MSc

A factorial experiment involving coconut (Cocos nucifera L.) and three multipurpose tree species (Ailanthus triphysa (Dennst.) Alston., Grevillea robusta A. Cunn. and Vateria indica L.) in two planting geometries (single and double hedge) was established in an existing coconut plantation (14 years old) at Vellanikkara in June, 1992. Kacholam (Kaempferia L.), a herbaceous medicinal plant was introduced in this trial as a floor crop in May 1995. Monocultures of coconut and kacholam were also maintained. Objectives of the study included evaluating suitability of interplanting multipurpose trees in coconut plantations, assessing the consequential changes in growth of multipurpose trees productivity of coconut and kacholam and inter alia characterise the above and below ground interactions between field and tree crop components.
Coconut yield was not adversely affected by interplanting multipurpose trees until the multipurpose trees were about 4 years old. Multipurpose trees exhibited wide variations in their growth and crown characteristics. Consequently the light availability beneath the canopy was highly dependent on the multipurpose tree species. Availability of photosynthetically active radiation (PAR) was inversely proportional to the stand leaf area index. Available PAR ranged from 18-45 % and 22-45% of that in the open at 50 and 150 cm above ground level respectively. Planting geometry did not influence this parameter significantly.
Kacholam grown in the open (sole crop) exhibited better growth as compared to kacholam grown in association with coconut and multipurpose trees. Nevertheless, rhizome yield (at final harvest) was comparable in all the situations. Tissue nutrient content of kacholam was also independent of multipurpose trees. The results suggests the moderate shade tolerant nature of kacholam, which can be highly useful in intercropping. However, no strong relationship could be established between light availability and rhizome yield.
Multipurpose trees exhibited considerable root activity in the coconut rhizosphere, as evident from the data on 32P recovery. However, competition for nutrients between the two components was not evident, probably due to the juvenile nature (4 years old) of the multipurpose trees. Even at this stage, the three multipurpose trees exhibited discernable difference in foliar 32P activity. Cross-feeding of kacholam by coconut roots scavenging kacholam beds was noticed.
Three to four years of tree growth did not alter the soil nutrient status very substantially. An increase in soil pH and available potassium was, however, observed. Nevertheless, kacholam cultivation resulted in a modest decline in soil nutrient status.