The optimal nitrogen rates for carrots in specific fields may be much less than generally accepted recommendations. This conclusion was made by scientists at the University of California based on the results of the research. This information is important against the background of the rise in prices for mineral fertilizers all over the world.
Most carrot growers apply more nitrogen fertilizers than required. Although carrots require special growing conditions and a sufficient amount of mineral nitrogen and water, the excess does not benefit the culture. Carrots have a deep and branched root system, so they are able to access the residual nitrogen of the previous season, which has gone deeper into the soil profile.
The nitrogen requirements of carrots for optimal root crop yields depend on climate, soil type and residual nitrogen in the soil.
Reduced yields can often be observed when high doses of nitrogen fertilizer are applied during planting, so the use of slow release fertilizers is preferable from a production and environmental standpoint.
Excessive watering causes various deformations of carrot roots, therefore, it is necessary to carefully control irrigation during the growing season. Although nitrogen fertilization does not significantly increase crop water consumption due to increased leaf area, it markedly increases water use efficiency up to an application rate of 120 kg nitrogen per hectare.
A study by American scientists showed that the highest yield of root crops was achieved on sandy and loamy soils with 75% of the soil moisture capacity of the field and the application of 150 kg of nitrogen per hectare.
Nitrogen uptake in carrots is usually low in the first 40-50 days, so growers are advised to limit their fertilization during this period. While frequent watering is recommended at the same time, it is necessary to control the amount of water at each watering to reduce the leaching of residual nitrogen. After all, his contribution can be significant, especially in a monoculture environment.
The results of the study showed that a significant amount of nitrogen remained in the carrot tops during harvest, potentially contributing to the accumulation of an average of 42–44% of the total nitrogen in the plant (tops and roots) in the next season.
It is recommended to always make a preliminary assessment of the nitrogen content of the soil to a depth of 60 cm and then recalculate the application rates based on this information. This practice is an excellent tool for increasing yields and improving quality at the lowest economic and environmental cost.