Abstract
A field experiment was conducted at Instructional Farm, College of Agriculture, Junagadh Agricultural University, Junagadh during rabi 2011-12 and 2012-13 to study the real time nitrogen management using leaf colour chart (LCC) in maize (Zea mays L.). Basal dose of 20-50 kg N-P2O5/ ha was applied in all the treatments. Top dressing of 60 or 80 N in form of Urea in two splits at LCC 2, 3, 4 and 5 were compared with fixed time N application [50 kg N/ha at 30 DAS + 30 kg N/ha at 60 days after sowing (DAS)]. Top dressing of 50 kg N/ha + 30 kg N/ha when LCC=4 or LCC=5 significantly improved growth and yield attributes viz., plant height, dry matter accumulation/plant, number of leaves/plant, stem diameter, number of internodes/ plant, leaf area index, cob length, cob girth, number of cobs/plant, number of grains/cob, grain weight/plant and 1000-grain weight along with higher grain and stover yields, grain protein content and economic returns over fixed time application of 50 kg N/ha at 30 DAS + 30 kg N/ha at 60 DAS.
Highlights
Climate change poses serious threats on crop productivity
Correlation between leaf colour chart (LCC) shades, leaf N content and leaf chlorophyll content: A positive and highly significant correlation was found between LCC shades, leaf N content and leaf chlorophyll content (Table 1) which indicates that the LCC could be effectively used to decide the timings of fertilizer N application in standing crop for better synchronization of crop N demand with supply
Effect on growth and yield: Real time application of 80 kg N/ha in two splits at LCC 4, being at par with application of 80 kg N/ha in two splits at LCC 5 and application of 60 kg N/ha in two splits at LCC 4, significantly improved growth attributes like plant height, dry matter accumulation/plant, number of leaves/plant, stem diameter, number of internodes/ plant and leaf area index (LAI) compared to that in fixed time application of 80 kg N/ha (Table 2). This could be attributed to better synchronization of N supply with crop N demand leading to higher N uptake due to real time application of 80 kg N/ha in two splits at LCC 4
Summary
Climate change poses serious threats on crop productivity. Global warming may change growth and development pattern of crop plant, which alters most of the physiological and biochemical processes in plant. Improving fertilizer nitrogen (N)use efficiency in maize is vital to improve and sustain high crop yields but to reduce post field application N losses to the environment. As N requirement of maize plant is not same throughout the growth period it is necessary to adjust fertilizer N application with the timings of plant N requirement to enhance N-use efficiency in maize. The real time N management approach can help increase N use efficiency by matching time of fertilizer application with plant need. The guidelines evolved using LCC helps adopt crop demand-driven N applications and result in high crop productivity and economic returns and reduce N losses to the environment (Ahlawat, 2008; Singh et al, 2002; Singh et al, 2007a and b)
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