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Analysis of physical and chemical characteristics of commercial substrates and comparison with a compost of organic waste.

Short title: Analysis of substrates and compost

1. Introduction

Substrates are natural or artificial materials where plant roots develop and fix to meet their needs for air, water and nutrients. Among the substrate properties (physical, chemical and biological) the physical properties are crucial because of the relationship between air and water in the substrate (Verdonck et al., 1983). Particle size, which determines the density and porosity of the substrate, has a fundamental influence on the volume of air and water held by the substrate (Waller and Wilson, 1984). For this reason, smaller containers require lower density substrates (Fermino, 2002) to avoid constraint on growth of plant roots (Singh and Sinju, 1998).

The fertility of a substrate also depends on the availability in essential nutrients for plants, which depends on the chemical form in which nutrients are and other chemical characteristics such as pH and cation exchange capacity (CEC) that influence the movement of nutrients between less and more available forms to plants. The pH value, for example, is crucial because it strongly affects the availability of micronutrients (Bailey et al., 2000). As for pH, plants vary in their tolerance to salinity levels, and the value of electrical conductivity (EC) is indicative of the concentration of ionized salts in the substrate (Rhoades et al., 1989).

The organic materials used in most substrates include peat, shredded bark, sawdust and coconut fiber, and materials of mineral origin such as vermiculite, perlite and pumice (Kampf 2000). The replacement of peat by bark, pumice, coconut fibre, vermiculite, perlite and rock wool by professional producers in the last decades is due to the performance of these materials for certain specific purposes and not properly for peat replacement. Other raw materials used in mixtures for substrates include: rice hulls (natural, carbonized or burned), polystyrene, sand, subproducts like wood fibre, composted household waste and remaining of pruning, humus, and mineral soil (Verdonck, 1984; Fonteno, 1996, Burger et al. 1997; Schie, 1999; Kampf, 2000).

The increasing limitations on peat exploitation, for environmental reasons, increase the demand for alternative organic materials to produce substrates. Among these, the products resulting from the composting of organic solid waste have often been tested in mixtures with peat and pine bark, in particular for the production of substrates for use in pots. Among the problems that have limited the use of high proportions of these composts, we highlight the high values of EC, pH and heavy metals, low porosity and large variations in physical and chemical properties of these materials (Raviv, 1998; Ribeiro et al. 2000; Fietje and Spiers, 2000; Vavrina, 1995). However, it has been suggested the possibility of replacing peat in the substrate of up to 30% or, in certain situations, up to 50% by volume. Under specific crop conditions it may be possible to use organic waste composts without other materials (Reis et al., 2000, Ribeiro et al., 2007).

In this study we compared the physical and chemical characteristics of 16 major commercial substrates and composts of source-separated organic fraction of municipal solid wastes (MSWC) with different maturation time periods, with the aim of analyzing the limitations of these composts as peat replacement for substrate preparation and to recommend changes for composting process of MSW in order to improve compost characteristics and their use in substrates.

2. Materials and Methods

Sixteen substrates and a compost of source separated municipal organic solid waste at three different maturation stages were analyzed (in triplicate) for a number of physical and chemical characteristics (Table 1). Substrates included two block-peat (BP) based substrates, four substrates for plug trays (PT), seven for pot plants (PP) and three for cultivation bags (CB). Composting of the organic waste took place over a period of 30 days followed by 45 days of maturation with forced ventilation, and an additional maturation period without forced ventilation ranging from 22 days for the fresher compost (C99d) and 95 days for the commercial compost (C170d) to 488 days for the most mature compost (C563d). The original materials used for composting MSW were: "organics", "green", and "rejects", in similar proportions (v/v). The "organics" included material from restaurants and large producers (cooperatives, market suppliers, horticultural plants). The "green" included shredded branches, grass clippings and other organic materials from cleaning of gardens. The "reject" material came from the screeners in the recirculation process, before and after composting, and consisted especially of large woody material.

Dry matter content (DM) was determined by drying 40-50 g of material at 105[grados]C to constant weight and the OM content was determined by calcination of the samples at 560[grados]C (Martinez, 1992) . Mineral matter (MM) was calculated by difference of organic matter (OM) for the total dry weight. Organic carbon was calculated from the concentration of OM divided by the constant 1.8 (Goncalves and Baptista, 2001). Bulk density (dry material) was estimated using an adaptation of the method of De Boodt et al. (1974). Total porosity (total pore space) was calculated based on the ratio between the bulk density and the real density according to the method of De Boodt et al. (1974). Shrinkage evaluation was based on the volume loss experienced by the substrate, after a drying process, as proposed by Martinez (1992).

For the texture analysis a series of sieves were used with the following measures of mesh (mm): 40, 25, 16, 10, 5, 2, 1, 0.5, 0.25 and 0.125. The water retention capacity was evaluated by subjecting samples to a substrate moistened suction force determined to a maximum equivalent of a water column of 100 cm ([aproximadamente igual a] 10 kPa) limit from which it is admitted that the plants growing on substrates may begin to suffer growth restriction. The levels of air and water with increasing applied suction were calculated according to the method of De Boodt et al. (1974). Air content as the difference in volume (%) between the total pore space (0 cm suction) and the moisture content at 10 cm suction, easily available water as the volume of water released from the substrate when the suction increases from 10 cm to 50 cm, and buffering capacity as the volume of water released from the substrate when the suction increases from 50 cm to 100 cm.

The pH and EC values were determined according to the method proposed by Gabriels and Verdonck (1991) in the aqueous extract 1:2 (v/v). The cation exchange capacity (CEC) was evaluated by the method reported by Harada and Inoko (1979) and the result was expressed in relation to MS and MO of the substrate. Kjeldahl N was determined by the conventional method and the digestion carried out with sulphuric acid. The nitrate nitrogen (N[O.sub.3]-N) and ammonia nitrogen (N[H.sub.4.sup.+]-N) were extracted with a solution of Ca[Cl.sub.2]/DTPA (Alt and Peters, 1993). N[H.sub.4.sup.+]-N was determined by direct distillation of the extract and [NO.sub.3.sup.-]-N by distillation after prior reduction with Devard alloy.Total N was calculated by the sum of Kjeldahl N and the N[O.sub.3.sup.-]-N whereas organic N was calculated as the difference between Kjeldahl N and N[H.sub.4.sup.+]-N.

The content of nutrients (P, K, Ca, Mg, Na, Fe, Cu, Zn, Mn) was determined using an extract with an aqueous solution of Ca[Cl.sub.2]/DTPA (Alt and Peters, 1993). To obtain the extracts, samples containing 25 g of fresh weight, taking into account the moisture content of the material were used, and 200 mL of extractant was added. The extracts were shaken for 1 hour and filtered out. The phosphorus content was analysed by colorimetry, potassium and sodium by flame photometry and the other nutrients by atomic absorption spectrophotometry. The analysis of variance (ANOVA) between treatment characteristics was performed by the general linear model procedure of SPSS 15.0 for Windows (SPSS Inc.). A probability level of p <0.05 was applied to determine statistical significance between treatment analysis. 3. Results and Discussion

Dry matter (DM) content of the commercial substrates (with the exception of BP1) ranged between 26% and 53% (Table 2). However, it was much higher in MSWC (76% to 83%), suggesting the need to raise its moisture content for use on substrate mixtures. The substrates recommended for BP and PT are peat based and for this reason they have very high values of OM, ranging from 87% to 98% (Table 2) while substrates recommended for PP (with the exception of PP2) had more than 75% of OM. The OM content of MSWC was lower (53% to 71%) and decreased with increasing time of maturation.

Most substrates showed a neutral to slightly acid reaction and very acidic for substrates PT1 and PP7. In contrast, MSWC had an alkaline reaction (Table 2). Although most crops grow best with a pH varying between 5.5 and 6.5 some crops, for example, azaleas and hydrangeas, prefer a more acid reaction (Bailey et al., 2000). Therefore, it is necessary to know the ideal pH value for each species. The MSWC, with a storage for a period exceeding one year slightly decreased pH, presumably due to nitrification and volatilization of ammonia (N[H.sub.3]). The electrical conductivity (EC) of most substrates (Table 2) was below 1 dS [m.sup.-1]. Therefore, it is likely that these substrates do not cause injury to seed germination or root growth. The cases where the EC was greater than 1 dS [m.sup.-1] were likely due to the fact of adding fertilizer to the substrates. In contrast to commercial substrates, the MSWC had a very high EC value. Therefore, materials with high salt content must be rejected in the composting process of MSW, specifically some waste from restaurants, particularly from sea food. Cation exchange capacity (CEC) increased (Table 2) for BP and PT substrates (152 [cmol.sub.+] [kg.sup.-1] DM) because of the presence of black peat, compared to substrates for PP (92 [cmol.sub.+] [kg.sup.-1] DM) or CB (85 [cmol.sub.+] [kg.sup.-1]). Although the MSWC showed a CEC similar to the CB when it was expressed as a function of OM, the same was not true when expressed in terms of MS. In this case, the MSWC had an average CEC of 53 [cmol.sub.+] [kg.sup.-1] and substrates for CB 69 [cmol.sub.+] [kg.sup.-1] DM. The lower CEC in the substrate is directly related to the need for greater control technology for fertilization.

The real density (RD) of the substrates reflects the relationship between OM and MM contents, so it is justified that only one substrate (PP2) had a RD value above those of MSWC because it had also a lower OM content. RD of MSWC increased with time (unpublished results) because of mineralization progress during compost maturation increasing thus, the ash content of composts and so the ratio between MM and OM. This increase in the RD of MSWC increases transport costs and requires greater effort for manipulation compared to commercial substrates.

Abad et al. (2001) defined the bulk density requirement of an ideal substrate as < 0.40 g [cm.sup.-3].

Bulk density (BD) was always below the limit of 0.4 (Table 3) recommended by Abad et al. (2001) for substrates, and total pore space (TPS) exceeded (except in MSWC-C563d) the value of 85% of the total volume of the substrate recommended by Verdonck and Gabriels (1992). The TPS ranged from the minimum of 84% in C563d (Table 3) to a maximum of 94% found in BP1 and PP7 characterized by their low BD, showing the fact that these two physical characteristics are inversely related. The decrease in TPS of MSWC with the duration of the maturation period (such as increased BD) is explained by compression of the compost over time and particle size reduction?.

The high shrinkage of the substrates recommended for BP and PT (39%) resulted from the high content of black peat in these substrates (Table 3). The average shrinkage of PP was 26% and of CB was 23%. Compared with these commercial substrates, the MSWC had a low shrinkage (15%). From the viewpoint of particle size of a substrate, to allow water supply and adequate ventilation, coarse texture materials, with particles between 0.25 and 2.5 mm or a size minimum between 0.5 and 1.0 mm are recommended (Reis, 2007). In substrates studied here (Figure 1), particles with size greater than 2 mm increased from 26% to 37% and 45% (w/w) respectively for BP and PT to those recommended for PP and CB. In contrast, the particles smaller than 0.5 mm decreased from 30% to 28% and 22% respectively in the same order of substrates.

Boot and Verdonck (1972) suggested that the air capacity of a substrate (AC) must exceed 20% (v/v) of the total volume of the substrate. However, this value depends on the intended purpose for the substrate. For germination and vegetative propagation the AC can vary between 10 and 15% of the volume of the substrate, or be even lower, while for plant growth in greenhouse AC should range between 15 and 25% and for perennial crops this value can be above 25%. According to Fonteno (1996) the AC should be 20% for PP with a diameter of 15 cm, 13% for PP with 10 cm in diameter and less than 8% to PT. In this study, the AC was equal or lower than 10% in three BP substrates or PT, and below 15% for the other three substrates (Table 3). In PP substrates, with the exception of PP7, the AC was always above 20% and in CB ranged between 35% and 43%. The MSWC showed an AC value (25% to 46%) similar to that of the CB, which limits their use in substrates for BP or PT.

According to Boot and Verdonck (1972) the easily available water (EAW) should represent 20-30% of the volume of the substrate and buffering capacity (BC) 4-10%. EAW values are reached or exceeded by most substrates, with the exception of PP6 and CB. MSWC (on average), with 21% and 2% respectively for EAW and BC, is within the adequate range of EAW but not that appointed for BC. The volume of less available water (LAW) is above 43% for BP but decreases for the remaining substrates to 32% for PP and 31% for CB. The MSWC values ranged from 22% to 27% of LAW (Figure 2).

The C/N ratio (Table 4), on average, increased for CB (44) compared to PP (39), BP and PT (35). The highest value was found in PP6 (76) and is explained by the presence of pine bark in this substrate. In contrast to commercial fertilizers, the C/N ratio was much lower for the MSWC (11-13). The decrease in C/N ratio between types of substrates, and between these and MSWC, relates directly to the respective levels of nitrogen (N). Organic N (Table 4), which represents nearly all of N, increased slightly for the substrates BP and PT (14 g [kg.sup.-1]), compared to PP (13 g [kg.sup.-1]) or CB (10 g [kg.sup.-1]). Compared with the substrates, the N content in organic MSWC was much higher (25 to 30 g [kg.sup.-1]). The low C/N ratio of MSWC results from the low C/N ratio of the mixture of original material used in the composting process. Food waste and plant debris, such as grass clippings and vegetable market scrap, for example, are often used materials in the production of MSWC that have a very low C/N ratio and need to be mixed with materials C-rich to ensure an efficient composting process and to minimize N loss through volatilization, resulting in agronomic and environmental damage.

The concentration of N[O.sub.3.sup.-]-N is highly variable among substrates (Table 4), because some are fertilized with varying rates of N fertilizers, while others are not supplemented with any mineral fertilizer, or only with low rates of slow-release fertilizers, as for CB, which are continuously fertilized during the growing season. MSWC, despite having an high content of organic N and N[H.sub.4.sup.+]-N, showed a relatively low N[O.sub.3.sup.-]-N content, probably because nitrification was reduced by lack of moisture in composts during the maturation period and it was not supplemented with any mineral fertilizer. The content of N[H.sub.4.sup.+]-N of the substrates was generally low whereas the N[H.sub.4.sup.+]-N content of MSWC was very high, probably due to appreciable amounts of OM easily mineralizable still present in the composts and because the mineral N resulting from the mineralization was not fully nitrified, probably, in both cases, for lack of moisture in MSWC which is necessary to microbial growth.

The phosphorus (P) and potassium (K) available in the substrates are highly variable, due to the composition of organic and inorganic materials that they incorporate and fertilizers used to supplement the substrates. However, P content (Table 4) tends to decrease in the substrates recommended for smaller containers, while the reciprocal is true for K. The P content of MSWC was slightly higher than that of the majority of the commercial substrates, while K content was ten times higher suggesting that the materials used to produce MSWC should be selected taking into account the composition of K to avoid nutrient imbalances from the MSWC.

Calcium (Ca) and magnesium (Mg) content showed small differences between most substrates (Table 5). However, when comparing the substrates for smaller containers (BP and PT) with substrates for PP and CB, there was a tendency to increase the Ca content and decrease the Mg content. Unlike P and K, the levels of these nutrients (Ca and Mg) in MSWC are below those of substrates. This was particularly true for Ca content which was about ten times lower, despite having a higher pH value. This suggests that the high pH value of MSWC is due to the presence of ammonia and not to the presence of alkaline substances rich in calcium such as calcium carbonate. The sodium (Na) was highly variable among substrates (Table 5) but was not related to container size. The content of Na in MSWC was very high and therefore a limiting factor for the use of MSWC as a substrate constituent. Among the Na-rich materials used for composting the MSW are the wastes from the restaurants, which confirms the suggestion previously indicated that the MSWC to be part of substrates should result from selected waste materials with decreased EC and increased C/N ratio.

The iron content (Fe) was rather variable among different substrates (Table 5) and did not vary with container. On average, the amount of extractable Fe in MSWC was about half that of the substrates. The same is true for copper (Cu) in MSWC which was less than one-third of that found for the average of substrates (Table 5), and there was an explicit tendency in the variation of Cu content depending on the size of container to which the substrate is recommended. The amount of zinc (Zn) was not highly variable amongst the substrates (Table 5), with the exception of CB3, which has a very high content of Zn. The Zn content of MSWC was slightly above that found for most substrates but it is not expected to be a limiting factor for its use as a substrate.

4. Conclusions

The comparative analysis between the substrates and analyzed the MSWC identified as major problems for the use of MSWC in the composition of substrates: their low C/N ratio, low moisture content, high pH and EC and very high levels of N[H.sub.4.sup.+], Na and K. These problems can be minimized by the choice of materials used in compost, which should be richer in carbon and have lower salinity, and by increasing the moisture content during the maturation process, avoiding the drying of the material, to promote the mineralization of remaining degradable OM and nitrification of N[H.sub.4.sup.+]. Due to above mentioned limitations, the incorporation of compost on substrates for block-peat based substrates and plug trays is not recommended. On the contrary, MSWC may be used as substrate component for cultivation bags and some pot plants, in different proportions, depending on the container size and on the crop characteristics, mainly if produced from organic materials with increased C/N ratios. In these circumstances, improving the quality of MSW composts together with the growing pressure to reduce the exploitation of peat, it is likely to increase their use for the production of substrates.

[FIGURE 1 OMITTED]

[FIGURE 2 OMITTED]

References

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Burger, D.W., Hartz, T.K., Forister, G.W. 1997. Composted green waste as a container medium amendment for the production of ornamental plants. HortSci. 32: 57-60

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Fonteno, W.C. 1996. Growing media: types and physical/chemical properties. Em: Red, D.W. (ed.), A Growers Guide to Water, Media, and Nutrition for Greenhouse Crops. Ball Publishers, Batavia: 93-122

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Goncalves, M.S., Baptista, M. 2001. Proposta de regulamentacao sobre qualidade do composto para utilizacao na agricultura. Laboratorio Quimico Agricola Rebelo da Silva, INIA, MADRP, Lisboa

Harada, Y., Inoko, A. 1979. The measurement of the Cation-Exchange Capacity of compost for the estimation of the Degree of Maturaty. Soil Sci and Plant Nut. 26: 127-134

Kampf, A.N. 2000. Substrato. Em: Kampf, A.N. (Coord.) Producao comercial de plantas ornamentais. Agropecuaria, Guaiba, Brasil

Martinez, F.X. 1992. Propuesta de metodologia para la determinacion de las propiedades fisicas de los substratos. Actas de las I Jornadas de Substratos de la SECH 294: 55-65

Raviv, M. 1998. Horticultural uses of composted material. Acta Hort. 469: 225-234

Reis, M., Inacio, H., Rosa, A., Caco, J., Monteito, A. 2000. Grape marc compost as an alternative growing media for greenhouse tomato. Acta Hort. 554: 75-81

Reis, M. 2007. Material vegetal e viveiros. Em: Mourao, I. (ed.), Manual de Horticultura no Modo de Producao Biologico. Escola Superior Agraria de Ponte de Lima: 19-52

Ribeiro H.M., Romero, A.M., Pereira, H., Borges, P., Cabral, F., Vasconcelos, E. 2007. Evaluation of a compost obtained from forestry wastes and solid phase of pig slurry as a substrate for seedlings production. Bioresour. Technol. 98: 3294-3297

Ribeiro, H.M., Vasconcelos E., Santos, J.Q. 2000. Fertilisation of potted geranium with a municipal solid waste compost. Bioresour. Technol. 73: 247-249

Rhoades, J.M., Mantheghi, N.A., Shouse P.J., Alves, W.J. 1989. Soil electrical conductivity and soil salinity: New formulations and calibrations. Soil Sci. Soc. Am. J. 53: 433-439

Schie, W. van. 1999. Standardization of substrates. Acta Hort. 481: 71-77

Singh, B.P., Sinju, U.M. 1998. Soil physical and morphological properties and root growth. Hort Sci. 33: 966-971

Spiers, T.M., Fietje, G. 2000. Green waste compost as a component in soilless growing media. Compost Sci. Util. 8: 19-23

Vavrina, C. 1995. Municipal solid waste materials as soilless media for tomato transplant. Proc of the Florida State Hortic. Soc. 108: 232-234

Verdonck, O.F. 1984. Reviewing and evaluation of new materials used as substrates. Acta Hort. 150: 155-160

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Brito, L.M. (1, 2), Paiva, A. (1), Reis, M. (3), Ribeiro, H.M. (4)

(1) Escola Superior Agraria, Instituto Politecnico de Viana do Castelo, Refoios, 4990-706 Ponte de Lima, Portugal. E-mail: miguelbrito@esa.ipvc.pt

(2) Mountain Research Centre (CIMO), Campus de Sta Apolonia, Apartado 1172, 5301-855 Braganca, Portugal

(3) Faculdade de Ciencias e Tecnologia de Gambelas, Universidade do Algarve, 8005-139 Faro, Portugal

(4) UIQA, Inst. Superior de Agronomia, Universidade Tecnica de Lisboa, Tapada da Ajuda, 1349-017 Lisboa, Portugal.
Table 1. Acronyms of substrates for block-peat (BP), plug trays
(PT), pot plants (PP), cultivation bags (CB) and organic municipal
waste composts (C) with different time (d) of composting and
maturation

Acronym        Substrate materials            Acronym

BP1         Block based on black peat           PP5
BP2         Block based on black peat           PP6
PT1       WP (60%) and black peat (40%)         PP7
PT2       WP (80%) and black peat (20%)         CB1
PT3       WP (50%) and black peat (50%)         CB2
PT4       WP (70%) and black peat (30%)         CB3
PP1           Black peat and perlite            C99d
PP2               Green compost                C170d
PP3       WP (70%) and black peat (30%)        C563d
PP4                                       Pine bark, peat
                                          and horse manure

Acronym               Substrate materials

BP1       WP (68%), peat mixture, coconut fibre, clay
BP2        Pine bark compost, peat, manure and clay
PT1         WP, black peat and coconut fibre (30%)
PT2               Pine bark compost and peat
PT3          Coconut fibre, pine bark and perlite
PT4         Organic waste compost and vermicompost
PP1           Organic waste compost with 99 days
PP2           Organic waste compost with 170 days
PP3           Organic waste compost with 563 days
PP4            Pine bark, peat and horse manure

WP: White peat moss.

Table 2. Dry matter content (DM), organic matter content (OM), pH,
electrical conductivity (EC) and cation exchange capacity (CEC)
based on DM and on OM weight, of substrates for block-peat (BP),
plug trays (PT), pot plants (PP), cultivation bags (CB) and organic
municipal waste composts (C) with different time (d) of composting
and maturation. Mean value [+ o -] standard variation

Substrate       DM (%)         OM (%, DM)            pH

BP1         27 [+ o -] 0.0   89 [+ o -] 0.2   6.1 [+ o -] 0.02
BP2         30 [+ o -] 0.2   89 [+ o -] 0.1   5.6 [+ o -] 0.12
PT1         68 [+ o -] 1.3   87 [+ o -] 0.1   3.8 [+ o -] 0.06
PT2         39 [+ o -] 0.1   92 [+ o -] 0.1   5.8 [+ o -] 0.09
PT3         31 [+ o -] 0.1   98 [+ o -] 0.1   6.2 [+ o -] 0.05
PT4         26 [+ o -] 0.0   94 [+ o -] 0.7   5.1 [+ o -] 0.03
PP1         32 [+ o -] 0.2   94 [+ o -] 3.8   5.7 [+ o -] 0.08
PP2         53 [+ o -] 0.7   56 [+ o -] 1.5   7.2 [+ o -] 0.11
PP3         35 [+ o -] 1.1   85 [+ o -] 0.2   5.3 [+ o -] 0.04
PP4         44 [+ o -] 1.0   88 [+ o -] 0.2   6.2 [+ o -] 0.02
PP5         33 [+ o -] 0.7   86 [+ o -] 0.6   5.9 [+ o -] 0.09
PP6         41 [+ o -] 0.5   76 [+ o -] 1.1   6.8 [+ o -] 0.00
PP7         52 [+ o -] 1.4   77 [+ o -] 0.4   4.8 [+ o -] 0.10
CB1         37 [+ o -] 0.7   72 [+ o -] 0.5   6.6 [+ o -] 0.13
CB2         35 [+ o -] 0.3   86 [+ o -] 0.5   5.6 [+ o -] 0.22
CB3         26 [+ o -] 1.0   86 [+ o -] 1.7   6.8 [+ o -] 0.02
C99d        76 [+ o -] 0.3   71 [+ o -] 1.1   8.5 [+ o -] 0.03
C170d       79 [+ o -] 0.2   62 [+ o -] 1.9   8.5 [+ o -] 0.02
C563d       83 [+ o -] 0.2   53 [+ o -] 1.3   7.9 [+ o -] 0.04

Substrate   EC(dS [m.sup.-1])           CEC ([cmol.sub.+]
                                           [kg.sup.-1])

                                     (DM)             (OM)

BP1         0.57 [+ o -] 0.03   157 [+ o -] 5    177 [+ o -] 6
BP2         0.79 [+ o -] 0.03   140 [+ o -] 11   157 [+ o -] 12
PT1         0.19 [+ o -] 0.02   146 [+ o -] 11   167 [+ o -] 12
PT2         0.46 [+ o -] 0.01    98 [+ o -] 1    106 [+ o -] 0
PT3         0.70 [+ o -] 0.24   151 [+ o -] 8    155 [+ o -] 8
PT4         0.97 [+ o -] 0.02   142 [+ o -] 3    152 [+ o -] 3
PP1         1.52 [+ o -] 0.04    79 [+ o -] 10    84 [+ o -] 12
PP2         0.27 [+ o -] 0.05    55 [+ o -] 10    99 [+ o -] 20
PP3         0.91 [+ o -] 0.02    76 [+ o -] 3     89 [+ o -] 4
PP4         1.59 [+ o -] 1.19    58 [+ o -] 6     67 [+ o -] 7
PP5         0.66 [+ o -] 0.02   112 [+ o -] 8    130 [+ o -] 10
PP6         0.15 [+ o -] 0.00    66 [+ o -] 13    88 [+ o -] 16
PP7         1.13 [+ o -] 0.09    66 [+ o -] 3     86 [+ o -] 4
CB1         0.33 [+ o -] 0.02    68 [+ o -] 5     94 [+ o -] 8
CB2         0.37 [+ o -] 0.04    58 [+ o -] 3     68 [+ o -] 3
CB3         0.18 [+ o -] 0.01    81 [+ o -] 6     93 [+ o -] 5
C99d        5.35 [+ o -] 0.43    53 [+ o -] 1     77 [+ o -] 2
C170d       5.89 [+ o -] 0.34    52 [+ o -] 3     85 [+ o -] 8
C563d       9.53 [+ o -] 0.50    54 [+ o -] 3     94 [+ o -] 16

Table 3. Bulk density (BD), total pore space (TPS), shrinkage (SHR),
air capacity (AC), easily available water (EAW) and buffering
capacity (BC) of substrates for block-peat (BP), plug trays (PT),
pot plants (PP), cultivation bags (CB) and organic municipal waste
composts (C) with different time (d) of composting and maturation.
Mean value [+ o -] standard variation

Substrate   BD (g [cm.sup.-3])    TPS (%, v/v)     SHR (%, v/v)

BP1         0.14 [+ o -] 0.001   91 [+ o -] 0.1   46 [+ o -] 6.9
BP2         0.17 [+ o -] 0.006   89 [+ o -] 0.4   48 [+ o -] 0.6
PT1         0.09 [+ o -] 0.003   94 [+ o -] 0.2   21 [+ o -] 6.8
PT2         0.13 [+ o -] 0.001   91 [+ o -] 0.1   32 [+ o -] 5.4
PT3         0.12 [+ o -] 0.004   92 [+ o -] 0.3   39 [+ o -] 2.8
PT4         0.10 [+ o -] 0.006   93 [+ o -] 0.4   50 [+ o -] 3.4
PP1         0.16 [+ o -] 0.005   89 [+ o -] 0.3   33 [+ o -] 1.7
PP2         0.25 [+ o -] 0.012   86 [+ o -] 0.7   21 [+ o -] 3.7
PP3         0.10 [+ o -] 0.004   93 [+ o -] 0.3   29 [+ o -] 1.6
PP4         0.21 [+ o -] 0.003   86 [+ o -] 0.2   15 [+ o -] 1.8
PP5         0.12 [+ o -] 0.008   92 [+ o -] 0.5   31 [+ o -] 1.6
PP6         0.21 [+ o -] 0.005   87 [+ o -] 0.3   25 [+ o -] 5.7
PP7         0.09 [+ o -] 0.008   94 [+ o -] 0.5   26 [+ o -] 2.1
CB1         0.18 [+ o -] 0.011   89 [+ o -] 0.6   20 [+ o -] 2.1
CB2         0.15 [+ o -] 0.006   91 [+ o -] 0.4   23 [+ o -] 2.6
CB3         0.14 [+ o -] 0.005   91 [+ o -] 0.3   27 [+ o -] 4.1
C99d        0.18 [+ o -] 0.003   90 [+ o -] 0.1   17 [+ o -] 1.7
C170d       0.24 [+ o -] 0.009   86 [+ o -] 0.4   15 [+ o -] 3.5
C563d       0.30 [+ o -] 0.019   84 [+ o -] 1.0   12 [+ o -] 4.5

Substrate     AC (%,v/v)       EAW (%, v/v)       BC (%,v/v)

BP1          10 [+ o -] 5    32.2 [+ o -] 4.5    5.5 [+ o -]0.6
BP2          15 [+ o -] 1    24.8 [+ o -] 1.4    4.6 [+ o -]0.4
PT1          27 [+ o -] 5    33.5 [+ o -] 5.4    3.3 [+ o -] 0.7
PT2          27 [+ o -] 2    26.8 [+ o -] 0.8    5.4 [+ o -] 1.0
PT3           9 [+ o -] 5    33.2 [+ o -] 5.4    9.5 [+ o -] 4.1
PT4           3 [+ o -] 1    43.5 [+ o -] 1.8    9.4 [+ o -] 0.3
PP1          22 [+ o -] 4    25.9 [+ o -] 4.0    4.4 [+ o -] 0.3
PP2          27 [+ o -] 5    28.5 [+ o -] 3.8    3.4 [+ o -] 1.5
PP3          39 [+ o -] 20   24.6 [+ o -] 18.4   4.0 [+ o -]0.7
PP4          22 [+ o -] 16   24.6 [+ o -] 14.5   3.3 [+ o -]1.1
PP5          29 [+ o -] 4    21.5 [+ o -] 4.7    3.9 [+ o -]1.6
PP6          42 [+ o -] 1    12.5 [+ o -] 1.4    2.8 [+ o -]0.1
PP7          12 [+ o -] 14   47.0 [+ o -] 11.9   7.8 [+ o -] 0.8
CB1          39 [+ o -] 6    18.8 [+ o -] 5.9    3.5 [+ o -]0.7
CB2          44 [+ o -] 10   14.8 [+ o -] 8.8    2.0 [+ o -] 0.2
CB3          36 [+ o -] 1    14.5 [+ o -] 0.7    4.1 [+ o -]0.1
C99d         43 [+ o -] 3    21.2 [+ o -] 1.8    1.4 [+ o -] 0.1
C170d        35 [+ o -] 5    22.4 [+ o -] 3.5    2.3 [+ o -]1.5
C563d        37 [+ o -] 2    19.2 [+ o -] 3.3    3.2 [+ o -] 0.7

Table 4. C-N ratio and contents of organic N, mineral, N, P and K
(DM basis) of substrates for block-peat (BP), plug trays (PT), pot
plants (PP), cultivation bags (CB) and organic municipal waste
composts (C) with different time (d) of composting and maturation.
Mean value [+ o -] standard variation

Substrate        C/N            organic         N[H.sub.4.sup.+]
                             (g [kg.sup.-1])   -N (mg [kg.sup.-1])

BP1         33 [+ o -] 0.5   14 [+ o -] 0.2      153 [+ o -] 9
BP2         35 [+ o -] 1.2   13 [+ o -] 0.5      447 [+ o -] 45
PT1         31 [+ o -] 0.2   15 [+ o -] 0.1      216 [+ o -] 1
PT2         39 [+ o -] 0.8   12 [+ o -] 0.3      205 [+ o -] 7
PT3         41 [+ o -] 0.7   12 [+ o -] 0.2      196 [+ o -] 8
PT4         31 [+ o -] 0.3   15 [+ o -] 0.1      190 [+ o -] 1
PP1         26 [+ o -] 0.8   19 [+ o -] 0.2       74 [+ o -] 8
PP2         51 [+ o -] 2.7    6 [+ o -] 0.2       48 [+ o -] 5
PP3         37 [+ o -] 0.6   11 [+ o -] 0.2      390 [+ o -] 19
PP4         29 [+ o -] 0.3   17 [+ o -] 0.1       98 [+ o -] 6
PP5         25 [+ o -] 0.3   18 [+ o -] 0.3      121 [+ o -] 14
PP6         76 [+ o -] 1.0    5 [+ o -] 0.1       36 [+ o -] 6
PP7         30 [+ o -] 0.4   11 [+ o -] 0.1     1462 [+ o -] 10
CB1         41 [+ o -] 1.2   10 [+ o -] 0.2      119 [+ o -] 12
CB2         42 [+ o -] 0.5   11 [+ o -] 0.1       78 [+ o -] 13
CB3         49 [+ o -] 1.3   10 [+ o -] 0.2       59 [+ o -] 10
C99d        13 [+ o -] 0.1   30 [+ o -] 0.5     1355 [+ o -] 19
C170d       12 [+ o -] 0.4   26 [+ o -] 0.2     1579 [+ o -] 11
C563d       11 [+ o -] 0.2   25 [+ o -] 0.1     1179 [+ o -] 15

Substrate   N[O.sub.3.sup.-]   P (g [kg.sup.-1])   K (g [kg.sup.-1])
               N (mg [kg.
                sup.-1])

BP1          748 [+ o -] 9      4.5 [+ o -] 0.1     22 [+ o -] 0.2
BP2          546 [+ o -] 9      4.6 [+ o -] 0.2     15 [+ o -] 0.1
PT1          183 [+ o -] 6      2.3 [+ o -] 0.1      5 [+ o -] 0.1
PT2          634 [+ o -] 7      2.4 [+ o -] 0.2     21 [+ o -] 0.1
PT3          634 [+ o -] 9      4.7 [+ o -] 0.1     22 [+ o -] 0.1
PT4         1490 [+ o -] 10     5.2 [+ o -] 0.1     27 [+ o -] 0.2
PP1          805 [+ o -] 8      7.6 [+ o -] 0.7     38 [+ o -] 0.8
PP2           51 [+ o -] 9      0.4 [+ o -] 0.1     26 [+ o -] 0.1
PP3         1468 [+ o -] 32     4.1 [+ o -] 0.1     28 [+ o -] 0.1
PP4          256 [+ o -] 15     0.4 [+ o -] 0.3     27 [+ o -] 0.2
PP5         1039 [+ o -] 14     9.7 [+ o -] 0.7     30 [+ o -] 0.4
PP6           33 [+ o -] 0      0.5 [+ o -] 0.1     22 [+ o -] 0.1
PP7         1525 [+ o -] 8      1.7 [+ o -] 0.2     22 [+ o -] 0.3
CB1           92 [+ o -] 7      0.5 [+ o -] 0.1     22 [+ o -] 0.1
CB2           61 [+ o -] 8      1.2 [+ o -] 0.1     23 [+ o -] 0.1
CB3           77 [+ o -] 10     0.4 [+ o -] 0.1     37 [+ o -] 0.2
C99d         243 [+ o -] 2      7.0 [+ o -] 0.6    237 [+ o -] 0.5
C170d        206 [+ o -] 5      4.1 [+ o -] 0.4    244 [+ o -] 1.5
C563d        298 [+ o -] 6      6.8 [+ o -] 0.2    278 [+ o -] 1.0

Table 5. Nutrient contents of substrates for block-peat (BP), plug
trays (PT), pot plants (PP), cultivation bags (CB) and organic
municipal waste composts (C) with different time (d) of composting
and maturation. Mean value [+ o -] standard variation

Substrate       Ca (g            Mg (g             Na (g
             [kg.sup.-1])     [kg.sup.-1])      [kg.sup.-1])

BP1         40 [+ o -] 0.4    9 [+ o -] 0.1     7 [+ o -] 0.1
BP2         16 [+ o -] 0.4   18 [+ o -] 0.3     8 [+ o -] 0.1
PT1         19 [+ o -] 0.3    4 [+ o -] 0.1     2 [+ o -] 0.1
PT2         52 [+ o -] 0.8   11 [+ o -] 0.2     9 [+ o -] 0.1
PT3         32 [+ o -] 1.3    9 [+ o -] 0.2     7 [+ o -] 0.0
PT4         33 [+ o -] 0.9   30 [+ o -] 0.5    12 [+ o -] 0.1
PP1         51 [+ o -] 0.7   11 [+ o -] 0.3    15 [+ o -] 0.3
PP2         30 [+ o -] 0.6    8 [+ o -] 0.1     6 [+ o -] 0.1
PP3         49 [+ o -] 0.6   12 [+ o -] 0.1     9 [+ o -] 0.1
PP4         32 [+ o -] 0.5    8 [+ o -] 1.2    10 [+ o -] 0.1
PP5         49 [+ o -] 0.4    8 [+ o -] 0.2     7 [+ o -] 0.1
PP6         34 [+ o -] 0.8   10 [+ o -] 0.4     8 [+ o -] 0.1
PP7         24 [+ o -] 0.4   13 [+ o -] 0.2     9 [+ o -] 0.1
CB1         42 [+ o -] 0.3    8 [+ o -] 0.1     5 [+ o -] 0.1
CB2         42 [+ o -] 1.1    7 [+ o -] 0.2     5 [+ o -] 0.1
CB3         67 [+ o -] 1.3    8 [+ o -] 0.1    16 [+ o -] 0.1
C99d         6 [+ o -] 0.1    6 [+ o -] 0.1   139 [+ o -] 0.1
C170d        4 [+ o -] 0.2    5 [+ o -] 0.1   131 [+ o -] 0.3
C563d        3 [+ o -] 0.1    6 [+ o -] 0.1   154 [+ o -] 0.5

Substrate       Fe (g           Cu (mg           Zn (mg
             [kg.sup.-1])     [kg.sup.-1])     [kg.sup.-1])

BP1         11 [+ o -] 0.1   487 [+ o -] 44    530 [+ o -] 17
BP2          7 [+ o -] 0.3   489 [+ o -] 69    296 [+ o -] 15
PT1          5 [+ o -] 0.1   145 [+ o -] 18    203 [+ o -] 10
PT2         12 [+ o -] 0.1   220 [+ o -] 54    243 [+ o -] 12
PT3          9 [+ o -] 0.1   404 [+ o -] 1     448 [+ o -] 15
PT4         10 [+ o -] 0.1   673 [+ o -] 46    385 [+ o -] 10
PP1          8 [+ o -] 0.2   243 [+ o -] 37    379 [+ o -] 14
PP2         13 [+ o -] 0.1   175 [+ o -] 23    544 [+ o -] 5
PP3          9 [+ o -] 0.5   281 [+ o -] 34    254 [+ o -] 13
PP4          7 [+ o -] 0.1   191 [+ o -] 1     302 [+ o -] 6
PP5          8 [+ o -] 0.2   277 [+ o -] 36    292 [+ o -] 21
PP6         15 [+ o -] 0.2   274 [+ o -] 29    469 [+ o -] 7
PP7          8 [+ o -] 0.1   559 [+ o -] 0     286 [+ o -] 9
CB1          6 [+ o -] 0.1   208 [+ o -] 32    238 [+ o -] 12
CB2          9 [+ o -] 0.1   227 [+ o -] 35    368 [+ o -] 14
CB3         13 [+ o -] 0.4   559 [+ o -] 48   1454 [+ o -] 11
C99d         5 [+ o -] 0.1   112 [+ o -] 14    675 [+ o -] 16
C170d        5 [+ o -] 0.1    94 [+ o -] 1     692 [+ o -] 13
C563d        5 [+ o -] 0.1    86 [+ o -] 7     597 [+ o -] 10
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Author:Brito, L.M.; Paiva, A.; Reis, M.; Ribeiro, H.M.
Publication:Spanish Journal of Rural Development
Date:Nov 1, 2010
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