Rosa M. Belda

Composting versus vermicomposting: A comparative study of organic matter evolution through straight and combined processes

Changes in physical and chemical characteristics of an organic waste (tomato crop waste) throughout composting (COM), vermicomposting (VER) and the combination of both processes (C+V) were assessed at five selected stages. COM consisted of a combination of the static Rutgers system with forced aeration and pile turning. For VER Eisenia worms were fed with the raw material. For C+V pre-composted material was added to the worms. Particle size decreased during COM, yet it increased during VER and C+V due to the amalgamation of small particles. pH was alkaline throughout the processes. Heavy irrigation during vermicomposting resulted in greater decrease of EC and greater leaching of organic matter, total nitrogen and most macronutrients in VER and C+V than in COM. Final materials were not phytotoxic but compost could have salinity related problems. Thus, COM, VER and C+V produced treated organic material, which could be suitable for horticultural purposes.

Composted organic wastes from the pharmaceutical and agro-food industries induce soil bioactivity and nodulation in alfalfa

BACKGROUND Environmentally friendly agriculture needs to reduce the use of synthetic fertilizers and to reclaim nutrients from organic wastes. In this study the effect of five doses (0, 12, 24, 48 and 96 t ha(-1) ) of two two-phase olive mill waste (TPOMW)-based composts on the bioactivity and chemical characteristics of an agricultural soil and their potential to fertilize alfalfa (Medicago sativa) and stimulate nodulation were assessed during a two-year incubation experiment. The two composts were prepared either with the olive mill waste alone (compost A), which served as control, or mixed with a liquid fatty-proteinaceous hydrolyzate waste (FPH) from the pharmaceutical industry (compost AH). RESULTS Compost AH resulted in greater N immobilization than compost A because the former supplied the soil with easily degradable C and N, which increased microbial biomass and activity. Both compost mineralizations during the first year of incubation supplied the soil with more nutrients (mainly N), more so with A than with AH. Nevertheless, plant growth was similar in soils amended with either A or AH. Both composts induced nodulation similarly and the highest dose (96 t ha(-1) ) increased the formation of nodules by a factor of 11 compared with the four lower doses. CONCLUSION TPOMW serves as an effective ground material for co-composting with liquid wastes such as FPH. TPOMW supplies key nutrients and stimulates nodulation in alfalfa.

Assessment of biochar and hydrochar as minor to major constituents of growing media for containerized tomato production

BACKGROUND Chars are emerging materials as constituents of growth media. However, chars of different origin differ in their characteristics and more studies are needed to ratify them for such a role. The characteristics of coir mixed with 0%, 10%, 25%, 50%, 75%, and 100% (v/v) of two biochars, from forest waste (BCH-FW) and from olive mill waste (BCH-OMW), and one hydrochar, from forest waste (HYD-FW), and their effects on growth, yield and fruit quality of two tomato cultivars (Gransol RZ and Cuarenteno) were assessed. RESULTS Chars negatively affected plant growth and yield but not fruit quality. The effect was related to the char dose and was larger in HYD-FW and BCH-FW than in BCH-OMW, despite the high salinity of the latter, and more acute in Cuarenteno than in Gransol RZ. The results were discussed on the basis of the large particle size of BCH-FW, which could have caused low nutrient solution retention and, hence, reduced plant nutrient uptake, and the high water-holding capacity, poor aeration and large CO2 emission of HYD-FW, which could lead to root anoxia. CONCLUSION BCH-OMW can be used at high proportion in media for tomato cultivation. The use of BCH-FW at a high proportion might be taken into consideration after adjusting particle size, yet this needs additional assays. HYD-FW is inadequate for soilless containerized tomato cultivation.

Application of the “Delapuente” Equation in Field Trials of Wheat

Abstract The equation, y = bx α + cx 2α is used to describe the incidence of nutrients in the leaf at flowering in terms of dry matter production. The results for five fields of wheat were extremely satisfactory and gave the following results: of 15 possible combinations (five fields × three distinct leaves) the equation fitted well to 13 in the case of nitrogen, 11 for calcium and nine for iron; for phosphorus the results were good in seven cases, with six each for the nutrients potassium, magnesium and manganese. The best fits were for nitrogen, and declined in terms of goodness of fit in the order magnesium, calcium, potassium, manganese, iron, and phosphorus. Other forms of equation that are typically used in this work were less applicable and of poorer statistical significance. The action of a nutrient on the plant defines the parameters b (of positive sign, indicating stimulation) and c (usually negative implying inhibition) and the exponent α, responsible for the shape of the curve. In passing from leaf 1 to leaf 3, α generally declines, so that the first leaf (where the point of inflexion is closest to the maximum) is very close to its maximum development and at a late stage as a sink. The other leaves, particularly the third, are in a declining dry matter phase and therefore “source” organs. The different physiological state of the leaves is also reflected in the values of the parameters b and c; particularly well here in that large differences can be observed according to the different nutrients. Thus, in the case of nitrogen, both parameters increase (in absolute terms) according to leaf number thereby indicating greater effects, both stimulatory and inhibitory, on the dry matter content of the third leaf for a given nutrient concentration. The contrary is the case for calcium and magnesium. The high values of the parameters for magnesium indicate a strong influence on the plant. The three parameters, then, quantify the action of a nutrient, including all the conditions of the plant culture. However, the form of the curve will be more strictly related to the specific organ and its physiological state.