Establishing a new citrus orchard

Citrus trees can be grown in a wide range of climatic and soil conditions. But proper site selection remains the key to successful organic production. Climate has a significant effect on nearly all aspects of citrus growth and quality development:

• Extremely hot temperatures that exist in some African countries are damaging to citrus. Ideal temperatures range from 13 °C to 38 °C. At higher temperatures, flowers and leaves drop prematurely.
• Rainfall or irrigation throughout most of the year is necessary for citrus, however, dry and hot temperatures during the day and cool temperatures at night are favourable conditions for good colour development.

Although citrus grows in a wide variety of soils all over Africa, it grows best in deep soils of medium texture and moderate depth, with good drainage and high fertility. Moderate pH conditions between 5 and 7 are preferable for citrus, as they generally allow adequate availability of nutrients. Adequate drainage is also needed, as tree growth is reduced in poorly drained soils or where compacted soil layers are present in the root zone. Furthermore, poor drainage causes problems with Phytophthora and other soil borne diseases.

Yields in subtropical climates peak at 20 to 25 years, while yields in tropical regions reach a maximum at 10 to 15 years already because of the higher pest and disease pressure in these regions.

Some months before planting citrus trees, farmers can sow vigorous legumes like velvet bean (Mucuna spp.), sunhemp (Crotalaria spp.), or lablab (Lablab purpureus), which are then slashed and mulched shortly before planting the citrus trees. Then the soil will be enriched with organic matter and nitrogen, both stimulating soil microbial activity.

An optimum plant density that permits optimal light interception and aeration is achieved at a tree spacing of around 8 m by 8 m. This leaves some space for intercropping. The citrus seedlings should be planted well, making sure that the budding point remains above the ground to avoid exposing the scion to root rot diseases and to make sure it does not start rooting itself. It is recommended to apply compost into the planting holes to encourage quick establishment of the plants. Depending on the planting season, supplementary watering or irrigation may be required to support the growth of the young seedlings.

Shoots that grow below the budding union must be removed. These shoots, if not removed, will retard growth or kill the scion part of the budded shoot.

Establishing a new orchard has the advantage that the farmer can create an optimal organic system by applying the following strategies:

• Creating diversity - In the citrus orchard, diversity can be created by mixing different cultivars in the same orchard, growing specific cover crops in the alleyways and under the trees, as well as planting hedges and wild flower fallow plots around and in the orchard.
• Intercropping - For smallholder farmers, relying on citrus production alone is not sufficient. Citrus in Africa is in most cases intercropped with annual crops, for example maize and beans at establishment stage for about two seasons or with fruit trees such as mangoes or any other long-term trees at a much wider spacing. The space to grow additional crops is limited to alleyways. Successful examples are intercropped beans and maize for subsistence supply, as it is practiced in Kenya, or intercropped with Aloe vera, as practiced in South Africa. The orchard can also be intercropped with legume cover crops in the later stages of growth.
• Plant density - Using a plant density that permits optimal light interception and good aeration is necessary to control fungal infections. Citrus trees need wide spacing of about 8 m to 8 m to offer enough space for intercropping as well as allowing good aeration of the orchard. Sufficient spacing is also necessary to allow for application of compost and management of pests and diseases.