Ignacio Irigoyen

Ammonium oxidation kinetics in the presence of nitrification inhibitors DCD and DMPP at various temperatures

Use of N-based fertilisers in combination with nitrification inhibitors lengthens N presence in the ammonium form in soil (N-NH4+), with beneficial effects for agriculture and related ecosystems. The efficiency of these inhibitors depends on several factors, the most important being soil temperature. This paper studies the effects of soil temperature on the kinetics of N-NH4+ loss in the presence of the DCD and DMPP nitrification inhibitors. For a 105-day period, 3 chambers, each with 12 containers holding 500 g of dry soil, were incubated at 10, 20, and 30°C. Ammonium sulfate was applied to 4 containers in each chamber; in another 4 containers Basammon Stabil, a N fertiliser with DCD, was used; and Entec 26, a fertiliser with DMPP, was used in the remaining 4 containers. Soil ammonium content was periodically determined for each container. Both DCD and DMPP lengthened ammonium presence in soil in a similar manner. However, their effectiveness was drastically decreased at increased soil temperatures. Thus, when using these inhibitors, soil temperature should be taken into account, especially in warm climate areas.

Organic Complexed Superphosphates (CSP): Physicochemical Characterization and Agronomical Properties

A new type of superphosphate (organic complexed superphosphate (CSP)) has been developed by the introduction of organic chelating agents, preferably a humic acid (HA), into the chemical reaction of single superphosphate (SSP) production. This modification yielded a product containing monocalcium phosphate complexed by the chelating organic agent through Ca bridges. Theoretically, the presence of these monocalcium-phosphate-humic complexes (MPHC) inhibits phosphate fixation in soil, thus increasing P fertilizer efficiency. This study investigateed the structural and functional features of CSP fertilizers produced employing diverse HA with different structural features. To this end were used complementary analytical techniques: solid-phase ³¹P NMR, ¹³C NMR, laser-confocal microscopy, X-ray diffraction, and molecular modeling. Finally, the agronomical efficiency of four CSP have been compared with that of SSP as P sources for wheat plants grown in both alkaline and acidic soils in greenhouse pot trials under controlled conditions. The results obtained from the diverse analytical studies showed the formation of MPHC in CSP. Plant-soil studies showed that CSP products were more efficient than SSP in providing available phosphate for wheat plants cultivated in various soils with different physicochemical features. This fact is probably associated with the ability of CSP complexes to inhibit phosphate fixation in soil.

Short term physiological implications of NBPT application on the N metabolism of Pisum sativum and Spinacea oleracea.

The application of urease inhibitors in conjunction with urea fertilizers as a means of reducing N loss due to ammonia volatilization requires an in-depth study of the physiological effects of these inhibitors on plants. The aim of this study was to determine how the urease inhibitor N-(n-butyl) thiophosphoric triamide (NBPT) affects N metabolism in pea and spinach. Plants were cultivated in pure hydroponic culture with urea as the sole N source. After 2 weeks of growth for pea, and 3 weeks for spinach, half of the plants received NBPT in their nutrient solution. Urease activity, urea and ammonium content, free amino acid composition and soluble protein were determined in leaves and roots at days 0, 1, 2, 4, 7 and 9, and the NBPT content in these tissues was determined 48h after inhibitor application. The results suggest that the effects of NBPT on spinach and pea urease activity differ, with pea being most affected by this treatment, and that the NBPT absorbed by the plant caused a clear inhibition of the urease activity in pea leaf and roots. The high urea concentration observed in leaves was associated with the development of necrotic leaf margins, and was further evidence of NBPT inhibition in these plants. A decrease in the ammonium content in roots, where N assimilation mainly takes place, was also observed. Consequently, total amino acid contents were drastically reduced upon NBPT treatment, indicating a strong alteration of the N metabolism. Furthermore, the amino acid profile showed that amidic amino acids were major components of the reduced pool of amino acids. In contrast, NBPT was absorbed to a much lesser degree by spinach plants than pea plants (35% less) and did not produce a clear inhibition of urease activity in this species.

The influence of 3,4-dimethylpyrazole phosphate and dicyandiamide on reducing nitrate accumulation in spinach under Mediterranean conditions

The European Union has limited the maximum nitrate (NO 3 - ) content allowed for industrial processed spinach (Spinacia oleracea L.) to 2000 mg/kg fresh weight in order to avoid human pathologies associated with. uptake of high amounts of nitrate. Nitrification inhibitors (NIs) 3,4-dimethylpyrazole phosphate (DMPP) and dicyandiamide (DCD) allow changing of the molecular form (NH 4 + or NO - 3 ) in which soil mineral N is available for plants. Enhancing ammonium nutrition has successfully reduced the amount of nitrate accumulated in plants in hydroponic culture. Therefore, fertilizers containing NIs have been proposed to reduce nitrate accumulated by vegetables grown in field conditions. Basammon Stabil® (BS) and Entec 26®-(E26) are commercial fertilizers containing DCD and DMPP respectively. In the present paper, the effect of applying ammonium sulphate nitrate (ASN), BS and E26 at three rates (0, 150 and 250 kg N/ha) to spinach crops cultivated under Mediterranean growing conditions for industrial processing is analysed. During 1998 and 1999, eight field split-plot trials with four replicates were carried out in the Ebro Valley, northern Spain, during different seasons and with various soil types. The fertilizer effects were influenced by the season and the type of soil. In spring, fertilizers containing NIs increased the mineral N (Nmin) in the soil and greatly reduced nitrate accumulation in the crop. In autumn, with less solar radiation, the nitrate accumulation was more than 2000 mg/kg fresh weight on many occasions and the effect of NIs was smaller. The present paper concluded that, under Mediterranean growing conditions, DCD can reduce nitrate accumulation in spinach between 18 and 61% and DMPP between 33 and 84% without reducing yield or changing other quality characteristics. NIs are especially useful in the spring, when soil temperature is low and solar radiation interception by the crop is high.

Meat waste as feedstock for home composting: Effects on the process and quality of compost.

Home composting is a powerful tool, which is spreading in different parts of the world, to reduce the generation of municipal waste. However, there is debate concerning the appropriateness, in terms of domestic hygiene and safety, of keeping a composter bin in the household deputed to kitchen waste of animal origin, such as meat or fish scraps and pet droppings. The purpose of our work was to study how the addition of meat scraps to household waste influences the composting process and the quality of the final compost obtained. We compared four raw material mixtures, characterized by a different combination of vegetable and meat waste and different ratios of woody bulking agent. Changes in temperature, mass and volume, phenotypic microbial diversity (by Biolog™) and organic matter humification were determined during the process. At the end of the experiment, the four composts were weighed and characterized by physicochemical analysis. In addition, the presence of viable weed seeds was investigated and a germination bioassay was carried out to determine the level of phytotoxicity. Finally, the levels of pathogens (Escherichia coli and Salmonella spp.) were also determined in the final compost. Here we show that the presence of meat waste as raw feedstock for composting in bins can improve the activity of the process, the physicochemical characteristics and maturity of the compost obtained, without significantly affecting its salinity, pH and phytotoxicity. Pathogen levels were low, showing that they can be controlled by an intensive management and proper handling of the composter bins.

Effect of defoliation on garlic yield.

The results of the four trials to determine the effects of different defoliation treatments on garlic yield, carried out in the Central Ebro Valley (Spain), are presented. Four defoliation levels of 0 (control), 33, 66 and 100% were applied at seven different developmental stages. The results demonstrate a close relationship between yield reduction and the defoliation treatment inflicted. The higher the defoliation level, the higher the yield reduction. Defoliation imposed at the onset of bulb formation resulted in maximum yield reduction.

Effect of defoliation on onion crop yield

Results of five trials to determine the effects of different defoliation treatments on onion (Allium cepa L.) crop yield carried out in southern Navarre, in the Central Ebro Valley (Spain) are presented. Yield losses caused by defoliation levels of 0, 33, 66, and 100% inflicted using shears at different plant growth stages were evaluated. The results demonstrated a relationship between yield loss, the defoliation treatment applied, and plant phenological stage. Onset of bulb formation was the most critical growth stage for determining the effect of defoliation on the yield, and yield losses increased with increasing the defoliation treatment. The results were employed to calculate a set of regression equations used in turn to construct curves applicable in evaluating final crop yield losses in onions due to defoliation from such causes as hail storms, wind, insect attack, and other types of mechanical damage.

Isotopic composition of maize as related to N-fertilization and irrigation in the Mediterranean region

Nitrate leaching as a result of excessive application of N-fertilizers and water use is a major problem of vulnerable regions. The farming of maize requires high N fertilization and water inputs in Spain. Isotopic techniques may provide information on the processes involved in the N and C cycles in farmed areas. The aim of this work was studying the impact of sprinkler and furrow irrigation and N input on maize (Zea mays L.) yields, and whether isotopic composition can be used as indicator of best farming practices. Trials were set up in Tudela (Spain) with three rates of N fertilization (0, 240 and 320 kg urea-N ha-1) and two irrigation systems (furrow and sprinkler). Yield, nitrogen content, irrigation parameters, N fate and C and N isotope composition were determined. The rate of N fertilization required to obtain the same yield is considerably higher under furrow irrigation, since the crop has less N at its disposal in furrow irrigation as a result of higher loss of nitrogen by NO3--N leaching and denitrification. A lower δ13C in plants under furrow irrigation was recorded.The δ15N value of plant increased with the application rate of N under furrow irrigation.

Yield and quality of sugar snap pea in the Ebro Valley: sowing date and seed density

Sugar snap pea (Pisum sativum L. var. macrocarpon Ser.) is an edible-podded sweet pea that is being considered as a new totally mechanized crop to supply raw material to the agri-food industry of the Ebro Valley (Northern Spain). It is of great interest from an agronomic and commercial standpoint but neither its agronomic behaviour nor its adaptation to the area are known. The objective of this study was to determine the effect of sowing date and seed density on the growth and yield of the sugar snap pea at industrial scale. Six randomized blocks experiments with four replicates were conducted on irrigated land in Villafranca (Navarra, Spain) in 1998, 1999, and 2000. Three experiments for testing sowing dates (Mar., Apr., and May) and another three for seed densities (from 75 to 150 plants m-2) were performed. Phenological development, thermal integral and qualitative and quantitative yield controls were performed. Sugar snap pea required 960 oC d-1 (Tb = 3 oC) from sowing to harvest. The early sowings gave more biomass, but yield was similar. However, Harvest Index and crop morphology varied. The sowing densities had similar yields sowing that sugar snap pea has a bigger adaptation availability. Sugar snap peas can be satisfactorily cultivated at industrial scale in the zone with sowings between Mar. and May and with seeding densities between 75 and 150 plants m-2.

Integració d’un galliner i un compostador per al tractament de la fracció orgànica dels residus municipals (FORM): sis mesos d’experiència de l’Avi-Compo a Noain (Navarra)

Este trabajo ha sido subvencionado parcialmente por la Comision de Ciencia y Tecnologia del Gobierno de Espana (MCyT proyecto AGL2012-37815-C05-05).