Henrique M. Ribeiro

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.

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.

Mineralization dynamics in soil fertilized with seaweed-fish waste compost.

BACKGROUND Seaweed and fish waste can be composted together to obtain fertilizer with high organic matter and nutrient contents. The nutrients, however, are mostly in organic form and must be mineralized to make them available to plants. The objective of this work was to establish a usage guideline for the compost by studying its mineralization dynamics. Also, the release of inorganic N and C from soil fertilized with the compost was monitored and modelled. RESULTS C and N were released throughout the assay, to an extent significantly dependent on fertilizer rate. Mineralization of both elements fitted a first-order exponential model, and each fertilizer rate required using a specific fitting model. An increased rate favoured mineralization (especially of carbon). After 90 days, 2.3% of C and 7.7% of N were mineralized (and 23.3% of total nitrogen made plant available) with the higher rate. CONCLUSION C mineralization was slow because organic matter in the compost was very stable. On the other hand, the relatively high initial content in mineral N of the compost increased gradually by the effect of mineralization. The amount of N available would suffice to meet the requirements of moderately demanding crops at the lower fertilizer rate, and even those of more demanding crops at the higher rate.

Effect of ash from sugarcane bagasse and wood co-combustion on corn growth and soil properties

In a pot experiment with corn (Zea mays L. cv. Moncada) and an incubation study, ash from co-combustion of sugarcane bagasse and eucalyptus wood was evaluated for use as a potential alternative to conventional agricultural limestone. Ash was effective as liming agent. Soil pH increased from 5.1 to 5.9 in a Haplic Arenosol and from 5.3 to 6.0 in a Haplic Cambisol. pH of the ash-amended soils were similar to those amended with calcitic and dolomitic limestone. Soil extractable P and K increased by 254% and 869% in the Haplic Cambisol and by 183% and 208% in the Haplic Arenosol. Application of ash to soil was associated with an increase in corn yield of 32% in the Haplic Cambisol and 11% in the Haplic Arenosol relative to the unamended treatments. The uptake of K by corn was greatly enhanced after ash application, increasing from 319 to 1079 mg K pot−1 in the Haplic Cambisol and from 397 to 729 mg K pot−1 in the Haplic Arenosol. Results supported the view that ash is a by-product that can become an increasingly valuable amendment as it acts both as a liming material and as a P and K fertilizer.

An evaluation of three municipal solid wastes composts

Treatment of municipal solid wastes by the composting technology is increasing in Portugal, as it seems to be a good alternative for the valorization of this wastes. In Portugal this technology started in the 1970s and at present three “industrial composting units” are implemented.