Efectos del clima y de la estrategia de fertilización en el balance de nitrógeno en un cultivo al exterior en contenedor de Viburnum tinus L.

Little information is currently available on how fertilization management affects leachate composition and the plant nitrogen (N) uptake of crops under Mediterranean climate. The objectives of this study were to determine the effect of different fertilization strategies and doses on the composition of the leachates and the use of N by plants, to establish a N balance for the different fertilization strategies and doses used and to establish a linear regression model to predict N concentration in leachates from an outdoor potted crop of Viburnum tinus L. ‘Eve Price’. Two fertilizations strategies, i.e. continuous fertigation (NS) and incorporated controlled-release fertilizer (CRF), were applied to the crop. The treatments were two NS doses (NSA: 57.4 mg NO3--NL-1 and NSB: 43.4 mg NO3--NL-1) and two CRF doses (CRFC: 5 g L-1 and CRFD: 7 g L-1).The NO3--N concentration in the leachates from the CRF treatments was high in the first weeks of growing (100-300 mg L-1). The efficiency of use of N was greater in the NSA treatment (9.2 g g-1). When CRFC was applied there was an increased loss of N by leaching (48 % of the total N). The concentration of N in the leachates for both fertilization strategies was found to be correlated with the variables substrate temperature and precipitation. Therefore, these variables must be considered when determining the dose of fertilizer to be added to a crop, especially when CRF are chosen, to avoid high losses of N by leaching.Existe poca información sobre el efecto de la estrategia de fertilización en la composición de los lixiviados y la absorción de nitrógeno (N) por un cultivo en clima mediterráneo. Los objetivos de este estudio fueron determinar el efecto de diferentes estrategias de fertilización y dosis en la composición de los lixiviados y en el uso del N por las plantas, establecer un balance de N basado en la estrategia de fertilización y dosis aplicadas y establecer un modelo lineal para predecir la concentración de N en los lixiviados de un cultivo de Viburnum tinus L. `Eve Price´. Se aplicaron al cultivo fertilizantes mediante fertirrigación continua (NS) o mediante la incorporación de fertilizantes de liberación controlada (CRF). Los tratamientos fueron dos dosis de NS (NSA: 57,4 mg NO3--N L-1 y NSB: 43,4 mg NO3--N L-1) o dos dosis de CRF (CRFC: 5 g L-1 y CRFD: 7 g L-1). La mayor concentración de NO3--N en los lixiviados se detectó al aplicar CRF (100-300 mg L-1). Las plantas del tratamiento NSA usaron el N más eficientemente (9,2 g g-1). Las pérdidas de N por lixiviación aumentaron significativamente al aplicar el tratamiento CRFC (48% del N total). La concentración de N en los lixiviados de todos los tratamientos se correlacionó con las variables temperatura del sustrato y precipitación, por lo que éstas deben ser consideradas para determinar la dosis de fertilizantes a añadir a un cultivo, especialmente cuando se usan CRF, y así evitar elevadas pérdidas de N por lixiviación

Oxyfertigation of a greenhouse tomato crop grown on rockwool slabs and irrigated with treated wastewater: Oxygen content dynamics and crop response

This work assesses the seasonal dynamics of the substrate oxygen content and the response to nutrient solution oxygen enrichment (oxyfertigation) of an autumn-spring tomato crop grown on rockwool slabs and irrigated with treated wastewater of very low dissolved oxygen (DO) content under Mediterranean greenhouse conditions. DO values in the nutrient solution were clearly higher for the oxygen-enriched (14.6mgL-1) tomato crop than for the non-enriched one (4.5mgL-1). However, DO values in the substrate solution were similar for both oxygen treatments (mean seasonal values of 5.1 and 4.8mgL-1 for the enriched and the non-enriched one, respectively), except for a short crop period at the end of the cycle when they were significantly higher for the oxygen-enriched crop. For both treatments, substrate DO values were highest for the winter period and decreased progressively during the spring period, reaching minimum values of around or below 3mgL-1 at the end of the spring. The oxygen enrichment of the nutrient solution did not affect any of the irrigation and fertigation parameters evaluated in the tomato crop: water uptake, volumetric water content of the substrate, electrical conductivity (EC) or nutrient concentration in the leached nutrient solution. Moreover, the oxygen enrichment of the nutrient solution did not affect the aboveground biomass and the biomass partitioning, the fresh weight of total and marketable tomato fruits or the tomato fruit quality parameters. Overall, it appears that oxygen deficiency conditions did not occur as the substrate DO values were higher than, or about, 3mgL-1 throughout most of the tomato crop cycle for both treatments and the rockwool slabs maintained good aeration conditions throughout the whole cycle.Solanum lycopersicum Dissolved oxygen Fruit yield Hypoxia Soilless culture Substrate

Peat Substitutes for the Production of an Ornamental Mediterranean Shrub (Nerium oleander L.)

The results of recent surveys in Catalonia have shown that most nurseries use standard substrates prepared and supplied by specialized companies. But the main component of these substrates is peat, a non-renewable resource that must be transported considerable distances to production areas such as Catalonia. Including agricultural by-products from the same region in substrates for growing potted ornamental plants could make it possible to replace some or all of the peat in the substrates used for some of the species grown, especially those whose characteristics and origin make them less demanding in terms of the results usually guaranteed by peat moss. An experiment was carried out with the aim of assessing the effects of different alternative substrates to peat moss made with raw materials available in the region where the nurseries growing woody ornamental plants are located, such as composted pine bark and composted manure from pig and cattle farms. The results of growing a high-volume Mediterranean species such as Nerium oleander L. show that it is possible to achieve agronomic results comparable to those obtained with conventional substrates by replacing peat with these composts