Strategies for nano-nitrogen use and scheduling to improve use-efficiency and minimize environmental losses in rice-wheat system
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Date
2023-09-20
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CCSHAU, Hisar
Abstract
Nitrogen (N) is the most frequently limiting plant nutrient for crop growth and yield. N fertilization is very important in crop production due to its requirement in high amount by plants for vital function in practically all metabolic activities, and also due to high losses linked with soil-plant system during cropping cycle. It needs to be applied in amounts more than the actual requirement of crop because of its low recovery (30-50%) and its losses in different forms. Therefore, there is an urgent need for improving N use efficiency in agricultural crop production. The existing strategy of fixed-rate, fixed-time (blanket) fertilizer application has proven ineffective for increasing NUE beyond certain limits. The enhanced efficiency fertilizers (EEFs) are being developed on a continual basis to manage the release of N from fertilizers, allowing for increased absorption and utilization by plants, minimizing losses and boosting crop output per unit of fertilizer. Nanofertilizer is one such type of EEFs wherein the nutrients are present in form of nanoparticles (0-100 nm). Nano-N is one of the first nanotechnology based fertilizers which was released by IFFCO (Indian Farmers Fertilizer Cooperative Limited) for agricultural application in India and worldwide. Conceptually, Nano-N can contribute to lessening the environmental N leakages from agricultural areas through reduced leaching and gaseous emissions, both of which contribute to pollution and climate change. Though preliminary studies suggest Nano-N to be very effective as it reduces the losses of N to environment due to its foliar application mode it may not suffice meeting the plant N requirement for protein synthesis if used alone. The precision and use efficiency apart a ottle of Nano-N contains only 20 g of N compared to a ag of prilled urea which has 20 kg N. Keeping these factors in view, a field experiment was initiated in 2020 at ICAR-Central Soil Salinity Research Institute (CSSRI), Karnal, India to develop strategies for Nano-N use and scheduling to improve use-efficiency and minimize environmental losses in rice-wheat system under different combination with prilled urea and precision application techniques. The present experiment was carried out with eight treatments in total: four treatments with replacement of prilled urea by nano-N namely, 33% replacement (R33), 50% replacement (R50), 66% replacement (R66), 100% replacement (R100); two precision-scheduling treatments namely, application of nano-N based on leaf colour chart (LCC) values after basal dose of prilled urea (M-LCC), and application of nano-N based on GreenSeeker (GS) values after basal dose of prilled urea (M-GS) and two control treatments included „100% recommended N through prilled urea‟ (R0; no replacement) and „no N fertilizer at all‟ (No-N) treatment to observe their impact on environmental loses, growth, physiology, yield parameters, and use efficiency of nitrogen under rice-wheat system. The findings showed that the incremental replacement of conventional urea with nano-N resulted in decreased environmental losses of reactive N (N2O and NO3). No decrease in the available soil N pool was noticed upto 33% replacement (1 split dose replacement) of urea with Nano-N. The available N in the soil showed a noticeable decrease when nano-N replaced conventional urea by 50% or more. Therefore, only one split dose replacement of conventional urea with nano-N would avoid N mining over time, unless N addition from any other source is provided. Upto 50% replacement of conventional urea with nano-N, the plant growth parameters were statistically at par with the treatment having 100% conventional urea. The overall assessment suggests that at least one dose of conventional urea (1 out of 3 splits) may be replaced with nano-N without a reduction in yield in basmati rice crop and upto 50% replacement with nano-N in wheat crop without yield loss yet significant gain in use efficiency.