Enhancing Nutrient Use Efficiency through Nano ...

Indian J. Fert., Vol. 11 (12), pp. 46-51 (6 pages)

Enhancing Nutrient Use Efficiency through Nano Technological Interventions J.C. Tarafdar, Indira Rathore and Esther Thomas ICAR-Central Arid Zone, Research Institute, Jodhpur 342 003, Rajasthan

Nanotechnology has the potential to revolutionize the agricultural systems by nanostructure formulation of fertilisers which has mechanisms of targeted delivery or controlled release and conditional release, or could release their active ingredients in responding to environmental triggers and biological demand more precisely. Nano-fertilisers are the nano-particles-based fertilisers, where supply of the nutrients is made precisely for maximum plant growth after stimulating the plant capability, have higher use efficiency, exploiting plant unavailable nutrients in the rhizosphere, and can be delivered on real time basis into the rhizosphere or can be made available to plant by foliar spray. Studies have shown that the use of nanofertiliser causes an increase in nutrients use efficiency, reduces the doses of application dramatically and the frequency of the application along with the cost of the fertiliser. Hence, nanotechnology has a great potential for achieving sustainable agriculture, especially in the developing countries.

INTRODUCTION Nanotechnology is the revolutionary technology where the particle size ranges between 1 and 100 nm at least in one dimension. Due to their high surface area and high reactivity better penetration into the cell these can activate plant and microbial activities resulting in more nutrient use efficiency. Nanoparticles may trigger enzymes and polysaccharide release and act as effective catalysts in plant and microbial metabolism. These are commonly referred to as a generic technology that offers better built, safer, long-testing, costeffective and smart products that will find wide applications in agriculture. Nanotechnologybased products and their applications in agriculture may include nanonutrients, nano pesticides, nanoscale carriers, nanosensors, nano chips, nano cellulose, nano barcode, quantum dots, etc. Thus, fast growing technology is already having a significant commercial impact, which will certainly increase geometrically in the future. Fertilisers have an axial role in enhancing the food production in developing countries especially after the introduction of high yielding and fertiliser responsive crop varieties. In spite of this, it is known that yields of many crops have begun to decline or are facing stagnation as a result of

imbalanced fertilisation and decrease in soil organic matter content. In the past few decades, use efficiencies of N, P, and K fertilisers have remained constant as 30-35%, 15-20% and 35-40%, respectively, leaving a major portion of added fertilisers to accumulate in the soil or enter into aquatic system causing eutrophication (1). In order to address issues of low fertiliser use efficiency, imbalanced fertilisation, multi-nutrient deficiencies and decline of soil organic matter, it is indeed need of the day to evolve the nanobased fertiliser formulations with multiple functions. Realizing that the effective use of modern technology is needed to improve the nutrient use efficiency, nanotechnology has a potential to revolutionize the agricultural systems. Nanofertiliser technology is very innovative and some of the reports and patents strongly suggest that there is a vast scope for the formulation of the nanofertilisers. Significant increase in yields has been observed due to foliar application of nanoparticles as fertiliser (2,3). Preliminary result suggests that balanced fertilisation may be achieved through nanotechnology (4). Currently, the nitrogen use efficiency is low due to the loss of 50-70% of the nitrogen supplied in the form of conventional fertilisers. New nutrient delivery systems that exploit the porous Indian Journal of Fertilisers, December 2015 46

nanoscale parts of plants could reduce nitrogen loss by promoting enhanced plant N uptake. Fertilisers encapsulated in nanoparticles will increase the uptake of nutrients (5). In the next generation of nanofertilisers, the release of the nutrients can be triggered by an environmental condition or simply released at desired specific time. The present paper discusses the nutrient use efficiency enhancement through nanotechnological interventions. Nanonutrient Production An essential feature for the nanoparticle synthesis is the preparation of the particles of specific size and shape. For agricultural use it is preferable to have particle having size less than 20 nm, polydispersity index less than 1, zeta potential value apart from +30mV and -30mV and mostly cubed shaped particle to enter through the plant pores (6). Nanoparticles can be synthesized by physical, chemical, physicochemical (aerosol) and biological technique. Grinding, thermal evaporation, sputtering and Pulse Laser Deposition technique are important physical methods. Chemical synthesis, a very powerful way of synthesis, includes the technique like sol gel, co-precipitation, microwave synthesis, micro- encapsulation, hydro thermal methods, polyvinyl pyrolidene (PVP) method and sonochemistry. The aerosol method includes

nutrients are expensive and used in large quantities at national level, any increase in use efficiency will lead to a substantial cut in nutrient requirement and huge economic benefit at national level.

Figure 1. Biosynthesis of protein encapsulated nano-particles

furnace method, flame method, electro chemistry, CVD (chemical vapour deposition) method PVD (physical vapour deposition) method. Biological methods offer a safe and ecologically-sound approach for nanoparticle fabrication as an alternative for physical, chemical, and aerosol methods. The main advantages of biological methods are that the particles are usually encapsulated by mother protein, therefore, unless the protein layers break, the particles are stable; so these can be used for agricultural purposes. Figure 1 clearly demonstrates how protein layer encapsulates each and every nanoparticle. There are various means of biological synthesis of nanoparticles where selected microbial proteins are used to break down salts into their respective nano forms. The biosynthesis of nanoparticles may be possible after using bacteria, fungi, plants, biomolecules, herbs and microwave-assisted biosynthesis. Nutrient Use Efficiency Improving nutrient use efficiency (NUE) is a worthy goal and fundamental challenge faced by the fertiliser industry and agriculture in general. The rise in fertiliser prices, huge government

subsidy and stagnant crop prices, exerted pressure on the personnel concerned to improve NUE. Most agricultural soils in India have low native fertility and successful and sustained crop production on these soils requires regular nutrient inputs. The quantum of nutrients available for recycling via crop residues and animal manures is greatly inadequate to compensate for the amounts removed in crop production. Thus, mineral fertilisers have come to play a key role in areas with low fertility soils, where increased agricultural production is required to meet growing food demand. Chemical fertilisers as source of plant nutrients are considered as the major contributor to enhance crop production and maintaining soil productivity. Though the consumption of chemical fertilisers in India increased steadily over the years, the use efficiency of nutrients applied as fertilisers continues to remain awfully low in specially P (15-20%) and micronutrients (25%) like zinc, iron, copper. When nutrient inputs are used inefficiently then both cost of cultivation and threat of biosphere pollution increase. Thus, the economy and ecology highlights the compulsive need for more efficient use of nutrients in crop production. Since, fertiliser

Nutrient use efficiency may be defined as yield per unit input. In agriculture this is usually related to the input of fertiliser, whereas in scientific literature the NUE is often expressed as fresh weight or product yield per content of nutrient. Improvement of NUE is an essential pre-requisite for expansion of crop production in marginal lands with low nutrient availability. NUE depends not only on the ability of crop plants to efficiently take up the nutrients from the soil, but also on transport, storage, mobilization, uses within the plant, and even on the environment. Two major approaches may be taken to understand NUE. Firstly, the response of plants to nutrient deficiency stress can be explored to identify processes affected by such stress and those that may serve to sustain growth at low nutrient input. A second approach makes use of natural or induced genetic variation. Tremendous improvement of NUE was observed in plants after application of nanoparticles. In general, 3-4 times improvement in use efficiency was noticed of P, Zn, Fe and Mg nanoparticles. The effect on P use efficiency is presented as Figure 2. The results clearly showed that use efficiency of P can be improved many folds when P is applied as nanoform. Application of Nano-P also helps in improving the organic acid concentration in the rhizosphere and P uptake by the plants (Table 1). The use efficiency of the micronutrients like zinc and iron has improved many-fold with the application as nano form (Table 2). Response of nano-particles on root

Indian Journal of Fertilisers, December 2015 47

growth and development was studied under arid different crops. The results showed effect of nano-P on root growth (improvement of root length up to 32%, root area 20.6%, biomass 10.2%, root nodulation 67.7%). Similar results were observed with the application of nano Zn, Fe, Mg where increase in root length varied between 2-7%, root area 4-18% and dry biomass 1-5% while nodulation increased between 3-47%. The Mg nanoparticle application also showed 19-21% more light absorption on mungbean and wheat. Figure 2. Comparison of P use efficiency of single super phosphate (SSP), soluble P (KH2PO4) and Nano-P Table 1. Per cent improvement in organic acid concentration* in the rhizosphere and P uptake by the plants Crops

Organic acid concentration

P uptake

Clusterbean Moth bean

23.2 19.5

27.2 23.5

Mung bean Pearl millet

20.7 15.5

22.7 17.3

*Nano-P application @ 640 mg ha-1 Table 2. Per cent use efficiency of Zn and Fe (average of four crops) Micronutrient* Mega particle Nanoparticle as fertiliser