Effect of Environmentally Benign Nano-nitrogen, Potassium, Zinc on Growth and Yield Enhancement in Triticum aestivum

Wheat is an essential food commodity and is produced on 220 million hectares area across the world. India is the second largest producer of wheat in the world. According to the UN report, India’s population will be around 1.45 billion in 2028. To feed such a huge population, India need to produce 140 metric tonnes of wheat by 2050 which is 46 % higher over the current wheat production level. This increased productivity target will have to fulfill from more limited inputs of fertilizer, irrigation and other inputs because of increasing resource crunch and environmental concerns (Vision 2050, Indian Institute of Wheat and Barley Research, ICAR).

Starting from seed germination till seed maturation wheat plant requires several macronutrients and micronutrients. Nitrogen is an essential macronutrient which is essential structural component of Rubisco, proteins, nucleic acids, chlorophyll as well as of some hormones (Ata-Ul-Karim et al., 2016). It also helps in grain yield enhancement too (Gul et al., 2019; Kaur and Sharma, 2018). Potassium is also a macronutrient and plays major role in protein synthesis, enzyme activation, carbohydrate metabolism, osmoregulation and yield enhancement (Wang et al., 2013; Sharma et al., 2019). Zinc is a micronutrient required for indole acetic acid (IAA) synthesis, chlorophyll synthesis, carbohydrates formation (Vitosh et al., 1994) and helps in increasing yield and quality (Gowthami and Ananda, 2019; Dore et al., 2018).

The accepted balanced nutrient use ratio of N:K is 4:1 in India but majority of states shows deviation from this ratio (FAI 2000-2007). This ratio for Haryana state is 80:1 and for Punjab state it is 40:1. This shows the highly unbalanced nutrient application status in India (Pathak et al., 2010). Some of adverse effects of excessive use of chemical fertilizers are like hardening of soil, pollution of water and air, release of greenhouse gases which ultimately cause negative impact on environment and human health (Chinnamuthu and Boopathi, 2009).

Nowadays, focus is on the exploration of various applications of the nanotechnology for use in agriculture and other related fields which have brighter prospects ahead. The main advantage of nanofertilizers over the conventional chemical fertilizers is that they show slow-release mechanism after an initial burst while chemical fertilizers are released heavily in the initial stage followed by the release of less and non-uniform quantities in later periods (Fujinuma and Balster, 2007).

In our present work we proposed the foliar application of biosynthesized nitrogen, potassium, zinc oxide nanofertilizer (Nano-N, K, Zn) in wheat and evaluation of their impact on growth, yield and development of wheat for two years. We also tried to find out the optimum concentration of Nano-N, K, Zn at which plants show overall better functioning. In current study we also tried to compare the effects of Nano-N, K, Zn with conventional Bulk/chemical nitrogen, potassium, zinc fertilizer (Bulk-N, K, Zn) and control.

Seeds of wheat variety HD2967 were treated with 0.1% mercuric chloride and then washed with double distilled water. Seeds were sown in pots in November of 2018 and 2019 (Rabi season of 2018-19, 2019-20). Pots used were 15 inches in height. This whole setup was maintained in the Guru Jambheshwar University of Science and Technology Hisar, Haryana. Climate of the area is local steppe type. Average temperature is 25.1°C, annual precipitation is 455.1 mm and soil is sandy loam. No external supplements were provided to the plants. Five different setups were maintained for this study- (1) Control - Plants with no external Nitrogen, Potassium, Zinc supplement (2) Bulk fertilizers - Plants supplemented with bulk/chemical Nitrogen (urea), zinc (zinc nitrate hexahydrate) and Potassium (potassium sulphate)  (3) Nano-1 - plants subjected to 40, 20, 40 ppm Nano-N, K, Zn application respectively (4) Nano-2 - plants subjected to 80, 40, 80 ppm Nano-N, K, Zn application respectively and (5) Nano-3 - plants subjected to 120, 60, 120 ppm Nano-N, K, Zn application respectively. Each setup was maintained in seven pots with four plants in each pot. First foliar spray was done two weeks after germination of seeds, followed by second and third spray at five and eight weeks after the seed germination. Pots of each setup were grown to maturity of wheat and various morphological parameters were studied including shoot length, root length, shoot fresh weight, root fresh weight, shoot dry weight and root dry weight. Yield related parameters like number of spikes, spike length, seeds per spike, 100 grain weight and yield per pot were also recorded after crop harvesting in the month of April 2019 and 2020. The significance of effects of different foliar application of nanofertilizers and their interactions on morphological and yield related parameters was evaluated by analysis of variance (ANOVA) using IBM SPSS Statistics 20 at 5% and 1% probability level and comparison between treatment means was done by Duncan Multiple Range Test.

During two years of experimental period, minimal variations were recorded in the climatic conditions at the trial location. The data obtained in the two year pot trial period were pooled and analyzed for the effect of different foliar treatments and trial year, on the morphological and yield related parameters. Considering the foliar treatments and number of trial years, a 2- way ANOVA was performed which can provide the contribution of the sources individually as well as due to their interactions on the observed variations in the wheat characteristics. The results of two-way analysis of variance (Table 1) showed that individual impact of foliar treatment on wheat characteristics was significant but the year of trial and interaction of foliar treatments and trial years have no significant effect on wheat characteristics. All the studied traits of wheat plants showed significant difference (p<0.01) after foliar treatment with nanofertilizers and bulk fertilizers.



Data presented in Table 2 showed that all three levels of nanofertilizers i.e. nano-1, nano-2, nano-3 treatments resulted in statistically significant increase (p<0.05) in fresh and dry weight of root and fresh weight of shoot when compared to bulk fertilizers and control plants (Fig 1).



When the crop was harvested at maturity and grain yield was recorded, we observed that grain yield showed significant improvement after foliar treatments. In case of nano-2 treatment, yield obtained per pot was 23.87 g which was significantly much higher than nano-1 spray (19.70 g), nano-3 spray (16.94g), bulk fertilizers (7.54g) and control (4.38g). Hundred seed weight, plant height, root length, number of spikes per pot and seeds per spike also showed that foliar treatment with all three levels of nanofertilizers brought significant increase (p<0.05) over both bulk fertilizers and control plants. Average number of spikes per pot was 15.21 under nano-2 spray which was significantly (p<0.05) much greater than nano-1 spray (9.07), nano-3 spray (8.29), bulk fertilizers (6.36) and control (4.21).



Our results are in confirmation with earlier study of nano chitosan NPK fertilizer on wheat (Aziz et al. 2016). Application of nano NPK fertilizer loaded on chitosan resulted in significant increase in all yield variables in comparison to control plants and normal NPK supplied plants. Application of nano NPK resulted in increase in leaf number, leaf area, plant height and stem diameter as compared to control plants in coffee plants (Ha et al., 2019). Our work is in harmony with the findings of Raliya and Tarafdar, 2013 in clusterbean plants where application of nano zinc oxide resulted in increase in shoot length (27.1%), root area (73.5%), root length (66.3%) and plant biomass (27.1%) as compare to control plants. Similar type of results were obtained in pearl millet where application of nano-nitrogen resulted an increase in root area (539%), root length (159%) and total biomass (157%) as compared to the control plants (Thomas et al., 2016). Increase in yield and morphological parameters can be attributed to the essential role played by nitrogen, zinc and potassium in plant growth and development.

We hereby report the first study assessing the combined effect of nano form of three nutrients i.e. nitrogen, potassium and zinc and comparing their effect with their bulk/chemical counterpart along-with control group. This can provide a new insight into using a combination of N, K, Zn for agriculture purposes.

Application of nanofertilizers in wheat plant brought about statistically significant changes in plant development. All the three levels of nanofertilizers application resulted in increase morphological and yield related parameters like increase in plant height, root length, number of spikes, seeds per spike, 100 seed weight and yield etc. Maximum yield was obtained under nano-2 application (23.87 g) while lowest yield was obtained in control group (4.38 g). Most significant results were obtained at nano-2 nanofertilizers application. Thus our work presents a novel approach of using combination of nitrogen, potassium and zinc nanofertilizers for the increment of growth as well as yield of wheat crop.

We acknowledge the support provided to us by Guru Jambheshwar University of Science and Technology, Hisar, Haryana, India.

All authors declare that they have no conflict of interest.