Impact of split application of nitrogen and harvesting schedule on yield and quality of sweet corn (Zea mays var. saccharata L.) under South Saurashtra condition

Introduction

Maize (Zea mays L.) ranks as the third most important cereal crop globally, following rice and wheat, yet it surpasses them in terms of overall production and productivity. Owing to its remarkable genetic yield potential, it is popularly referred to as the "Queen of cereals." Currently, maize is cultivated on about 150 million hectares across nearly 160 countries, covering a wide range of soils, climatic conditions, biodiversity, and management systems (Meena et al., 2019) [26] . In India, maize contributes approximately 9% to the national food basket and around 5% to the world's dietary energy intake as a staple food (Kumar et al., 2012) [12] . The crop's production in the country has grown over twelvefold, from just 1.73 million tonnes in 1950-51 to 21.73 million tonnes by 2010-11, and it now covers 9.22 million hectares with an average productivity of 2.92 t/ha (ASG, 2011). At present, India produces 21.81 million tonnes of maize from 8.69 million hectares, achieving an average yield of 2509 kg/ha. Looking ahead, the demand for maize in India by 2050 is projected to rise sharply to nearly 121 million tonnes (Amarasinghe and Singh, 2008) [5] . Sweet corn is a distinct type of maize grown primarily for table consumption. It is widely recognized as one of the most popular vegetable crops in developed nations such as the USA and countries in Europe. Nearly 40% of the produce is frozen while the remaining portion is processed and canned. In recent years, sweet corn has gained increasing popularity in India, especially in regions where maize is already cultivated. As a high-value crop, its demand is expanding in star hotels for culinary uses, particularly in soup preparation. Farmers located near urban areas can grow sweet corn as a profitable enterprise (Wahiidullah et al., 2022). An additional advantage of sweet corn is that after harvesting the green ears, the crop biomass remains in a succulent stage and serves as nutritious green fodder for livestock. Its short crop duration makes it suitable for integration into diverse cropping systems. Studies have shown that it performs well when intercropped with low-canopy species such as groundnut, green gram, and black gram, as well as with long-duration, high-canopy crops like red gram. The adoption of improved cultivars, proper plant stand and balanced nutrient management significantly influence yield, nutrient uptake and quality traits of maize (Massey and Gaur, 2013) [25] . Efficient fertilizer use is also closely linked with irrigation management (Malam and Solanki, 2022). Given India's favourable climatic conditions across most states, emphasis should be placed on developing and promoting early-maturing varieties, which allow cultivation during kharif, rabi and spring seasons not only for field maize but also for sweet corn. Harvest timing is equally critical; delayed harvest may lead to both quantitative and qualitative yield losses due to physiological and morphological changes in the grain. Maximum grain yield and seed quality are achieved when harvest is carried out soon after physiological maturity. Conversely, leaving grains in the field until moisture content drops below 20% results in weight loss from respiration and increases the risk of mechanical injury during harvest (Lauren et al., 2007) [21] . With these considerations, the present investigation was undertaken to evaluate the performance of sweet corn (Zea mays var. saccharata L.) varieties under different nitrogen split-application schedules and harvesting times at the Instructional Farm, Junagadh Agricultural University (JAU), Junagadh, under the South Saurashtra agroclimatic conditions.

Material and Methods

A field experiment was conducted during the rabi season of 2019-20 at the Instructional Farm, College of Agriculture, Junagadh Agricultural University, Junagadh (Gujarat). The study site is located in the southern part of the state, within the South Saurashtra agro-climatic zone. Geographically, it lies at 20°51′ N latitude and 70°31′ E longitude with an average altitude of 83 meters above mean sea level. The investigation aimed to assess the performance of sweet corn (Zea mays var. saccharata L.) varieties under different nitrogen splitapplication schedules and harvesting times in this region. The experimental soil was medium black in texture, moderately supplied with available nitrogen, phosphorus, potassium and slightly alkaline in reaction, with a pH of 7.7. The net experimental plot measured 4.00 m × 3.60 m and included a total of eighteen treatment combinations. The main plot treatments comprised two sweet corn varieties (V1: Sugar-75 and V2: Sweet-16) along with three nitrogen split application schedules: N1 -50% as basal + 50% at knee-height stage; N2 -25% as basal + 50% at knee-height + 25% at tasseling stage; and N3 -33.3% as basal + 33.3% at knee-height + 33.3% at tasseling stage. The sub-plot treatments included three harvesting times: T1 -20 days after silking, T2 -30 days after silking and T3 -40 days after silking. The study followed a split-plot design with three replications. Both varieties (Sugar-75 and Sweet-16) were cultivated according to the recommended package of practices. No major incidence of insect pests or diseases occurred during the experiment. The recommended fertilizer dose (RDF) for sweet corn was 120:60:00 kg NPK per hectare. A uniform dose of 60 kg P₂O₅ per hectare was applied, while nitrogen was supplied in splits as per the treatments. Urea (46% N) and Di-Ammonium Phosphate (46% P₂O₅) served as the nutrient sources. Nitrogen application was distributed in three phasesbasal, knee-height, and tasseling stage.

Effect of varieties Yield attributes and yield

A noticeable improvement in yield components of Sugar-75 was reflected in higher productivity, particularly in terms of green cob, fresh kernel, and green fodder yields (Table 1). The superior performance of Sugar-75 compared to Sweet-16 can be attributed to better reproductive growth of the crop. Enhanced accumulation of photosynthates, as indicated by greater biomass production, together with efficient uptake of key nutrients such as N, P and K, likely contributed to higher biomass build-up. This, in turn, improved yield attributes, leading to increased green cob and green fodder yields in Sugar-75. The results of the present investigation are in close accordance with the findings of Wang (1995) [57] , O'Neill et al., (2004) [35] , Saleem et al., (2009) [41] , Erdal et al., (2011) [13] , Zamir (2011) [59] , Suthar et al., (2012) [49] , Opsi et al., (2013) [36] , Tadesse et al., (2013) [51] , Barary et al., (2014) [10] , Dhaka et al., (2014) [12] , Modhej et al., (2014) [28] , Om et al., (2014), Nand (2015) [30] , Szymanek et al., (2015) [50] , Panison et al., (2016) [27] , Banotra et al., (2017) [9] , Majid et al., (2017) [23] , Mehta et al., (2017) [36] , Riliang Gu et al., (2017) [38] , Ahmad et al., (2018) [3] , Muhammad et al., (2018) [29] , Nawaz et al., (2019) [31] , Olaiya et al., (2020) [32] and Adhikari et al., (2021) [2] . Quality Quality parameters viz., protein content in kernel, protein yield, sugar content in kernel and sugar yield (Table 2) were significantly affected by sweet corn variety, Sugar-75 recorded numerically higher protein content in kernel than variety Sweet-16. Significantly maximum protein yield was recorded by sweet corn variety Sugar-75. Sweet corn variety Sugar-75 also exhibited numerically higher sugar content in kernels and a significantly greater sugar yield. The enhancement in kernel protein content, protein yield and sugar accumulation in Sugar-75 can be attributed to its higher nitrogen concentration in both kernels and fodder. Since nitrogen is a fundamental component of proteins, enzymes, chlorophyll and plays a central role in carbohydrate and protein metabolism, the superior protein levels in Sugar-75 are most likely due to its greater nitrogen uptake compared with Sweet-16. These findings are complete agreement with the finding of Wang (1995) [57] , Erdal et al., (2011) [13] , Suthar et al., (2012) [49] , Om et al., (2014), Nand (2015) [30] , Szymanek et al., (2015) [50] and Panison et al., (2016) [37] .

Nutrient content and uptake

The data presented in Table 5, Table 9, and Table 11 indicated that variety Sugar-75 consistently recorded numerically higher concentrations of nitrogen, phosphorus and potassium in both kernels and fodder at harvest compared to Sweet-16. Likewise, the uptake of N, P and K by kernels and fodder was significantly greater in Sugar-75. This superiority may be attributed to its enhanced efficiency in nutrient absorption, translocation and utilization. The higher dry matter accumulation in Sugar-75 further supports the hypothesis that adequate metabolites were supplied from shoots to roots, promoting better root development and thereby improving nutrient extraction from the soil. Since nutrients stored in vegetative tissues are largely remobilized towards kernels and fodder during reproductive stages, the observed increase in nutrient concentration in Sugar-75 was expected. Ultimately, the combined effects of greater dry matter accumulation and nutrient content contributed to higher total NPK uptake by kernels and fodder in Sugar-75. The results are in close conformity with the findings of Suthar et al., (2012) [49] , Massey and Gaur (2013) [25] , Dhaka et al., (2014) [12] and Banotra et al., (2017) [9] .

Effect of split application of nitrogen Yield attributes and yield

The findings (Table 1) demonstrated that applying nitrogen in the sequence of 25% as basal, 50% at the knee-height stage and 25% at the tasseling stage significantly enhanced yield attributes, particularly green cob yield, fresh kernel yield and green fodder yield. The improvement in cob and fodder yields under this nitrogen management practice can be attributed to its integrated effect on growth and yield components, underscoring the importance of these traits in determining overall productivity. Split application of nitrogen ensures a steady nutrient supply throughout the crop growth cycle, thereby promoting sustained vegetative development, efficient photosynthesis and effective partitioning of assimilates towards economic sinks. This strategy maintains a balanced source-sink relationship by strengthening both the nutrient-absorbing vegetative organs and the assimilate-storing reproductive structures. As a result, the cumulative effect of these processes led to significant improvements in green cob and fodder yields. The outcomes of the present investigation are in close agreement with the findings of Krishnamoorthy et al., (1974) [19] , Sanjeev et al., (1997) [42] , Fedotkin and Kravtsov (2001) [14] , Gokmen et al., (2001) [15] , Mkhabela et al., (2001) [4] , Waqas (2002), Younas et al., (2002) [58] , Gungula et al., (2003) [16] , Rizwan et al., (2003) [39] , Sharar et al., (2003) [44] , Derby et al., (2004) [11] , Zeidan et al., (2006) [60] , Mollah et al., (2007), Ullah et al., (2007) [53] , Wajid et al., (2007) [56] , Onasanya et al., (2009) [34] , Saleem et al., (2009) [41] , Tadesse et al., (2013) [51] , Hejazi and Soleymani (2014) [17] , Adhikari et al., (2016) [2] , Sharifi and Namvar (2016) [45] , Singh et al., (2016), Anwar et al., (2017) [7] , Majid et al., (2017) [23] , Zerihun and Feyisa Hailu (2017) [61] , Anjum et al., (2018) [6] , Shrestha et al., (2018) [48] , Umesh et al., (2018) [54] , Olaiya et al., (2020) [32] and Adhikari et al., (2021) [1] .

Quality

The enhancement in kernel protein content, sugar content, protein yield, and sugar yield (Table 2) under the nitrogen schedule of 25% as basal, 50% at knee-height stage, and 25% at tasseling stage appears to be associated with higher nitrogen accumulation in the kernels. Nitrogen plays a crucial role in carbohydrate utilization and protein synthesis, as an adequate supply creates favourable conditions for converting carbohydrates stored in vegetative tissues into proteins. Sweet corn receiving this split application of nitrogen exhibited significantly higher protein content and yield compared to other nitrogen application schedules. The results of present research experiment indicated higher protein content in kernel under the influence of time of split application of nitrogen to sweet corn is in close conformity with findings of Jena et al., (2013) [18] , Zerihun and Feyisa Hailu (2017) [61] , and Umesh et al., (2018) [54] .

Nutrient content and uptake

The plant analysis results (Tables 5, 9 and11) demonstrated that applying nitrogen as 25% basal, 50% at the knee-height stage and 25% at tasseling slightly increased the concentrations of N, P and K in both kernels and fodder. Similarly, the uptake of these nutrients was positively influenced under this split application compared to other nitrogen schedules. The observed improvement in nutrient content can be attributed to enhanced soil nutrient availability along with more efficient absorption, translocation and assimilation within the plant. In crop systems, absorbed nutrients are maintained at critical levels to support metabolic processes and the growth of developing organs. Therefore, a well-timed split application of nitrogen ensured a continuous supply of nutrients, maintained cellular nutrient balance, promoted robust vegetative growth, and facilitated efficient translocation toward economic sinks such as green cobs and fodder. The combined effect of improved nutrient accumulation and concentration ultimately resulted in higher NPK uptake under this nitrogen management practice. The results are in close vicinity with the findings of Shivay and Singh (2000) [47] , Shrestha et al., (2018) [48] , Umesh et al., (2018) [54] .

Effect of harvesting schedule Yield attributes and yield

The harvesting schedule of sweet corn significantly influenced yield attributes and overall productivity. Among the different harvesting times, harvesting green cobs 30 days after silking resulted in the highest green cob yield, fresh kernel yield and green fodder yield (Table 1). A delayed harvest allows the crop more time for photosynthesis, leading to greater accumulation of assimilates in the plant system and consequently higher yields of both green cob and fodder. Daynard et al. (1969) also reported a linear relationship between kernel yield and the duration of the grain-filling period. In the present study, green cob and green fodder yields followed a similar trend, reaching their optimum levels when harvested 30 days after silking. Harvesting beyond this stage did not lead to significant yield increases, likely due to the onset of senescence in the lower leaves. The more or less similar results were also reported by Shaheb et al., (2009) [43] , Barary et al., (2014) [10] , Panison et al., (2016) [37] , Riliang et al., (2017) and Sahu (2018) [40] .

Quality

The protein content and yield as well as sugar content and sugar yield plays an important role in deciding the quality of sweet corn. The protein and sugar content in kernel were not affected significantly due to harvesting schedule of sweet corn green cob, but protein yield and sugar yield (Table 2) were recorded significantly maximum when sweet corn green cobs were harvested 30 days after silking. At the early phase of grain formation, there is less protein and sugar in kernel, which enhanced progressively with time. The low protein and sugar content in kernel at early harvesting of sweet corn green cob (20 days after silking) which was increased to the maximum values when sweet corn green cob harvested at 30 days after silking in case of protein content and harvesting of sweet corn green cob 40 days after silking in case of sugar content. Protein yield increased with delay in harvesting of sweet corn green cob and reach to peak when green cob of sweet corn harvested 30 days after silking. Whereas, sugar yield increased with delayed in harvesting. Similar results were also reported by Mahemoud et al., (2007) [22] , Shehzad et al., (2012) [46] , Szymanek et al., (2015) [50] and Panison et al., (2016) [37] .

Nutrient content and uptake

Availability of nutrients in soil solution and absorption capacity of the plant determine the nutrient content in plant. N content (Table 5), phosphorus content (Table 9) and potassium content (Table 11) showed the non-significant effect of harvesting schedule of green cob of sweet corn. Uptake of NPK by plants largely depends on the yield and nutrient content of produce. NPK uptake by kernel and fodder increased with delayed in harvesting and maximum removal of NPK by kernel and fodder were recorded when crop was harvested 30 days after silking. Results of present investigation confirms the findings of Sahu (2018) [40] .

Interaction effect

The interaction effect among sweet corn varieties, nitrogen split application and harvesting schedule was found to be significant for protein yield (Table 3). The highest protein yield of 871 kg ha⁻¹ was recorded for Sugar-75 fertilized with 33.3% N as basal, 33.3% N at knee-height and 33.3% N at tasseling with green cob harvested 30 days after silking (V1N3T2). This was statistically comparable to the treatment combinations V1N2T1, V1N2T3, V1N2T2 and V2N2T2. Similarly, the interaction among varieties, nitrogen application and harvesting schedule was significant for kernel sugar content (Table 4). The maximum sugar content of 4.36% was observed in Sugar-75 fertilized with 25% N as basal, 50% N at knee-height, and 25% N at tasseling, with green cobs harvested 20 days after silking (V1N2T1). This was closely followed by the treatment combination V1N1T3. Interaction effect of sweet corn varieties, split application of nitrogen and harvesting schedules of green cob was found significant for nitrogen uptake by dry kernel (Table 6). Significantly maximum nitrogen removal dry kernel of 34.86 kg ha -1 was recorded when sweet corn variety Sugar-75 (V1) was fertilized with 33.3% N as basal + 33.3% N at knee height stage + 33.3% N at tasseling stage (N3) and green cob of sweet corn harvested 30 days after silking (V1N3T2) and it was found at par with treatment combinations V1N2T1, V1N2T3 and V2N2T2. Interaction effect between sweet corn varieties and harvesting schedule also found significant for nitrogen removal by dry fodder (Table 7). Significantly higher removal of nitrogen by dry fodder of 42.76 kg ha -1 was observed when sweet corn variety Sugar-75 was harvested 40 days after silking and it was found statistically on par with treatment combination V1T1, V1T2, and V2T2. Similarly, interaction effect of sweet corn varieties, split application of nitrogen and harvesting schedules of green cob found significant for nitrogen uptake by dry fodder (Table 8). Significantly higher removal of nitrogen by dry fodder of 49.01 kg ha -1 was observed when sweet corn variety Sugar-75 (V1) was fertilized with 25.0% N as basal + 50.0% N at knee height stage + 25.0% N at tasseling stage (N2) and green cob of sweet corn harvested 30 days after silking (T2) and it was found statistically on same bar with treatment combinations V1N1T1, V1N2T1, V1N2T3, and V1N3T3. Among various split application of nitrogen levels effect on sweet corn produce their significant influence on phosphorus removal by dry kernel of sweet corn. Significantly maximum phosphorus removal by dry kernel (5.27 kg ha -1 ) when sweet corn was fertilized with 25.0% N as basal + 50.0% N at knee height stage + 25.0% N at tasseling stage (N2) and it was closely followed by N3. Interaction effect among sweet corn varieties, split application of nitrogen and harvesting schedules of green cobs found significant for phosphorus uptake by dry kernel (Table 10). Significantly maximum phosphorus uptake of 6.49 kg ha -1 was observed when sweet corn variety Sugar-75 was fertilized with 33.3% N as basal + 33.3% N at knee height stage + 33.3% N at tasseling stage (N3) and harvesting of green cob 30 days after silking and it was found comparable with treatment combinations V1N2T2 and V1N2T3.

Conclusion

Based on the findings of this one-year field study, it can be concluded that under the clayey soils of the South Saurashtra agro-climatic zone, sweet corn variety Sugar-75 achieves higher fresh kernel and green fodder yields when fertilized with nitrogen in three splits-25% as basal, 50% at knee-height, and 25% at tasseling-and harvested 30 days after silking, along with the adoption of other recommended package of practices.

Table 1:

Green cob yield, fresh kernel yield and green fodder yield as influenced by varieties, split application of nitrogen and harvesting schedule

Treatments

Green cob Yield (kg ha -1 ) Fresh kernel yield (kg ha -1 ) Green fodder yield (kg ha -

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