Ernesto Vasconcelos

Fertilisation of potted geranium with a municipal solid waste compost

Abstract A greenhouse pot study was conducted to evaluate the use of a municipal solid waste compost (MSWC) as a fertilizer for potted geranium (Pelargonium x hortorum Bailey) cv. Meridonna. MSWC was mixed with a peat-based growing-media at rates of 0%, 10%, 20%, 30%, 40% and 50% by volume. Plants grew in those mixes for 90 days, with no additional fertilization. MSWC increased the electrical conductivity (saturated extract) of the growth-media linearly from 1.4 mS cm−1 at 0% to 12 mS cm−1 at 50% MSWC. 10% and 20% MSWC promoted the highest plant growth, although these plants showed low leaf concentrations of nitrogen and phosphorus. The lowest yield was obtained at 0% MSWC caused by a low level of available nutrients in the growth-media. Application rates of MSWC >20% reduced plant growth as a consequence of the high level of salts, and rates ⩾40% resulted in high levels of copper. The results of this experiment showed that potassium, magnesium, calcium and micronutrients requirements of geranium were provided with 20% MSWC, indicating that this crop could be grown in peat-based substrates with 15–20% of MSWC, as long as adequate amounts of nitrogen and phosphorus were being provided.

Use of pulp mill inorganic wastes as alternative liming materials

A laboratory aerobic incubation study was performed during 18 weeks under controlled conditions to assess the effects of applying different doses of pulp mill inorganic wastes on the physical-chemical properties of an acid Dystric Cambissol. Three different inorganic wastes were tested - wood ash, dregs and grits, and an agriculture limestone was used as reference. Results showed that increasing the dose applied of the different inorganic wastes tested always led to significant raises of soil pH at different incubation times demonstrating that its use as alternative-liming materials could be a valid and less expensive option to the use of commercial agricultural limestone. Moreover, no immediate concerns seem to be expected related to soil exchangeable sodium (Na) content, at least for the doses needed to increase soil pH until the targeted value 6.5. Particularly for wood ash a pronounced increase on soil extractable potassium and phosphorous was observed, indicating that besides the liming effect this waste can contribute to improve soil fertility by supplying significant available amounts of these nutrients. Finally, metals do not seem to be a limiting factor for the application to land of these by-products.

Treatment by acidification followed by solid-liquid separation affects slurry and slurry fractions composition and their potential of N mineralization.

The aim of the present work was to assess the effect of treatments by acidification, solid-liquid separation or acidification followed by solid-liquid separation on the physical and chemical composition of pig slurry (S) and pig slurry fractions (non acidified and acidified solid (SF and ASF) and liquid (LF and ALF) fractions), as well as on the potential of N mineralization of these pig slurry derived materials. Acidification strongly decrease the inorganic carbon content of S, SF and LF and it also affects the distribution of P, Ca and Mg between the solid and liquid fraction leading to an ALF more equilibrated than LF in terms of nutrients. Acidification increases the potential of organic N mineralization in SF and decreases the potential of N immobilization in S and LF. It can be concluded that the proposed treatment generates valuable slurry fractions with distinct characteristics and potential of N mineralization that may be incorporated to soil at different periods after sowing to comply with plant nutrient requirements.

Effect of polyacrylate polymers with different counter ions on the growth and mineral composition of perennial ryegrass

Abstract Enhanced plant growth following the application of hydrophilic polymers has been assumed to result from increased water supply. However, little attention has been paid to the contribution of counter ions to plant nutrition or to their effects on soil characteristics, such as pH, that might influence plant growth and nutrient availability. We investigated the effects of polyacrylate polymers with different counter cations, sodium (Na+) and potassium (K+) or NH4 +, on some characteristics of an acid soil, and on dry matter accumulation, water use efficiency, and the mineral composition of perennial ryegrass. Addition of polymers to the soil enhanced plant growth to a greater extent than did liming. The presence of the Na‐polymer or the Na—NH4 +‐polymer resulted in the greatest biomass accumulations by perennial ryegrass. Evapotranspiration was greatest in the soil amended with the Na‐polymer and similar in soils amended with the Na K‐polymer or the Na NH4 +‐polymer. Total plant dry matter was corre...

Effects of solid phase from pig slurry on iron, copper, zinc, and manganese content of soil and wheat plants

Abstract A two‐year lysimeter experiment was conducted using winter wheat plants on two texturally contrasting soils (soil A and soil B). The main objective of this study was to evaluate the influence of increasing doses (5, 10, 15, 20, and 251 ha‐1) of solid phase from pig slurry (SP) on soil extractable copper (Cu), zinc (Zn), iron (Fe), and manganese (Mn) and on wheat micronutrients composition and uptake. As the control, a basic dressing of NPK fertilizer was applied. Results showed that increasing additions of SP significantly enhanced extractable Cu, Zn, Fe, and Mn content on the topsoil for both soils tested. In addition, a significant increase was detected for extractable Cu, Zn, and Mn content with increasing application rates of SP for subsoil A, but no significant differences were detected for subsoil B. A significant increase in the contents of Fe, Mn, and Zn in the plants as well as total uptakes were observed from increasing doses of SP. Copper content in the plants was not significantly aff...

Effects of solid phase from pig slurry on soil chemical characteristics, nitrate leaching, composition, and yield of wheat

Abstract A two years lysimeter experiment was carried out using wheat plants (Triticum aestivum L. cv. Lotti) on two texturally contrasting soils. The main purpose of this study was to evaluate the influence of increasing applications (5,10, 15,20, and 25 t.ha‐1) of solid phase (SP) from pig slurry on soil nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), and sodium (Na) content, nitrate‐N (NO3‐N) leaching as well as on wheat composition and yield. As the control, a basic dressing of NPK fertilizer was applied. Results showed that plant growth was stimulated by increasing amounts of SP, yet the additions of 15 to 20 t SP ha‐1 led to similar effects on yield as that for the control. An accumulation of P on both soils was observed as well as a significant increase on NO3‐N leaching due to increasing rates of SP added to the soils. The N and P content in wheat plants (straw and grain) increased with increasing rates of applied SP.

Nitrogen and carbon availability of liquid and solid fractions of pig slurry obtained using different separation technologies

Solid–liquid separation is now a common slurry management on European farms and many separation techniques are now available. The choice of technique used is based mostly on financial reasons even if the dry matter separation efficiency is also considered. Nevertheless, previous studies showed that the separation technique used influenced the composition of the resulting liquid (LF) and solid (SF) fractions. Hence, our hypothesis is that separation technique influences the C and N dynamics in soils amended with the resulting SF and LF. A laboratory incubation was performed with a sandy soil to assess the influence of five different separation techniques on the N and C dynamics in soil amended with the resulting LF and SF, namely the potential of each fraction for N and organic matter supply to plant and soil systems. Our results showed that the separation technique affects significantly the soil C pools in soils amended with the resulting LF and SF. Nevertheless, the differences between SFs were very low, whereas higher C losses were observed from LFs obtained with active separation techniques such as sieving relative to passive techniques such as sediment settling. The N dynamics in soils amended with the different SF obtained were similar but the extent of NH4+ immobilization differs with the LF considered. Furthermore, higher and faster nitrification was observed with LFs obtained by sediment settling and centrifugation relative to sieving. A higher N mineralization relative to untreated slurry was observed in most fractions and the N mineralization rates were significantly influenced by the separation technique.

Evaluation of a sewage sludge based compost for the production of container tree seedlings

The effect of a sewage sludge based compost as a substrate component on the growth and nutrient status of two containerised tree seedlings (Pinus pinea L. and Pinus pinaster Ait.) was evaluated. Compost was mixed with a sphagnum peat at rates of 25, 50, 75 and 100% by volume and no additional fertilisation was applied. A control treatment consisting of 100% sphagnum peat and 3.5 g.L−1 of a controlled release fertiliser was used. Seedling and harvesting were carried out in March and October 1997, respectively. Plant growth increased with increasing doses of compost up to 50%. In fact, an increase of the total dry weight, plant height and diameter of the colar was observed. On the contrary, additions of compost greater than 75% led to a growth reduction. Despite this fact, plant growth in all compost treatments was always lower than in control treatment with fertilisation. The growth reduction that occurred in the 75% and, mainly, in the 100% compost treatments is likely a consequence of water stress since the available water (v.v−1) of these substrates (13% and 5%, respectively) was quite low. The 50% compost treatment seems to supply all P, Ca, Mg, Cu, Zn and Mn needed for satisfactory plant growth. In addition, compost shows a liming effect, that is important when the basic substrate is acid.

Lysimetric study of eucalypt residue management effects on N leaching and mineralization

The effects of woody residues from Eucalyptus globulus Labill. plantations on N losses were assessed through a lysimetric experiment. Treatments were: (NW) forest floor litter and non-woody residues (leaves, bark, twigs) incorporated into the soil; (IP) as NW plus woody residues (branches) cut in 20-cm long pieces and incorporated into the soil; (IC) as IP, but with branches chopped into chips; (SP) non-woody and woody residues (pieces) placed on the soil surface; (SC) as SP plus branches chopped into chips; and (CT) absence of organic residues. Leaching of N-NO3− and N-NH4+ was followed during a six-year period and N mineralization was evaluated at the end of the experiment. Non-woody residues enhanced N leaching as compared with the control. Conversely, woody residues decreased N losses. Although differences between treatments were not significant at the end of the experiment, incorporation and fragmentation of woody residues resulted in the more favourable management option regarding the reduction of N leaching observed at short-term. As high amounts of residues were used, the effect observed on decrease N leaching could be higher than that existing in Portuguese eucalypt plantations.RésuméLes effets des restitutions de matière ligneuse de plantations d’ Eucalyptus globulus Labill. sur la lixiviation d’azote ont été mesurés au travers d’une expérience de lysimétrie. Ont été comparés les traitements : (NW) litière au sol et restitutions non ligneuses (feuilles, rameaux, écorce) incorporés au sol; (IP) comme NW plus restitutions ligneuses (branches) coupés en morceaux de 20 cm de longueur et incorporés au sol; (IC) comme IP, mais les branches étant coupés en copeaux; (SP) restitutions non ligneuses et ligneuses placées à la surface du sol; (SC) comme SP mais branches coupées en copeaux; (CT) absence de restitutions organiques. La lixiviation de N-NO3− et N-NH4+ a été suivie pendant 6 années, et la minéralisation d’azote a été mesurée à la fin de l’expérience. L’apport de restitutions non ligneuses augmente la lixiviation par rapport au témoin (CT); inversement les restitutions ligneuses on diminué les pertes d’azote. Bien que les différences inter traitement ne soient pas significatives à la fin de l’expérience, l’incorporation et la fragmentation de résidus ligneux paraissent une option plus favorable vis à vis de la réduction de la lixiviation de nitrate. Comme nous avons pratiqué des apports très élevés vis à vis de la situation courante des forêts d’eucalyptus au Portugal, la réduction des pertes par l’incorporation de résidu ligneux a pu être artificiellement augmentée.

Nitrate accumulation, yield and leaf quality of turnip greens in response to nitrogen fertilisation

Two pot and two open-field experiments were conducted to determine the influence of N fertilisation on nitrate accumulation, yield, and leaf quality of turnip greens (“Nabiças”, Brassica rapa var. rapa). The pot experiments were conducted: (1) in a controlled environment (24 h photoperiod at 250±25 μmol s-1 m-2, and 20±1 °C ), and (2) outdoors (315 w m-2 mean solar radiation, and daily mean air temperature between 19 and 26 °C). The response of plant biomass to N from 0 to 250 g m-3 of pot-soil, in each of the two experiments, was characterised by a steep increase in weight until the level of N reached 100 g m-3, with a tendency to stabilisation thereafter. There was a clear turning point around 100 g m-3 N, beyond which plant biomass did not significantly increase in response to N application. When fertilisation with N was increased from at 100 to 250 g m-3, plant fresh weight increased by 7.4 and 8.6% and nitrate concentration by 279 and 1315%, respectively, in both growth-room and outdoors pot experiments, showing that turnip greens may easily reach conditions of luxury consumption of N. In the two open-field experiments, turnip plants were grown in a clay soil, in winter and in spring at Lisbon, Portugal. Increasing N fertilisation from 0 to 200 kg ha-1 resulted in plants with higher fresh weight both in winter and spring. Plant nitrate concentration in winter was higher than in spring at the same applied N. The increase of plant fresh weight in response to N had a clear asymptotic tendency at N exceeding 160 kg ha-1, but the increase of leaf nitrate had a linear trend showing a clear tendency for nitrate accumulation in the leaves. N induced a darker green leaf colour but had no effect on leaf taste and texture. Increasing N fertilisation up to 200 kg ha-1 seemed to be an effective means of improving yield and quality of turnip greens and of shortening the cropping cycle.