Irrigation in Cotton (Gossypium sp.)

Soil type	Crop duration	Irrigation interval	No. of irrigations	Depth of each irrigation (cm)	Total crop water requirement (cm)
Black soils	180 days	20 days	5 -6	6 cm	80 - 90 cm
Light/red/sandy loam soils	170-180 days	15 days	8 -10	5 cm	80 - 90 cm

• Schedule irrigation at 0.6 IW/CPE throughout the crop growth.

Methods of irrigation

• Adopt furrow method of irrigation with following specifications.
• Adopt Alternatively Alternate Furrow Irrigation (AAFI) in heavy soils (Vertisols), which saves time, labour, irrigation water (to the extent of 30%) and minimizes the long term ill effects of irrigation on soil properties.

Particulars	In heavy or black soils	In light or red soils or sandy loam soils
Furrow length	100-150 m	60-90 m
Slope in furrows	0.1 - 0.2 %	0.2 -0.4%
Stream size	2 - 3 lit/sec	3 - 4 lit/sec

 Critical stages of irrigation

Critical Stages of crop growth	Days after sowing (DAS)
Sympodial branching and square formation stage	45 -50
Flowering and fruiting stage	75 - 85
Peak boll formation	95 - 105
Boll development and boll opening stage	115-125

• Heavy and frequent irrigation enhances the vegetative growth leading to ineffectiveness of plant protection measures, resulting in higher incidence of pest/diseases.
• Provide drainage in heavy soils to avoid water logging due to low infiltration rate
• Under canal command areas where in the canal opening is not assured at scheduled time, ensure early sowing with protective irrigation by open/bore well water.
• Under constraints of irrigation water, foliar spray of Kaolin (60 g/lit) with 1 g teepol or soap, at 3 days after last irrigation reduces transpiration losses from the crop canopy, thus helps the crop to utilize the available soil moisture efficiently.