Effects of Nitrogen Fertilizer Rate with Urease and Nitrification Inhibitors on Certain Morphological Traits and Quality of Sugarcane (Saccharum officinarum L.)

Abstract

In this study, we investigated the effects of the N fertilizer rates (commonly applied by farmers compared to rate based on soil analysis) with an appropriate N fertilizer rate associated with urease inhibitors (UIs), nitrification inhibitors (NIs) and their combinations (UINIs) on sugarcane (Saccharum officinarum L.) growth, morphological traits, and quality. The treatments consisted of 2 UIs (N-(n-butyl) thiophosphoric triamide (NBPT) and garlic (Allium sativum L.)) and 3 NIs (dimethylpyrazole phosphate (DMPP), ground neem seed (Azadirachta indica A. Juss. var. siamensis Valeton) and praxelis (Praxelis clematidea (Griseb.) R.M. King & H. Rob)). The results showed that increasing the N fertilizer rate encouraged sugarcane growth by up to 4.5% and increased N content by 16.2% in the cane yield. Adding inhibitors produced positive responses in plant growth and yield, possibly due to prolonging N fertilizer in the soil and extending the supply of N to the plant. Compared to biological inhibitors, the synthetic inhibitors resulted in longer stalk lengths but lower stalk diameters. The inhibitor treatments significantly enhanced the aboveground biomass and N content in plants by up to 41.5 and 41.9%, respectively, compared to only fertilizer. The inhibitor treatments in commercial cane sugar (CCS) increased by up to 13.6%. However, decreasing the N fertilizer rate with addition of inhibitors assisted in keeping mineral N in the soil, which further enhanced N uptake and led to improved plant growth and yield. Added DMPP showed the potential to slow down N loss from soil, which enhanced rapid growth and resulted in higher aboveground biomass.