The ability to produce crops, particularly those crops associated with food and fiber, is the multidisciplinary science of intensively cultivating plants to be used by humans for food, medicinal purposes, or aesthetic satisfaction.
Crop production is largely determined by a variety of environmental conditions, including soil,water, light, temperature, and atmosphere. Therefore, horticulture science is primarily concerned with the study of how to manipulate the plants or these environmental factors to achieve maximum yield.
Because there is tremendous diversity in horticultural plants, the field is subdivided into pomology, the growth and production of fruit crops; olericulture, the growth and production of vegetable crops; landscape horticulture, the growth and production of trees and shrubs; and floriculture, the growth and production of flower and foliage plants. Each of these subdivisions is based on a fundamental knowledge of plant-soil interactions, soil science, plant physiology, and plant morphology.
Horticulture science is concerned with all aspects of crop production, from the collection and germination of seed to the final marketing of the products. Plant propagation, protection, and harvesting are three areas of particular interest to horticulturists.
Generally, propagation from seed is the most common and least expensive way of propagating plants. In order to prevent cross-pollination from undesirable varieties, plants to be used for seed production are grown in genetic isolation from other, similar plants.
At maturity, the seed is collected and is usually stored at low temperatures and less than 50 to 65 percent relative humidity to maintain full viability. The seed is often tested for viability prior to planting to determine the percentage of seed that should germinate.
At the appropriate time, the seed is usually treated with a fungicide to ensure an adequate crop stand and planted under proper temperature, water, and light conditions. For most crops, the seed is germinated in small containers, and the seedlings are then transplanted to the field or greenhouse.
For some plants, almost any part of the root, stem, or leaf can be vegetatively propagated, but chemical treatment of the detached portion to ensure regeneration of the missing tissue is often required.
For other plants, a variety of specific vegetative plant tissues, including the roots, bulbs, corms, rhizomes, tubers, and runners, must be used for propagation.
Individual runners are used for propagation purposes, but a number of cuttings can be propagated from one rhizome. Tubers are propagated by slicing the organ into several pieces, each of which must contain an “eye,” or bud. Corms and bulbs are propagated by planting the entire structure.
A relatively new process of generating plants from cell cultures grown in the laboratory, called tissue culture, is a method often used to propagate pure lines of crops with a very high economic value.
Grafting, a specialized form of vegetative propagation, is particularly useful in tree farming. The shoot from one plant with a desirable fruit quality can be grafted onto the root stock of another, more vigorous plant with a less desirable fruit quality.
Weeds are defined as unwanted plants and are considered to be pests because they compete with crop plants for water, sunlight, and nutrients. If left unchecked, weeds will drastically reduce crop yields because they tend to produce a large amount of seed and grow rapidly.
Weed control is generally accomplished either by physically removing the weed or by use of a variety of herbicides that have been developed to chemically control weeds. Herbicides are selected on the basis of their ability to control weeds and, at the same time, cause little or no damage to the desired plant.
Plant protection from microbes, nematodes, and insects generally involves either preventing or restricting pest invasion of the plant, developing plant varieties that will resist or at least tolerate the invasion, or a combination of both methods.
The application of chemicals, use of biological agents, isolation of an infected crop by quarantine, and cultural practices that routinely remove infected plants or plant tissues are examples of control methods. A large number of different bactericides, fungicides, nematocides, and insecticides has been developed in recent years.
Because many of these chemicals are harmful to other animals, including humans, the use of pesticides, and insecticides in particular, requires extreme caution. There is an increasing interest in the use of biological control methods because many of the chemical pesticides pose a threat to the environment.
The development and use of pest-resistant crop varieties and the introduction of natural enemies that will not only reduce the pest population but also live harmoniously in the existing environment are two of the more promising biological measures being employed.
Hence, the harvesting process requires considerable planning to ensure that the appropriate equipment and an adequate labor supply are available when the crop is ready to be harvested. Predicting the harvest date is of paramount importance in the planning process.
The length of the harvest window, the length of the growing season that is necessary for a given plant to mature under normal environmental conditions at a given geographic location, and the influence of unexpected weather changes on the growing season all have to be considered in the planning process. Because nature is unpredictable, even the best planning schedules sometimes have to be readjusted in midseason.
Some crops are picked from the plant by hand and then mechanically conveyed from the field, while other crops are harvested entirely by hand. New mechanical harvesting equipment is continually being developed by agricultural engineers, and crops that lend themselves to mechanical harvesting are growing in importance as the manual labor force continues to shrink.
After harvest, most crops are generally stored for varying lengths of time, from a few days to several months. Because post harvest storage can affect both the quality and appearance of the product, considerable care is given as to how the crop is stored.
Sometimes storage improves the quality and appearance, while in other cases, it causes them to deteriorate. The ideal storage conditions are those that maintain the product as close to harvest condition as possible.
New technologies must be developed with the environment in mind, and much of this new technology will center on advances in genetic engineering. New crop varieties that will both provide higher yields and reduce the dependency on chemical pesticides by exhibiting greater resistance to a variety of pests will have to be developed.
The future development of higher yielding crops that can be harvested mechanically and the production of new types of equipment to facilitate the harvesting process will also be important improvements in the horticulture industry.