Have you nailed your crop nutrition?
Getting your crop nutrition spot on is essential for maximising cotton yield. Too little nutrition will reduce the crops' yield potential, while too much fertiliser can impact your profitability through increased costs, contamination of groundwater, excessive vegetative growth in the crop, and related insect, disease and harvest problems. And, increased cropping intensity can also result in the progressive depletion of soil nutrients - requiring more fertiliser to replace lost nutrition.
So careful monitoring and management of nutrient levels is important to ensure yield potential is reached, without inefficient fertiliser application. Without regular monitoring, nutrition deficiencies may not be identified until symptoms appear - which may be too late! At that point, a reduction in yield is likely, despite remedial fertiliser applications.
So, it's important to get your crop nutrition right.
What do you need to know?
The key fertilisers used in cotton production at 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) 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.
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 cultivar will increase NFUE.
Phosphorus (P) is a highly immobile nutrient. 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.
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, restricting plant capacity to take up sufficient K at peak demand.
So, what should you do on your farm?
- Plan: Conduct soil sampling to determine physical and chemical soil properties. Calculate crop nutritional requirements related to expected yield, cropping history, cropping system nutrient losses, and soil conditions. Develop a long term crop nutrition plan to optimise nutrient use efficiency.
- Monitor: Regularly monitor crop nutrient status and conduct tissue analysis through leaf and petiole testing to assess deficiencies. During the growing season monitor plants and adjust crop nutrient programs for a targeted yield.
- Manage: Implement a fertiliser plan and crop nutrition program before deficiencies in soil nutrients limit crop production.
For more best practice information on crop nutrition, visit the myBMP Soil Health module.
Where should you go for more information?
- NUTRIpak: A manual of cotton nutrition, designed to inform growers and consultants of the importance of providing crops with a sufficient supply of nutrients and improving fertiliser management.
- SOILpak: Aims to provide a range of best soil management practices to optimise crop and pasture yields.
- Australian Cotton Production Manual
- 2016 reseach tour booklet: CottonInfo cotton nutrition tour booklet
- 2018 research tour booklet: CottonInfo optimising irrigation and nitrogen tour booklet
- CottonInfo case study: The nitrogen challenge - trial results show cost savings
- CottonInfo on-farm nitrogen trials and N-use practices report 2017
- CottonInfo paper for the 17th Australian Cotton Conference: Nitrogen fertiliser use efficiency across the regions
- CRDC Spotlight magazine article (Spring 2014 edition): Improving nitrogen use efficiency in cotton
- Nutrient sampling guidelines for cotton
- Australian Soil Fertility Manual (CSIRO)
- Physiology of Cotton (Springer)
- NutriLOGIC: NutriLOGIC helps interpret soil and leaf analyses for all major nutrients, and indicates when fertiliser application maybe warranted for individual fields. Growers need only enter the sampling dates, and the chemical analyses from their laboratory report.
- Three part webinar on nutrition and the Emissions Reduction Fund: