Real Time Nitrogen Management of Maize using CCM 200 Plus During Dry Season in Eastern Coastal Plains of India

Globally, maize (Zea mays L.) plays a crucial role in meeting the demands for both food and fodder (Shiferaw et al., 2011) due to its efficient ability to thrive under various biotic and abiotic stresses (Waqas et al., 2021). To ensure food security for the expanding population amidst shifting climate patterns, it is imperative to embrace efficient crop management strategies that boost crop productivity while preserving the environment. The crop productivity is significantly influenced by the timing and application of nutrients, particularly nitrogen (Singh et al., 2016, Yu et al., 2012, Mathukia et al., 2014). Nitrogen, being mobile in soil, is prone to losses, leading to low nitrogen use efficiency, which typically ranges from 30 to 40% (Kumar et al., 2021). To effectively tackle this problem, it is necessary to synchronize nitrogen application with the crop’s nitrogen demand during its growth period and this is possible through the adoption of optical sensors (Boregowda et al., 2019). These sensors utilize leaf colour as an indicator to measure the need for fertilizer nitrogen thus enabling realtime monitoring at regular intervals to optimize nitrogen requirement (Sagar et al., 2024).
       
Research findings suggest that implementing real-time nitrogen management using chlorophyll meters has shown to enhance nitrogen use efficiency in crops (Sagar et al., 2023, Singh et al., 2011). The SPAD 502 chlorophyll meter has been extensively studied and is commonly used to assess crop nitrogen demand (Singh et al., 2016). However, newer chlorophyll meters like the CCM-200 plus by Opti-Sciences Inc. and the atLEAF CHL PLUS by FT Green LLC are gaining traction due to their cost-effectiveness while operating on the same principle as the SPAD 502 developed by Konica Minolta, Inc. Nevertheless, there is a lack of exploration regarding the optimal chlorophyll content index (CCI) threshold observed by CCM-200 plus for scheduling nitrogen topdressing in maize in the Eastern Coastal Plains of India. Hence, this study aims to address this gap in research.
       
During the summer season of 2022-23, a study was carried out at P.G. Research Farm located at 18°48¢18²N and 84°10¢44²E at an elevation of 88 m MSL. The experimental site featured sandy loam soil with a slightly acidic pH. Further, it exhibited lower levels of organic carbon and soil available nitrogen while demonstrating moderate levels of soil available phosphorous and potassium. The experiment was laid out in randomized block design (RBD) and replicated thrice. The “Hybrid Corn Seed 4226” of VNR seed company was sown at a spacing of 60 cm × 25 cm by dibbling the seed. The treatments consisted of absolute N control (No N), Fixed time nitrogen management (FTNM) and six real time nitrogen management (RTNM) treatments having three chlorophyll content indices (CCI) <35, CCI<40, CCI<45 with and without basal N application thus constituting eight treatments. The recommended dose of fertilizers (120:60:60 kg N, P₂O₅, K₂O per ha respectively) was applied through urea, single super phosphate and muriate of potash, respectively. The full dose of phosphorous and potassium fertilizers was applied as a basal irrespective of treatments. In the treatment FTNM, the nitrogen was applied in three splits - 50% basal, 25% at knee-high stage and the remaining 25% at the tasselling stage. The CCM-200 plus chlorophyll meter was used to assess crop N need at 10 days interval starting from 25 DAS till 50% silking from 10 randomly selected plant leaves from each plot and the top dressing was scheduled by application of 30 kg N/ha when the CCI values fall below the threshold values in the treatments (Fig 1). All the parameters recorded were subjected to analysis of variance (ANOVA) using “agricolae” package in R Studio and the results were inferred by standard statistical procedures (Gomez and Gomez, 1984).
 

       
The maize yield showed similar outcomes when nitrogen was applied as topdressing, along with the basal N application, upon reaching CCI thresholds below 40 and 45. These yields were significantly higher than situations without basal nitrogen application at CCI<45, CCI<35 with basal nitrogen and FTNM. Further, the maize yield obtained with CCI<35 with basal N were statistically similar to CCI<40 without basal nitrogen. Conversely, CCI<35 without basal nitrogen produced significantly lower yield than all other treatments except for the absolute control, with the latter yielding significantly less than CCI<35 without basal nitrogen (Fig 2A, Fig 2B and Fig 2C).
 

 

 

       
The VNR 4226 hybrid maize leaf failed to attain the critical value of 45 at any crop growth stage, prompting the application of nitrogen five times, each at 30 kg/ha, enhancing nitrogen availability during various growth stages, resulting in larger cobs and increased grain count per row which are important yield attributing characters and helped the crop to produce higher grain yield (Table 1).
 
 
 
Despite applying 120 kg N/ha in four splits for CCI<40 and 150 kg N/ha in five splits for CCI<45 with basal N application, comparable grain yields suggest improved synchronization between crop nitrogen requirements and four-split N application in the CCI<40 with basal N application. Further, in the CCI<45 treatment with basal N application, the timely and optimal nitrogen availability in the root zone, aligned with peak nitrogen demand, facilitated accelerated removal of soil nitrogen by plant roots due to favourable weather and soil conditions (Singh et al., 2022, Muratore et al., 2021). This resulted in greater accumulation and distribution of photosynthates into the sink, leading to higher N uptake by grain, stover and overall total N uptake (Fig 3).
 

       
The treatment CCI<40 with basal N application demonstrated a statistically similar outcome to the CCI<45 with basal N application, with an additional advantage of saving 30 kg/ha of nitrogen with four splits instead of five. These findings emphasized improved N uptake with minimal losses by aligning crop N uptake with crop N demand (Ladha et al., 2005). The yield under four splits of N application in CCI<40 with basal N application treatment was significantly higher than that of FTNM where N was applied in three splits with 120 kg N/ha. However, the stover and biological yield in these treatments were statistically comparable.
       
The maize yield observed with CCI<35 with basal N was on par with that of CCI<40 without basal N. The nitrogen applied in these two treatments was 90 kg/ha in three splits. Under CCI<40 without basal treatment, the N was applied at 30 kg each at 25, 35 and 45 days after sowing and in CCI<35 with basal N application it was applied at 0, 35 and 45 days after sowing. Under lower level of N rate, skipping N at sowing may not reduce the yield of maize provided, N is applied at 25 days after sowing. This type of response is because upto V6 leaf stage   of maize, the crop consumes only 15% of total nitrogen requirement and after V6 leaf stage, the nitrogen uptake in maize plants was observed to hasten and reaches maximum rate near the silking stage (Jat et al., 2008). However, at higher level of N application (120 kg N/ha), skipping of basal N application (Treatments CCI< 45 without basal N) was found to be disadvantageous (Atnafu et al., 2021 and Balemi et al., 2019). Further, in contrast to general level of applying 50% N as basal (FTNM), application of 25% of recommended N as basal in RTNM could not bring any significant variation of grain, stover and biological yield of maize compared to former treatment (Jat et al., 2008).

The study results suggests that the application of nitrogen fertilizer in four splits at 30 kg/ha in each split as per the guidance of CCI<40 with basal N application, is more appropriate and effective approach than the conventional practice of applying a fixed amount of nitrogen at recommended time intervals in Eastern Coastal Plains of India.

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.