Vertical Diversity of Soil Dehydrogenase and Phosphatase Activity under Coconut (Cocos nucifera L.) and Arecanut (Areca catechu L.) Plantations in Different Agro-climatic Zones of Karnataka, India

Abstract

The present study was conducted to investigate the vertical diversity of soil dehydrogenase and phosphatase activity under coconut (Cocos nucifera L.,) and arecanut (Areca catechu L.,) plantations within four soil depths (0–30, 30–60, 60–90, and 90–120 cm) and to determine the factors controlling the distribution across the different agro-climatic zones of Karnataka. A total of 176 soil samples from 30 soil profiles were collected from coconut and arecanut plantations representing 5 different agroclimatic zones (ACZ) and three soil types (Lixisols, Сambisols, and Acrisols) and analyzed for three major soil enzymes viz. dehydrogenase (DHA), acid phosphatase (ACP) and alkaline phosphatase (ALP). The results revealed that the pooled mean of DHA activity was higher in arecanut (7.44 µg TPF g^–1 h^–1) than coconut (5.75 µg TPF g^–1 h^–1) and the same pattern has been noticed in both ACP (84.041 and 48.19 µg PnP g^–1 h^–1 for arecanut and coconut plantations) and ALP (63.57 and 32.14 µg PnP g^–1 h^–1 for arecanut and coconut plantations). The impact of climate on soil enzyme activity showed that the southern dry zone (SDZ) was high in DHA (10.5 µg TPF g^–1 h^–1) and ALP (77.98 µg PnP g^–1 h^–1) activities followed by the eastern dry zone and the lowest was noticed in the coastal zone (CZ). However, ACP activity was higher in CZ (110.24 µg PnP g^–1 h^–1) and lower in SDZ (33.85 µg PnP g^–1 h^–1). As soil depth increases enzyme activity is decreased and nearly 50% of enzyme activities are restricted within 0–30 cm soil depth. We observed that greater activity of DHA and ALP was noticed in Lixisols than in Acrisols and Cambisols, whereas higher activity of ACP was found in Acrisols. Our analysis showed that the type of plantations, climate and soil type significantly affect the distribution of enzymes in soil.