Assessment of enzyme activity at different growth stages in groundnut-wheat cropping sequence under AICRP-LTFE soils

Abstract

The current study was carried out during the Kharif-2023 and Rabi-2023-24 seasons as part of the All India Coordinated Research Project on “Long Term Fertilizer Experiment” at the Instructional Farm, College of Agriculture, Junagadh Agricultural University, Junagadh. This experiment, initiated in 1999, aimed to evaluate the impact of various fertilizer applications, with or without organic manure, on soil enzyme activities at different growth stages in a groundnut-wheat cropping sequence. A total of 12 treatments were evaluated: T1 - 50% NPK, T2 - 100% NPK, T3 - 150% NPK, T4 - 100% NPK + ZnSO₄ at 50 kg ha⁻¹, T5 - NPK as per soil test recommendations, T6 - 100% NP, T7 - 100% N, T8 - 50% NPK + FYM at 10 t ha⁻¹ to groundnut and 100% NPK to wheat, T9 - FYM at 10 t ha⁻¹ for groundnut and 15 t ha⁻¹ for wheat, T10 - 50% NPK + Rhizobium + PSM for groundnut and 100% NPK to wheat, T11 - 100% NPK of the recommended dose for the groundnut-wheat system (P as SSP), and T12 - Control. The findings indicated that the highest dehydrogenase activity was recorded at the flowering stage of groundnut (79.22 μg TPF g⁻¹ soil 24 hr⁻¹) and at the CRI stage in wheat (77.30 μg TPF g⁻¹ soil 24 hr⁻¹) with the treatment of 50% NPK + FYM at 10 t ha⁻¹ to groundnut and 100% NPK to wheat. Additionally, enzyme activities such as acid phosphatase, alkaline phosphatase, β-glucosidase, arylsulfatase, and urease were significantly elevated (39.46, 67.41, 71.95, 24.97 μg PNP g⁻¹ hr⁻¹ and 12.48 µg NH₄-N g⁻¹ hr⁻¹ respectively) at the pod formation stage of groundnut and during flowering in wheat (55.38, 74.75, 36.15, 12.79 μg PNP g⁻¹ hr⁻¹ and 36.98 µg NH₄-N g⁻¹ hr⁻¹ respectively) under the same treatment.