Alley Cropping System – Functions, Objectives, Benefits

Introduction on Alley Cropping System in India

Alley cropping system is planting rows of trees at wide spacing with a companion crop grown in the Alleyways between the rows. Alley cropping improves farm income, crop production, and protects crops. It allows the farmer to effectively use available resources and yield more benefits. Selecting suitable associated crops and mitigating the competition between trees and crops. In this article we also discuss the below topics;

• What is the Alley cropping
• How does Alley cropping prevent soil erosion?
• What is the potential benefit of using the Alley cropping system?
• Objectives of Alley cropping
• Benefits of Alley cropping

A Step By Step Guide to Alley Cropping System

Alley cropping system is the cultivation of food, forage, or specialty crops between rows of trees. This system is a larger version of intercropping or companion planting conducted over a longer time scale. Alley cropping can diversify farm income, improve landscape aesthetics, increase crop production, increase crop yield, and provide protection and conservation benefits to crops. By combining annual crops and perennial crops that yield multiple products and profits at different times, a landowner can use available space, time, and resources more effectively. One main disadvantage of the Alley cropping system is that additional labour is required to prune the trees. In general, the Alley cropping system advantages appear to outweigh the disadvantages.

Farmers may also use Alley cropping to transition from one farming system to another system. The annual crops grown in Alley cropping can provide short-term annual income until the trees are mature. The versatile nature of this system allows a producer to react to markets, labour limitations, and changing goals. Like all agroforestry systems, Alley cropping must be considered as part of the whole farm operation.

Alley cropping systems are a way of combining crop and tree production on the same plot, with an economic and environmental objective. Generally, they consist of;

• Tree rows (usually a mix of valuable hardwood species) established on cropland.
• Interstitial space between the trees is cropped with a range of species like cereals (for example, wheat, corn, and barley), oilseed, or protein crops (rapeseed, soya, fava beans, vetch, and peas, sunflower), vegetables, or vines.
• Alley cropping system maintains the agricultural potential whilst generating new incomes, which makes it an appropriate option even on high-value agricultural lands.
• Tree rows are arranged in wide-spaced parallel lines 28 to 40 meters to limit competition for light with crops. Trees are established on grass strips of at least 2 meters wide, which allow cultivation up to 1 meter from the trunk on both sides.
• With 5% of the area occupied by the rows (tree density changes from 50-250/hectare initially to 30-50/hectare in mature systems), the loss of crop productivity is low and the production of quality timber can provide extra income over time.
• The large tree spacing accelerates their radial growth.
• They improve larger crowns but, due to low density, they do not compete with each other (the average distance between two trees is 6 to 8 meters).

Difference between Alley Cropping and Intercropping

Alley cropping system is the cultivation of food, forage, or specialty crops between rows of trees. It is a larger version of intercropping planting conducted over a longer time scale.

Design Considerations for Alley Cropping System

Harvest timing – Inter-row crop production must be timed to avoid interfering with a potential woody crop harvest. In most cases, this is avoided because crops are grown during the early years of tree establishment when there is disruption by cropping activities.

Crop marketing – It is important before starting a new crop to understand how and where the crop will be marketed. To assist in this, an enterprise budget with a cash flow plan is necessary. This is critical and valuable for smaller, niche markets such as herbs, florals, and specialty vegetables.

Equipment use – It should be spaced widely enough to allow proper handling of mechanized equipment. This includes space for the growth of the tree crowns. Rows and Alleys should be arranged to facilitate easy operation of the widest machinery to avoid damage to machinery and crops.

Field Management – Alley cropping should be designed to optimize the use of light, water, and nutrients between woody plants and the inter-crops. Severe competition can reduce crop and tree growth, particularly during dry periods. Competition can be reduced by proper variety selection, spatial arrangement, and timing of planting and harvest, as well as by pruning tree limbs or roots. Weeds will need to be controlled in the tree rows for the first 3 to 5 years of establishment.

System Design – The woody plants can be planted in single or multiple rows. The woody rows may include plants that produce berries, wildlife food, florals, or other products. The inter-planted annual crops can be even more diverse and grasses for hay, cotton, soybeans, vegetables, ethnic herbs, or various combinations of other crops. Crop choices depend on the priorities for production and landowner preferences.

Woody Plant Selection Factors are;

• Adapted to site and soils
• Produce appropriate shade
• Minimal roots at the surface
• Potential multiple products
• Growth does not compete with inter-row crops

When designing an Alley cropping system, a landowner considers a few things;

• Amount of rainfall and sun direction.
• Compatibility of trees and shrubs with crops to minimize competition for nutrients, water, and light.
• Spacing between and within rows.
• Maintenance requirements and available equipment.
• The tree and crop species must be suited to the soils, climate, and site.
• Plant species and spacing should ensure accessibility for timely management activities such as spraying, pruning, or harvesting.
• The size of equipment used for the Alley cropping system will in part dictate the width of the Alleys.
• Also, take into account growth in both height and width of trees and shrubs on either side of the Alleys.
• Optimal tree row orientation mainly depends on the specific Alley crop and Alley width. Tree rows planted on contours or aligned in a key line system can help reduce soil erosion.
• Managing light for crops is important. As trees and shrubs produce they will create more shade on the companion crops. To address this change, trees can be thinned that are more shade-tolerant or have a complementary growing season with the trees.
• Competition for space, water, and nutrients in the soil is also an issue for design this system. Then, try to choose plants that have root structures that are less likely to compete for valuable resources.
• Understand the producer’s goals for the system. Most producers have other goals beyond maximizing income. Wildlife and water quality are also common interests of producers in this system.

Basic Groups of Companion Crops in Alley Cropping System

Alley cropping utilizes five basic groups of companion crops between rows, with different types of crops in each group. The five basic groups are;

• Row/cereal crops (corn, soybeans, wheat, barley, oats, potatoes, peas, and beans)
• Forage crops like fescue, orchard grass, bluegrass, ryegrass, brome, timothy, clover, and alfalfa.
• Specialty crops like landscape or decorative woody floral plants like blue spruce, dogwood, redbud; Christmas trees; small fruit and nut trees; or medicinal crops such as goldenseal or ginseng. The production of some specialty crops can be enhanced in the shade of the tree rows.
• Coppice biomass crops including poplars, willows, silver maple, birches; herbaceous crops like switchgrass.
• Vegetable crops like squash, cabbage, beans, asparagus, pepper, melon, and tomato

As shade levels increase, cool-season plants will perform better than warm-season plants.

Alley Cropping Functions

• Alley cropping impacts some landscape managements including water management, soil quality, and pest management.
• This impacts water management by altering the hydrologic cycle through increased water infiltration via disruption of overland flow by the tree or grass strip. Water cycled through the system is more thoroughly filtered and any excess is gradually released.
• The soil quality and nutrient cycling are impacted as deeply rooted trees exploit lower soil horizons and additional nitrogen is added to the nutrient pool if a nitrogen-fixing tree is used. Reduced soil erosion by wind and water help to keep soil quality. Though, additional moisture is added to the site through interception of rainfall by the tree canopy.
• Microclimates are modified due to reductions in wind velocity which reduces air temperature levels and evapotranspiration of intercropped plants and soil.
• This system creates habitat to build up biodiversity and associated populations of natural enemies of insects, diseases, or weed pests.
• This system practices help intercept, fix and biodegrade sediments, nutrients, pesticides, and other biological pollutants present on the site.
• It improves wildlife habitat by providing food, cover, and travel lanes for a variety of wildlife species.
• Not all of these functions exist with each application of Alley cropping. The function is mainly dependent upon the way the plant components are manipulated in the design process.

Row Spacing in Alley Cropping Program

Spacing between rows and individual trees is critical in designing an Alley cropping system.

1. Between-row spacing changes depending upon a variety of management decisions. For example, trees planted for wood fiber production will need less between-row spacing than if nut production is emphasized.

2. Within row spacing varies with the intent of the Alley cropping program. For example;

• Plant trees on close spacing to provide an immediate effect for erosion control;
• Plant on a wider spacing to allow sufficient space for trees to fully develop their crowns for nut development for nut tree production.

Benefits and Advantages of Alley Cropping System

Improved soil health – Alley cropping is a good option for areas prone to erosion or in a degraded shape, particularly when the tree and shrub rows are planted along contours. Woody roots in this system help reduce soil erosion, add organic carbon to the soil, recycle and add nutrients, and improve nutrient retention.

Protecting crops – Alley cropping reduces damage from insect pests by reducing crop visibility and creating habitat more favorable to beneficial insects.

Improved crop health – In this system, tree and shrub canopies protect the inter-crops against wind damage. Reducing wind affects aids in pollination activities by beneficial insects thus increasing crop yields.

Income diversification – Crop production during the years before nut trees come into bearing or hardwood timber is harvested creates cash flow and diversifies farm income, thus improving the return on long-term investments in trees.

Shelter – Trees planting in rows reduce wind speed, thereby controlling wind erosion. They also make sheltered microclimates that improve the yield and quality of crops growing in the Alleys.

Wildlife – Alley cropping system increases the biodiversity of cropland which creates new habitat for wildlife.

Why Practice Alley Cropping?

Alley cropping can have many ecological and economic advantages.

Reduced soil erosion – Particularly when established in sloping areas, Alley cropping can slow erosion, thereby improving water quality.

Improved crop performance – Added organic matter from shrubs and trees can increase soil productivity. This system also creates a microclimate from the increased shade and reduced wind, which in turn increases water use efficiency by crops. Though, the additional organic matter from the mulch improves soil structure with many rewards to the crops.

Reduced use of chemical fertilizers and pesticides – In the Alley cropping system, weeds are better controlled, and increased nutrient flow improves soil fertility without the use of fertilizers.

Minimized nitrogen leaching – Minimizing nitrogen leaching mainly improves water quality.

Promotion of biodiversity – Planting diverse vegetation provides wildlife with more potential habitat.

Establishing an Alley Cropping System

The decisions around the Alley cropping system are due to many factors and press the need to use a design process. The idea with the Alley cropping is to bring diversity to the farm in terms of crop yields and economic resilience; all of which hinge upon creative human interaction with nature.  With that, Alleys can be set up on the farm efficiently in combination with earthworks. 

The Alley of trees can be just one single row but also can be several rows of trees or shrubs. This makes sense from a soil microbiology perspective as keeping a good fungal environment for trees is important. The Alleys will be more bacterial driven so creating three lines of offset trees maybe the best way to go in the end. These trees and shrubs on the outer zone can be more short-term harvests of food, timber, or simply biomass. 

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Alley cropping can be established depending on the landowner’s objectives. There are several ways of establishing Alley cropping;

• Convert existing orchard into an Alley cropping by integrating agronomic or forage crops. Then, the tinning of the orchard may be employed to allow for the establishment of Alley cropping systems.
• Cultivate forage crops between rows of trees or shrubs, which can be used for livestock.
• Alternative perennial crops such as medicinal plants or Christmas trees within tall field crops like corn.

Limitations and Disadvantages of Alley Cropping System

Alley cropping requires more intensive technical skill and marketing knowledge.

The following limitations should be considered;

• Alley cropping requires more intensive management including specialized equipment
• Requires a marketing infrastructure for the tree products that could not be present in the local area
• Trees can be an obstacle to crop cultivation if not carefully planned and designed
• Trees compete with companion crops for sun and nutrients
• Companion crops compete with trees for moisture and nutrients
• Herbicide drift from crops may damage trees
• More complex pesticide application
• Competition between crops and trees for water and nutrients
• Longer time-horizon for cash flow
• A more diverse skillset
• Possible challenges for equipment use
• Changing the Alley crop over time
• Lower crop yields for some commodity crops

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