoi-like combined with the application of 75 or 100 kg N.ha-1.year-1 produced the highest mycorrhizal colonization percentages, visual density and spore density, so as dry matter (DM) nutrient contents and DM yieldssimilar to those obtained with 30 t of cattle dung.ha-1 plus150 kg N.ha-1.year-1 without inoculation. The effects of G. hoi-like inoculation on the mycorrhizal structures and on the reduction of both fertilizer dosages was observed during the first two years of the experiment. [ABSTRACT FROM AUTHOR]

The following results were obtained for an experiment done with three levels of nitrogen and three planting densities to determine the best response by the rice genotype IIAC-20 in the spring season, and the level of association that these conditions establish on the components of the agricultural yields using the sendero coefficient analysis. It placed in manifestation the importance of the number of rice pods per m² as the variant that influence most significantly in the agricultural yields. In relation to the distinct combinations evaluated, 120kg.ha of nitrogen with a planting density of 120kg.ha produces the highest yields with a high efficiency in the use of fertilisers. The biplot analysis of the principal components gained the association of the different combinations of nitrogen and planting densities with respect to the characters evaluated, demonstrating how the increased dosage of nitrogen increase the plant height but not the agricultural yields. [ABSTRACT FROM AUTHOR]

In Cuba are applied high amounts of Nitrogen on potato in relation with the average yields obtained. With the aim of define in representative soil-clime conditions the best amounts of Nitrogen for that crop and to prove if the actually recommended amounts decrease the yield because of favouring diseases, three trials were carried out under production conditions in two soils in the province of Villa Clara, Cuba (Typical Red Ferralític soil and Arenic Lixiviated Yellowish Ferralític soil). As control was used the Nitrogen amounts usually applied (220-230 kg ha-1) and lower amounts were tested (160-180-200 kg ha-1 in the first trial; 115-150-185 kg ha-1 in the second and 140-170-200 kg ha-1 in the third one). The Nitrogen was applied at a rate of 80 kg ha-1 as the formula 9 -- 13 -- 17 at plantation and the remainder amount, 30 days later, as formula plus urea. The potato sorts utilized were Chieftain, Romano and Red Scarlet. Each treatment consisted of 4 plots at random with 4 furrows of 340m long. The results showed that the N amounts usually applied under production conditions in Cuba are excessive even for high tuber yields for the country (30t ha-1), so that starting with relatively low amounts, the increasing application of the nutrient decrease the yield; that is associated to an increase of plant diseases such as Phytophthora infestans, Alternaria solani and Erwinia spp. Application of amounts according to the expected yields are recommended; those amounts do not shall surpass 180 kg ha-1 for yields until 30 tha-1. [ABSTRACT FROM AUTHOR]

The aim of this study was to determine the effect of nitrogen application at different moments during the apple crop cycle on the population of soil microorganisms in terms of microbial biomass carbon, enzymatic activity and edaphic properties. Nitrate content, total nitrogen, organic carbon, microbial biomass carbon, deshidrogenase and catalase activity were determined and the carbon mineralization index, the proportion of microbial biomass carbon in organic carbon and the metabolic coefficient (qCO2) were calculated. Nitrogen was applied as ammonium nitrate (NH4NO3) at two rates, 100 (N1) and 200 kg N ha-1 (N2), and on two times, 50% at petal fall (October) and the rest at harvest (March), and the results compared with a control treatment without N (N0). The experiment was repeated over two growing seasons, 2005-2006 and 2006-2007. Soil samples were taken before and after each fertilization. Nitrogen addition had differential effects on soils chemical and biological properties depending on the season and plant phenology. In autumn and spring, soil nitrates (NO3-) increased significantly and soil biota was modified during both growing seasons. In the 2005-2006 season, spring nitrogen additions increased soil biota activity in terms of C-BM, RE and Dh-asa; whereas in the second growing season, 2006-2007, nitrogen addition had no effect on soil chemical and biological properties. Soil biological activity was affected by orchard management practices, fertilization and pruning. [ABSTRACT FROM AUTHOR]

Copyright of Agro Sur is the property of Universidad Austral de Chile, Facultad de Ciencias Agrarias and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Agro Sur is the property of Universidad Austral de Chile, Facultad de Ciencias Agrarias and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The abundance and the low cost of the irrigation water in the Upper Río Negro Valley entail to the inefficient use of the resource, mainly during the first part of the spring when the growers irrigate frequently for passive frost control. Such situation allows us to infer that nitrates derived from either the soil or the fertilizer is prone to be leached from the soil profile during most part of the growing season. Actuality there are no local studies to show the variation seasonal concentration of soil nitrates in the rooting zone of the fruit trees, therefore we initiated a study with the aims of: a) to measure the concentration of nitrate in the soil profile occupied with roots from the stage of flowering to the beginning of leaf fall, with nitrogen fertilization in two equal doses and without nitrogen, a different profundity the extraction; b) to determine the efficiency of irrigation of the orchard irrigated by flooding. Two concentrations of nitrogen were experimented, applied as ammonium nitrate in two opportunities, 50% at petal fall and the rest at harvest and a control treatment without N (N0), corresponding a dose the 100 Kg ha-1 (N1) and 200 kg ha-1 (N2), period 2004-2005 and 2005-2006. Soil samples at three soil depths (0-30, 30-60 and 60-90 cm) were taken in the beginning of flowering and previous any irrigation and then from October to April after each irrigation. The concentration of nitrates along the season remained in 22 mg kg-1 in the top soil and decreased 50% in the 30-60 cm soil depth. In N1 and N2 the concentration increased sharply after the application of the fertilizer and reached concentrations in the 0-30 cm of 175 mg kg-1 and 300 mg kg-1 in N1 and N2, respectively. However 30 days after the application of N1 and 60 days after the application of N2 the concentrations of nitrates were similar to N0. The volume of water applied per hectare was 1712-2400 mm with a 30% efficiency. The results showed that the effect of the fertilizer application lasted a short period of time and the irrigation efficiency should be improved in order to avoid nitrate leaching. [ABSTRACT FROM AUTHOR]

This study was carried out to identify the availability of lysine in maize cultivators and its relationship to nitrogen fertilization and plant population density by means of S. commune. Maize varieties QPM, opaque-2, synthetic-white and yellow kernels were evaluated at the Universidad Autónoma Agraria Antonio Narro (UAAAN) in Coahuila, México, during 2005. There were three levels of plant population density and four for nitrogen fertilization. Kernel lysine content was determined by utilizing a microbiologic method (Schizophyllum commune) and a comparative scale that permitted a selection of high and low lysine content cultivators. In the field experiment a complete block design was utilized and arranged as a split-plot design. In the laboratory experiments, a complete randomized design and multiple ranges Duncan's test were utilized. Lysine content was estimated to range from 18,73% to 21,29% and from 9,04% to 10,36% for embryo and endosperm, respectively. For cultivators Opaque-2, contained 35.1% germ protein and 60,7% endosperm protein. Lysine contents varied from 17% in white-kernel varieties to 58% in Opaque-2 hybrid. Lysine content was highly affected by the genetic structure of the individuals and environment factors, but mostly by plant population density and nitrogen fertilization. [ABSTRACT FROM AUTHOR]

The trials were conducted in 2003 and 2004 at the Calabacito and Guarumal Experiment Stations and on farms at Mariato, Veraguas and Tonosi, Los Santos. Nitrogen rates of 0, 40, 80, 120, 160 and 200 kg/ha were applied as urea. All plots received 100 kg P2O5/ha as triple superphosphate and 50 kg K2O/ha as potassium chloride. Rice varieties IDIAP 2503 and CHI 0330 were compared at Calabacito and Guarumal; varieties IDIAP 2503 and CR 5272 were compared at Tonosi, and variety Colombia XXI was used at Mariato. A randomized complete block design with four replications was used in all experiments. There was a significant yield response to applied N in all experiments. Maximum grain yields in 2003 ranged from 3.3 t/ha at Mariato to 5.7 t/ha at Tonosi. Optimum N rates were 44 kg/ha for IDIAP 2503 and 84 kg/ ha for CR 5272. both at Tonosi, and 71 kg/ha for Colombia XXI at Mariato. For the experiment at Calabacito in 2004, there was no yield response by variety CHI 0330 above 55kg applied N/ha and fertilizer N use efficiency was estimated to be 35%; optimum fertilizer N for IDIAP 2503 was 155 kg/ha with a 25% use efficiency. Critical foliar N at flowering for both varieties at Calabacito was 3.06%. Optimum fertilizer N levels at Guarumal were 119 kg/ha for IDIAP 2503 and 105 kg/ha for CHI 0330, with critical foliar N levels of 2.9 and 2.57%, respectively. [ABSTRACT FROM AUTHOR]

During more than 15 years investigations in experimental stations and in production conditions were carried out with the hypothesis that a decrease of the amounts of nitrogen applied on potato at present was possible without yield affectation while the environmental damages could be diminished. Results of some of representative experiments carried out in three important soils are showed. Increasing amounts of nitrogen as urea or ammonium nitrated were tested in experimental stations (0-220 kg N/ha) and the best amounts previously obtained were compared in validation tests with those applied in production conditions that year (from 186 to 220 kg N/ha), as ammonium sulphate as component of a complete formula plus the other sources previously mentioned. The fertilizer was split in two applications: one at the plantation moment and another one 25-30 days later. The results showed that the N amounts usually applied under production conditions (more than 180 kg N/ha) were unnecessary high for yields until 35 t/ha and could decrease the yields, even causing the annulment of the potential fertilizers effect, affecting the potato tuber formation and favouring the incidence of diseases in addition to represent a danger for the underground waters of the respective zones that in occasions have reached concentrations not advisable for human consume. The most convenient amounts ranged generally between 120 and 150 kg N/ha. [ABSTRACT FROM AUTHOR]

Wheat crop and livestock raising are an important source of income in the center east of the country. The livestock yield relies on perennial forage resources and yearly forage crops during the winter. Winter grasses are an essential part of the forage chain in the fattening season for cattle or milk production in this region. The so-called dual purpose wheat (DPW) refers to using this crop with two aims: cattle grazing and crop yield. Thus, the dual purpose wheat is a forage option in farming and livestock raising mixed systems. During the winter season there exists a decline in forage supply and at the same time the demand for grain crops increases. In this way DPW may produce greater efficiency in the utilization of the available resources. Due to the irrational use of the soil, nitrogen (N) is in great shortage in most of the country's surface. According to bibliography nitrogenous fertilization increases dry matter (DM) yield and hastens the cycle of forage utilization as well. The percentage of wheat gross protein (GP) increases while non structural soluble carbohydrates tend to diminish. Nevertheless, nitrogenous fertilization seems to have no pronounced effect on the other nutritional components. [ABSTRACT FROM AUTHOR]