Development of Controlled Release Fertilizer from Double-Boiled Linseed and Mustard Oil-Based Formulations: Surface Morphology, Nutrient Release and Performance of Wheat in Sub-tropical Inceptisol

Abstract

Synchronization of nutrient release from fertilizers and plant nutrient demand could optimize the nutrient use efficiency and crop productivity, particularly for nitrogen (N) and phosphorus (P). N and P both have low nutrient use efficiency, while P has a use efficiency of only 15–20%. Four oil formulations (Oil-1, Oil-2, Oil-3 and Oil-4) were prepared from double-boiled linseed oil (DBLO) and mustard oil (MO) at different mass proportions. Oil formulations were characterized physically by observing surface wrinkle formation using Otsu’s algorithm for binary threshold images. Commercial di-ammonium phosphate (DAP) was coated with prepared oil formulations at 0, 4 and 8% (w/w) and assessed through scanning electron microscopy (SEM), while their nutrient release pattern in soil was studied at different temperatures (20 and 30°C) regimes. Finally net house pot culture experiment was conducted with wheat (Triticum aestivum L.) at different P doses (0, 25 and 50 mg P kg−1 soil) and P sources (uncoated DAP, 4%-Oil-1-DAP, 8%-Oil-1-DAP) with/without Aspergillus awamori. The binary threshold image directed Oil-1 had the lowest surface wrinkle, and SEM images also depicted Oil-1 coated DAP which had smooth surface morphology. Soil incubation data indicated that N is more temperature sensitive than P, and surface coating with oil formulation could extend the period of nutrient release. During soil incubation of oil formulation-coated DAP, N and P release was comparatively slow at higher coating levels. In pot culture experiment, the wheat grain, straw yield, relative chlorophyll, grain protein, soil mineral N, available P, inorganic P and dehydrogenase activity were significantly improved with the increased doses of P and A. awamori inoculation; however, microbial inoculation had non-significant effects on crop and soil parameters. Except post-harvest soil organic P, other parameters were strongly and positively correlated with grain yield of wheat. Coating with hydrophobic oil formulation could extend the nutrient release period with minimal intervention. In terms of crop and soil parameters, both 4%-Oil-1-DAP and 8%-Oil-1-DAP treated pots performed better than the uncoated DAP, but 4%-Oil-1-DAP could be considered as best for annual crops like wheat. For perennial crops, higher coating level could be more beneficial. © The Author(s) under exclusive licence to Sociedad Chilena de la Ciencia del Suelo 2024.