Need based nitrogen management using the chlorophyll meter and leaf colour chart in rice and wheat in South Asia: a review

• Published in: Nutrient cycling in agroecosystems Vol. 88; no. 3; pp. 361 - 380
• Main Authors: Varinderpal-Singh, Bijay-Singh, Yadvinder-Singh, Thind, H. S, Gupta, R. K
• Format: Journal Article
• Language: English
• Published: Dordrecht Dordrecht : Springer Netherlands 01-12-2010; Springer Netherlands; Springer Nature B.V
• Subjects: Agricultural economics; Agriculture; application timing; Biomedical and Life Sciences; Chlorophyll; Color; cooperatives; cost effectiveness; Crop production; Crops; Diagnostic software; Diagnostic systems; Farmers; fertilizer rates; fertilizer requirements; fertilizer use reduction; Fertilizers; Leaves; Life Sciences; Nitrogen; nitrogen fertilizers; nutrient availability; nutrient requirements; nutrient use efficiency; Oryza; Oryza sativa; Plant growth; plant nutrition; Research Article; Rice; top dressings; Triticum aestivum; Wheat; South Asia; Asia; SPAD meter; Leaf colour chart; N use efficiency; Crop N demand; Wheat; Rice
• ISSN: 1385-1314; 1573-0867
• DOI: 10.1007/s10705-010-9363-7

Fertilizer nitrogen (N) is one of the major inputs in rice-wheat production systems in South Asia. As fertilizer N has generally been managed following blanket recommendations consisting of two or three split applications of preset rates of the total amount of N, improvement in N use efficiency could not be achieved beyond a limit. Feeding crop N needs is the most appropriate fertilizer N management strategy to further improve N use efficiency. Since plant growth reflects the total N supply from all sources, plant N status at any given time should be a better indicator of the N availability. The chlorophyll meter and leaf colour chart have emerged as diagnostic tools which can indirectly estimate crop N status of the growing crops and help define time and quantity of in-season fertilizer N top dressings in rice and wheat. Supplemental fertilizer N applications are thus synchronized with the N needs of crop. The chlorophyll meter may not be owned by South Asian farmers individually, but it can be made available to farmers through village cooperatives, extension specialists, and crop consultants. Leaf colour chart, a simple and cost-effective device has already penetrated into South Asian farming and increasing numbers of farmers are finding it helpful in efficiently managing N fertilizers. This paper reviews the results of investigations carried out using these diagnostic tools in managing need based N applications in rice and wheat in South Asia.