The Cloud Factory II: gravoturbulent kinematics of resolved molecular clouds in a galactic potential

Interstellar matter and star formatio

Determination of the uptake and translocation of nitrogen applied at different growth stages of a melon crop (Cucumis melo L.) using 15N isotope.

In order to establish a rational nitrogen (N) fertilisation and reduce groundwater contamination, a clearer understanding of the N distribution through the growing season and its dynamics inside the plant is crucial. In two successive years, a melon crop (Cucumis melo L. cv. Sancho) was grown under field conditions to determine the uptake of N fertiliser, applied by means of fertigation at different stages of plant growth, and to follow the translocation of N in the plant using 15N-labelled N. In 2006, two experiments were carried out. In the first experiment, labelled 15N fertiliser was supplied at the female-bloom stage and in the second, at the end of fruit ripening. Labelled 15N fertiliser was made from 15NH415NO3 (10 at.% 15N) and 9.6 kg N ha−1 were applied in each experiment over 6 days (1.6 kg N ha−1 d−1). In 2007, the 15N treatment consisted of applying 20.4 kg N ha−1 as 15NH415NO3 (10 at.% 15N) in the middle of fruit growth, over 6 days (3.4 kg N ha−1 d−1). In addition, 93 and 95 kg N ha−1 were supplied daily by fertigation as ammonium nitrate in 2006 and 2007, respectively. The results obtained in 2006 suggest that the uptake of N derived from labelled fertiliser by the above-ground parts of the plants was not affected by the time of fertiliser application. At the female-flowering and fruit-ripening stages, the N content derived from 15N-labelled fertiliser was close to 0.435 g m−2 (about 45% of the N applied), while in the middle of fruit growth it was 1.45 g m−2 (71% of the N applied). The N application time affected the amount of N derived from labelled fertiliser that was translocated to the fruits. When the N was supplied later, the N translocation was lower, ranging between 54% at female flowering and 32% at the end of fruit ripening. Approximately 85% of the N translocated came from the leaf when the N was applied at female flowering or in the middle of fruit growth. This value decreased to 72% when the 15N application was at the end of fruit ripening. The ammonium nitrate became available to the plant between 2 and 2.5 weeks after its application. Although the leaf N uptake varied during the crop cycle, the N absorption rate in the whole plant was linear, suggesting that the melon crop could be fertilised with constant daily N amounts until 2–3 weeks before the last harvest

Optimización de la dosis de nitrógeno en suelos poco profundos, irrigados, bajo cultivo de maíz

A method of evaluating net nitrogen (N) mineralization in shallow petrocalcic soils, based on N balances in non-fertilized plots, is proposed. During 1999, 2000 and 2001, estimated N mineralized in an irrigated maize crop (6.5 months) in Central Spain was: 73.3, 56.2 and 60.5 kg ha-1, respectively. The relationship between EUF-Norg (organic nitrogen extracted from soil by electroultrafiltration) and mean mineralized N, in this experiment during the three seasons, was 1 mg EUF-Norg 100 g-1 soil equivalent to 30 kg N ha-1. The calibration was applied to EUF-Norg values from soil samples analysed before sowing. These values, together with the mineral N, were used to estimate available N and consequently the optimal N rate. To evaluate the effect of N fertilizer rate on NO3 leaching and in N fertilizer-use efficiency (NFUE) three different rates of N were tested in 2000 and 2001: optimal N rate (NO), conventional N rate (NC) and a control no N (C). The NO rates for the maize crop were 150 and 130 kg N ha-1 in 2000 and 2001, respectively. Nitrogen losses of nitrate due to leaching were lower with NO than with the NC rate of 300 kg N ha-1. The NFUE values were higher for NO at 78.8% and 83.5% in 2000 and 2001, respectively than for NC at 48.7% and 49.3% in 2000 and 2001, respectively). However, in spite of the different levels of applied N, there was no difference in grain yield among treatments.Se propone una metodología para evaluar el nitrógeno (N) mineralizado en suelos petrocálcicos poco profundos, basada en los balances de N en parcelas no fertilizadas. Durante los años 1999, 2000 y 2001 el N mineralizado en un cultivo de maíz irrigado (6,5 meses) en la zona centro de España fue 73,3, 56,2 y 60,5 kg ha-1, respectivamente. La relación observada en este experimento, entre EUF-Norg (nitrógeno orgánico extraído por electroultrafiltración) y el N mineralizado durante los tres periodos de cultivo (valores medios), fue 1 mg EUF-Norg 100 g-1 suelo=30 kg N ha-1. Esta calibración se aplicó a los valores de EUF-Norg correspondientes a las muestras de suelo tomadas antes del cultivo. Para evaluar el efecto de las dosis de fertilizante sobre la lixiviación de nitrato y la eficiencia del uso de fertilizante nitrogenado (NFUE), se determinó el N asimilable y la dosis óptima de N, en base a esta calibración, junto con el N mineral del suelo. Los tratamientos aplicados fueron los siguientes: dosis óptima de N (NO), dosis convencional (NC) y control sin fertilizar (C). Las NO estimadas fueron 150 y 130 kg ha-1, en 2000 y 2001, respectivamente. El nitrato perdido por lixiviación fue menor en la NO que en la NC de 300 kg N ha-1. Los valores de NFUE fueron más altos para NO (78,8% y 83,5% en 2000 y 2001, respectivamente) que para NC (48,7% y 49,3% en 2000 y 2001, respectivamente). Sin embargo, a pesar de las diferencias en las dosis de N aplicadas en ambos tratamientos, no se observó ningún efecto sobre la producción de grano

Effect of Applying Soluble and Coated Phosphate Fertilizers on Phosphate Availability in Calcareous Soils and on P Absorption by a Rye-Grass Crop

6 páginas, 4 figyras y 2 tablas estadísticasThe effect of using several phosphoric fertilizers on phosphate availability in calcareous soils with a high phosphorus fixation capacity was studied. Tests were run with commercial fertilizers, differing in the ionic species provided (urea phosphate, triple superphosphate, simple superphosphate, and diammonium phosphate), and experimental controlled-release fertilizers (lignin-coated triple superphosphate and rosin-coated diammonium phosphate), each providing phosphate to the soil at a different rate. Simultaneous experiments were run (in calcareous soils) with a plant (glasshouse test) and with no plant (incubation test). Phosphate availability and, therefore, plant phosphorus absorption increased in such soils when fertilizing with urea phosphate (UP) or with lignin-coated triple superphosphate (TSPL-11). Other fertilizers such as uncoated superphosphates or diammonium phosphate (DAP) did not significantly increase P availability compared to the unfertilized soil. The electroultrafiltration (EUF) technique was also used for predicting the P absorbed by a crop in calcareous soils after applying a phosphate fertilizer.Peer reviewe