Barnyard grass (Echinochola crus-galli (L.) Beauv) locally known as “Dhidden” is distributed in rice growing areas of Pakistan. It is troublesome weed in rice because at early growth stage, it resembles rice plants and cannot be easily separated from the seedlings.

A similar ecological requirement of rice crop and barnyard grass and aggressive growth behaviour makes barnyard grass the worst weed of rice crop. Barnyard grass removes huge amount of nutrients, especially nitrogen at higher doses as compared to rice.

Similarities in morphology, physiology, and growth habits of barnyard grass with rice, pose double-edged control problem in terms of stiffer competition for the same growth and development requirements and of similar vulnerable stages to control (germination to four leaf stage), resulting in narrow margin of selectivity where post-emergence control measures are used. Barnyard grass have almost identical growth habit and growth requirements, hence practices which benefit rice will also benefit this weed, while practices which harm barnyard grass will also harm rice. With proper management practices, it can be manipulated to make growing conditions more favourable to rice and less favourable to barnyard grass.

Considering huge loss in terms of rice yield reduction (90 per cent) caused by the barnyard grass, and significant contribution of rice crop to the economy of Pakistan, a two-year research study leading to PhD degree was conducted under the supervision of professor Dr Zahid Ata, at the Department of Agronomy, University of Agriculture, Faisalabad. Salient findings of the research are given in the following paragraphs for the benefit of scientists and the farming community.

In laboratory trials, it was observed that the water extract of rice husk significantly inhibited the germination and seedling growth of barnyard grass while the water extract of barnyard grass significantly suppressed the germination and seedling growth of rice, indicating interalleopathic behaviour of both the crop and weed. Moreover strong allelopathic effect of Sorgaab (sorghum water extract) was observed on the germination and seedling growth of both rice and barnyard grass, providing the possible manipulation of sorghum allelopathic properties for managing barnyard grass. In competitive experiments, it was found that barnyard grass during the early stages of growth up to 20 days after transplanting do not influence the rice yield (fine rice cv. Bsmsti-385) but after 20 days till maturity it competed vigorously by reducing the rice yield up to 38 per cent while 4 plans m-2 of barnyard grass had non-significant effect on rice yield indicating that 4 plants m-2 as the economic threshold level irrespective of the nitrogen levels. While 16 barnyard grass plants m-2 reduced the rice yield from 16-32 per cent under different nitrogen levels (0,60,120,180 kg ha-1).

After determining the competitive capability and the competition duration of barnyard grass in rice the strategy adopted for its control must be sustainable, economical and environment friendly. To achieve these objectives weed control methods prevalent in Pakistan as hand weeding and chemical weed control were compared with a new technology evolved at weed science laboratory of agriculture university Faisalabad which is foliar spraying of Sorgaab (sorghum water extract containing naturally produced allelochemicals in mature sorghum plants). The common practice of controlling weeds with standing water was not included in the study because of the soil conditions prevailing at Faisalabad, where it is not possible to ensure the standing water.

The findings of this field study revealed that hand pulling (20 days after transplanting) provided effective control of barnyard grass (90 per cent) and increased the rice yield by 30 per cent but was uneconomical due to higher cost of hand pulling. Chemical control with herbicides as butachlore (60 CE) @ 1.2kg a.i. ha-1 applied at 3-4 days after transplanting, gave effective control of barnyard grass up to 94 per cent and increased the yield by 35 per cent, while the marginal rate of return for herbicide was 570 per cent, whereas the use of one foliar spray of Sorgaab 20 days after transplanting controlled barnyard grass up to 38 per cent and increased the rice yield by 20 per cent with the highest marginal rate of return (2750 per cent).

From the results of investigation it could be concluded that barnyard grass is a serious weed of rice and it must be controlled to ensure higher rice crop yields. For controlling the barnyard grass, environment friendly, sustainable and economical approaches like naturally-produced products as Sorgaab (sorghum water extract) may be used because the herbicide causes environmental and health hazards. However studies to improve the effectiveness of natural products by mixing different crop/plant water extracts as sunflower, neem, tobacco, eucalyptus and sorghum and relatively non-toxic organic compounds may be continued.