Compost

1.2.1 Requirements to compost as growing media When compost is used as a growing medium in organic greenhouse production a number of requirements should be fulfilled. First, the compost structure must be suitable for plant growth. Water retention, air filled porosity and volume weights are important parameters in a growing medium (Gruda and Schnitzler, 2004) and are dependent on particle size and geometry. Hence, the particle size distribution should allow pores of different sizes to be formed...

Summary

Organic production of greenhouse crops has developed during the last decade. Greenhouse crops in general, have higher nutrient demands than field grown crops and therefore, in order to optimise production it is essential to focus on the growing media and fertilisation. The studies comprised in this dissertation describe the suitability of compost as a growing medium for organic greenhouse crops. The choice and composition of plant material as well as shredding of material and management of...

References

The physical properties of compost. Compost Science & Utilization 11, 238-264. Agosin, E., Monties, B., Odier, E., 1985. Structural changes in wheat straw components during decay by lignin-degrading white-rot fungi in relation to improvement of digestibility for ruminants. Journal of the Science of Food and Agriculture 36, 925-935. Allaire, S. E., Caron, J., Duchesne, I., Parent, L. E., Rioux, J. A., 1996. Air-filled porosity, gas relative diffusivity, and...

Measuring compost structure

Compost structural properties were quantified by measurements of particle size distribution and water retention capacity (Dresboll and Thorup-Kristensen, submitted B). As these were the initial tentative comparisons between composts based on different structural material, these parameters were expected to be sufficient. Particle size is generally determined by sieve fractionation (Agnew and Leonard, 2003), but this has been found to underestimate the fractions of small particles. Thus, in order...

Physical properties

The physical properties of compost are key factors in determining its quality as a growing medium. Physical properties are of great concern, because in contrast to the nutritional properties, they cannot easily be changed when inadequate. In horticultural greenhouse systems water is often applied in a short period of time such as in ebb-flood systems or locally as when using drip irrigation. Thus, horticultural media must be able to absorb water fast and be able to distribute the water in the...

Results

Ankom220 Fiber Analyzer

There were no significant differences in decomposition of the four different materials expressed as weight loss after one week. Initial losses were about 5 of total dry weight Fig. 1a . After three weeks the weight losses of 14 at the apical part of the wheat straw differed significantly p lt 0.05 from the basal part of the wheat straw, the hemp and Mischanthus straw, whereas no significant difference was observed between the basal part of the wheat straw and the hemp straw. At the end of the...

Results and Discussion

Hemp Greenhouse Production

The N mineralisation was similar for the wheat and Mischanthus composts Fig.la and 1b despite the difference in material. In the hemp compost more mineralised N was observed reflecting the higher initial N content and thus much lower C N ratio. No significant differences was observed between the wheat and Mischanthus compost, whereas the hemp compost had significant higher NO3- and NH4 contents all through the composting experiment except the NH4 content at initiation. The high initial NO3-...

Choice of material anatomical and economical considerations

Plant material to be used as growing medium must be chosen carefully in order to obtain sufficient physical properties in the end product. Based on results from the SEM studies as well as water retention capacities and particle size distribution, hemp was expected to be a suitable structural component in plant based compost Dresboll and Magid, submitted Dresboll and Thorup-Kristensen, submitted B . Although a large part of the hemp stem is readily degraded, the remaining parts seem to be...

Organic greenhouse production

Organic production in Denmark has evolved during the last decades. The number of organic farms has increased from 400 in 1989 to 3500 in 2003 Danish Plant Directorate, 2003 . However, the organic greenhouse production has not followed the same steep increase. The greenhouse vegetable production covers only 6.2 ha Danish Plant Directorate, 2003 corresponding to less than 5 of total greenhouse vegetable production, and production of ornamentals and herbs are almost non-existing. One of the major...

N mineralisationimmobilisationturnover

The degradability of organic material depends on the chemical composition of the material as well as the concentration of N. At the initiation of a composting process most of the N in the material is found incorporated in organic compounds Fig. 3 , principally as part of the structure of proteins and simple peptides S nchez-Monedero et al., 2001 . The total N concentration can increase during the composting process. This is referred to as a concentration effect and is the consequence of the...

Composting

Phases During Composting Carbon Dioxide

Composting is an aerobic process where microorganisms break down organic matter. During this process carbon dioxide, heat and water are produced Fig.1 . It is a dynamic process carried out by a rapid succession of mixed microbial populations. Under optimal conditions, composting proceeds through three phases 1 the mesophilic phase with moderate temperatures below 40 C lasting a few days, 2 the thermophilic phase characterised by high temperatures 40-70 C , which lasts from a few days to several...

Parameters affecting the composting process

The end product of a composting process is dependent on different parameters. In order to produce a suitable growing medium for containerised plants, it is essential to understand how the composting processes can be influenced, and how the different parameters interact. C N ratio is an important variable correlated to mass loss during composting Eiland et al., 2001a . C N ratios of approximately 25 have been suggested as optimal for composting Bernal et al., 1996 . If the C N ratio is above...

Methods

Experimental design and materials Decomposition studies were conducted on air-dried straw of Mischanthus Mischanthus oogiformis L. , hemp Cannabis sativa L. and wheat Triticum aestivum L. . After harvest the hemp straw was left in the field and an initial decomposition process occurred. During this degradation the external bast fibres are released from the stem, this process is called retting. Materials were selected in order to produce compost of easily available plant residues wheat...

Differences in degradability of plant species

Cell Wall Breakdown Rumen

Plant species differ in their anatomical arrangement. Roughly, differences in stem anatomy between monocots and dicots can be distinguished by the distribution of the vascular bundles Mauseth, 1988 . However, the distribution of the ground tissues also varies between species of both monocots and dicots and the monocots tend to have more cells with lignified cell walls outside the vascular tissue than do dicots. Besides being dependent on the chemical composition of the material which differs...

Management of the composting process

Composting Process

The initial content of mineralised N in compost used as growing media is important, as availability of nutrients is essential for seedling growth. Management of composting processes in order to control the mineralisation patterns can thus be of great importance. Control of a composting process and the properties of the end product can be achieved by at least two different strategies. One strategy is to adjust process parameters, such as moisture level, temperature or oxygen content Beck-Friis...

Introduction

Organic production of herbs, ornamentals and greenhouse vegetables has developed during the last decades. Growing media for this production are generally based on peat or mixtures of peat and composted material such as animal manure Eklind et al., 2001 . However, as there is increasing focus on exploitation of the peat bogs, and organic animal manure can be sparse a more appropriate growing medium might be produced by composting plant residues. When using compost as growing medium for...