Timing of planting
Being a long season crop, cotton must be established as early as is practical. However, the earliest dates for planting cotton are controlled by legislation necessitated by the need to maintain a specified dead season for the control of pink bollworm.
Earliest planting dates are:
S.E lowveld – 5 October
Remainder of the country – 20 October
The cotton seed is small and is a very weak germinator. If planted too deep, germination will be slow and uneven giving a poor crop stand. It is therefore important to ensure a shallow uniform depth of planting. In general the depth must not exceed 20mm.
An average of 20kg /ha of acid de-linted seed can be used where seed is placed at planting stations. Three to five seeds may be placed at each station depending on soil type and soil physical conditions.
The generally recommended spacing is 1,0m between rows and 0.3m within rows. For dry land crops and in cooler areas, where growing conditions are not as good, closer spacings are advisable. For very late plantings and in areas where conditions are marginal due to soil type, rainfall reliability and low temperature, the spacing can be reduced from 1m to 0.9m between rows and 15cm to 20cm in row.
Where an initial crop stand is poor, gap filling is only recommended for gaps in the row of 1m or greater. If the stand is extremely poor then replanting is often recommended but the decision lies with the farmer. If refilling is considered necessary it should be done as soon after emergence as possible (within 3 to 5 days) so that the new plants can catch up with the rest.
Thinning is done in order to establish the required plant population. This is done as early as possible when the seedlings are well established. This can start about five days after emergence and should be completed by the time the crop is three weeks old.
Where soil potash is good and depending on rainfall or irrigation a general rate of 200 -400kg of Cottonfert 5:18:10 (Compound L) or its variations can be applied. Alternatively farmers can use high analysis fertilizers like 6:27:20 at lower rates (150-300kg/ha). Where the soil potash is poor a high K fertilizer e.g. 5:15:25 can be used at a rate of 200-400kg/ha. Where there are imbalances of potash and phosphates these can be corrected by using MOP or SSP For top dressing the general requirement is 50 – 150 kg/ha.
Fertilizer requirements (50 kg bags per ha) for Cotton
|Good Rich Soils||Medium Soils||Poor Sand Soils|
|Compound L||4 – 5||3 – 5||6 – 8|
|Ammonium Nitrate||1||1 – 2||2 – 3|
|Urea||Less than 1||1 – 1.5||1.5 – 3|
In young cotton, weeds compete with the cotton plants for nutrients, moisture and light. Late weeds interfere with picking, contaminate the bolls thereby decreasing quality. Weeds in general may act as hosts for some pests like cutworms and eelworms. Since crop grows slowly at first, weed control is critical during the first 8 weeks of growth. The most crucial weeding stages are from planting to flowering and during boll splitting.
Herbicides that can be used in cotton
|Trade / common name||Active ingredient||Time of application||Persistence||Rate / Ha||Weeds controlled|
Cottorex Super SC
|Pre-emergence||Med – Long||2.5 – 5L||Broad leaf weeds. Can be used with a grass herbicide|
|Fluometuron||Pre-emergence||Med – Long||4.5 – 6.4L||Broad leaf weeds. Can be used with a grass herbicide|
|Codal Gold 412 DC||Prometryn/S Metolachlor||Pre- emergence||Med – long||2.5 – 4.0 L||Most annual broad leaf and grass. Can be tank mixed with glyphosate.|
|Lasso/ Alachlor||Alachlor||Pre-emergence||Short – med||2.0 – 2.5L||Annual grasses and some broad leaf weeds|
|Dual 720 EC
|Metalochlor||Pre-emergence||medium||1.25 – 1.75L||Annual grasses and yellow nutsedge and some broad leaf weeds|
|Dual Magnum 960
|S metalochlor||Pre-emergence||medium||0.7 – 0.9 L||Annual grasses and nutsedges and some broad leaf weeds.|
|Diuron 80% WP||Diuron||Post-emergence directed||short||1.0 – 2.0L||Broad leaf weeds|
|Ametryne 50EC||Ametryne||Post emergence directed||short||2.0 – 2.5L||Yellow nutsedge, annual grasses and some broad leaf weeds|
|Agil||propaquzafop||Post emergence||Very short||100g/L||Annual and perennial grasses including shamva grass|
|Fusillade||Fluazifop-P-butyl||Post emergence||Very short||1L||Annual and perennial grasses|
|Focus ultra||Cycloxydim||Post emergence||Very short||1.5L||Annual and perennial grasses including shamva grass|