Maintaining a balance between crop removal and soil supply sustains lint yield and quality of cotton, maximising nutrient efficiency. Balanced nutrition also prevents nutrient deficiencies and reduces the risk of adverse off-site consequences of over application.

Cotton nutrition planning should consider:

• Crop rotation
• Stubble management
• Tillage practices
• Use of legumes, manures and composts
• Soil chemistry (salinity, sodicity) that may limit root development and exploration
• Water availability (irrigation deficits or starting soil moisture levels in rainfed production)
• Soil physical condition
• Fertiliser formulation

Nutrient supply
Nutrient supply is dependent on residual nutrient reserves in the soil from a previous crop, in-crop mineralisation of nutrients from soil organic matter, and the application of nutrients in the form of synthetic fertilisers or organic compounds. As part of crop management, routine soil analysis indicates the fertility level of your soil at that point in time. For crop budgeting purposes, the ideal time of the year to soil sample is in the cooler months of July and August when soil microbial activity is reduced. Once soil nutrient levels have been measured and seasonal nutrient tactics developed, fertiliser requirements for your crop can be accurately calculated. Crop nutrient tactics take into consideration historical and expected yield, cropping history, cropping system and nutrient losses, crop use efficiencies, plant nutrient recovery and uptake, and soil condition and characteristics.
There is considerable variability in the supply of nutrients from the soil both across a farm and within a field. The use of historical yield maps, land-forming cut and fill maps or soil surveying equipment, such as electromagnetic surveys (EM surveys), can be used to guide fertiliser inputs within fields. An important aspect for budgeting the crop’s nutrient supply is that for most nutrients more than 50% is taken up during the flowering period. This has two major implications; first, you need to ensure adequate nutrition is available in the soil by the start of flowering because plant uptake increases dramatically during this period and deficiency can occur quickly; second, late application of most nutrients has little impact on plant fruiting development and yield.

Key nutrients
The key fertilisers used in cotton production are nitrogen (N), phosphorous (P), and potassium (K). Deficiencies are rare in other essential nutrients such as copper, boron, calcium, magnesium, sulphur, manganese, iron, zinc, cobalt and molybdenum.

• Nitrogen (N)
  Nitrogen (N) application is the most significant fertiliser input cost for Australian cotton growers. Nitrogenous fertiliser use has increased to the point where significantly more is being applied to commercial crops than industry best practice recommends and is required in most circumstances.
  Nitrogen fertiliser use efficiency (NFUE): NFUE can be calculated as lint yield (kg/ha) divided by the total amount of fertiliser N applied. Long term measurement and monitoring strategies are required to distinguish between seasonally unavoidable low NFUE and low NFUE related to broader production system problems that can be addressed. Four broad factors influence nitrogen use efficiency:  soil type, irrigation practices, weather conditions and N application management. Poor NFUE from both pre and in-crop N application results from mechanisms such as volatilisation, denitrification and leaching, or temporary unavailability due to soil processes such as immobilisation. Optimal management of weeds, disease, sowing date, rate and variety will increase NFUE. 
• Phosphorus (P)
  Phosphorus (P) is highly immobile. Despite a high P content, many soils have low P availability, particularly under alkaline conditions. Phosphorus deficiency causes reduced seedling vigour, poor plant establishment and root development, delayed fruiting and maturity. 
• Potassium (K)
  Adequate potassium levels may improve yield and fibre quality and reduce the incidence and severity of plant diseases. K deficiency symptoms vary depending on the growth stage of the crop. Premature senescence is a potassium related disorder that can occur regardless of the supply of potassium from the soil. It is caused by the interaction of high boll loads and stresses such as water logging, cool, cloudy weather or subsoil constraints such as compaction, which restricts the plant's capacity to take up sufficient K at peak demand.