Monday, July 15, 2024
General Agriculture

Cropping Systems Definition and Methods

Cropping system is not only interested in the types of crops grown, but also on how those crops are distributed on the field at any given time and how this distribution changes over time. In addition, the level of management and amount of resource inputs are integral aspects of a cropping system.

This article will explain to you the various cropping systems and the conditions that give rise to such cropping systems. The advantages and disadvantages of each cropping system are also treated.

Definition of Cropping System

The term cropping system is used to describe the pattern in which crops are grown in a given area over a period of time and includes the technical and managerial resources that are utilized.

In short, when we talk about the cropping system of a given area, we are not only interested in how those crops are distributed on the field at any given time but also how this distribution changes over time.

In addition, the level of management and amount of resource inputs are integral aspects of a cropping system.

Cropping systems are classified based on the following criteria;

The distribution of crops in time, i.e. whether shifting cultivation, continuous cropping, monoculture, or crop rotation is practiced.

The distribution of the crops in space on the field, i.e. whether intercropping or sole cropping is practiced.

The level of management and resources utilized to produce the crop, i.e. whether production is intensive or extensive.

The type of crop grown, i.e. whether orchard, arable cropping, pasturing, forestry, etc. is practiced.

1. Shifting Cultivation

In this system, the farm is not at a permanent location. Instead, a piece of land is cleared, farmed for a few years and then abandoned in preference for a new site. While the new site is being farmed, natural vegetation is allowed to grow on the old site.

Eventually, after several years of bush fallows, the farmer returns to the original location. The practice of moving the home along with the farm is discontinued and in its place the practice of making home stationary is common in tropical Africa.

Common Features of Shifting Cultivation

The farmer first selects a site which has been under bush fallow for several years.

Clears the vegetation by burning.

Crops are then grown on the field for one, two or three years, starting with crops with high nutrients requirement and ending with crops that has low nutrients requirement.

Low levels of technology, input and management.

Most of the operations are carried out using simple hand tools and the labour requirements are high while the yields are correspondingly low.

Factors Necessitating Shifting Cultivation

Declining of soil fertility and increasing population.

Unusually high incidence of diseases and pests.

Social or religious customs may dictate the abandonment of site before its fertility level has become marginal.

Disadvantages of Shifting Cultivation

It tends to discourage high level of inputs.

Because the farms stays in one location only for a short while, there is no incentive to invest in permanent structures such as store sheds, irrigation and even certain pest control soil erosion or soil conservation measure that may have a long-term benefits.

It requires a great deal of land to maintain the system.

Low efficiency in land utilization.

Low efficiency in labour utilization.

2. Continuous Cropping

In contrast to shifting cultivation, continuous cropping implies the cultivation of the same piece of land year after year. Fallowing may occur, but it never occurs more than a season or two.

The absence of a protracted fallow periods means that other soil management practices must be employed in order to maintain high soil fertility.

Agricultural Practices for Maintaining Soil Fertility under Continuous Cropping

Application of fertilizers and other soil amendments in order to boost fertility.

Judicious selection of the crops and crop combinations to be grown. Crop rotations and carefully planned intercrop combination are indispensable.

Introducing short term fallow periods in to the cropping cycle. A leguminous cover crop can be planted on the fallow land so as to aid the fixation of nitrogen by legumes during the fallow period and through increasing the soil organic matter content when the fallow crop is ploughed under

Advantages of Continuous Cropping

Land utilization under continuous cropping is extremely efficient. A very high percentage of land is under crops at any given time.

It is possible and economically feasible, to erect permanent structures on the farm site.

3. Crop Rotation

The practice of growing different kinds of crops, one at a time, in a definite sequence on the same piece of land is referred to as crop rotation. In designing a good crop rotation, the farmer must decide what crops to have in the rotation, in what sequence the crops should occur, and for how many years or season each cycle of the rotation must run.

A good rotation that provides for maintenance or improvement of soil productivity usually includes a legume crop to promote fixation of nitrogen, a grass or legume sod crop for maintenance of humus, a cultivated or inter-tilled crop for weed control and fertilizers. Perennial legumes and grasses may leave two to three tons of dry weight per acre of roots residues in the soil when plowed down.

Factors that Affect Crop Rotation

The choice of a rotation for a particular farm depends upon the following:

Adaptation of the crops to a particular soil, climate, and economic conditions.

Prevalence of weeds, plant diseases, and insect pests may also limit the kinds of crops that can be grown in a locality.

Crops may be selected for rotation so as to spread labour throughout the year.

Factors to Consider in Deciding the Sequence of Crops (Principles Of Crop Rotation)

The target crop (the main crop) should be planted immediately after the legumes or fallow period. At this time the fertility of the soil is at its peak and the optimum realizable yield of the target crop is possible.

Crops which are known to have a high demand for nutrients are also timed for the first season after the fallow.

Crops which are deep feeders should alternate with shallow feeders. In this way, nutrient removal occurs uniformly from the various soil layers rather than occurring in only one layer.

Crops that are botanically similar or are likely to be attacked by the same diseases and pests should not normally follow each other in the rotation.

Yams, for example, should not follow cowpeas in rotation if the root-knot nematode is prevalent, as the nematodes left over from the cowpea crop will severely reduce yam yields.

However, if the nematode problem does not exist in the area, yam could conveniently follow cowpeas.

The number of years for which each cycle of the rotation should run is determined by the number of crops in the rotation, the length of their growing seasons and how frequent the farmer can grow the target crop without running into problems of disease and soil fertility.

For example, the time interval between the harvesting of the target crop and its being planted again on the same piece of land should be long enough to prevent the carry- over of pathogens in crop residues from one cycle to the next.

Types of Crop Rotation

In planning crop rotation, the farmer may decide to consider his entire field as one plot. He then rotates the crops in sequence on the field.

At any given time, there is only a crop on the field, and that crop would not return again until the next cycle some years later.

This system, however, has certain disadvantages:

The growing of one crop means that the demand for labour occurs in peaks. Labour demand is more evenly spread if many crops are grown simultaneously.

The risk of crop failure is ever present, and the risk is greater where only one crop is grown.

Since each crop occurs on the farm only once every several years, specialized facilities for the target crop, can only be utilized once in several years, a situation which is definitely inefficient.

Most farmers who practice crop rotation find it more convenient to divide their field into as many plots as there are years in the rotation. The farmer then starts with a different crop on each plot and progress through the rotation.

In this scheme, all the crops are present on the farm at any given time. Example of such type of rotation is given below.

Table: Example of a 3-Year Crop Rotation Found in


Year 1Year 2Year 3
Plot ACottonGuinea cornGroundnuts
Plot BGuinea cornGroundnutsCotton
Plot CGroundnutsCottonGuinea corn

Advantages of Crop Rotation

It is an effective means of controlling diseases and pests. The pathogens and pests of a particular crop are more likely to die off when their host crop is followed by a completely different non-host crop.

Cropping Systems

Many insects are destructive to only one kind of crop. The life cycle is broken when crops grown are unfavourable to the development of the insect pest. Cotton root-knot can be reduced by the growth of immune crops in the rotation.

Crop rotation is the most effective practical method for controlling many farm weeds. Some weeds are particularly adapted to cultivated crops, the absence of such host crop in the field for many years due to rotation, effectively control the weeds. Rotation may include smother crop as a means of controlling certain weeds.

The type of crop rotation where the field is divided into several plots, offers the farmer some insurance against crop failure, and enables him to spread out his labour needs.

Read Also : Measures of Improving Field Crop Production

Crop rotation is an effective means of reducing erosion in comparison with continuous cropping. Grass legumes mixtures in a rotation have been very effective in the reduction of erosion.

4. Monoculture

This is the practice of incessantly cultivating the same type of crop on the same piece of land year after year. For example, sugar cane farming.

Disadvantages of Monoculture

In monoculture diseases and pests of the particular crop always have their host present, and therefore have the opportunity to build up over the years.

Monoculture encourages rapid depletion of soil nutrients and destruction of the soil structures.

The risk of crop failure is great and ever present.

Advantages of Monoculture

The main advantage of monoculture is that it permits maximum concentration of production effort on a single target crop.

5. Intercropping

The practice of growing one crop variety in pure stands on a field is referred to as sole cropping.

In this practice, only one crop variety occupies the land at any one time. The alternative practice of growing two or more crops simultaneously on the same field is called intercropping.

The various crops in the intercrop do not necessarily have to be sown or harvested at the same time; the main requirement is that they are on the field at the same time for a significant part of their growing periods.

Types of Intercropping

Row inter cropping: This is when the various crops are grown in separate rows.

Mixed cropping: This is when the various crops are grown intermingled more or less at random with each other.

Relay inter-cropping: This is when a second crop variety is sown between the stands of an existing sole crop just before the first crop is harvested. As such, both the first and second crops spend most of their field lives as sole crop, and grow together on the field for only a brief period.

Factors that Determine the Crops Combination and Spatial Arrangement

Tillage practices: When ridges have been made, the spatial arrangement of the various crops may be determined by particular needs of each crop.

For example, yam which requires a deep layer of tilled soil, is planted at the top of the mounds, while rice because of its high moisture requirement, is planted in the lower ground between the mounds.

Other crops such as maize, pumpkins and melons are planted at intermediate positions between the rice and the yams.

The crop the farmer considers as target crop and which one is considered a subsidiary influence the proportion of the crops.

Nature of the crops themselves: A few strands of pumpkin or melon occupy a lot of land and have high economic yield, whereas rice strands, for example, would have to be much more numerous to be meaningful.

Evaluating Yield from Intercropping

The relative yield of each component crop in an intercropping situation is the yield of that component in the intercropping situation divided by what that crop would have yielded as a sole crop, covering the same area as the intercrop and managed at the same level.

Suppose, for example, that a field with a crop combination of maize and cowpeas yields 1.5 tonnes/hectare of maize and 0.25 tons/ha. of cowpeas. If the expected sole crop yield of maize is 2.0 t/ha and that of cowpeas is 0.5 t/ha.

Then the relative yield of maize is 1.5/2.0 = 0.75 and the relative yield of cowpeas is 0.25/0.50 = 0.50.

The sum of the relative yields of the various component crops in the intercrop is sometimes called the relative yield total.

A little reflection of how many times the land area used for intercrop would be required to produce the same yields of the component crops when they are grown as sole crops. The relative yield total is therefore more conventionally referred to as land equivalent ratio (LER).

Mathematically:

LER = relative yield of crop A and relative yield of crop B + relative yield of crop n

In the maize/cowpeas combination considered above the LER = 0.75 + 0.25 = 1.25. An LER greater than 1.0 implies that for that particular crop combination, intercropping yielded more than growing the same number of stands of each crop as sole crops.

An LER of less than 1.0 implies that the intercropping was less beneficial than sole cropping.

LER can also be calculated based on the monetary value of the yield obtained from the various intercrop and sole crop situation and make comparisons on this basis.

Calculating LER by comparing the total energy value of the yield in kilo calories in various situations and compared the values to determine which arrangement was most beneficial.

Advantages of Inter cropping

In a carefully planned intercropping the LER is usually greater than one. This means that there is yield advantage in growing crops together than growing each one separately. This advantage may rise from several sources.

The crops may complement one another in their use of field time. The periods of their peak demands for light, water, nutrients and other resources may differ, so that in general there is a more efficient utilization of the resources available.

For example, during the two or three month that yam takes to sprout and establish adequately on the field, a quick intercrop of maize or melon would beneficially utilize the field resources during this period.

The component crop may complement each other in their use of space. For example, an intercrop of a deep rooted crop can exploit various horizons of the soil.

An intercrop may be able to utilize resources which the main crop may not be able to utilize or which may even be disadvantageous to it.

Certain crops may exert specific beneficial effect on others. For example, plantains intercropped with young cocoa seedlings provide shade for the seedlings. Similarly, in an intercrop of a legume with a cereal crop, the cereal would benefit from the nitrogen fixed by the legumes.

By having many crops growing simultaneously on the field the farmer is more or less buffered against failure of one of the crop.

Intercropping allows for a more uniform distribution of labour throughout the year.

When one component of an intercrop combination fails, the other combinations are able to utilize the resources that would have been available to the failed crop and so yield better than they would have done otherwise. In other words there is yield stability.

The spread of diseases and pests is less rapid than in sole cropping. This is probably because the mean distances between the plants of the same component crops are greater.

In many instances, the other component crops are not susceptible to the particular disease or pest afflicting one component and may act as physical barriers to the spread of diseases and pest.

Disadvantages of Inter cropping

Since many crops exist together on the field, it is not possible to tailor production practices to the needs of any particular crop.

Control of pests and diseases is particularly difficult because pesticides which have been developed to control a disease on one particular component crop may have deleterious effect on other crops in the combination.

It is difficult to mechanize operations such as planting, weeding and harvesting.

Cropping Systems in Africa

Shifting cultivation and intercropping are the predominant practice among the peasant farmers of Tropical Africa while the large scale farmers of East and Southern Africa as well as irrigated agriculture of the Nile valley in Egypt practice sole cropping with crop rotation. In each of these cases continuous cropping is the rule rather than shifting cultivation.

Plantation agriculture mainly practices sole cropping such as oil palm, cocoa, rubber, coffee and tea. In some instance, they may be intercropped with food crops when the plantation is still young.

For arable cash crop such as tobacco and groundnuts, sole cropping is the rule but the sole crop may be subjected to shifting cultivation, or to continuous cropping with rotation.

In conclusion, cropping systems is basically concerned with the distribution of crops in time and space as well the resources expended in the production of crop and the types of crops that are grown.

Cropping system of a given area is influenced by climatic conditions, resources available and level of management skills of the farmer. The principles of crop rotation, advantages and disadvantages of various cropping systems were highlighted in this unit.

Read Also : Ways To Generate Money From Bulky Wastes

Agric4Profits

Benadine Nonye is an agricultural consultant and a writer with several years of professional experience in the agriculture industry. - National Diploma in Agricultural Technology - Bachelor's Degree in Agricultural Science - Master's Degree in Science Education - PhD Student in Agricultural Economics and Environmental Policy... Visit My Websites On: 1. Agric4Profits.com - Your Comprehensive Practical Agricultural Knowledge and Farmer’s Guide Website! 2. WealthinWastes.com - For Effective Environmental Management through Proper Waste Management and Recycling Practices! Join Me On: Twitter: @benadinenonye - Instagram: benadinenonye - LinkedIn: benadinenonye - YouTube: Agric4Profits TV and WealthInWastes TV - Pinterest: BenadineNonye4u - Facebook: BenadineNonye

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