Steps to check weed growth

In the wheat-paddy rotation, a predominant crop cycle in the north-western India, weeds cause 20-50 per cent loss in the yield.

These weeds thrive on nutrients, soil moisture, space meant for principal crops and hard to get rid off, despite various methods evolved by agricultural scientists.

Research on weeds is going on at Punjab Agricultural University (PAU), Ludhiana, where agronomists US Walia, Lall Singh Brar and Buta Singh have observed that weeds erode 25 per cent to 75 per cent of the fertilisers, thereby reducing the yield of the associated crops.

Scientists have also observed that competition for soil moisture is all the more in the rain-fed areas of Punjab as compared to the irrigated tracks.

Also, the yield and grain losses in cultivated crops are more in slow-growing crops as compared to the quick growing ones.

Walia, Brar and Singh have now come up with an illustrated research bulletin 'Recommendations for weed control in field crops"�1970-2005'.

The bulletin is about extent of losses caused by weeds in principal crops, spray techniques, weed control recommendations-their advantages, disadvantages, weeds of rabi and kharif, mode of action of herbicides etc.

A variety of weed control measures, mechanical, cultural, agronomic and chemical have helped to some extent. Yet, about 90 per cent to 95 per cent of the total area under paddy and 80 per cent to 85 per cent area under wheat is treated with herbicides in Punjab.

PAU agronomists have observed that temperature also plays a part in enabling the weeds to grow. Thus by adopting the agronomic, mechanical, cultural, chemical practices, much difference can be made to either contain or eliminate the menace of weeds.

Simple steps like crop rotation, adjusting date of sowing, selection of quick growing crop species, close cross or bi-directional sowing and increase in growth density help elbow out weeds.

Even scientific application and placement of fertiliser, zero tillage, mulching, and irrigation management enable farmers to over come the nuisance value of weeds.

According to PAU agronomists, weeds add to the cost of cultivation. If it is manual and mechanical weeding, it means higher labour and machinery costs. If it is chemical, it means use of costly herbicides.

In the process, new problems have arisen. Primarily these are excessive use of herbicides, which leads to resistance in weeds, shifting in weed flora, environment pollution and pesticide residue in soil, crop produce and grains.

PAU agronomists have observed that for Phalaris minor in weed is a major problem. Temperature for the conducive growth of this weed is less suitable for its germination up to first week of November.

Therefore, farmers are advised to sow wheat either in the last week of October or in the first week of November, which will mean low infestation of this weed.

Adoption of barseem in rabi can eliminate Phalaris minor in wheat. Similarly, to weed out 'itsit' or 'chupati' adoption of transplanted paddy in kharif instead of maize, cotton is recommended.