MSc

A field research was undertaken at Vellanikkara, Kerala to assess the understorey productivity of coconut and homegarden through intercropping with three selected herbaceous medicinal crops viz. Zingiber officinale (ginger), Curcuma longa L. (turmeric) and Kaempferia galangal L. (galangal). These landuse systems by virtue of spatial and temporal advantages offer good scope for integrating shade tolerant crops and thereby offer supplementary returns to the farmer. The biochemical changes in the understorey crops and the biophysical attributes influencing the productivity of the land management systems were studied. Additionally soil carbon sequestration in both the given land use systems and a treeless open plot was estimated.
The intercrop growth considerably varied among the land use systems both in vegetative growth and rhizome yields. Growth observations at various sampling period revealed considerably higher plant heights of ginger and turmeric in shaded condition than treeless open. As regards leaf spread galangal performed well in the coconut garden followed by homegarden and treeless open. All the intercrops exhibited higher root length in treeless open plots, except galangal for which coconut was the best. Invariably root production was lowest in homegarden. Tiller production at final stages showed highest in treeless open. Contrary to the plant height growth trends, homegarden recorded lowest tiller production at final stages of sampling.
Understorey productivity for ginger in terms of rhizome yield at final harvest followed the order treeless open (3.45 Mg ha-1), coconut (2.86 Mg ha-1), and homegarden (1.49 Mg ha-1). Turmeric rhizome production showed considerable variation with intercropping system with highest yield from open area (7.01 Mg ha-1) and the lowest from homegarden (1.77 Mg ha-1). Highest Galangal yields were reported in the treeless open (3.05) while homegarden represented lowest production (2.04 Mg ha-1). Understorey photosynthetically active radiation (PAR) transmittance presumed to have a cardinal influence on intercrop growth which was highest for coconut (37%) and lowest under homegarden (17%). Turmeric and galangal showed strong positive correlation with understorey PAR. Regression equation relating PAR with rhizome yields showed statistical soundness with high value of coefficient of determination (r2).
Leaf Area Index varied between the homegarden and coconut considerably with higher value for homegarden (3.84) while the same for pure coconut plantation was
considerably low (2.21). The oleoresin concentration in all the intercrops was found to be greatest in homegarden followed by coconut and treeless open. Soil physico-chemical attributes were assessed at periodic intervals in all the landuse system and results indicate overall better condition prevailed in the homegarden in terms of organic carbon content, soil bulk density, total N, available P and exchangeable K which however registered lowest values in the treeless open. Similar was the trend in soil carbon sequestration with homegarden giving higher values (67.45 Mg ha-1) followed by coconut (59.65 Mg ha-1) lowest by treeless open soil (55.1 Mg ha-1).
Result converges to the generalisation that despite better soil physico-chemical attributes, understory productivity in the homegarden is by and large decided by the PAR availability. Hence there is need to develop stand structure that optimize the productivity in homegarden through judicious stand density regulation and tree management practices.