Quality and Productivity Improvement of Fodder Maize (Zea mays L.) Through the Foliar Application of Urea with Zinc

India’s agricultural production methods are built on mixed farming, where crops and animals are the two main enterprises. In order to maximize family income, farmers combine these two businesses to diversify their resource utilization. The primary source of work and livelihood for 70% of the people in rural regions, livestock production is the backbone of Indian agriculture, with the national GDP contributing 7%. The production of fodder must blossom, as must its productivity, to fulfill the demands of the perpetually increasing livestock population. However, the area devoted to the production of fodder has decreased because of the expansion of the cultivation of cereals and cash crops. As a result of a decreasing proportion of land accessible for the production of fodder, there is a huge strain from livestock on the total amount of feed and fodder available.
       
Currently, the nation has a net deficit of concentrate feeds of 64%, dry leftover of agricultural products 21.9% and 61.1% green fodder (Chaudhary et al., 2012). Maize is the 3^rd predominant crop grown for human consumption, behind rice and wheat. In addition to being utilized as a food grain crop, it is also grown for vegetables and grazing. Maize, which has a high concentration of water-soluble carbohydrates and a low protein content, is regarded as the ideal crop to create silage due to its poor buffering capacity and ease of ensiling. Considering that maize is a grain, nutrition management is crucial, particularly in India’s northwest and in the Indian great plains, where an intense cereal-cereal cropping system is predominant. Wider adoption of high-quality and high-protein maize will occur if hybrids are created that maintain improved nutritional quality while performing agronomically similarly to regular hybrids (Subba et al., 2022).
       
Since fodder maize is toxic-free, it may be given to animals without risk at any stage of crop development (Kumar et al., 2016). Reducing the accompanying loss in production has required the creation of quality protein maize (QPM) hybrids that are resistant to terminal stress conditions (Teja et al., 2024). Crop plants need nitrogen as one of the essential nutrients for growth and development. When used correctly, nitrogen is crucial for developing protoplast and protein, which promote cell division and launch cognitive processes. The addition of nitrogen not only increases maize’s fodder output but also enhances other aspects of its quality, particularly its protein content (Haque et al., 2001). According to reports, adding nitrogen to maize increases the nutritional value of the feed by raising the amount of crude protein and lowering the amount of fiber. The development of management strategies for greater fodder output per unit area of this crop might benefit from research on nitrogen management. On the other hand, agricultural plants require zinc to grow and develop properly. It is an essential source of crop nutrition since in plants need it to carry out different enzymatic reactions, oxidation reactions and metabolic processes. In addition, numerous enzymes are required for the metabolism of nitrogen, the transmission the energy and creation of proteins depends on zinc (Hafeez et al., 2013).
       
Therefore, the current study was conducted to examine the combined effect of various levels of urea and zinc and to determine their dose suitable for increasing the yield and quality of maize. A research study in the field was accomplished at Agricultural Research Farm, Department of Agronomy, School of Agriculture, Lovely Professional University, Phagwara, Punjab during the Rabi season in 2022-23 to study the effect of urea and zinc as a foliar application on quality parameters of fodder maize (Zea mays L.). The main aim of this experimental trial was to study the effect of urea and zinc as foliar applications on the quality of fodder maize crops.

The experimental work was directed at Agricultural Research Farm, Department of Agronomy, School of Agriculture, Lovely Professional University, Phagwara, Punjab during Rabi season in 2022-23, which lies in the zone of Northern Plain between 75.69^oE and 31.24^oN. The field’s climate comes under the Agro-ecological sub-region (Northern Plain, hot sub-humid eco region, Punjab) and agro-climatic zone (Trans Gangetic Plain region). The area comes under the semi-arid zone with an annual rainfall of 600 mm. The soil of the empirical field had pH 8.4, electrical conductivity 0.410 mmhos cm-1, 0.45% organic carbon and 0.776% organic matter. Available nitrogen, phosphorus and potassium were 322.56, 25.10 and 70.56 kg ha^-1. The empirical design was conducted in randomize block design (RBD) with three replications and nine treatments (T₁: Absolute control; T₂: RDF + 0.25% Zinc; T₃: RDF + 0.50% Zinc; T₄: RDF + 1% Urea; T₅: RDF + 1% Urea + 0.25% Zinc; T₆: RDF + 1% Urea + 0.50% Zinc; T₇: RDF + 2% Urea; T₈: RDF + 2% Urea + 0.25% Zinc; T₉: RDF + 2% Urea + 0.50% Zinc). The recommended dose of fertilizers (RDF) were applied @ 60 kg nitrogen ha^-1, 40 kg Phosphorus ha^-1 and 20 kg Potassium ha^-1 through Urea, Di-ammonium phosphate (DAP) and Muriate of potash (MOP). Zinc was supplied through the zinc oxide suspension concentrate (39.5% Zn). The half dose of nitrogen and full dose of phosphorus and potassium were applied as basal dose and the other half of nitrogen was applied as two split doses at 25 days after sowing (DAS) and 45 DAS in granular form. Percentage of zinc and urea were applied as two foliar sprays at 30 DAS and 50 DAS. In this case, nitrogen was supplied by urea as per the recommendation of fodder maize and also the percentage of urea was applied by mixing with water. That means nitrogen in the form of urea was applied in both solid and liquid form. We used the hybrid fodder maize seed which belongs to the variety of Laxmi® 207 with a seed rate of 40 kg/ha.
       
The samples of green fodder were collected at 45 DAS and 65 DAS. After collection, the fresh weight was taken and kept in a hot air oven at 65±5^oC for drying. After that, the fully dried samples were collected, weighed them and calculated the dry fodder yield. The dried samples of plants were grounded through the mixture grinder machine for quality analysis. The dusted materials were chemically analyzed for total ash (AOAC, 2005, method 942.05), ether extract (AOAC, 2005, method 920.39), crude fibre and Kjeldahl nitrogen (AOAC, 2005, method 984.13). The crude protein of the plant was calculated from the nitrogen concentration by multiplying 6.25. The procedure of Van Soest​ et al. (1991) was followed for the determination of neutral detergent fibre (NDF). AOAC, 2005, method 973.18 was followed for the determination of acid detergent fibre (ADF). Total carbohydrate was estimated as the sum of total ash, ether extract and crude fibre subtracted from 100. Hemicellulose was calculated by the subtraction of ADF% from NDF%. Acid detergent lignin (ADL) was estimated by the following Klason method. Cellulose was calculated by the subtraction of ADL% from ADF% in the plant. Other quality parameters viz. dry matter intake (DMI), digestible crude protein (DCP), net energy for lactation (NEL), total digestible nutrients (TDN) and dry matter digestibility (DMD)were calculated by the following equations:
DMI (%)= 120/NDF% (Horrocks and Vallentine 1999).
DCP (%) = (0.929 x CP%) - 3.52  (Demarquilly and Weiss 1970).
NEL (Mcal/kg) = [1.044 - (0.0119 x  ADF%)] x 2.205 (Horrocks and Vallentine 1999).
TDN (%) = (-1.291 x ADF%) + 101.35 (Horrocks and Vallentine, 1999).
DMD (%) = 88.9 - (0.779 x ADF%) (Horrocks and Vallentine 1999).
4.184 is used as a conversion factor of Mcal/kg to MJ/kg in the case of NEL.
       
The analysis of variance (ANOVA) technique was used for analyzing the experimental data for randomized block design (RBD). Least significant differences (LSD) and Duncan test were used for various parameters to see the significant differences among treatment mean at 0.05 probability level by using SPSS software.

Crude protein, ether extract and total ash yield
 
Different treatments significantly affected CP, EE and TA yield (Table 1). The foliar spray of 2 % urea and 0.50 % zinc along with RDF showed significantly higher CP, EE and TA yield than the absolute control and other treatments during both observable days (45 DAS and 65 DAS). The result showed that the application of the proper amount of fertilizer along with 2% urea and 0.5% zinc as foliar application TA content increases as the crop slowly matures due to less dilution of minerals and a large number of minerals were accumulated which increased the digestibility of dry matter (Kar et al., 2016). An adequate supply of macronutrients, as well as micronutrients during the crop-growing period, increased the CP, TA and EE yield. Crude fat/ ether extract was additionally influenced by the crop’s harvesting phase since it decreases with maturity (Ayub et al., 2001). The result showed that the application of the proper amount of fertilizer along with 2% urea and 0.5% zinc as foliar application CP content increases due to more uptake, retained and utilized nitrogen and zinc. Nitrogen metabolism is also influenced by the zinc activity for this reason nitrogen uptake and contents of protein also increased (Cakmak, 2002; Alloway, 2004). Many researchers showed that protein content also increased by the application of nitrogen and zinc (Asif et al., 2013).


 
Nutritional values/energy
 
After determining and calculating all quality parameters, we have shown that digestible crude protein (DCP), dry matter intake (DMI), dry matter digestibility (DMD), total digestible nutrients (TDN) and net energy for lactation (NEL) contents were significantly influenced by the nutrients (Table 2). The higher value of DCP, DMI, DMD, TDN and NEL was shown by the application of T₉ treatment as compared to the value of absolute control and other treatment conditions. NDF is inversely correlated with DMI and TDN. Hence, the reduction of NDF led to the improvement of DMI and TDN. On the other hand, ADF is inversely correlated with DMD and NEL. Hence, the reduction of ADF led to the improvement of DMD and NEL. Salama and Zeid (2016) similarly observed that these fodder quality indicators had better values as a result of reduced fiber percentages.


 
Fibre fractions
 
The nutrient management strategies significantly caused the variations in the case of the fractions of fibre contents. The higher values of ADF, NDF, ADL, Cellulose and CF were observed by the determination in the case of absolute control condition as compared to other treatment conditions (Table 3). But, Hemicellulose content was higher in case of T₇, T₈, T₉ as compared to the absolute control condition due to the application of zinc (Fig 1). Since fractions of fibre (ADF, NDF, ADL, Cellulose and CF) contents are inversely proportional to CP, EEand TA yield, for lowering fibre fractions it may be one reason (Tondey et al., 2021). The amount of fibre components is substantially decreased by the greater intake of important nutrients, especially nitrogen (Yadav et al., 2007). Plant’s structural components, the ADF and NDF, which are made of cellulose, hemicellulose and lignin, play a crucial role in forage digestibility. Less ADF and NDF values indicated that fodder is good in quality. The data of present study reported that reduction of the value of ADF, NDF, ADL and CF contents of fodder maize was statistically significant. Islam et al., (2008) reported that ADF content was increased by the increase of nitrogen content.




 
Carbohydrates fractions
 
In pre sent study, it was noticed that the total carbohydrate content is significantly influenced by the application of nitrogen and zinc on forage maize. Carbohydrates are a structural component of plants and is composed of structural carbohydrates and non-structural carbohydrates. The main energy source for your livestock is carbohydrates. The data of the present study reported that higher carbohydrates were shown in T₇ at 45 DAS (Fig 2). However, the higher value of total carbohydrates was shown in T₇, T₈ and T₉ at 65 DAS (Fig 2). In comparison of sugarcane (78.55%) and sorghum (73.18%), fodder maize crop has the greatest percentage of carbohydrates (83.30%) when the required quantity of nitrogen is applied, according to a study by Kar et al., (2016). Because maize crops contain the most carbohydrates, they have a high energy value as a reliable fodder crop.


 
Dry fodder yield (DFY)
 
The experiment evaluated different treatments for enhancing dry fodder yield in a crop (Fig 3). The absolute control treatment (T₁) yielded 31.24 q ha^-1. Application of RDF along with various concentrations of zinc (T₂: 0.25% ; T₃: 0.50%) led to enhanced the yields of 61.55 q ha^-1 and 67.74 q ha^-1, respectively. In the addition of 1% urea along with RDF and various concentrations of zinc (T₄: no application of zinc, T₅: 0.25%, T₆: 0.50%) led to increased the yields of 71.07 q ha^-1, 78.64 q ha^-1 and 81.87 q ha^-1, respectively. Similarly, the addition of 2% urea along with RDF and various concentrations of zinc (T₇: no application of zinc, T₈: 0.25%, T9: 0.50%) led to increased the yields of 92.14 q ha^-1, 102.67 q ha^-1 and 118.59 q ha^-1, respectively. The application of urea and zinc on foliar application showed positive effects on green fodder yield, likely due to enhanced nutrient availability and utilization. Notably, the yield improvements varied based on the concentration of urea and zinc. These finding align with previous research highlighting the benefits of nitrogen and zinc application on fodder maize (Jamil et al., 2015; Kumar et al., 2015; Kumar and Bohra, 2014).

From the present study, it is concluded that application of RDF + 2% Urea + 0.50% Zinc improves the fodder quality with crude protein, ether extract, total ash, nutritional values / Energy, carbohydrates fractions, dry fodder yield and by decreasing fibre fractions. Exploring the synergistic effects of combining urea and zinc foliar application. Assessing the impact of urea and zinc foliar application on nutrient use efficiency, particularly nitrogen and zinc uptake and utilization by maize plants. Overall further research and practical application of urea and zinc foliar application in maize production have the potential to enhance crop productivity and quality, improve nutrient management practices and contribute to sustainability of agricultural systems. The results are based on only single season, which must be experimented and repetition through more experiments to obtain valid conclusions and suggest the farmers as the best treatment.

We are highly thankful to Department of Agriculture, Lovely professional University for their cooperation during fieldwork and providing the financial support for the research work.

All authors declare that they have no conflicts of interest.