Response of Rabi maize to different irrigation schedules and plant densities for growth and yield characters

Introduction

Maize (Zea mays L.), commonly known as corn, stands as one of the most significant cereal crops globally and is often referred to as the "queen of cereals" due to its exceptional genetic yield potential and wide adaptability. Its unique C4 photosynthetic pathway offers higher photosynthetic efficiency and better water and nitrogen use efficiency than many other cereals (Ranum et al., 2014) [14] . In India, maize has gained increasing importance in recent decades owing to its diverse utility as food, feed, fodder, and a key raw material in industrial processing sectors, including starch, ethanol, and biofuels (Khan et al., 2008) [9] . Rabi maize cultivation, especially under irrigated conditions, has witnessed considerable expansion due to the increasing demand for maize-based products and the availability of improved hybrids that perform well in cooler climates. The success of rabi maize, however, largely depends on the availability and scheduling of irrigation. Unlike kharif maize, which benefits from monsoonal rains, rabi maize is completely dependent on supplementary irrigation. This makes efficient water management a vital aspect for achieving optimal crop growth and yield. Water stress at critical growth stages, particularly during tasseling, silking, and grain filling, can significantly impair physiological processes, kernel development, and final yield (Zaidi et al., 2015) [17] . On the other hand, over-irrigation not only leads to water wastage but can also cause nutrient leaching and increased disease incidence. Therefore, applying the right amount of water at the right time using scientifically developed irrigation schedules becomes essential to optimize both water use and crop performance. Among various irrigation scheduling methods, climatological approaches based on the IW/CPE (Irrigation Water/Cumulative Pan Evaporation) ratio have been found effective in maximizing water-use efficiency and yield (Prihar & Sandhu, 1987) [13] . These methods align irrigation with the actual evapotranspiration needs of the crop and local weather conditions, thus providing a scientific basis for sustainable water management. The present investigation was undertaken to evaluate the response of rabi maize to different irrigation schedules based on IW/CPE ratios with the objective of identifying the most suitable irrigation regime for improving growth attributes, yield components, and overall productivity under late rabi conditions.

Materials and Methods

Observations Recorded

Five plants were tagged in each net plot area for recording observations that did not involve destructive sampling. All the observations were recorded on these plants at 30, 60, 90 DAS and at harvest. Five plants in the second row from the border row in each plot were cut at each time for recording dry matter accumulation.

Pre-Harvest Observations

Post-Harvest Observations

The data recorded on various parameters of crop was subjected to statistical scrutiny by the method of analysis of variance outlined by Panse and Sukhatme (1985). Statistical significance was tested by 'F' value at 5 percent level of probability. Wherever the 'F' value found significant, critical difference (CD) was worked out at 5 percent level of probability.

Results and Discussion

Plant height of maize increased progressively with crop age, significantly influenced by irrigation schedules and planting densities but not by their interaction. Irrigation at 1.2 IW/CPE ratios resulted in the tallest plants, comparable to 1.0 IW/CPE but significantly superior to 0.8 and 0.6 ratios. Higher moisture availability under 1.2 IW/CPE likely enhanced cell elongation and nutrient uptake, aligning with findings by Hussain et al. (2001) [8] and Shivakumar et al. (2011) [16] . Among planting densities, 45 cm × 20 cm (S₃) produced taller plants at harvest, attributed to reduced interplant competition and better resource utilization, consistent with observations by Gozubenli et al. (2003). Dry matter accumulation was highest under 1.2 IW/CPE, significantly surpassing lower irrigation regimes. This trend reflects improved photosynthetic activity and nutrient mobility under adequate moisture, as noted by Reddy et al. (2012) [15] . Similarly, higher planting densities (S₃) yielded greater dry matter due to increased plant numbers per unit area, corroborating Hugar and Halikatti (2015) [7] . CGR peaked at 1.2 IW/CPE during 30-60 DAS, with similar results for 1.0 IW/CPE. Higher planting densities (S₃) also enhanced CGR, likely due to efficient light interception and resource use, as reported by Prasanna et al. (2019) [12] . Irrigation at 1.2 IW/CPE accelerated tasseling and silking (60.3 and 67.5 days, respectively), while 0.6 IW/CPE delayed these stages due to moisture stress, supporting Adamu et al. (2014) [1] . Lower planting densities (S₁) promoted earlier flowering, whereas higher densities (S₃) delayed it, reflecting resource competition (Arvadiya et al., 2012) [2] . For cob length and weight, 1.2 IW/CPE produced the longest and heaviest cobs, statistically similar to 1.0 IW/CPE. Lower densities (S₁) outperformed higher densities (S₃), likely due to reduced competition for nutrients and light (Muniswamy et al., 2007) [10] . For kernel rows and kernels per cob, 1.2 IW/CPE and S₁ spacing maximized these traits, with water stress under 0.6 IW/CPE and highdensity crowding (S₃) negatively impacting kernel development (Bharathi et al., 2007) [3] . Kernel yield was highest under 1.2 IW/CPE (43.8% more than 0.6 IW/CPE) and S₃ density (25.1% higher than S₁), demonstrating the dominance of plant population in yield determination (Borras et al., 2003) [4] . Stover yield followed trends similar to kernel yield, with 1.2 IW/CPE and S₃ yielding the most biomass, as observed by Dutta et al. (2016) [5] . Harvest index remained unaffected by treatments, indicating stable partitioning efficiency.

Conclusion

Irrigation scheduled at a 1.2 IW/CPE ratio resulted in significantly higher growth and yield-attributing parameters in maize, leading to a marked increase in both kernel and stover yields, closely followed by the 1.0 IW/CPE ratio. Higher plant density (1,11,111 plants ha⁻¹) resulted in increased grain and stover yields in maize. The interaction between irrigation scheduling and planting densities did not significantly affect growth parameters, yield attributes, or overall yield.

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