Influence of Organics and Inorganics on Microbial Population and Enzyme Activities in the Rhizosphere of Kiwifruit (Actinidia deliciosa) in Western Himalayas

Abstract

Very limited information is available on how different nutrient management practices influence soil microbial populations and enzyme activities (dehydrogenase and acid phosphatase), especially in the lower Himalayan soils of India. To address this gap, we evaluated three nutrient management approaches—Subhash Palekar’s Natural Farming System (SPNFS), an Organic Farming-Based System (OFBS), and a Chemical Fertilizer- Based System (CFBS) using six-year old kiwifruit (Actinidia deliciosa cv. Allison) as test crop at Dr. Y.S. Parmar University of Horticulture and Forestry, Solan, Himachal Pradesh during 2018–19 and 2019–20. Here three nutrient management systems were tested to assess the changes in soil microbial populations and enzyme activities in the surface (0–15 cm) and sub-surface soil (15-30 cm) soil layers. The SPNFS-based treatment having 30 L Jeevaamrit, 3 kg Ghana Jeevaamrit, and 40 kg FYM per vine, recorded the highest biological activity (pooled analysis) and had bacterial, fungal, and actinomycetes populations of 200 × 105, 25 × 10³, and 22 × 10³ cfu g-¹ soil, respectively. Correspondingly, dehydrogenase activity increased to 35.8 μg TPF g-¹ h-¹ and acid phosphatase activity reached to 119.8 μg PNP g-¹ h-¹. The treatment having 100% recommended dose of N through vermicompost + poultry manure on 50:50 basis + 40 kg FYM resulted in bacterial, fungal and actinomycetes populations to the tune of 166 × 105, 19 × 10³ and 13 × 10³ cfu g-¹ soil, respectively, along with dehydrogenase activity of 34.6 μg TPF g-¹ h-¹ and acid phosphatase activity of 116.5 μg PNP g-¹ h-¹, wherein lowest values were observed in T1 (800 g N, 600 g P2O5, 800 g K2O and 40 kg FYM. There was a strong positive association between acid phosphatase activity and bacterial population (r=0.934**), fungal population (r=0.807**), and actinomycetes population (r=0.786**). Acid phosphatase activity was highly correlated with dehydrogenase activity (r=0.894**), suggesting that improved microbial abundance directly enhances the soil enzymatic activity in the rhizosphere of kiwifruit.