Will side dressed Nitrogen impact cotton root growth

Development of a vigorous and extensive root system is very important in the early development phase of a cotton crop life cycle. Cotton has a relatively coarse root, which is very different to the fibrous root systems of wheat or sorghum, being less effective at accessing nutrients from a smaller volume of soil. Root development reaches a maximum by approximately 60 days after planting (Figure 1). After this time, root activity begins to decline as the boll load develops and carbohydrates are increasingly directed toward developing the fruit.

Will side dressed Nitrogen impact cotton root growth
Daily nitrogen uptake peaks shortly after root activity has reached its maximum. This highlights the importance of developing an extensive root systems, enabling the plant to explore a large volume of soil and take up nutrients at the required rate.

Cotton’s root system is made up of a main tap root and an extensive system of lateral branches. Initially, root growth is more rapid than above ground growth, as can be seen in photo 1.

Cleaning furrows or controlling weeds with an Inter-row cultivator will prune roots and damage root development. The type of cultivation will influence the degree of damage, eg shallow inter-row cultivation may have a smaller effect while knifing in anhydrous ammonia to the recommended depth and position will be more aggressive and this will result in more root damage. Physical damage will increase the risk of disease entry, causing secondary issues. 

The second impact on root growth is the soil structural decline caused by cultivation. Compaction from heavy tractors and reduced pore space limit oxygen porosity and water movement while negatively affecting root growth.

If you are only cultivating your cotton fields to apply nitrogen, then consider water running Yara Liquids N26 to apply in-crop nitrogen. 

For more information, contact your local Yara Sales Agronomist or click here to see how easy it is to calculate your N26 application rate.

Figure 1

Figure 1

Cotton root growth relative to time after planting

Figure 2

Figure 2

Daily nutrient uptake (kg/ha) relative to time after planting