The present study was conducted at research garden, Punjab Forestry Research Institute, Faisalabad. The objectives of the study were to evaluate the growth of poplar (Populus deltoides AY-48) trees at different densities under wheat-fodder maize agroforestry system. To determine the effect of poplar tree intercropping on growth, yield and quality of wheat-fodder maize and to compare the economics of agroforestry system with conventional arable farming.
The study was laidout during Feb, 1994 using RCB design with three replications at poplar tree densities of 3.66 x 6.10m, 3.66 x 9.10m and 3.66 x 12.10m. For this study poplar tree growth data, wheat and fodder maize growth and yield data were recorded at tree age of 6-8 years (1999-2000 & 2000-2001). Comparison of poplar trees growth under intercropping system at different tree densities was done with sole poplar tree crop. Similarly growth and yield of wheat-fodder maize under intercropping system was compared with sole crops to determine the effects of intercropping. Economics of agroforestry system at various tree densities was also compared with conventional farming practices. Similarly post harvest soil fertility (Organic matter, Nitrogen, Phosphorus and Potassium) of experimental site was studied for determining effects of intercropping on soil nutrient status.
The salient findings of this study were as under:
1. Intercropping of wheat-fodder maize crops and tree densities has positive effect on poplar tree growth.
2. Wheat grain yield decreased under different poplt1r tree densities; however, this decline in yield was not significant at tree densities of 3.66 x 9.10m and 3.66 x 12.10m.
3. Poplar tree intercropping has no significant effect on wheat grain quality.
4. Poplar tree intercropping has some negative effect on grain weight and size but this effect decreased with the increase in tree spacing.
5. Poplar tree intercropping significantly decreased fodder maize fresh yield. However, this effect was diluted with increase in spacing amongst trees.
6. Land Equivalent Ratio (LER) studies revealed that there was overall 74-52% yield advantage in agroforestry over conventional monocropping.
7. Soil fertility increased under agroforestry systems compared to conventional farming system.
8. Intercropping of poplar tree in wheat-fodder maize cropping system was economical at all tree densities in terms of net benefits, benefit-cost ratio and internal rate of return. However through marginal analyses it was found that intercropping in tree density 3.66 x 9.10m was most economical.
9. Rotation age of 8 years was the best one for intercropping at the tree densities tested.
10. For pure forestry at the spacing of 3.05 x 3.05m, the rotation age of 4 years was found to be the best one as it was not economically viable after that age.
11. Intercropping of wheat-fodder maize in poplar trees at tested densities was economical at tree age of 7 and 8 years. So intercropping should continue throughout the rotation age of poplar trees.