INTRODUCTION
Agriculture isthe science, art or practice of tilling the earth to produce and rearing of animals. Whereas according to the Concise Oxford English dictionary, it can also be defined as the science or practice of farming including the growing of crops and rearing of animals.
Multiple cropping is the practice of growing two or more crops in the same space during a single growing season. The various patterns of multiple cropping reflect essentially two underlying principles; that growing of individual crops in sequence- sequential cropping –or of growing crops simultaneously.
Crops are grown sequentially one after another so that time is used to obtain more production, or crops can be mixed and grown together simultaneously intercropped. With letter, since the participating crops have different growth requirements, mixtures of crops of similar length to maturity can have higher productivity than single crop. However, crops commonly used in mixtures usually differ in maturity, so their growth requirements are further separated in time, and competition between them is lower.
Multiple cropping is mostly practiced in developing countries and to some extent in developed countries. These countries include Uganda, Kenya Tanzanian, Sudan, USA, Libya and others.
CHARACTERISTICS OF MULTIPLE CROPPING SYSTEMS
There is plantation of two or more crops in the space during a growing season. More than one type of crop is usually incorporated in the same piece of land during the growing season.
It requires large tracts of land; this type of system requires large area of land that can be used for production of the crops.
It also requires a lot of capital to start; capital is required for the smooth running of farming activities such as purchase of seeds and employment of equipment in the farm.
It is labor intensive; it requires labor that can be used in cultivation and management practices that will be undertaken.
CRITERIA FOR THE SELECTION OF CROPS IN MULTIPLE CROPPING SYSTEMS
Multiple cropping has proved successful because of the right criteria of selection of crops. Agriculturalists and farmers select component crops for multiple based on criteria below.
Duration of crops: One crop is of long duration and the other is of short duration. When choosing the crops to be grown, the time taken by the different crops to mature should be considered as this will determine the productivity of the crops.
Growth habit: Thetwo component crops grow to different heights with different canopy. The taller crops should not a dense canopy that cuts out light from those below. The maize plant canopy does allow a reasonable of light for shorter plants like beans and plants.
Root pattern: Onecropcomponentshouldbedeeprootedwhereastheother is shallow rooted. The roots should not explore the same soil layer, that is plants with a shallow root system should be intercropped with plants with a deep root system for example bananas (shallow rooters) and avocado (deep rooter). This is aimed at avoiding competition for nutrients and moisture. At the same time, nutrients from different soil layers are exploited.
Water need: One crop component should require comparatively lesser water than the other. This is to avoid competition of the plants for water.
Nutrient demand: one crop component should require more nutrients and the other lesser nutrients.
Crops belonging to the same family: Theseshould not be planted together as they are attacked by the same pests and diseases for example tomatoes, egg plants, and ntula; and maize, sorghum and millet.
TYPES OF MULTIPLE CROPPING SYSTEMS
Inter cropping: This means the growing of more than one crop in rows where the minor are planted between the rows of the major crops. For instance, the crops like canola, mustard, garlic, tobacco, water melon, musk melon can successfully be intercropped with sugarcane crop. This can be done into several ways;
Row cropping: This is the planting of two or more different crops at the same time in alternating rows. For example, planting a row of maize, then a row of Irish potatoes, then a row of maize again, until your field is covered.
Strip cropping: This involves planting of several rows of one crop next to several rows of another. For example planting four rows of maize, then two rows of cowpeas, then four more rows of maize until your field is covered. In this method also you plant more rows of the crop you want most.
Alley cropping: Here, there is planting of agroforestry tree species, then several rows of a food crop, then another row of trees, until your field is covered. The trees will protect crops from wind, and the tree roots will bring up plant nutrients and water from deeper soil layers.
Relay cropping: This is another type of multiple cropping where by an annual crop is grown under an already established one, for example a garden of maize and beans. After about three months, the beans are harvested. In relay cropping two or more annual crops are grown together although not planted at the same time. This method reduces the need for re-ploughing the garden and ensures continuous soil cover by the crop from direct sun heat or being eroded by rain water.
Mixed cropping: This is another type of multiple cropping which comprises simultaneous growing of two or more cops on the same piece of land with the sowing, maturity, and harvesting. Mixed cropping is especially important for fodder, crops where it can provide enormous quantities of feedstuff for supporting sustainable live stock production. Mixed cropping of oats and berseems is suitable for enhancing fodder stuff to feed live stock.
Advantages of multiple cropping
Multiple cropping could also help in maintaining soil fertility provided suitable crops such as legumes are included in the cropping system. For example intercropping of a legume crop with others could increase the process of nitrogen fixation that would enhance the nutrient status of the soil.
An important aspect of multiple cropping is the utilization of nutrients more efficiently as the crops growing on the same piece of land simultaneously would have different nutritional requirements.
Diverse foods outputs are obtained through multiple cropping, thus providing a chance of choice for using food commodities. Multiple cropping is also important from marketing point of view. As we are getting more than one crop simultaneously so even if the selling price of one commodity is less in the market, the other will be there to compensate.
Multiple cropping narrows the space available for weeds to grow and hamper their growth through exudation of allelochemicals. Nevertheless, weeds are the hidden enemy of crops imparting irreversible damages to resources. Weed’s suppression through multiple cropping will thus lead to enhanced food production.
Soil erosion control in that multiple cropping systems result in efficient use of land resources. Some of these systems provide year-round coverage of crop land, thus reducing erosion and sustaining top soil.
There is also minimisation of pest damage as crops of a particular species are more prone to a particular type of pest infestation. When different types of crops are grown together, chances of pest infestation are reduced as one crop may provide cover to the other against such agents through biological control. For example, canola is intercropped with wheat to shift aphid from wheat to canola and okra intercropped with cotton diverts insect pests towards the latter.
No risk of crop failure, the risk of total crop failure due to uncertain monsoon is reduced if two crops of different nature are grown simultaneously as a mixed crop.
Increases in yield, component crops have effect on one another. For example legume crops have a beneficial effect on cereal or non legume crops as they help in fixing nitrogen in the soil. There is high yield by this method.
Multiple cropping also optimizes production from small plots thus helping farmers cope land shortages since a variety of crops are grown on the same piece of land.
The integration of many farm enterprises gives farm families several advantages. More crops can be planted in a small space. For example, intercropping and relay cropping can allow a farmer to plant two crops-like maize and beans- in his field at the same time. The production of crops is usually spread over a longer period of the year, allowing for better vegetative cover to protect the soil.
DISADVANTAGES OF MULTIPLE CROPPING
Sometimes pests and diseases may get more favorable environment to flourish thus damaging and deteriorating crop yields. The presence of crops in the field throughout the year allows crop pests to survive more easily. Some pests can shift from one crop to another. For example aphids can move to cotton plants during the dry season.
The large number of different crops in the field makes it difficult to weed and spacing to get optimum plant population is not easy.
New technologies such as modern weeding tools and improved varieties may be difficult to be introduced. Also, it is not easy to carryout operations such as spraying.
Sometimes, it wastes fertilizers that have to be given even to those crops in the mixture which are less profitable.
Multiple cropping also makes mechanization almost impossible after planting and during harvesting for example the use of tractors and combine harvesters respectively.
ROLES OF THE SYSTEMS IN THE ENVIRONMENT
Erosion control and runoff management; the growing of the different types of crops provides a canopy which reduces the impacts of rainfall on the soil and hence reduction in chances of erosion. Cover for the soil from the other agents of erosion as their leaf falls cover the soil and their roots hold the soils together.
Strengthening of nutrient cycling mechanism leading to savings in fertilizer use. The growing of different species varieties of crops help in nutrient cycling and fixation in the soil. These assist in the reduction of other costs and in maintaining the fertility of the soil naturally.
HOW MULTIPLE CROPPING AFFECTS THE ENVIRONMENT.
Due to the continuous growing of different crops in the same area, there is maximum uptake of the soil nutrients by the different crops thus reducing the fertility of the soils.
With the longer growing season required by the cultivation of more crops in the same piece of land, the effects on productivity of environmental changes from one location to another is expected to increase. This is to be expected because variation among locations in terms of water availability, a major determinant of yield is most pronounced at the early and later parts of the growing season. This will lead to more uptake of water by the crops thus depriving the soil of its water.
Annual row multiple cropping leaves the soil bare and exposed to erosion too most of the year, especially when fields are ploughed immediately after harvest thus resulting into soil degradation.
CONCLUSION:
In conclusion multiple cropping systems results in efficient use of land resources. Some of these systems provide year- round coverage of crop land, thus reducing erosion and sustaining top soil. Multiple cropping systems often allow fall seeded crops to emerge and establish good above ground growth before winter and spring weeds can get established. This increases the competitive edge of the cash crop and in some cases reduces the amount of herbicides required for weed control.
REFERENCES
Eldon. D. Enger and Bradley.F. Smith (2004). Environmental science, a study of interrelationship .Published by Mc Gram-Hill companies lnc. 9th edition New York.
NK Uberoi Foreword by Dilip Biswas (2003). Environmental management 2nd edition .Excel. Books New Delhi India.
Cunningham and Saigo (1990). Environmental science; a global concern. 3rd edition Brown Communication. Inc. USA.
http://www.answers.com/topic/multiple-cropping//ixzz1GhZN5We9
Founded in 2008, Mambis Agroforestry Nursery Project in Papua New Guinea’s Enga Province, is leading the way to a more environmentally sustainable future. Deforestation has caused many problems in the region including erosion, deadly landslides, loss of topsoil fertility, lack of fuel and timber wood, and more. The project’s Director, Peter Sambak Tanda, has already planted thousands of young trees and is not only educating his neighbors about environmental stewardship, he’s demonstrating it. For more information, visit mambisagroforestry.wordpress.com or email mambisagroforestry@gmail.com
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