It is mentioned on chart. You have to match with leaf colour.

The leaf nitrogen concentration (LNC) is highly correlated with chlorophyll content. To measure it, there are many devices like leaf colour chart (LCC), SPAD, at LEAF+ of chlorophyll or nitrogen. As these devices are cost effective and unavailable with all farmers, LCC provides prospects to the farmers for estimating plant N requirement in actual time for effective fertilizer use and augmented rice yields.N deficiency can easily be rectified with no devastation of plant parts. Nowadays, the leaf colour chart is being successfully used worldwide for the proper rate of nitrogen application and thus boosting the greatest productivity

Thanks a lot

I think you will find that the amount of N required is only predicted quantitatively for an environment based on experience

I recommend @Prem Baboo for suitable answer. The leaf colour and the colour chart can be matched to determine the status. Best wishes.

Dear colleague,

May I suggest you go through the relevant portions of the attached publications to find the right answer to your question?

Thank you Bijay Singh for sharing important materials

Hi Dr Tessema Tesfaye Atumo . I hope the following link might help: Article Leaf Colour Chart vis-a-vis Nitrogen Management in Different...

Kindly see the following link: https://www.cambridge.org/core/journals/experimental-agriculture/article/fixedtime-corrective-dose-fertilizer-nitrogen-management-in-wheat-using-atleaf-meter-and-leaf-colour-chart/AD79C1FF2B11B83F83FECE1E9F6A31F0

I suggest also the following link : https://www.google.com/amp/s/krishijagran.com/featured/how-to-provide-right-nitrogen-dose-in-paddy-by-leaf-colour-chart/%3Famp%3D1

Thank you @Aref Wazwaz for your support.

You are most welcome dear

Dr Tessema Tesfaye Atumo .

Wish you the best always.

Two options (real-time and fixed-time) are recommended for applying fertilizer N using an LCC. In the real-time option, farmers monitor the color of leaves at regular intervals of 7–10 days and N is applied whenever the color is below a critical threshold value. In the fixed-time option, N is applied at a preset timing, and the dose can be adjusted upward or downward based on leaf color. There is no one-size-fits-all option to use LCC. The appropriate timing, critical threshold value, and dosage should be determined through experimentation before dissemination. I recommend going through the following references to deepen your knowledge:

Ali A. M., Thind H. S., Sharma S., Yadvinder-Singh (2015). Site-specific nitrogen management in dry direct-seeded rice using chlorophyll meter and leaf colour chart. Pedosphere, 25 (1), 72-81.

Ali, A.M., Ibrahim, S.M., Hassany, W.M. and El-Sadek, A.N. (2021). Fixed-time corrective dose fertilizer nitrogen management in wheat using atLeaf meter and leaf colour chart. Experimental Agriculture, 57(4), pp.232-243.

Bijay-Singh, Varinderpal-Singh and Ali A.M. (2020). Site-specific fertilizer nitrogen management in cereals in South Asia. In “Sustainable Agriculture Reviews 39”, Springer.

This article might be useful..

Real-time nitrogen management in aerobic rice by adopting leaf color chart (LCC) as influenced by silicon 10.1080/01904167.2016.1263333

Phasing of N application at critical developmental stages is more important for efficient utilization of applied N by paddy. Monitoring of plant N status is important in improving the balance between crop N demand and N supply from soil and applied fertilizer. Because leaf nitrogen content is closely related to photosynthetic rate and biomass production, it is a sensitive indicator of the dynamic changes in crop N demand within a growing season. Leaf colour intensity is directly related to leaf chlorophyll content which, in turn, is related to leaf N status. Two options (real-time and fixed-time) are recommended for applying fertilizer N using an LCC. In the real-time option, farmers monitor the color of leaves at regular intervals of 7–10 days and N is applied whenever the color is below a critical threshold value. In the fixed-time option, N is applied at a preset timing, and the dose can be adjusted upward or downward based on leaf color. Farmers generally use leaf colour as a visual and subjective indicator for the crop’s nitrogen status and need for N fertilizer application. Simple diagnostic tools as Leaf Colour Chart (LCC) and the SPAD meter have been developed to monitor plant N status for fine tuning of N management. They allow farmers to adjust N applications in real time i.e. based on the present plant N status, which is closely related to the indigenous N supply and season-specific climatic conditions that affect crop growth. The SSNM approach aims to apply nutrients at optimal rates and times to achieve high yield and high efficiency of nutrient use by the crop, leading to high cash value of the harvest per unit of fertilizer invested.