Getting began with lettuce

Lettuce (Lactuca sativa) has been cultivated for hundreds of years as a leafy vegetable. Immediately, it’s grown worldwide and regarded one of the crucial vital salad crops. In some nations, equivalent to China, it is usually consumed cooked.

In South Africa, lettuce is primarily grown for the native contemporary market with cultivation concentrated within the Western Cape, KwaZulu-Natal, Mpumalanga, Gauteng, Jap Cape, Limpopo and North West provinces.

In South Africa, 4 fundamental kinds of lettuce are generally cultivated:

• Crisphead (Iceberg): Identified for its tightly packed, agency heads, this selection is well-suited to open-field manufacturing and handles long-distance cargo.
• Butterhead: Recognised by its mushy, waxy leaves and gentle flavour, this sort is much less tolerant of warmth and fewer appropriate for area manufacturing or long-distance shipments.
• Looseleaf: Somewhat than forming a head, its leaves develop immediately from the stem. It grows effectively each within the area and below safety and might be shipped lengthy distance.
• Romaine (Cos): This selection has slender leaves, an oval form, darkish, closely ribbed outer leaves and lighter inside foliage. It’s considerably extra cold-resistant than the opposite sorts, in a position to tolerate temperatures as little as -5°C and is normally grown within the area.

Deciding on the suitable cultivars for various planting occasions and native situations is vital to reaching good yields and crop high quality. Farmers are suggested to seek the advice of their native seed firm for the most recent cultivar data and suggestions.

The KwaZulu-Natal Division of Agriculture and Rural Growth (KZN DARD) provides that “frequent testing of newly launched cultivars ought to change into routine follow for the intense producer.”

Marco Rugani of Toscana Herbs and Contemporary Produce in Muldersdrift emphasises the significance of planning forward: “You need to select a spread with the lower date in thoughts. It’s no good planting in a hotter local weather after which chopping the harvest within the chilly.”

KZN DARD notes that temperature and soil moisture, along with right cultivar alternative, are among the many most vital elements affecting the success of lettuce manufacturing. Rugani agrees.

“Lettuce has particular climatic necessities, and enough water can be crucial, particularly when the crop is heading simply earlier than harvest.” (“Heading” is the time period used to explain when lettuce leaves start to overlap and kind a compact, rounded head).

As a temperate crop, lettuce tolerates winter chilly and light-weight frost, though tolerance to each chilly and warmth can differ between cultivars. Heavy frost will harm the leaves and heads. The crop is delicate to temperature fluctuations and germinates greatest between 15 to twenty°C, whereas temperatures greater than 25°C might inhibit germination. Optimum progress is within the 12°C to twenty°C vary.

Though market demand for lettuce peaks in summer season, rising it throughout this season presents a number of challenges. Ailments are extra prevalent, and excessive temperatures improve the chance of bolting (the untimely manufacturing of flowers and seeds).

Bolting can be exacerbated by progress stress, equivalent to inadequate water. Excessive temperatures (above 27°C) can cut back head high quality and palatability and trigger tipburn or seed stalk formation. For summer season manufacturing, farmers should select varieties with a tolerance to bolting and good illness resistance.

Whereas lettuce has excessive moisture necessities, it may be grown in quite a lot of soils, from mild sandy to heavy clay, supplied water and nutrient availability are managed appropriately. It grows optimally in well-drained, fertile loams wealthy in natural matter.

“Deep, well-drained soils are appropriate for many crops, together with lettuce, however the latter, with its shallow root system, might be grown fairly efficiently on comparatively shallow soils, supplied a beneficial soil moisture regime might be maintained,” says KZN DARD.

Correct soil preparation is important. The soil must be labored to a superb tilth, clods eradicated, and the floor should be stage to advertise uniform emergence. Raised beds 20cm to 30cm excessive are perfect for lettuce manufacturing within the area, serving to to stop harm from soil compaction and waterlogging because of extreme rainfall.

This methodology additionally improves air circulation across the crops, which might decrease the chance of illness.

Many business farmers use greenhouse seedlings, which might be transplanted all year long if situations are appropriate. Throughout the summer season months, seedlings should be correctly hardened off earlier than planting to scale back warmth stress. Making use of mulch throughout this era can be advisable to decrease soil temperature, cool crops, retain moisture and cut back soil splash that may result in illness.

Underneath optimum rising situations, lettuce might be sown immediately within the area at a depth of 10 to 15mm. Sowing occasions will differ by area:

• Chilly areas with heavy frost: Sow from January to April and once more July to December.
• Sizzling, frost-free areas: Sow from February to August/September.
• Heat areas with mild frost: Sowing is feasible year-round.

The seeding fee is round 1,5kg per hectare however might be as excessive as 3kg. In-row plant spacing varies from 250mm to 350mm and inter-row spacing from 350mm to 450mm, whereas plant populations can vary from 60 000 to 100 000 crops per hectare.

“Spacing and plant populations can have a marked impact on whole yield and on head measurement. Nevertheless, because the inter-plant competitors will increase with higher-density plantings, head measurement turns into smaller. Head measurement is a vital high quality issue, with the bigger heads usually commanding greater costs,” explains KZN DARD.

Seedlings typically emerge inside two to seven days after planting. 5 to 6 weeks after sowing, seedlings must be thinned out to realize the specified spacing. A few of these seedlings might also be transplanted in seed trays or seedbeds.

With a shallow root system, and roots solely penetrating to a depth of 300mm, the crop requires frequent mild irrigation, ideally by way of drip irrigation. Nutrient functions also needs to be restricted to this depth.

Over-irrigating past this depth wastes water and causes nutrient leaching, KZN DARD factors out. All through the rising interval, lettuce requires common irrigation, with a discount when the heads have totally fashioned to keep away from high quality points and illness stress.

Fertilisation

“The soil is a useful resource that must be managed and monitored meticulously,” advises seed firm Starke Ayers.

“It’s important {that a} grower have soil samples of the meant rising space analysed by an accredited laboratory to find out the nutrient standing of the soil. Based mostly on soil evaluation outcomes a fertilisation programme can then be developed. The grower ought to do that train each season or each time a brand new crop is planted on the land.”

The corporate additionally recommends water testing, as water high quality can considerably have an effect on plant progress. Excessive calcium ranges in irrigation water, for instance, can increase soil pH, affecting nutrient availability and plant efficiency.

KZN DARD says whereas it’s not potential to make correct fertiliser suggestions with out soil evaluation, the approximate absorption of vitamins by a very good crop of 40 tons per hectare is 110kg nitrogen (N), 14kg phosphorus (P) and 190kg potassium (Ok).

Typical ailments

To cut back the chance of illness build-up, KZN DARD recommends a three-year crop rotation.

“Few of the organisms inflicting ailments of lettuce assault different vegetable crops, so most different greens might be included in a rotation with lettuce,” it says. “Nevertheless, Sclerotinia rot can have an effect on many vegetable crops and, ought to this be an issue, the selection of appropriate rotational crops is extra restricted.”

Moist and funky situations create a beneficial atmosphere for Sclerotinia rot, a fungal pathogen that causes leaf discolouration, stem and crown rot, and a attribute white mould. One other widespread fungal illness is powdery mildew. It presents as spots of white to greyish, powdery progress on the higher and decrease sides of leaves. This illness wants heat, dry situations and primarily impacts mature lettuce.

Bacterial rot complicated may happen when crops are confused or broken. Micro organism penetrate the leaves inflicting leaf spots and eventual rotting.

For management of those and different typical lettuce ailments, the nationwide agriculture division advises rotation with non-host crops equivalent to onions.

“At all times attempt to plant disease-resistant cultivars, use disease-free seeds and use solely registered chemical substances. Discard infested crops and take away them from the sphere. At all times preserve your area freed from weeds.”

For extra data on lettuce manufacturing, farmers can discover planting guides for every province per selection, in addition to illness data on the Sakata Seed web site www.sakata.co.za. To search out out about accessible business farming seeds, go to the Starke Ayres web site www.starkeayres.com.

Quick Details

The 4 fundamental kinds of lettuce are crisphead, butterhead, looseleaf and romaine.

• Deciding on the suitable cultivar and punctiliously managing temperature and soil moisture are important to profitable crop manufacturing.
• Crop rotation each three years with different greens helps to stop ailments.

Sources:
http://www.daff.gov.za/pictures/Branches/Economicapercent20Developmentpercent20Tradepercent20andpercent20Marketing/advertising and marketing/annual-publications/greens/lettuce-market-value-chain-profile-2021.pdf (intro)
https://agrierp.com/weblog/most-profitable-crops/#:~:textual content=Theypercent20(%20saladpercent20greenspercent20likepercent20lettucepercent20and,profitablepercent20cropspercent20forpercent20smallpercent20andpercent20bigpercent20farms. (why plant lettuce)
https://www.nda.gov.za/pictures/Branches/Economicapercent20Developmentpercent20Tradepercent20andpercent20Marketing/advertising and marketing/annual-publications/greens/lettuce-market-value-chain-profile-2021.pdf (SA market)
https://www.doc-developpement-durable.org/file/Tradition/Plantes-Medicinales-Aromatiques/FICHES_PLANTES/ProdGuideLettuce.pdf (that is the outdated DAFF’s publication –  manufacturing data)
https://seedcogroup.com/bw/greens/wp-content/uploads/2021/12/Lettuce.pdf (summer season manufacturing and seedling manufacturing)
https://www.kzndard.gov.za/pictures/Paperwork/Horticulture/Veg_prod/lettuce.pdf (manufacturing)
https://www.starkeayres.com/uploads/recordsdata/Lettuce-Manufacturing-Guideline-2019.pdf (manufacturing)
https://southafrica.co.za/lettuce-planting.html (planting seedlings)
https://extension.usu.edu/planthealth/ipm/notes_ag/veg-drop-sclerotinia (sclerotinia)
https://ipm.ucanr.edu/agriculture/lettuce/powdery-mildew/#gsc.tab=0 (powdery mildew)