Asparagus Farming In Kenya, Growers Guide
system that provides adequate fertility while maintaining effective weed management. A well managed asparagus stand may stay productive for 15 years or more
Uses of Asparagus
Asparagus spears can be eaten raw or cooked. They are low in calories and very low in sodium. Asparagus is a particularly good source of vitamin B6, calcium, magnesium , zinc, vitamin A, vitamin C, vitamin E, vitamin K, thiamin, riboflavin, rutin, niacin, folic acid, iron, phosphorus, potassium, copper, manganese, selenium, chromium, dietary fiber, and protein.
Asparagus Growth Requirements
Growing from seed
Asparagus seed requires a minimum of 10˚C to germinate, however germination success and seedling development are enhanced at temperatures between 15-30˚C. The optimum temperature for asparagus seed germination is 24˚C. Germination may also be enhanced by soaking seedlings in water at 32˚C for three to four days prior to sowing. Soil should be at least 15˚C when sowing asparagus seed.
Asparagus transplants can be started in a greenhouse in middle to late February and transplanted into the field after eight to 12 weeks or when soil has reached an adequate temperature (15˚C).
Asparagus crowns are started in nursery beds and left in the ground for one year; plants are dug up in the spring and then replanted as soon as possible. Selection of the best crowns is essential. Damaged, diseased or under sized (less than 25g) crowns should be discarded. Selection of the best asparagus crowns is essential, all damaged, diseased or under sized (less than 25g) crowns should be discarded, this may be up to 40 per cent of the crowns in the nursery beds. Crowns should be planted at a depth of 15-20 cm.
Permanent field spacing for plants should be at a distance of 1.25-1.75 metres between rows and a
spacing of 30-45 cm between plants within the row. Asparagus seed should be planted at a depth of between 2.5-4 cm. Crowns should be placed in a 15- 20 cm deep furrow and covered with 5 cm of soil. Soil should continue to be added through the season, usually during cultivation to control weeds.
The first two to three years of establishment are critical for the productivity and yield of the mature
asparagus stand. During these first couple years young asparagus plantings can suffer from weed competition, inadequate soil moisture and/or soil fertility. It is also highly detrimental to over harvest plants during the first years of establishment.
After the last harvest of the season the asparagus bed should be shallowly cultivated to control weeds and incorporate nitrogen fertilizer. Care must be taken to not damage the root system of the asparagus during these activities. The remaining stems will begin to unfurl their frond-like leaves which will photosynthesize and capture energy to recover from the harvest period and store reserves for winter dormancy and regrowth in the spring.
While stems are still green they are still connected to the root system of the plant and should not be removed. When the stems turn yellow they can be removed, however the stems tend to catch snow which can help insulate the plant during winter. The stems can be cut and incorporated in the spring before the plant breaks out of dormancy. Incorporation of dead stem tissue can add 10 tonnes of organic matter per hectare.
Pest and Disease
Disease: Asparagus rust (Puccinia asparagi)
Characteristics: Red/orange lesion develops on leaves and stems. This disease can cause premature defoliation of leaves which results in reduced yields in subsequent years.
Control: Monitor for the appearance of the disease so fungicides can be applied before significant buildup of infection and spore production. All infected material should be removed from the field or incorporated into the soil.
Disease: Fusarium crown and root rot (Fusarium oxysporum f.sp. asparagi) and (Fusarium moniliforme)
Characteristics: Rotted and hollow root system (both feeder and storage roots), can be accompanied by a red/ brown discoloration. Above ground parts can appear stunted and/or wilted. F. oxysporum can be found in most soils. F. moniliforme is capable of infecting both asparagus and corn.
Control: It is imperative that new asparagus planting be placed in fields that have not been used for asparagus or corn production within the last five years. Avoid damage to the asparagus roots during cultivation. Fungicides are generally ineffective against this disease; however soil fumigation prior to planting may reduce the population of Fusarium in the soil.
Disease: Botrytis blight (Botrytis cinerea)
Characteristics: Causes tan lesions with brownish borders, in more advanced cases fuzzy gray spores will be visible. Disease can completely kill newly emerging stems, and is most problematic when high moisture is present either during wet weather or when air is unable to move in the canopy.
Control: Botrytis is a common invader of wounded or weakened plant tissues and is also prevalent in storage. Reducing injuries to plants will reduce infection point. Remove and destroy infected tissues to reduce further spread. Trifloxystrobin registered for asparagus rust control will provide some control of Botrytis.
Insects: Common asparagus beetle (Crioceris asparagi) and spotted asparagus beetle (Crioceris
Characteristics: The most significant damage caused by these two beetles is feeding damage on stems and leaves of asparagus. Defoliation of stems can occur in serious cases, which can cause impacts on the following years yield. Larvae of the spotted asparagus beetle feed within berries, which will decrease seed yield.