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A two-year field experiment on the efficacy of nano diammonium phosphate (DAP) by scientists from the Punjab Agricultural University (PAU) has found a substantial decrease in wheat yields compared to conventional nitrogen fertiliser application.
A decline in plant height and nutrient content in wheat grain and straw, which is essential for protein production, was also observed.
This research revealed that the efficiency of nano DAP is still unclear, similar to concerns raised about the benefits of nano urea.
There was a 16.1 per cent decline in wheat grain yield with two sprays of nano DAP and zero application of recommended dosage of phosphorous (RDP) i.e. traditional DAP — grain yield was 47.61 quintals / hectare (q / ha) in the first treatment compared to 56.75 q / ha in the latter.
Plant height at maturity was 78.63 cm in the first scenario and 79.53 cm in the second.
The government claimed that nano DAP contains 8 per cent of nitrogen and 16 per cent of phosphorus, which can replace a 50 kg bag of traditional DAP.
Incidentally, the yield was almost similar in a scenario where 100 per cent RDP was combined with two sprays of nano DAP.
The research was done by Rajeev Sikka, Jeevanjot Dhaliwal and Mandeep Kaur in 2022 and 2023 on nano DAP released by Coromandel International Ltd, which is one of the three companies which have been granted permission to manufacture nano DAP by the government. The other two are Zuari Farm Hub Limited and Indian Farmers Fertiliser Cooperative Limited (IFFCO).
PAU soil scientists evaluated foliar application of nano DAP and traditional DAP under 12 different scenarios at the research farms of the Department of Soil Science, PAU Ludhiana. Apart from only traditional DAP and only nano DAP treatments, they also examined grain yield and plant height under a combination of both, like 50 per cent or 75 per cent RDP with one or two sprays of nano DAP.
The total plant uptake of nitrogen and phosphorous was 17.58 kg / ha when two sprays of nano DAP were done, compared to 26.60 kg / ha in case of traditional DAP.
DAP is the second-most consumed fertiliser in the country after urea and thus also the second after urea to be promoted by the government in liquid form in order to substantially reduce imports, cut down fertiliser subsidy bill and promote efficient use of chemical fertilisers.
Out of the estimated annual consumption of around 10-12.5 million tonnes of DAP, domestic production is around 4-5 million tonnes and the rest is imported.
In 2021, the government had launched nano urea but there have been continuous questions about its scientifically proven efficiency in being a better substitute for traditional granular urea.
“We observed a reduction in content of nitrogen and phosphorous nutrients with nano DAP. Phosphorous is a nutrient which also helps promote root growth so if roots are not growing well, they won’t be able to mine the nitrogen or other nutrients also. Same was the case with nano urea,” said Sikka, principal soil chemist, department of soil science, PAU.
A similar PAU research on nano urea had found that there was a 21.6 per cent decrease in wheat yield and a 13 per cent decrease in rice yields with its use.
Moreover, there was a drop in yield annually when nano urea was used. “This means that the magnitude of reduction will increase with each year, signifying that the soil is becoming poor,” he said.