The plant cycle stretches over an average of 160 – 180 days, depending on the cultivar planted, the production area and the number of day-degrees (heat units) available for crop development in relation to the planting date. Flowering commences at 70 days post-planting and peaks at 90 – 105 days post-planting. The first bolls form from 90 days onwards, with the first bolls opening on days 115 – 120 post-planting. Most bolls will be open around 120 – 160 days, whereafter harvesting can occur from 160 – 180 days depending on the length of the season for the specific area and the cultivar planted. Development depends on the temperature and heat units/day degrees (dd) available per day. A minimum of 1 300 dd are needed, but preferably around 1 500 dd to ensure mature fibre development.

Cotton requires temperatures above 20°C averages, especially between the flower and boll development phases, but not above 34°C. Temperatures above 36°C can be detrimental to growth. The ideal soil temperature (top 3 cm of soil) for successful germination is 17.5 – 18°C for ten days consistently. Cold spells after planting will influence seed vigour and germination. Minimum temperatures below 15.5°C during boll development will affect fibre quality and yield and cause the plant to cut-out. Plant cut-out starts with temperatures falling below 18°C. Cotton is sensitive to an early frost. The ideal average temperatures, especially during boll development, is 25°C. Historically, the optimal planting time used to be between 15 and 31 October, but planting dates vary per region and should be correlated with the minimum soil temperature, the number of day degrees available for the season. The type of cultivar planted, e.g., a short-seasoned or a long season cultivar will also influence the planting date.

Full sunshine for 70 – 90% of daylight hours is ideal, with little or no cloudy weather.

Cotton is a drought-resistant crop because of a well-developed taproot system, longer than 1 m. Regular irrigation is necessary to secure optimal yields. Plant at water field capacity of 100 cm depth, irrigate 15 – 20 cm directly after planting to provide adequate moisture for germination. After germination, no irrigation is necessary for the first three weeks; thereafter, irrigation can be provided weekly. The important periods are early flowering to peak flowering to the first boll formation period. For optimum yields, cotton requires a total of 500 – 650 mm irrigation and rainfall equivalent, depending on region, soil type and climate. Rainfed land requires 300 – 400 mm, depending on soil types and climate. Ideal irrigation intervals will be five days in most cases, evenly distributed during the season. Too much water during flowering and boll development will be detrimental, and intervals bigger than 5 – 7 days between irrigation can cause shedding of squares (contact Cotton SA for more detail on irrigation).

High levels of moisture in the air during boll ripening are detrimental. An open plant canopy is preferred with lower plant populations per hectare. Plant population densities are determined for each region depending on the cultivar planted.

Preferably deep, fertile, and well-drained soil is required. Cotton will do well on most soil types. Soil moisture can be determined accurately with a neutron probe or other methods. On sandy soil, smaller amounts of water will be applied at shorter intervals, while on heavier soils, more water can be applied at longer intervals. Cotton is susceptible to over-irrigation yet resistant to soils with relatively high pH but reacts poorly to acidic soils. Ideal soil pH is between 5.5 – 7.5, while ideal soil depth is 800 – 900 mm, or even deeper. The taproot can reach around 1 – 1.2 m.

Prepare a fine, even seedbed, take soil samples for fertiliser requirements, and nematode analyses if it is a concern in the area. There is only one registered chemical to control nematodes to be applied postemergence according to the label recommendations. The list of chemicals that are registered for cotton is available on the Agri-Intel website.

Fertilise according to the recommendations based on the soil analyses. Avoid over-fertilisation with N (nitrogen). For a yield of 5 tonnes/ha seed cotton, the withdrawal will be approximately N=180 – 250 kg/ha, P=30 – 40 kg/ha and K=80 – 150 kg/ha (total available). Less nitrogen is required on clay soils. Fertilisation should not be applied after eight weeks post-planting. Adapt your fertiliser applications in line with the prediction of your soil analyses, taking into consideration what is in the soil. Often not more than 150 – 180 N is needed not later than peak flowering.

Plant when the soil temperature is 17.5°C for ten days and longer. The ideal planting date is usually from late October onwards, while after the 1^st to 2^nd week in December, potential yields may decrease considerably up to 25%. If the soil is too cold (early planting), germination will be poor. If planting is late, pests at the end of the season will be a problem, and fibre development will not occur successfully. Plant-depth is 20 – 25 mm in heavy soils and 30 mm in sandy soils. Plant more than one seed per plant station to improve vigour to break the soil crust during germination when planted by hand on rainfed fields. Press soil down on planted seed lightly but do not compact soil. Irrigate 15 – 20 mm post-planting before emergence after 5 – 7 days. Rainfed fields need to have 20 – 35 mm of rain before planting in not more than two precipitations.

Production under irrigated conditions requires a plant population between 70 000 – 88 000 plants/ha, which can vary up to 100 000 plants/ha. High plant populations per hectare provide a closed canopy which is not ideal. Under dryland conditions, the plant populations use to be around 40 000 – 60 000 plants/ha. Producers currently plant between 50 000 – 60 000 plants/ha. Check the cultivar recommendations for the various production regions. Smallholder dryland farming should be in the vicinity of not more than 40 000 plants/ha. Dense plant populations tend to encourage boll rot near the bottom of the plant as a result of fungal infections secondary to insect damage.

Between row spacing of 91 – 100 cm, with interplant spacing around 15 – 20 cm for irrigated cotton, to accommodate the different mechanical harvesting processes. Farmers should make sure what kind of mechanical harvesting processes will be used. Production under dryland conditions commonly makes use of double skip-rows with a 91 cm inter-row spacing so-called tramlines. Row spacing for dryland practices varies from full rows to single-skip to double-skip rows to conserve soil moisture.

Growth regulators, i.e., mepikwat chloride, is necessary to limit vigorous growth and allow nutrient flow to bolls. The first bolls closest to the stem contribute 70 – 80% to the yield. Maximum plant height should not exceed 700 – 800 mm and need to be controlled by at least 2 – 3 dosages of a registered growth regulator. Spray at cotton cut-out when the last white flower, closest to the stem, is about 5 – 6 nodes from the plant top. The short season variety Candia has a short compact growth pattern and rarely requires spraying. Growth should, however, be monitored weekly, not to exceed more than 7.1 mm per week as in the case with other cultivars Cotton can grow vigorously under irrigation with the addition of fertiliser and during high rainfall periods. Plant height and internode length should be monitored weekly to decide on when to spray.

Defoliation is necessary for mechanical harvesting to obtain a high grade and good fibre characteristics. Refer to the list of registered products recommended by CropLife, on their Agri-Intel website, for defoliation products registered on cotton.

Average yields obtained under irrigation with current Bt-varieties should be approximately 3.6 – 5 tonnes/ha, or sometimes even more. Under dryland conditions, 1.2 – 2 tonnes/ha can be expected. Dryland areas that are carefully managed with modern techniques as precision farming can result in even higher yields. The potential for dryland production in South Africa lies in the expansion of hectarages, especially in areas where there is a water table. Current technologies make cotton more adaptable and profitable to cultivate in dryland areas in comparison with other crops. Seed cotton can be harvested by hand or machine. A spindle picker can harvest approximately 900 ha during the season, while a stripper can harvest around 1 200 ha per season, depending on the yields per hectare. Strippers are usually used for dryland farming when lower yields are obtained. A spindle picker, 6-row configuration, is more effective on irrigated cotton when a higher yield is expected. Handpicking is usually practised by small-scale farmers and calculated at a picking rate of around 30 – 35 kg per day per person.

Early-season pests include various thrips on seedlings, aphids, the Cotton stem weevil (Apion, in some areas), the Black cotton beetle (Syagrus, some areas); Mid-season pests like the bollworm complex especially on refugia, leafhoppers (Jassidae); whitefly, sometimes the Red spider mite, but rarely mealybugs. Late-season pests include the Green Vegetable stink bug, the “Mirid-bug”, Cotton stainers and Dusky cotton stainers. Avoid unregistered products and repetitive spraying of pyrethroids, carbamates and any organophosphates. Follow an Integrated Pest Management approach by scouting 24 plants per field weekly from the 4-leaf stage. It is crucial to note that no alternative pesticides other than those specifically approved for South African cotton may be used, be they synthetic chemical products or biological products. Contact Cotton SA to obtain thresholds for the various pests. Current stackgene Bt-technologies provide adequate bollworm control, but cotton should still be scouted to make sure of pest populations and to monitor secondary pests.