Escalating fertiliser prices and need for judicious use

By Dr Parakrama Waidyanatha

High Energy costs and the prevailing Ukrainian War have led to a huge increase in fertilizer prices, and farmers, especially in the developing countries, find it extremely difficult to provide the required fertiliser to crops. Natural gas prices account for 80% of the variable costs of the production of urea, the most widely used chemical fertiliser. Increased energy prices have been the main cause for increased prices of all key fertilisers as shown in the Table 1.

The Haber Bosch process of conversion of atmospheric nitrogen and hydrogen is the main method of production of ammonia and consequently urea. The process has been optimised over the last century bringing down the energy consumption by 75%. A new type of ruthenium catalyst is reported to reduce the power consumption of ammonia production. Further an electrochemical Haber-Bosch process, yet under research (Fig.1) is reported to produce ammonia with far less energy and carbon dioxide consumption. The Siemen’s Green Ammonia Plant (Fig. 2), also still at a testing stage, uses wind power to convert hydrogen and nitrogen to ammonia. Apart from its huge energy consumption of 1-2% of the global energy, the carbon dioxide released in the Haber Bosch process amounting to 420 million tons annually or 1.4 % of the global carbon dioxide production is a key contributor to global warming. . Hopefully the new technologies should bring down the cost of production in the foreseeable future and also help mitigate global warming.

Russia and Ukraine are two of the key global fertiliser suppliers, and Russia was the world’s largest exporter of urea fertilizer and the second largest exporter of potash (K) and phosphorus (P) fertilizer before the Ukrainian war . Fertiliser prices shot up 60% with the war, and China tightened its control on fertiliser exports, primarily nitrogenous and phosphate fertilizers, effectively shutting off supplies to the global market, and contributing to the surge in prices.

Need for Judicious Fertilizer Use

More than 50% of the N fertilisers is wasted globally . Research reveals that 60-70% of the soil applied fertilisers are lost due to erosion, run off and vaporisation. In our country the losses are probably highest from tea plantations because of the sloping lands. Ironically because chemical fertilisers were relatively cheap and comprised a small fraction of the total cost of production, there was little concern about wastage. For example, a decade ago subsidised paddy fertiliser was only about 2.5% of the cost of production and the cost of application was3%! Given the current exorbitant cost of fertilisers it is critically important to minimise the waste. In other words fertiliser should be applied judiciously. At the Major Economic Forum on Energy and Climate Change(MEF),the US President has announced a ‘Global Fertiliser Challenge’ to raise USD 100 million towards increasing fertiliser use efficiency.

‘Little and often’ is an oft-uttered phrase in judicious fertiliser use. All it means is increase the frequency of application and correspondingly decrease the quantity per application. This should be one fundamental approach now taking into account the relative cost of application and that of the fertiliser. Appropriate placement of fertiliser and forking it into the soil should conserve it substantially. The International Fertiliser Development Corporation (IFDC) pioneered the development of the urea deep placement technology in several countries in Asia and Africa. It involved the application of 1-3 grams of urea briquettes seven centimetres deep below the soil surface, decreasing the urea use by 30% while increasing yields by 15% in rice. Notably, emissions of nitrous oxide, a greenhouse gas 40 times more potent than carbon dioxide, were decreased 60—80% through this technology. In Bangladesh, reports reveal that this technology helped more than 2.5 million farmers, and their earnings increased by $220 per hectare per season, and saving the government $30 million per year on fertilizer subsidy.

Foliar Nutrient application

Records reveal that the practice of foliar application of chemical fertiliser dates back to 1844. It has been a common practice to cure specific nutrient deficiencies but to my knowledge it is not a regular practice for providing the total crop nutrient requirements, the usual one being soil application. Apart from being a crop scientist, the writer is also a tea smallholder with about a hectare of mature tea in plucking. With the banning of chemical fertiliser imports in 2021 and the rapid increase in fertilizer costs, I was at a loss as to how I could fertilise my tea. Being left with only a few bags of chemical fertiliser in my store from the pervious year, I decided to use it judiciously via foliar application. As already mentioned 60-70% of the fertiliser is reported to be lost via soil application. I sprayed over the last year in 10 rounds a 5% fertiliser solution comprising urea, muriate of potash and 1%zincsulphate. As the rockphosphate component in the mixture was insoluble, the solution was filtered and the insoluble rock phosphate was removed. So the mixture did not exceed 5% concentration, the usual maximum nutrient concentration recommended for foliar application. Having applied rock phosphate over the last several years, I was aware that the soil phosphorus levels should be adequate at least for an year. Further, response to phosphate fertiliser application is rarely observed in mature tea but should phosphorus be needed it could be incorporated in the foliar spray. Research reveals that triple superphosphate though soluble is not suitable for foliar application. Further, as shown in Table 2, the leaf penetration of phosphorus is very slow and hence the risk of wash off by rain is high, whereas nitrogen and potassium are quite rapid. Ideally an annual soil application of rock phosphate or a foliar application of a nutrient such as potassium phosphate in good weather appears to be the answer. In fact, potassium phosphate should be able to replace the muriate of potash in the rock phosphate in the conventional tea fertiliser mixtures in foliar fertilizer formulations. Alternatively, a soluble fertiliser such as diammonium phosphate could provide the phosphorus as well as nitrogen.

The foliar application has now proceeded for over an year in my farm and to my satisfaction, I have got a fresh leaf yield of 10,212kg (approximately 20424 kg made tea) comparable to what was obtained in the previous years.

The cost saving with foliar application is substantial being as high as 50% as seen from Table 3, some figures of which are hypothetical. The retail chemical fertiliser price has been considered as Rs 80 a kilo, the price of zinc sulphate as Rs 750 a kilo and the daily labour wage of Rs 1,000 as paid in the plantations.. Of course this is a mere observation and sustainability of the method needs investigation. Will the root systems complain when leaves take over its job? Ideally, the agricultural research institutes should research on the matter for accurate results and sustainability.

Nanofertilisers

Nanofertilisers comprise fertilizers with particle sizes smaller than 100 nanometers, facilitating entry into plants far more effectively than conventional fertilisers.There are reported to increase nutrient use efficiency, reduce wastage and increase crop productivity. They are synthesised from traditional fertiliser compounds by encapsulating fertiliser particles with nanomaterial and are reported to reduce the use of conventional fertiliser by more than 50%. They are also reported to be taken up more effectively during foliar application. As far as the writer is aware the production of nanofertilisers are yet essentially at a research stage but its potential appears enormous.

However, an Indian farmer organization called IFFCO is reported to market a nanourea fertiliser containing 4% urea at a price of Indian Rs. 240 per 500ml bottle supposedly with the same efficacy as a 50-kilo bag of conventional urea but 10% cheaper! Apparently, this was the product that was imported by the government last year following the banning of chemical fertiliser imports and distributed among farmers. However, the farmers complained that the product did not work!