Nitrogen fertilisation of irrigated maize under Mediterranean conditions

Nitrogen fertilisation of maize (Zea mays L.) has become an important economic and environmental issue, especially in high-yielding irrigated Mediterranean areas. Producers have traditionally applied more N fertiliser than required and, as a result, some environmental problems have appeared in recent decades. A 4-year study (2002–2005) was conducted and six N rates (0, 100, 150, 200, 250 and 300 kg N ha^?1 year^?1) were compared. Before planting 50 kg N ha^?1 were applied. The rest of the N was applied in two sidedresses, the first at V3–V4 developing stage and the second at V5–V6. Yield, biomass, grain N uptake, plant N uptake and SPAD-units were greatly influenced by both N fertilisation rate and soil NO₃^?-N content before planting and fertilising [Nini (0–90 cm)]. At the beginning of the experiment, Nini was very high (290 kg NO₃^?-N ha^?1) and there was therefore no yield response to N fertilisation in 2002. In 2003, 2004 and 2005, maximum grain yields were achieved with 96, 153 and 159 kg N ha^?1, respectively. Results showed that N fertilisation recommendations based only on plant N uptake were not correct and that Nini should always be taken into account. On the other hand, the minimum amount of N available for the crop [N applied with fertilisation plus Nini (0–90 cm)] necessary to achieve maximum grain yields was 258 kg N ha^?1. This value was similar to plant N uptake, suggesting that available N was able to predict N maize requirements and could be an interesting tool for improving maize N fertilisation.     

Stratified sampling in fruit orchards using cluster-based ancillary information maps: a comparative analysis to improve yield and quality estimates

Precision Agriculture - Estimation of yield or other fruit quality parameter is of great interest to farmers to decide on management actions just before harvesting and, in any case, to anticipate...     

Effect of Stover Management and Nitrogen Fertilization on N<Subscript>2</Subscript>O and CO<Subscript>2</Subscript> Emissions from Irrigated Maize in a High Nitrate Mediterranean Soil

A high soil nitrogen (N) content in irrigated areas quite often results in environmental problems. Improving the management practices of intensive agriculture can mitigate greenhouse gas (GHG) emissions. This study compared the effect of maize stover incorporation or removal together with different mineral N fertilizer rates (0, 200 and 300 kg N ha^?1) on the emission of nitrous oxide (N₂O) and carbon dioxide (CO₂) on a sprinkler-irrigated maize (Zea mays L.). The trail was conducted in the Ebro Valley (NE Spain) in a high nitrate-N soil (i.e. 200 g NO₃–N kg^?1). Nitrous oxide and CO₂ emissions were sampled weekly using a semi-static closed chamber and quantified using the photoacoustic technique in 2011 and 2012. Applying sidedress N fertilizer tended to increase N₂O emissions whereas stover incorporation did not have any clear effect. Nitrification was probably the main process leading to N₂O. Denitrification was limited by the low soil moisture content (WFPS <?54%), due to an adequate irrigation management. Emissions ranged from ??0.11 to 0.36% of the N applied, below the IPCC (2007) values. Nitrogen fertilization tended to reduce CO₂ emission, but only in 2011. Stover incorporation increased CO₂ emission. Nitrogen use efficiency decreased with increasing mineral fertilizer supply. The application of N in high N soils of the Ebro Valley is not necessary until the soil restores a normal mineral N content, regardless of stover management. This will combine productivity with keeping N₂O and CO₂ emissions under control provided irrigation is adequately managed. Testing soil NO₃ ^?–N contents before fertilizing would improve N fertilizer recommendations.     

Enriching Artemia nauplii with a high DHA‐containing lipid emulsion: search for an optimal protocol

This study aimed to investigate practical strategies to optimize the use of a high‐docosahexaenoic acid (DHA) lipid emulsion (M70), a product with great potential in live prey enrichments for marine larviculture. Considering its particularly high content in DHA (22:6n‐3), the adequate utilization of the emulsion for Artemia enrichments was evaluated in a series of six experiments. More specifically, the bioencapsulation efficiency of M70 into Artemia nauplii was tested under different experimental conditions of oxygen source, aeration flow, incubation temperature, concentration and dosage, as well as nauplial densities. Our results showed that an optimal utilization of M70 is achieved with incubation temperatures of 28°C, moderate aeration flows and nauplial densities of 300 ind per mL. In addition, the emulsion can be dispensed in the enrichment medium in one single dose of 0.8 g L^?1, with no apparent detrimental effects on its oxidative stability and Artemia nauplii survival during enrichment.     

Annual cool-season legumes for forage production in mild winter areas

The forage potential of several annual winter legumes – crimson clover ( Trifolium incarnatum L.), faba beans ( Vicia faba L.), forage peas ( Pisum sativum L.), serradella ( Ornithopus sativus Brot.) and vetches ( Vicia sativa L. and Vicia villosa Roth.) – was evaluated over two growing seasons in the wet and mild winter areas of Galicia (north-west Spain) with a moderately acid soil, at the two normal harvesting dates in the region, April and May.
The results indicate that, in April, serradella and crimson clover (in the warmer location), can produce dry-matter (DM) yields of 4–5 t ha⁻¹, which is similar to other winter forages in the same area, with an average growing season of 212–237 d, corresponding to about 339–420 accumulated degree–days above 10°C (GDD₁₀). In May, mainly in the warmer location, fava beans, peas and vetches yielded on average 4·7–8·5 t ha⁻¹ DM, with an average growing season of 166–206 d but with only 233–278 GDD₁₀ units. Faba bean, with an average of 8·5 t ha⁻¹ DM in the May harvest, was the highest producing forage legume. The results also suggest that some cool-season legumes could fit into double-cropping systems based on summer crops, such as maize, because of their forage yields and nutritive value. However, in order to produce consistent DM yields, the date of sowing is crucial; they must either be sown much earlier than the dates in this study or the harvests must be delayed until the end of April.     

Harvest management effects on alfalfa (Medicago sativaL.) production and quality in Mediterranean areas

The effects of plant harvest stage, autumn harvest dateand cultivars on alfalfa production and quality weredetermined in a 3-year field experiment established in1992. Harvesting stage influenced annual yield andquality. Late bud-first flower harvests increased harvestfrequency and forage quality in comparison with har-vestingat the full bloom stage while decreasing dry-matteryield by 18% (25·5 vs. 21·6 t ha 21 ). Harvestingstage significantly affected autumn forage productionand quality and yield at the first spring cut. Harvests atfull bloom allowed greater autumn and spring regrowththan cutting at the late bud stage, possibly because ofthe accumulation of higher root reserves. Autumn har-vestsand cultivar significantly influenced the yields atthe first spring cut in any growing season. Cuttingbefore the first frost in autumn reduced the vigour ofboth cultivars, and the subsequent yield at the first cutin any year, in comparison with harvests taken after ornear the first autumn frost. It is concluded that theeffects of the stage of harvesting alfalfa on dry-matterproduction and quality are important in theMediterranean environment of the Ebro Valley; theeffects of autumn management were observed mainlyon the yields of the subsequent first cut in spring but noton the total annual production.     

Antioxidant activity and phenolic composition of wild, edible, and medicinal fennel from different Mediterranean countries

Fennel (Foeniculum vulgare Mill.) is a typical aromatic plant of the Mediterranean area, long used as a medicinal and spice herb. Fennel is also well-known for its essential oil, which has been extensively studied for many years owing to its commercial importance. In this work, the antioxidant activity and the total phenolic and flavonoid contents, as well as the quantitative determination of individual flavonoids and phenolic acids of wild, edible, and medicinal fennel from different Mediterranean countries, have been determined. The antioxidant activity was measured as the free radical (DPPH), hydroxyl radical, and superoxide anion scavenging activities. Wild fennel was found to exhibit a radical scavenging activity, as well as a total phenolic and total flavonoid content, higher than those of both medicinal and edible fennels.     

Artificial radionuclides in waters of the lower section of the river Ebro (Northeast Spain)

The river Ebro, in Northeast Spain,discharges into the Mediterranean Sea after flowingthrough several large cities and agricultural, miningand industrial areas. The Ascó nuclear power plant(NPP) is located in the lower river section andcomprises two pressurised-water reactor (PWR) units,from which low-level liquid radioactive waste isreleased to river waters under authority control.During the period 1989 to 1993, we carried out 29sampling campaigns in order to determine ³H,⁹⁰Sr, ¹³⁴Cs, ¹³⁷Cs, ²³⁸Pu and^239,240Pu in Ebro river waters at differentlocations, both upstream and downstream from theAscó NPP. ³H, ¹³⁴Cs and ¹³⁷Csactivities showed large variability as they rangedfrom <1.4 to 117±3 Bq L^-1, <0.27 to22±1 mBq L^-1 and <0.36 to 35±1mBq L^-1, respectively. This behaviour, especiallyremarkable for tritium, was due to the detection oftank releases travelling downstream. Thecharacteristic NPP ¹³⁴Cs/¹³⁷Cs ratio wasfound to be 0.61±0.02 (N = 22). In the estuarinearea, ¹³⁷Cs traces from Mediterranean waters wereobserved and relatively enhanced tritium activitiesmight possibly be present due to the accumulation ofactivity in the estuary. ⁹⁰Sr and ^239,240Puactivities were homogeneous both in respect to timeand space, showing mean activities 6.9±0.2 mBq L^-1 (N = 10) and 1.36±0.10 mBq m^-3 (N = 3), respectively. These levels couldonly be attributed to nuclear weapons fallout leachedby continental waters, as the impact from the plantappears to be negligible and no other sources arepresent in the area.