Root level interactions in coconut cocoa system

Abstract

An investigation was undertaken at the Kerala Agricultural University during 1994-96 to study the root level interactions in pure and mixed stand of coconut and cocoa. The study was also aimed to assess the extent of soil nutrient depletion in coconut-cocoa systems. The seasonal effects on the root activity of coconut was also assessed. The most important findings of the investigation are abstracted below. Absorption of soil applied 32P did not differ in pure and mixed stand of coconut and cocoa. Coconut was a surface feeder in both cropping situations where the active roots were concentrated upto a depth of 30 cm. 32P uptake was not much influenced by lateral distance or depth of placement of radiolabel in pure and mixed cocoa. Maximum root activity was noticed at 30 cm depth in both pure and mixed stand of coconut. The lateral spread of the roots was more or less uniform upto a distance of 275 cm in both sole and mixed stand. Cocoa also was a surface feeder with active roots distributed uniformly upto a depth of 60 cm. Majority of the roots traverse a horizontal distance of 175 cm in sole and mixed cocoa. The available Ca, Mg and S were markedly high in mixed coconut whereas organic carbon, available Fe and Mn were high in sole coconut. Available P, K, Zn and Cu were more or less uniform in both sole and mixed stand of coconut. The organic carbon, available K, Ca, Mg were significantly high in soils of mixed cocoa whereas available Fe, Mn and Cu were more in soils of sole cocoa. Available P, S and Zn were in more or less same concentration in soils of both sole and mixed cocoa. The 32P uptake was higher during wet season as compared to dry season in monocrop of coconut. The absorption was more from the surface layers during wet season and root explored deeper soil layers during dry season. Irrigation in general improved absorption of radiolabel in coconut. The uptake was more from the surface soil under irrigated conditions than that under rainfed conditions.