<Emphasis Type="Italic">Oryza sativa</Emphasis> straw restricts <Emphasis Type="Italic">Phalaris minor</Emphasis> growth: allelochemicals or soil resource manipulation?

Unharvested stubbles or harvested straw of rice (Oryza sativa L.) gets incorporated into soil and interferes with the seedling growth of crop plants. In this paper, we investigated whether rice straw, either through releasing allelochemicals and/or through manipulating soil properties, influences seedling growth of Phalaris minor Retz., a non-native weed largely restricted to wheat (Triticum aestivum L.) fields. One hundred twenty grams of soil was amended with rice straw (0.5, 1, 2, 4, or 6 g/pot) and its effect on fresh shoot biomass of P. minor was examined. Any modification of rice straw phytotoxicity through the use of washed rice straw, activated charcoal, soil sterilization, or nitrogen fertilization was also studied. We carried out chemical and microbial analysis of soils to examine the role of soil properties in influencing P. minor growth. Incorporation of rice straw into soil suppressed the growth of P. minor through modifying soil properties. A dose-dependent increase in total phenolics was observed in soil amended with rice straw. Activated carbon or washing of rice straw, however, could not ameliorate the phytotoxic effects of rice straw. Our results provide initial evidence that rice straw restricts P. minor growth by manipulating soil chemical and microbiological properties. Authors contributions IJ conceived of and supervised the study, and wrote the paper; SK carried out the work.