Par définition, l’horticulture est la branche de l’agriculture qui s’occupe des cultures de jardin, généralement des fruits, des légumes et des plantes ornementales ; c’est à la fois une science et un art. Cet article traite de la production de légumes, l’une des plus importantes applications de l’horticulture, qui nourrit des milliards de personnes dans le monde. Nous aborderons certains des principaux éléments du cycle des cultures horticoles, de la graine au fruit, aux pépinières, ainsi que les principes clés de la nutrition des plantes et de la protection des cultures. A partir de ces éléments, nous vous présentons les principales composantes de la culture d’un produit sain et fructueux.
From this starting point, below are the key constituents of growing a healthy productive crop.
From seed to nursery
Starting our journey from the tiny but mighty seed, all crop plants have humble beginnings. Selecting the right seeds makes all the difference between the success and failure of a crop and ultimately the difference between profitability and loss. When selecting crops farmers must look out for the genetic traits of each variety: including its tolerance to climatic conditions, susceptibility to disease, and general productivity.
The use of hybrid varieties ensures the uniformity of crop health and yields. Genetic traits are refined and magnified through the careful selective breeding of powerful mother plants with superior genetic qualities; where hybrid vigor becomes the chief driving force behind these desired traits.
Before selecting the right variety farmers must have a full understanding of their land, water resource, and the climatic conditions faced at different times of the year. This plays a vital role in positioning a variety into its respective season to ensure proper growth, development and yields.
Following variety choices, nursery selection is the next essential step in this journey. As the name suggests, nurseries provide seeds with the right conditions and care for successful germination and development.
A professional nursery owner should have reliable knowledge of planting substrates, water quality and use alongside an understanding of basic seed germination requirements. In addition to the above, good hygiene practices at the nursery ensure that seedlings are healthy and uncontaminated by pests, diseases and weeds.
Another logistical aspect of nursery selection is the proximity of nurseries to farmlands; it is recommended that farmers select nurseries closer to their lands to reduce risk of stress, damage and contamination of seedlings during transport, alongside eliminating any delays in planting that might negatively impact plant development.
In recent years a lot of development has been made to the nursery business, with nursery owners adopting more advanced techniques in vegetable seedling production. For instance, germination chambers have become a necessity in every nursery to ensure the right crop specific conditions of temperature and humidity are met in order to have optimum germination percentages. Another recent development is the growing use of pesticides and fertilizers in seedling nurseries, this step guarantees the strongest healthiest seedlings that have better chances at production. Furthermore, an increasing number of nurseries have developed grafting techniques to improve crop performance and productivity.
Transplanting
Following the nursery stage, the next step of the journey from seed to fruit is the transplanting of seedlings into the ground. Soil preparation is an important prerequisite for this step. The main logic here is to ensure seedlings have the right soil conditions for growth and development. This includes having fertile soil that is free of pests and diseases. To achieve this, a list of biotic and abiotic solutions has become common practice. These include physical land management activities such as plowing and tilling, soil solarization and the application of fertilizers and pesticides of both chemical and organic origins.
Understanding the mode of action of these products and activities can help growers link specific crops with specific pests and crop stages. Ultimately allowing growers to grow healthy crops and foresee risks and prevent them from happening.
An example to that would be the application of preventive pesticides to seedlings and the land prior to transplanting. Dipping seedlings in fungicidal solutions often gives them protection from the moment they are in contact with the soil; similarly, with the control of insects and nematodes, preventive measures often give seedlings the protection they need to develop into healthy plants. Not to mention its importance in reducing seedling mortality, and eventually reducing yield and profit losses.
Irrigation
Irrigation basically encompasses the act of bringing water and nutrients to the plants when they are needed. Multiple crop-specificc irrigation systems are available in the market catering for the needs of different crops. Drippers and sprinklers are among the widest spread irrigation methods.
Depending on the crop stage and climatic conditions there isn’t really one formula for all crops. But the main logic here is to reduce the risks of water stress and ensure that plants have adequate soil moisture and nutrient content suitable for optimum plant development.
Another important aspect of irrigation is water quality. Using clean irrigation water that is free of contaminants such as harmful chemicals, sewage, plant pathogens and weed seeds plays an important role in the health of crops and the nutritional value of their fruits.
Furthermore, the use of the correct irrigation system also plays the very important role in delivering water to the plants efficiently and thus playing a significant role in reducing the consumption of water and conserving this valuable resource.
Fertilization
Having knowledge of plant nutritional requirements is key to successful vegetable production. Different crops have different requirements of macro and micro elements. The macro-elements which are generally needed in larger quantities include Nitrogen, Phosphorous, Potassium, Calcium and Sulfur. Whereas the micro-elements such as Iron, Boron, Zinc etc. are only required in minute amounts; sometimes in mere ppms. These elements are essential for plant growth and development, from the vegetative stage to flowering, fruit set and eventually fruit growth and maturation. Depending on the severity of deficiencies in these elements, their effects may range from having weak low yielding crops to complete crop failure.
Understanding crop requirements at different stages plays a vital role in formulating precise fertilization programs.
For instance, during early stages of crop development, plants require the element Phosphorous which is known to have a boosting effect on the roots and flower production. Moreover, phosphorous plays an essential role in energy production within plant cells; energy that plants require for growth and development.
During the vegetative stage, crops often consume larger amounts of Nitrogen. Often associated with leaf growth and stem elongation, nitrogen is also a key component of amino acids and proteins that play vital roles in almost every process of crop and fruit development including the nutrition we rely on for survival. Potassium on the other hand is mainly associated with fruit growth and maturity alongside drought tolerance; it also plays an essential role in the movement of nutrients, water, and carbohydrates within plant cells.
Despite the fact that micro-nutrients are only required in tiny amounts, they play key roles in vital processes within plant cells. These elements make up multiple enzymes that plants use throughout their lives, in addition to their role in photosynthesis, nitrogen fixation, and oxidation-reduction reactions.
Today a multitude of fertilizer formulations are available in the market including organic soil amendments. From granular pre-planting fertilizers to water-soluble fertilizers to foliar fertilizers specially formulated for easy absorption through the leaves.
Major pests and diseases and methods of control
As soon as seedlings are transplanted into the soil, insects are often the first to show up. Seeming to appear out of nowhere, in some cases, the speed of infestation often comes as a surprise to the unprepared growers.
In greenhouse culture, the same optimum conditions that allow plants to grow and develop rapidly also provide a fertile ground for pests and diseases. Warmer temperatures and high humidity levels within the greenhouse allow crops to grow and develop rapidly. Consequently, these same conditions give pests and diseases the right stage to spread and flourish. Insects and fungi are two of the main pests with the most significant effect on yields.
According to the FAO (Food and Agriculture Organization) crop losses related to pests and diseases may reach up to 20 to 40 %; in some cases, entire crops may be decimated due to improper pest control. As a result, spray programs need to be readily available for implementation as soon as crops are planted.
Having an understanding of pest life cycles and knowledge of pesticides and their active ingredients are important tools that aid farmers in combating pests and diseases. The timing of pesticide application makes all the difference when it comes to crop health and productivity. Knowing the effects of different pests and diseases also helps growers select and apply the right pesticides for every pest at every crop stage.
As a result, farmers will be able to cut down crop losses and unnecessary expenses; this is especially important today, following the large advancement in pesticide compounds and active ingredients.
The key crop pests witnessed in our region, span over a vast number of insect families, each with different requirements, life cycles, and damage levels. Having a basic understanding of these details would allow growers to formulate programs for pesticide applications in a timely manner for optimum results.
The major animal pests affecting vegetable crops include insects such as whiteflies, larvae, and caterpillars, and thrips, arachnids such as mites in addition to nematodes. Fungal and bacterial diseases on the other hand include damping off, wilts, blights, leaf spots, and rots.
The mentioned pests are of special concern due to their detrimental effects on plant health. Insects can directly kill seedlings by feeding on the, or affect them indirectly by transmitting bacterial and viral diseases that gradually cripple crops and affect productivity. Fungal diseases on the other hand are more often associated with elevated humidity levels making them more prominent during the rainy season. Fungal diseases are also characterized by the speed at which they spread, at times wreaking havoc in entire crops overnight when the conditions are right.
Through the planned use of preventive and curative spray programs in addition to integrated crop management practices growers can reduce and eliminate diseases, thus improving their chances in maximizing yield and profit.