Compost | EPFL Graph Search

Compost is a mixture of ingredients used as plant fertilizer and to improve soil's physical, chemical, and biological properties. It is commonly prepared by decomposing plant and food waste, recycling organic materials, and manure. The resulting mixture is rich in plant nutrients and beneficial organisms, such as bacteria, protozoa, nematodes, and fungi. Compost improves soil fertility in gardens, landscaping, horticulture, urban agriculture, and organic farming, reducing dependency on commercial chemical fertilizers. The benefits of compost include providing nutrients to crops as fertilizer, acting as a soil conditioner, increasing the humus or humic acid contents of the soil, and introducing beneficial microbes that help to suppress pathogens in the soil and reduce soil-borne diseases. At the simplest level, composting requires gathering a mix of "greens" (green waste) and "browns" (brown waste). Greens are materials rich in nitrogen, such as leaves, grass, and fo

Improving slash-and-burn agriculture in Central Menabe, Madagascar

Justine Marie Gay des Combes

Slash-and-burn agriculture is considered as an important driver of deforestation in the tropics. In Madagascar, a biodiversity hotspot, this type of agriculture particularly threatens the tropical forest cover. On the south-western coast of the island, in Central Menabe, the dry tropical forest of Kirindy suffers from an annual deforestation of 2.6%. At such alarming rate, the forest will have entirely disappeared by 2050. The attention of past research programs and conservation actions were mainly on studying the forest or the general interactions between local populations and the forest, with little focus on the slash-and-burn agricultural system itself. Hence, understanding the cultivation practices and assessing alternatives to them is crucial to improve the current forest conservation initiatives. The present thesis answers to the need of an in-depth study of the agricultural practices in Central Menabe. The project aims to (1) analyze the practices of slash-and-burn cultivation in Kirindy forest, (2) explore alternative slash-and-burn practices which may be more sustainable for the forest, (3) determine the implementation perspectives of these alternatives. In a first stage, we have characterized soil productivity along repetitive slash-and-burn cultivation cycles and the farmerâs perception of their agricultural system. Then, we experimented a selective slash-and-burn agriculture (where trees are left intentionally within the cultivated fields), coupled with compost amendment. Finally, we have assessed the implementation potential of that technique through interviews and participating workshops with local farmers. Our findings highlighted that soil depletion due to plant uptake and erosion or leaching by heavy rains, as well as weed invasion were important problems of slash-and-burn cultivation in Central Menabe. Farmers perceive weeding as a work overload. Decrease in grain yield due to slash-and-burn agriculture reaches about 40% after three years of cultivation on the same field (from 4 to 2.5 t ha-1), and decreases up to 75% after a single cyclonic rainy season (from 4 to 1 t ha-1). Further, we demonstrated that combining compost and wood ashes (from the burnings) seems a promising solution to sustain cultivation on the fields. Compost, combined with wood ashes, multiplied corn yield by 5 compared to traditional slash-and-burn agriculture. Growth rates were accelerated and phenology stages of maize plants advanced. Furthermore, this combination also increased soil security by improving the remaining stock of nutrients after a rain simulation. On the other hand, a partial remaining tree cover (selective slash-and-burn agriculture) improved corn yields only when the soil was amended with ashes, not with compost, nor the combination of both. Implementing composting in the forest dwelling communities appears to be a challenging task. Several barriers were highlighted, among them the most important was the water constraints during a consequent period of time related to compost maintenance. Alternative slash-and-burn practices have not been much studied so far because the use of fire was always considered as destructive. Thus, our result will contribute to the development of new forest management strategies which would balance conservation of habitats and rural communities agricultural needs, while minimizing the impact on primary forest.

EPFL2017

Reclamation of low fertility soils using by-products and fast-growing trees

Marc Adami

The world population being increasing, a good energy production management is therefore necessary. Biomass production through short forest rotation by using fast-growing trees appears as a sensible way to limit fossil fuel uses. In Mediterranean regions of south-east Spain, soils present weakened ecosystem with low organic matter and nutrients content which are prone to irremediable degradation processes. The very low fertility of those soils usually makes them unfit to food production and so tree plantation with amendment addition seems to be a possible solution in order to use those soil and improve their qualities. In this study, a low fertility soil was exposed to the addition of two types of amendment (a compost of “Alperujo” and one of biosolid) and to the plantation of two different fast-growing trees (poplars and eucalyptus) during a time period of four months. The soil quality was determined by measuring different selected biochemical (β-glucosidase, phosphatase, dehydrogenase and urease activities), chemical (pH, electrical conductivity, organic matter, phosphate, potassium, water-soluble carbon, N-Kjeldahl, permanganate oxidizable carbon and metal extractible with CaCl2) and plants (nutrients, and trace elements) parameters. No significant differences between the different conditions were found. This was due to the very short time period, the too small doses of compost additions and the very high spatial variability due to the field conditions. It seems however that the composts had a positive effect on the chemical and biochemical parameters in the plots planted with poplars as the results presented systematically higher values for the amended plots than for the control plots (without amendment addition). This was attributed to the fact that all poplars were dead at the time of the study and so the soil was not confronted to any interference by the rhizosphere. Most of the parameters (chemical as well as biochemical) of the soil were improved in the eucalyptus plots compared to the poplar ones. This suggests the stimulation of the nutrient cycles by the tree roots, which improved the conditions for the microorganisms, increasing therefore their metabolic activities. The effect of composts in the eucalyptus plots were therefore clearly less obvious, probably due to the fact that the rhizosphere have had more time (tree planted in July 2011) to influence the soil properties than the compost (added in November 2011). Although both composts contained a non negligible quantity of micronutrients and trace elements, the extractible by CaCl2 0.01M quantities in soil (representing the available quantity for plants) did not present values too high to be toxic for plants and were all in normal ranges. The biomass development of the trees seems to have been improved by the compost of “Alperujo”, but presented a very high spatial variability. The compost of biosolids for its part did not show any difference as compared to the control. Next studies should reveal more significant differences between the plots, the soil having more time to react to the new conditions. It is however recommended to increase the addition doses of composts (double or more) in order to show better their effects

2012

Utilisation de composés carbonés afin de diminuer la concentration de cadmium dans des végétaux comestibles de Nouvelle-Zélande

Guilhem Chanson

Cadmium (Cd) is a non‐essential trace element which is toxic at high concentrations. Cd is added to New Zealand soils through superphosphate fertilizer. The Cd is then absorbed by vegetables and may exceed the limit of 0.1 mg/kg value, thus leading to economic and health risks. Previous studies have shown that lignite can significantly reduce the absorption of Cd by pasture, and that this effect is dependent on soil type. In addition, other studies have shown that compost can reduce the absorption of some metals. The effects of these amendments were tested on Cd uptake by vegetables, as they are more sensitive to the toxic effects of Cd than pasture grass. We studied the absorption of Cd in vegetables grown in two New Zealand soils with and without Cd spiking. We also studied the effect of an amendment with compost and two amendments with lignite. The results show that the amendment with compost reduced the absorption of Cd in all plants studied. The decrease of the absorbed concentration was up to 60% in some cases. Amendments with lignite showed significant decreases and one significant increase in the concentration of Cd in vegetables. The decreases of Cd observed in the various amendments were not typically related to the extractable Cd concentration or to the soil pH. Finally, we observed no clear pattern concerning the absorption of other elements. Because of the highly variable composition of compost, a comprehensive study with different types of compost is recommended to better understand the effects of compost on Cd uptake by vegetables. In addition, a study on the persistence of compost into the soil should also be performed.

2013