Abstract:
A split plot experiment, involving ailanthus (Ailanthus triphysa (Dennst.) Alston.) at various population densities (3333, 2500, 1600 and 1111 TPHA) and fertiliser regimes (0:0:0, 50:25:25, 100:50:50 and 150:75:75; kg N:P2O5: K2O ha-1 Yr-1), initiated in June, 1991 was intercropped with ginger (Zingiber officinale Roscoe). Additional treatments included monocultures of ginger and ailanthus. Objectives were to assess the productivity of ginger as a component of an agrisilviculture ststem involving ailanthus, besides analysing the partitioning of solar radiation among the different components of the system and characterising the nature of below ground interactions between the field and tree crop components.
Ailanthus growth and its foliar chemical composition was not influenced by tree population density and fertiliser regimes. Light availability below the canopy was, however, strongly altered by tree population density. Availability of photosynthetically active radiation (PAR) was inversely proportional to stand density. Available PAR ranged from 35-72 per cent and 40-75 per cent of that in the open, at 50 and 150 cm above the ground level respectively. A strong relationship however, could not be established between light availability and foliar nitrogen content of the tree.
Ginger grown in the interspaces of ailanthus exhibited better growth as compared to the sole crop situation. Tissue nutrient content of ginger in the later stages were higher when grown as mixed crop. The tree population density of 2500 trees per hectare (TPHA) registered better growth of understorey ginger. Fresh and dry rhizome yield of ginger also was maximum at this density. However, no strong relationship could be established between light availability and rhizome yield of ginger. Fertilisers applied to the tree component of the system, did not influence the growth, yield and quality of ginger.
Three years of tree growth significantly reduced soil nutrient status below trees. A reduction in soil PH also was observed. Radiophosphorus recovered by ginger and ailanthus were not substantially altered by tree population density, lateral distance of application and cropping situation. However, ailanthus absorbed a substantial portion of the fertilisers applied to the ginger crop. Root activity of ailanthus suggests that 41-53 per cent of active roots are situated at about 40 cm from the tree trunk. Neighbouring trees in the high density stand registered a high recovery of 32P as compared to the low density stand, which may have important management implications.
