Sustainable Practices for Cotton Plant Care

The success of the harvest depends heavily on the weather and the quality of the soil. Let's take a closer look at the key growing conditions that are most important for cotton productivity:

Climate requirements: temperature and rainfall

The climate for growing cotton needs to be warm and humid. The plant thrives in areas with long frost-free periods and plenty of warmth and sunshine.

The optimal temperature for cotton growth throughout the active growing period is 21-37°C. Temperatures above 37 °C (100 °F) are dangerous for plant growth, but brief exposure to temperatures up to 43 °C (110 °F) does not usually cause serious damage if the air is moist. The plant is most profitably grown in areas with an annual rainfall of 850-1,100 mm. For high yields, at least 500 mm of evenly distributed rainfall is required.

Soil requirements: type and pH

Cotton can be grown virtually anywhere, as long as the soil is well-drained (usually true on gentle slopes). Nevertheless, sandy loam, rich in clay and organic matter, and containing normal amounts of nitrogen (N) and phosphorus (P), is generally considered to be the ideal soil for growing cotton. Loamy soils high in calcium carbonate usually produce the highest yields.

The optimum pH range for plant growth is slightly acidic to slightly alkaline (5.8 to 8.0). Yield losses are usually not significant until the pH falls below 5.5 in sandy loam soils and below 5.2 in silt loam soils.

Soil requirements for growing cotton vary among varieties due to differences in root systems and leaf area. American Highland varieties have deep roots and broad leaves and grow in deep, heavy, well-watered soils. In contrast, Indian desi varieties, with their shallow roots and small leaves, grow well in shallow, sandy soils with low moisture content.

Preparing the soil for cotton cultivation

Before starting the cotton planting season, the soil needs to be prepared. First, remove all debris and weeds. Then, plough or deep till the soil to loosen clumps and allow good air circulation. Ensure that the soil temperature reaches at least 15°C at 15cm underground and check this in the mornings for the next three days. When temperatures stabilize at this level, the soil is ready for cotton to be planted and grown.

Add compost or aged manure to the soil to improve soil structure, health, and fertility. Also, perform a soil test to determine the optimal levels of macronutrients (nitrogen, phosphorus, potassium) and micronutrients (calcium, magnesium, iron, zinc, etc.) for cotton growth and development.

Cotton Growing Practices

When choosing when to plant cotton, consider growing conditions rather than the calendar. The minimum soil temperature for planting cotton is 15°C (60°F) to ensure optimal germination. Plants sown in cooler soils are expected to have lower yields due to greater stand loss and potentially weaker surviving plants.

Due to machinery limitations, cotton planting distances have traditionally been 36 to 40 inches. Some farmers have switched to narrow-row cultivation, with seeds sown 15 inches apart, to increase plant density.

At the beginning of the growing season, young plants are weak. When deciding how deep to plant cotton, keep in mind that planting too deep can weaken seedlings, making them less likely to form robust plants and more susceptible to damage. Sow seeds at least 13 cm deep in moist soil to ensure optimal seed-to-soil contact, but no deeper than 38 cm to allow the seeds to develop as easily as possible.

Thorough care of the growing plant is important to optimize yields and ensure fiber quality. At the same time, sustainable plant care must strike a balance between plant needs, resource efficiency, and environmental protection.

Efficient Irrigation

Plants require more water in hotter, drier growing conditions. Cotton's water requirements in desert climates can reach up to 1,000-1,500 mm per year. In wet, warm climates, water requirements are typically as low as 500-760 mm (20-30 in).

Plant water consumption increases steadily from the early stages, when most of the water is lost by evaporation, to the later stages, when the plant is actively transpiring. Plants use the most water in the middle of the growing season, when the canopy is fully expanded and capsule loading is at its peak.

The amount of water required for the various stages of cotton cultivation can be determined using daily temperature measurements and estimated evapotranspiration.

Integrated Weed Control

Cotton seedlings are slow growing and therefore susceptible to weeds in the early stages. Crop productivity can drop dramatically when weeds shade and smother seedlings. In contrast, later in the crop's growing season, leaves cover the soil and suppress weed growth. For this reason, weed control is a priority during the first two months after planting.

Cotton seeds are planted deep in moist soil using denudation or planters, while weed seeds are left in the drier soil on top. Weeds growing between the rows are usually suppressed by applying herbicides or by tilling (this is especially effective for small weeds).

Preventive management of pests and diseases

Cotton has over 166 pests, not all of which are economically important. Different pests pose a risk at different stages of cotton growth:

From planting to flowering: spider mites and plant insects.

From flowering to harvest: cotton top moth, corn borer, armyworm, tobacco bud borer, whitefly, whitefly, stink bugs.

Plants can also be attacked by endemic bacteria, fungi and viruses. The most serious plant diseases include anthracnose, Alternaria leaf spot, leaf curl disease, Fusarium and Verticillium wilt, root and ear rot, and bacterial blight.

In 80-90% of cases, the disease develops on the leaves of the plant.

Most cotton seeds are already treated with insecticides and fungicides as part of a seed treatment strategy, and farmers also spray the soil and the growing plants with pesticides to get rid of weeds, pathogens and pests. However, excessive use of chemicals often leads to leaching, insecticide resistance, destruction of beneficial microorganisms and insects, and secondary disease and pest outbreaks. For this reason, early identification of pests and diseases in cotton plants and application of different treatment rates are very important to address these issues.

How long does cotton grow?

The typical growth period for cotton is 140 to 160 days. Specific numbers are usually given for the rate at which cotton grows and the duration of each stage, but these are approximate and will vary depending on growing conditions. For example, plants grow faster in high temperatures and slower in low temperatures.

The Cotton Harvesting Process

Cotton is usually ready for harvest when the nuts open, usually between midsummer and fall. Mature plants are particularly sensitive to the effects of rain, so timely harvesting is essential to protect the plant and maximise yield. Dry weather during cotton harvest is necessary for successful harvesting.

The capsules are removed from the stems using a machine called a picker. A rotating spindle picks up the seed cotton from the open spelt tubers and spins it for collection by buyers. Strippers are also a mechanical harvesting option. A roller with blades and brushes separates the open capsules from the branches and carries them onto a conveyor belt. In both methods, the seed cotton is forced into baskets using airflow before being transferred to a swage wagon. Pickers are generally used to harvest long-staple cotton and strippers are used to harvest short-staple cotton.

Once the cotton has already been harvested, the stalks are chopped to prevent insects from overwintering in the cotton. This plant material is left in the field as part of crop residue management to prevent soil erosion.