Abstract
Sugarcane mono-sequencing is one of the prominent systems of Uttar Pradesh but wide variations in cane yields are the main cause of concern across the cane producing zones. Hence, this study was undertaken to assess the causes of yield variations and impact of long-term sugarcane mono-sequencing on nutrient index (NI), microbial activity and soil quality. About 131, 198 and 122 composite soil samples (0-20 cm depth) were taken from cane producing Eastern zone (EZ), Central zone (CZ) and Western zone (WZ) of Uttar Pradesh, respectively and analyzed. Long-term sugarcane mono-sequencing depleted soil organic carbon (SOC), available nitrogen (Na), potassium (Ka), sulphur (Sa) and Zn as 48.9, 98.2, 39.0, 43.3 and 26.4% soil samples falls in low categories, respectively. However, soil degradation aggregated more in EZ soils due to acute deficiency of macro-nutrients as well as high content of Cu, Fe and Mn in low-lying areas. Total microbial counts (TCB, TCA, AZO), microbial biomass of carbon and nitrogen, basal soil respiration, acid and alkaline phosphatase were highest in WZ but Na, Pa, Ka, Sa, FDA, β-glucosidase and urease activity was greater in CZ soils. As a result, NI was more in CZ (2.19) followed EZ (1.98) and WZ (1.97), but soil quality index (SQI) was found in the order of CZ (0.795) >WZ (0.785) > EZ (0.708). The sensitivity index was lowest in CZ soils (1.420) followed by WZ (1.810) and EZ (1.915) indicated that WZ and EZ soils are more preferable and sensitive to perturbations and management practices. Na was the most vital soil quality indicator (contributed 25.7, 26.9 and 23.7% towards SQI development in EZ, CZ and WZ, respectively) followed by SOC, AZO and Sa. Under nutrient deficient zone, targeted yield equations may be useful for improving NI, SQI and sensitivity index to achieve sustainable cane productivity and soil quality.
Key words: Sugarcane monocropping, Nutrient index, Microbial activity, Minimum data set, Soil quality index.