Effect of urea and nano urea on the content and uptake of nutrients by wheat (Triticum aestivum L.) under calcareous soil

Introduction

Wheat (Triticum aestivum L.) a vital cereal crop is classified under the family "Poaceae" and the genus" Triticum." It is a self-fertilizing plant with a chromosome complement of (2n = 42). Often referred to as the monarch of cereal crops approximately 95% of wheat cultivated worldwide is hexa ploid bread wheat (Triticum aestivum L.) also known as common bread wheat, while the remaining 5% consists of tetra ploid durum wheat. Wheat constitutes 30% of the global cereal food production and serves as a fundamental food source for nearly 10 billion individuals across 43 countries. It supplies roughly 20% of the world's dietary calories and 55% of all carbohydrates. Nano fertilizers are fertilizers that contain nutrients in nano-porous materials (measuring 10 -9 m) that are either supplied in particle or emulsion forms with nano dimensions or covered with a thin polymer coating. These fertilizers have the ability to distribute nutrients within plants in a targeted manner, reducing waste and delaying chemical changes. While synthetic fertilizers usually release their nutrients in 4-10 days, nano fertilizers can release their nutrients over a period of 40-50 days. Because of leaching and volatilization, a synthetic urea fertilizer can rapidly lose more than 70% of its nitrogen content after application, leaving less than 20% that is easily absorbed by plants.

To address the different challenges, nano technology presents a promising a venue. It offers arrange of applications throughout the production, processing, storage, packaging and transport of agricultural goods (Scott and Chen, 2013) [13] . Nano fertilizers play a crucial role in agriculture's production phase potentially bolstering sustainable soil health and crop yield. By using nano fertilizers instead of traditional ones nutrients are delivered to plants in a gradual and controlled way.

Materials and Methods

The experimental soil was clayey in texture and neutral in reaction with pH 7.80, EC 0.41 dS/m, medium in available nitrogen 259 kg/ha, low in available phosphorus 26.00 kg/ha and medium in available potassium 257 kg/ha, low in available sulphur 9.00 mg/kg, medium in iron 7.40 mg/kg, high in manganese 10.5 mg/kg, medium in zinc 0.60 mg/kg, high in copper 1.63 mg/kg. The experiment consists of 11 treatments to evaluate combinations of RDF with nano urea in wheat (var. GJW-463). Eleven treatments comprising of absolute control (T 1 ), 0% RDN + 100% RDF of P & K (T 2 ), 75% RDN through urea + 1 foliar spray of nano urea @ 2 ml/lit at 20 DAS (T 3 ), 75% RDN through urea + 1 foliar spray of nano urea @ 4 ml/lit at 20 DAS (T 4 ), 75% RDN through urea + 1 foliar spray of nano urea @ 6 ml/lit at 20 DAS (T 5 ), 50% RDN through urea + 2 foliar spray of nano urea @ 2 ml/lit at 20 and 40DAS (T 6 ), 50% RDN through urea + 2 foliar spray of nano urea @ 4 ml/lit at 20 and 40 DAS (T 7 ), 50% RDN through urea + 2 foliar spray of nano urea @ 6 ml/lit at 20 and 40 DAS (T 8 ), 4 foliar spray of nano urea @ 2 ml/lit at 20, 40, 50 and 60 DAS (T 9 ), 75% RDN through urea + 1 foliar spray of 2% urea at 20 DAS (T 10 ), 50% RDN through urea + 2 foliar spray of 2% urea at 20 and 40 DAS (T 11 ) in randomized block design with three replications. Standard agronomic practices were adopted for raising healthy crop. In this study Nitrogen content (%) in grain and straw was determined by Micro Kjeldahl method (A.O.A.C., 1965), Phosphorus content (%) was determined by the vanado-molybdo phosphoric acid method (Jackson, 1974) [3] , Potassium content (%) of di-acid digested plant sample was determined using flame photometer (Jackson, 1974) [3] . Sulphur content (%) of diacid digested plant sample was determined using turbidimetry (Williams and Steinberg 1959) [19] . Micronutrient content of diacid digested plant sample was determined using Atomic Absorption Spectro photometry (Lindsay and Norwell 1978) [6] . Nutrient uptake by grain and straw were obtained by multiplication of nutrient content with grain and straw yield, respectively and divided by 100.

Results and Discussion

Effect of different treatments of urea and nano urea on the nutrient content of wheat

The data presented in Table-1 revealed that the application of 75% RDN through urea + 1 foliar spray of nano urea @ 6 ml/lit at 20 DAS (T 5 ) recorded significantly highest N content in straw 0.760%, 0.779% and 0.770% during 2023.24, 2024-25 and pooled results at 60 DAS, 0.570%, 0.583% and 0.577% during 2023-24, 2024-25 and pooled result at 90 DAS, 0.500%, 0.496% and 0.498% during 2023-24, 2024-25 and pooled results, respectively. N content in grain 2.04%, 2.10% and 2.07% during 2023-24, 2024-25 and pooled result. It was remains at par with T 3 , T 4 , T 8 and T 10 during 2023-24 at 60 DAS, T 3 , T 4 and T 10 during 2024-25 at 60 DAS as well as T 3 and T 4 during pooled result at 60 DAS. It also remains at par with T 4 during both year as well as pooled results at 90 DAS and at harvest. Treatment (T 4 ) also remains at par with T 5 during both the year. The significantly highest K content (%) in grain 0.410%, 0.421% and 0.415% was found with treatment 75% RDN through urea + 1 foliar spray of nano urea @ 6 ml/lit at 20 DAS (T 5 ), followed by T 4 during both year (Table 3). While other nutrient content like P content in grain and straw, K content in straw as well as S, Fe, Mn, Zn and Cu content in grain and straw were remain unaffected (Table 2, 3, 4, 5 and6).

Effect of different treatments of urea and nano urea on the nutrient uptake of wheat Data presented in Table 7 and 9 and10). The significant improvement in nutrient content and uptake in wheat under combined application of conventional urea and nano urea can be attributed to enhanced nitrogen use efficiency (NUE) and improved nutrient delivery mechanisms. Nano urea, due to its extremely small particle size and high surface area, enables efficient foliar absorption through stomatal openings and cuticular pathways, resulting in rapid entry and effective translocation of nitrogen within plant tissues. In contrast to conventional urea, which suffers substantial nitrogen losses through volatilization, leaching, and denitrification, nano urea ensures a slow and controlled release of nitrogen. This controlled availability synchronizes better with crop demand during critical growth stages, particularly during grain development, thereby enhancing nitrogen assimilation and its subsequent translocation from source (leaves) to sink (grains). Moreover, adequate nitrogen availability promotes chlorophyll synthesis, enzymatic activity, and photosynthetic efficiency, leading to higher biomass production. Since nutrient uptake is a function of both nutrient concentration and dry matter yield, increased biomass directly contributes to greater uptake of macro-and micronutrients (N, P, K, S, Fe, Zn, Mn, and Cu). Additionally, the integration of reduced basal nitrogen (75% RDN) with foliar nano urea application helps maintain nutrient balance in the soil-plant system, avoiding excessive nitrogen losses while ensuring sufficient availability. This balanced nutrition enhances root activity, nutrient mobility, and overall physiological efficiency of the plant, ultimately resulting in higher nutrient accumulation and uptake. The process by which plants use their roots to take up vital components from the soil or surrounding environment is known as nutrient absorption. In order to support a variety of metabolic processes and maintain plant growth and development, this process entails the active or passive movement of nutrients across root cell membranes, made possible by specific transport proteins. Nutrient uptake is mostly estimated by multiplying the crop's dry matter by the nutrient concentration. Nano urea enhances nitrogen uptake efficiency due to its nanosized particles, which improve foliar absorption and translocation (Subramanian and Sharmila Rahale, 2021) [17] . The superiority of T 5 could be attributed to better nitrogen utilization efficiency and balanced assimilation, whereas T 4 possibly led to saturation of uptake sites or induced metabolic imbalances. The higher nitrogen availability from soil coupled with enhanced foliar absorption of nano urea likely maximized nitrogen efficiency, as also reported by Mahajan et al. (2022) [7] , Patel et al., (2022) [8] , Sharma et al. (2022) [15] , Sharma et al. (2021) [14] in pearl millet, Barkha rani et al. (2019) [11] in sorghum, Hemdan et al. (2020) [2] in lupine plant, Kannoj et al. (2022) [4] in black wheat, Singh et al. (2023) [16] in wheat, Sarwar et al. (2021) [12] in sweet corn and Chavan et al. (2023) [1] in little millet, Ramirez-Rodriguez et al. (2020) [10] in wheat, Rajesh et al. (2021) [9] in sweet corn, Kumar et al. (2023) [5] in wheat, Upadhyay et al. (2023) [18] in maize.

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