Maximizing nutrient uptake in hybrid maize via advanced nitrogen management techniques

Introduction

Maize, globally renowned for adaptability, ranks third in India after rice and wheat. Its high production potential demands balanced nutrients. Timely nitrogen (N) application is crucial to prevent losses and maximize efficiency, synchronizing with peak crop demand for enhanced uptake and reduced environmental impact. According to Furuya (1987) [5] , farmers traditionally use leaf color as a visual cue for N application, often resulting in excessive use and poor recovery efficiency. Utilizing leaf spectral features helps determine need-based N treatments. Precision tools, such as the Leaf Colour Chart (LCC) and SPAD chlorophyll meter, have become essential in nitrogen management for maize. Originally designed for rice, the LCC can also be applied to maize, as supported by research (Balasubramanian et al., 1999 and 2000; Witt et al., 2005) [1, 2,. 11] . The LCC aids in need-based N application by considering crop demand and soil N availability. The SPAD meter, according to Mohanty et al. (2016) [7] , assesses crop N status and optimizes application timing. Recent advancements in optical sensor technology, like the Green Seeker, use visible and near-infrared (NIR) radiation to detect N stress and measure crop vigor (NDVI). Higher NDVI values indicate better plant health and potential yield, as noted by Harrell et al. (2011) [6] . This experiment aims to identify the optimal LCC, SPAD, and NDVI thresholds for N application in hybrid maize.

Materials and Methods

A field trial was conducted at the Agricultural Research Station in Rajendranagar, Hyderabad (17.19'N, 78.23'E) during the Kharif season of 2019-20 to evaluate hybrid maize under different nitrogen management tools. The experiment used a Randomized Complete Block Design with eight treatments and three replications. The soil was sandy loam with a pH of 7.46, low electrical conductivity (0.26 dS/m), 0.45% organic carbon, low nitrogen (238.4 kg/ha), high phosphorus (80.4 kg P2O5/ha), and high potassium (343.1 kg K2O/ha). Hybrid maize DHM-117 was planted at 60 cm x 20 cm spacing. Treatments included recommended nitrogen (RDN) at 200 kg/ha in three splits, LCC thresholds 3 and 4, SPAD thresholds 35 and 40, and Green Seeker NDVI thresholds 0.6 and 0.8, compared to absolute control. Fertilizers included 60 kg P2O5/ha and 50 kg K2O/ha, with 35% RDN as basal. Nitrogen application for remaining treatments was adjusted based on LCC, SPAD, and Green Seeker. Atrazine 50% WP was applied post-sowing, followed by manual weeding. Data on growth, yield, and nutrient uptake were collected and analyzed statistically. ---------0 0 0 T1-RDN (200 kg/ha in three equal splits), T2-LCC based N application at threshold 3, T3-LCC based N application at threshold 4, T4-SPAD based N application at threshold 35, T5-SPAD based N application at threshold 40, T6-Green seeker based N application at NDVI value 0.6, T7-Green seeker based N application at NDVI value 0.8, T8-Absolute control (no nitrogen) only P2O5 and K2O as basal.

Results and Discussion

Nitrogen uptake by plant at 30, 60, 90 DAS and harvest and major nutrient uptake by plants after harvest Table 2 shows nitrogen uptake by plants under precision nitrogen management. Green Seeker-based N application at NDVI 0.8 led to higher uptake, comparable to SPAD-based N at threshold 40 and lower NDVI thresholds, surpassing RDN. Improved scheduling and split application enhanced N uptake, benefiting dry matter production and N accumulation. According to De Datta (1981) [3] , synchronizing applied fertilizer N with crop needs ensures efficient N use. Reena et al.

(2017) [9] noted that higher N uptake is due to better N availability for growth. Similar results were obtained by Singh et al. (2016) [10] . Nutrient uptake after harvest, with Green Seekerbased N at NDVI 0.8 achieving higher N, P, and K uptake (225.5, 35.9, and 333.9 kg/ha, respectively). SPAD-based N at threshold 40 followed, outperforming RDN. Poorer uptake was noted in the absolute control. The synchronicity between N demand and supply boosted P and K uptake (Dobermann et al., 2002) [4] , with nitrogen's quick availability aiding P and K absorption, consistent with Ravi et al. (2007) [8] .

References

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