Allelopathic interference of Populus deltoides with some winter season crops

The performance of some winter season crops, namely Triticum aestivum, Lens culinaris, Phaseolus mungo, Avena sativa, Trifolium alexandrinum, Brassica juncea and Helianthus annuus was studied in association with Populus delto ides under alley cropping practice in two sets of fields in Punjab, North I ndia. In one, the parent soil was retained (S-p), while in the other, the p arent soil was replaced with soil collected from an area devoid of P. delto ides trees (S-r). Germination, plant height and biomass of the crops at 30 and 60 days after sowing (DAS) were reduced by 10 to 30% in both the P. del toides fields compared to the ones without trees (S-c). The observed reduct ion was more pronounced in S-p fields than in S-r fields. Maximum reduction was observed in the case of B. juncea and least in T. alexandrinum. Germin ation and seedling growth of all the test crops except A. sativa and T. aes tivum was found to be significantly reduced in response to the aqueous leac hates of P. deltoides leaves. Likewise, the seedling length and dry weight of L. culinaris and T. aestivum were significantly reduced in litter amende d soil. Litter and soil from P. deltoides fields were found to be rich in p hytotoxic phenolics, the amount of which was more in S-p fields compared to S-r and control fields (S-c). Based on the study, the observed reductions could be attributed to the allelopathic interference of the tree with the c rops through the release of phytotoxic phenolics from leaves and litter, wh ich are continuously added to the soil.