Gestão de fertilizantes de libertação gradual de nutrientes em relvados municipais

Os fertilizantes de libertação lenta podem ajudar a reduzir as perdas de azoto (N) para o meio ambiente, disponibilizando os nutrientes à medida da necessidade das plantas. Neste trabalho apresentam-se resultados da utilização de fertilizantes de libertação gradual de nutrientes em relvados da Câmara Municipal de Valpaços. Foram implementados os tratamentos: Floranid permanent 16:7:15 (adubo de libertação lenta, IBDU/Isodur); Basacote plus 9M 16:8:12 (adubo de libertação controlada, copolímero etlileno acrílico); Nitroteck 20:8:10 (fertilizante estabilizado, DCD como inibidor da nitrificação + revestimento de politerpeno); Nitrolusal (20,5% N); e uma modalidade testemunha sem N. Os fertilizantes foram aplicados à razão de 120 kg N ha-1 em 11 de Março de 2007. O nitrolusal foi fracionado em duas aplicações. Determinou-se a produção de biomassa, em cortes sequênciais de março a setembro, a dinâmica do N, recorrendo a membranas de troca aniónica enterradas no solo, e a dinâmica da vegetação através de levantamentos florísticos. Foram calculados índices de eficiência económica do uso dos fertilizantes. A produção de matéria seca foi significativamente diferente entre tratamentos. Basacote produziu mais que testemunha e menos que Floranid, Nitroteck e Nitrolusal. Basacote retardou a libertação de N relativamente aos outros fertilizantes. Os índices de eficiência económica foram favoráveis a Nitroteck e desfavoráveis a Basacote, devido à grande diferença nos preços

Nitrogen-use efficiency and economic efficiency of slow-release N fertilisers applied to irrigated turfs in a Mediterranean environment

The effect of three fertilisers that delay the bioavailability of nitrogen (N) in the soil was compared with ammonium nitrate and a zero N control in two irrigated turfs in NE Portugal. The fertilisers used were: Floranid permanent 16-7-15 (slow-release, IBDU/Isodur fertiliser); Basacote plus 9M 16-8-12 (controlled-release fertiliser, copolymer ethylene acrylic); Nitroteck 20-8-10 (stabilized fertiliser, dicyandiamide as nitrification inhibitor + coating with polyterpene) and Nitrolusal (ammonium nitrate, 20.5% N), applied all at a rate of 120 kg N ha-1. Nitrolusal was split into two fractions of 60 kg N ha-1. Phosphorus (P) and potassium (K) rates were balanced among treatments by using superphosphate (18% P2O5) and potassium chloride (60% K2O). The turf dry matter (DM) yield and N concentration in dry material were determined from several cuts of biomass throughout the growing season. Based on DM yield, N concentration in dry material and fertilisation costs, indices of N use efficiency and economic efficiency were estimated. Soil nitrate levels were monitored by using anion exchange membranes inserted directly into the soil. Basacote gave significantly lower DM yields than the other fertilised treatments. The apparent N recovery of Basacote was also the lowest. The results showed that Basacote released less N than that required for an adequate plant growth in the beginning of the growing season, hampered the flush of spring growth. Furthermore, the release period of this Basacote formulation, in the environmental conditions of these experiments, seemed to be longer than the length of the growing season. Nitroteck and Floranid yielded similar or even higher DM and apparent N recovery values than did Nitrolusal. The indices of economic efficiency ordered the fertilisers as Nitroteck > Nitrolusal > Floranid > Basacote or Nitrolusal > Nitroteck > Floranid > Basacote, if the costs of P and K fertilisers used to balance the P and K rates in the experimental design were, respectively, taken or not taken into account

Relaxation- and Decoherence-free subspaces in networks of weakly and strongly coupled resonators

We consider a network of interacting resonators and analyze the physical ingredients that enable the emergence of relaxation-free and decoherence-free subspaces. We investigate two different situations: i) when the whole network interacts with a common reservoir and ii) when each resonator, strongly coupled to each other, interacts with its own reservoir. Our main result is that both subspaces are generated when all the resonators couple with the same group of reservoir modes, thus building up a correlation (among these modes), which has the potential to shield particular network states against relaxation and/or decoherence.Comment: 5 page