The document was prepared in 1991 for the Food and Agriculture Organization of the United Nations (FAO : HTTP://www.FAO.org) under the technical supervision of W.O. BAUDOIN (wilfried.baudoin@fao.org), Agricultural Officer of the Horticultural Crops Group of the Plant Production and Protection Division.

The booklet, accompanied by numerous tables and illustrations, presents information on several mineral and organic soil mixes, on methods of their production by composting, and on the conditions of their use in horticultural crop productions.

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Introduction

Table of content of the booklet

Summary

Copyright

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INTRODUCTION

The document is not to be considered an exhaustive review, but a work manual leading to further exploration and research according to the country or the specific case studied. The existing information has thus been summarized for technical staff.

The first chapter deals with the different cultural substrata (soil mixes) that are most commonly used by horticulturists and describes the recommended methods of physical and chemical analysis.

In the second chapter the author makes an inventory, based on the bibliography, of the tropical resources in agricultural and agro-industrial residues that are of interest for the elaboration of a culture substrate. He also briefly describes different methods of transforming these products, including composting.

Quite naturally, every country should complete this information with deeper research into the organic and mineral materials that are locally available which may be interesting for use in horticulture.

The third chapter is specifically devoted to composting and to the critical stages to supervise during fabrication in order to obtain good-quality substrata.

In the forth and fifth chapters an analysis is carried out in order to determine a technically and economically efficient substrata production system. Practical advice is also provided, together with a short description of usable equipment and some examples of composting mixtures that give good results.

Finally, the last chapter consists of some examples for using specific substrata with several vegetables and ornamental crop species in soilless culture and young plant production in nurseries.

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Table of contents of the booklet

INTRODUCTION I  SUBSTRATA Kinds of substrata Substrata analysis methods Roles and qualities of the ideal substrate II  ORGANIC WASTES The problem of organic wastes List and composition Possible residue treatments III  COMPOSTING Process description Influence of the environment The different composting methods How to determine when the compost is ready

IV  SUBSTRATA PRODUCTION General production scheme Schedule of tasks Distribution and marketing Planning and estimated production costs V  PRACTICAL GUIDE Practical advice Production equipment Examples of possible mixtures VI  HORTICULTURAL CROP SPECIES Principles of soilless culture Vegetable crop species Ornamental crop species CONCLUSIONS

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Summary

Horticulture seems particularly effective in producing the financial surplus needed for development: it does not need large cultivation areas, requires important manpower, has a high productivity and above all has a high-profit production. Moreover, countries in the intertropical areas enjoy a climate that allows farmers to produce fruits, vegetables and ornamental plants the whole year round. These countries thus benefit from the remarkable opportunity for exporting high-quality products during those months when temperate countries can only produce them at high costs in greenhouses.

However, this prospect requires an improvement in cultural conditions as well as the creation or the extension of the preserving, packing and marketing sectors.

Adding value to agricultural and agro-industrial by-products also answers an ever increasing need in tropical countries with limited resources. The organic wastes produced in these countries represent an enormous potential.

Every policy for horticultural development and long-lasting increases in production should include better management of organic matter and simultaneous improvement of the plant (plant material breeding) and the soil (substrata production for nurseries and soilless culture).

In the process of intensifying market-gardening and ornamental plant productions, the quality and composition of the culture substrate (soil mix) plays an ever increasing role in obtaining high and lasting yields.

A culture substrate is a material which substitutes for the soil in playing the role of a support for the plant. The quality of a substrate is assessed mainly by looking at its physical properties, but in the case of organic materials the chemical and biochemical criteria are also important.

For propagation, too rough materials, high salinity materials and/or materials leading to a lack of nitrogen should be avoided. The substrata whose structure degrades rapidly (e.g. due to compaction or biochemical phenomena) should also be avoided. Production has to be homogeneous in terms of time, this requires low variation in the raw materials and a reliable production technique.

To help horticulturists, the main physico-chemical characteristics of some agricultural raw materials, by-products and residues have been listed in a synoptic table so as to ease consultation.

In order to improve soil quality or to produce a substrate or a compost, the horticulturist will have to choose the different materials he will use according to their availability and to economic conditions.

Most organic products can be composted but not all of them can lead to a high-quality substrate. To obtain an adequate substrate by composting, the materials should be carefully chosen :

• the materials should be available in sufficient quantities and have a homogeneous composition during the whole period of substrata processing (the whole year round if it is an industrial production) ;
• the transport of by-products should be limited as much as possible in order not to increase the production costs ;
• the mixing of 2 or 3 by-products will have to be carried out taking into account their "composting abilities" (see the definition in the booklet) in order to combine the 4 parameters : Carbon, Nitrogen, Fermentability, Porosity, in the compost.

Composting emerges thus as an appropriate technique for managing organic matter : in eliminating waste, soil mixes are produced.

From an economic point of view composting stands out because :

• capital investments can be very low ;
• running expenses (cost of production operations) are low and mainly limited to the working time and the transport of the materials ;
• it is a source of immediate profit for the horticulturist who would produce his own soil mixes.

From the human point of view, the production of substrata by means of composting during the dry season should reduce seasonal and hidden unemployment thanks to its great need and better use of manpower. Besides, the rise in revenue released by well managed horticultural production could slow down the drift from the land.

From a technological point of view, composting is a well-mastered technique and easy to popularize since it is simple, well-known and fairly safe. It is applicable to a factory as well as to a cooperative or to a horticultural concern.

One must not forget to strictly control the composting stage :

• compost aeration is undoubtedly the most important point to look after since composting is an aerobic process. The activity of the aerobic micro-organisms will be controlled by following the temperature development inside the compost heap ;
• an important rise in temperature should be maintained during a sufficiently long period of time to kill all pathogenic germs ;
• the compost humidity shall be checked: if the compost is too dry, it will not ferment properly; if it is too moist, it is liable to lead to anaerobic conditions that would prove harmful to the quality of the final product ;
• the maturation stage must not be neglected. It should be rather long (2 to 4 months) in order to avoid phytotoxicity in the substrate.

In the case of industrial substrata production, packaging, stocking, and commercialization (distribution and marketing) operations should not be forgotten.

Finally, it must be remembered that it is essential that the deliveries of substrata be homogeneous from the point of view of their physico-chemical characteristics and that these characteristics not vary from one delivery to the other.

Examples of applications are given for the use of substrata for intensive production and propagation practices such as soilless culture, the production of seedlings in the nursery as well as for the production of potted ornamentals.

This document is expected to awaked interest in using soil mixes in intensive horticultural cultivation and for recycling organic matter and agricultural by-products through composting, in order to maintain soil fertility and promote sustainable production system.

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© This booklet may not be reproduced, in whole or in part, by any method or process, without written permission from the Food and Agriculture Organization of the United Nations. (HTTP://www.FAO.org, wilfried.baudoin@fao.org)

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