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How to control weeds in upland rice

By Vision Reporter

Added 7th September 2010 03:00 AM

FARMERS have started growing NERICA rice, commonly known as Upland rice. Developed specifically for African conditions, the new variety can thrive in areas that in the past did not favour rice growing.

FARMERS have started growing NERICA rice, commonly known as Upland rice. Developed specifically for African conditions, the new variety can thrive in areas that in the past did not favour rice growing.

By Joshua Kato

FARMERS have started growing NERICA rice, commonly known as Upland rice. Developed specifically for African conditions, the new variety can thrive in areas that in the past did not favour rice growing.

But while it can withstand harsh weather conditions, the new rice variety remains vulnerable to weeds that afflict other cereals.

If not cleared in time, weeds can cause losses in yields varying from 10% to 90%.

Weeds compete with the rice for soil nutrients as well as light. Besides starving crops of vital nutrients, weeds often harbour harmful pests and diseases which eventually attack the rice. The weeds vary from region to region.

For instance in the northern parts of the country, the most common weeds that affect rain-fed upland include spear grass, barnyard grass, Bermuda grass, goose grass, wild millet, false star grass and several others.
Broad leaved weeds include spiny pigweed, fat hen, gallant soldier, tropical spider wort and in some areas the notorious and parasitic witch weed or striga.

How to control weeds

Prevention is the best option when it comes to weed control in upland rice. This involves thorough land preparation, removing all vegetation and burning it up to ensure that none is left to sprout up later.

Crop rotation is another effective preventive method. Proper spacing at the planting stage is also very important.

While a sowing rate of 50kg per hectare (two-and-a-half acres) is considered the ideal, sowing rates of 80kg-100kg per hectare have in some cases helped reduce weeds and at the same time boosted the rice yield.

Avoid applying nitrogen fertilizer, as it encourages weed germination.

Hand weeding, that is physically pulling out the weeds with the hands, especially at an early stage, is also recommended because it stops weed seed formation there by reducing the amount of seeds of weeds in the soil.

Preventive weeding may however carry immediate benefits for the rice crop, but over the years will help reduce the weed population in the area.

Farmers can also use mechanical control of weeds in rice. This may include using the hand hoe or spade. The first weeding must be done between 14 and 21 days after sprouting, while second hand weeding should be done 20 days after the first one. Mechanical weeding is however only possible if the crop was sown in straight lines. The other commonly used method of weed control is through the use of chemicals.

This is rated as the most effective method of weed control, although it is not sustainable. Several considerations however must be made when weeding with herbicides.

These include timing and the rate of application. Farmers must try to abide by the safety conditions given by the herbicide manufacturer.

It is advisable to use general purpose herbicides like Glyphosphate or Round Up during the land preparation stage, and selective varieties like Satunil within two weeks after the rice has sprouted.

Five litres of Satunil per acre is the usual recommended rate of application.

Information sourced from the Food and Agriculture Organisation

How to control weeds in upland rice

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