Effect of Integrated Nitrogen Management and Spacing on Soil Fertility Status and Soil Microbial Properties in Kalmegh (Andrographis paniculata)
M. Y. Reddy *
Department of Agronomy, Post Graduate Institute, Dr. PDKV, Akola, Maharashtra, India.
N. K. Patke
AICRP on Medicinal & Aromatic Plants and Betel vine Nagarjun Medicinal Plant Garden, Dr. PDKV, Akola, Maharashtra, India.
Y. A. Reddy
Department of Soil Science, Post Graduate Institute, Dr. PDKV, Akola, Maharashtra, India.
S. P. Wagh
Soil Science Section, Anand Niketan College of Agriculture, Warora, Maharashtra, India.
C. Kavyashree
Department of Agronomy, University of Agricultural Sciences, Raichur, Karnataka, India.
G. C. Sravya
Department of Agronomy, School of Agricultural Sciences, Karunya Institute of Technology and Sciences, Coimbatore, Tamil Nadu, India.
K. S. Reddy
Department of Agronomy, Sri Krishnadevaraya College of Agricultural Sciences (Affiliated to ANGRAU), Ananthapur, Andhra Pradesh, India.
J. K. Amrutha
Department of Agronomy, S.V. Agricultural College, ANGRAU, Tirupati-517 502, India.
M. Sainath Rao
Department of SPMA, Sri Krishnadevaraya College of Horticulture Sciences (Affiliated to Dr. YSRHU), Ananthapur, Andhra Pradesh, India.
*Author to whom correspondence should be addressed.
Abstract
The adoption of integrated nitrogen management (INM); which entails the combined application of organic and inorganic nitrogen sources; has been widely recognised for its role in improving nutrient availability; enhancing soil fertility; and promoting sustainable agricultural production systems. A field experiment was conducted to investigate the influence of integrated nitrogen management and plant geometry on soil fertility parameters and soil microbial properties in Kalmegh (Andrographis paniculata Nees.); a medicinally important crop. The experiment was laid out in a factorial randomised block design (FRBD); comprising four nitrogen source treatments with varying proportions of vermicompost and inorganic fertilisers; in combination with three plant spacing levels; thereby enabling a comprehensive assessment of their interactive effects on soil health indicators. Soil samples collected after harvest were analyzed for available nitrogen (N); phosphorus (P₂O₅); potassium (K₂O); and populations of major soil microorganisms such as actinomycetes; bacteria; and fungi. The results indicated that integrated nitrogen management had a significant influence on soil fertility status and microbial activity. Application of 100 per cent nitrogen through vermicompost resulted in significantly higher available soil nutrients; recording 189.90 kg ha⁻¹ of nitrogen; 24.91 kg ha⁻¹ of phosphorus; and 375.76 kg ha⁻¹ of potassium; compared to treatments receiving nitrogen solely through inorganic fertilizers. Vermicompost-based treatments also markedly improved soil biological properties by enhancing microbial populations; with the highest counts of actinomycetes (3.92 × 10⁴ cfu g⁻¹); bacteria (28.49 × 10⁶ cfu g⁻¹); and fungi (4.39 × 10⁵ cfu g⁻¹). This improvement may be attributed to increased organic matter content; better nutrient availability; and favorable soil conditions that support microbial proliferation. Plant spacing significantly influenced soil nutrient availability and bacterial population. Wider spacing (30 × 15 cm) resulted in higher available nitrogen; while spacing of 20 × 20 cm recorded higher phosphorus availability. The closest spacing (30 × 10 cm) registered maximum potassium availability and bacterial population. However; plant spacing did not significantly affect actinomycetes and fungal populations. Interaction effects between nitrogen sources and plant geometry were found to be non-significant for soil fertility and microbial parameters. The study concludes that integrated nitrogen management; particularly the application of vermicompost; combined with appropriate plant spacing; plays a crucial role in improving soil fertility status and enhancing soil microbial activity in Kalmegh cultivation; thereby contributing to sustainable soil health and long-term productivity.
Keywords: Kalmegh, integrated nutrient management, vermicompost, soil fertility, microbial population, plant geometry