Effect of Cultural Practices in Night on Weed Density and Weed Dry Matter

In order to evaluate the response of weed seeds to light, two experiments, at two different locations were conducted at Ferdowsi university of Mashhad in 2009. At the first experiment, field was ploughed in day and night. Weed density was evaluated 70 d after plough, with 1×1 quadrate. At the second experiment, at night treatment, ploughing, potato planting and weeding with cultivator were done at night. Weed sampling was done twice at 43 and 130 days after planting with 1×1 quadrate and weeds were identified and counted. Result showed pigweed (Amaranthus retroflexus L.), sowthistle (Sonchus oleraceus L.), crabgrass (Digitaria sanguinalis (L.) scop), jimsonweed (Datura stramonium L.) and mallow (Hibiscus trionum L.) did not observed at night plough, in contrast, night plough has no significance influence on common lambsquarters (Chenopodium album L.), and black nightshade (Solanum nigrum L.). Only common lambsquarters had similar appearance in two treatments, indicating insusceptibility of this weed to time of plough. Interestingly, at the second experiment, result was very similar. Potato yield was higher at night treatment, but not significant. This research showed that some cultural practice like plough, planting and weeding with cultivator in night can reduce weed density and weed dry matter.