Allelopathic interference of Populus deltoides with some winter season crops

Abstract

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 deltoides under alley cropping practice in two sets of fields in Punjab, North India. In one, the parent soil was retained (S_p), while in the other, the parent soil was replaced with soil collected from an area devoid of P. deltoides 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. deltoides fields compared to the ones without trees (S_c). The observed reduction 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. Germination and seedling growth of all the test crops except A. sativa and T. aestivum was found to be significantly reduced in response to the aqueous leachates of P. deltoides leaves. Likewise, the seedling length and dry weight of L. culinaris and T. aestivum were significantly reduced in litter amended soil. Litter and soil from P. deltoides fields were found to be rich in phytotoxic 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 crops through the release of phytotoxic phenolics from leaves and litter, which are continuously added to the soil.