WEED PREVENTION IN DIRECT SEEDED RICE FIELD IN WINTER-SPRING CROP 2020-2021

Weeds are one of the pests that often appear in the field, with high tolerance, strong growth, they compete for nutrients and water, affecting the growth and development of rice plants, and at the same time providing shelter. hides of rats and other harmful pests…

Winter-spring crop often has cold weather, prolonged rain and cold, so improper use of herbicides can affect the growth and development of rice plants. Therefore, the problem of weed control at the right time, in the right way is a very urgent requirement. To do this well, we need to identify the weeds present in the field to choose the appropriate herbicide and time to handle the herbicide.

I. CLASSIFICATION ACCORDING TO WEED

1. Classification by morphology

- Monocotyledonous weed: Grass weeds and sedge weeds such as Echinochloa sp, Leptochloa chinensis ,Fimbristylis miliacea ,Cyperus sp

- Dicotyledonous weed: Broad-leaved weedes such as Monochoria vaginalis , Marsilea quadrifollia ,Ludwigia octovalvis

2. Classification according to botanical characteristics

- Group of grass weeds :There are solid and hollow internodes, round body. The leaf blade is narrow, long, the secondary veins parallel to the main veins running from the leaf tip to the leaf collar. The stem is round and hollow, the leaves are alternate, attached to the stem in two rows. Roots are usually cluster roots, shallow roots.

- Group of sedge weeds: narrow leaves but shorter than the grass weed, the stem is usually solid with a triangular angle. Regardless of leaf sheath and leaf blade, leaves are attached to the stem in 3 rows around the stem. The base of the leaves forms a tube around the stem.

- Group of broadleaved weed: broad leaves, horizontal, opposite growth, leaf surface with few hairs , leaf veins arranged in different phenotypes (network shaped veins for dicotyledonous weed and leaf veins parallel to monnocotyledonous weed) .

II. MANAGEMENT AND PREVENTION OF WEED IN THE DIRECT SEEDED RICE FIELD.

1.     Cultivation method

- Plow and turn the soil before harrowing to sow for about 20-25 days to bury the remnants of weeds, ratoon rice and limit the germs of harmful organisms. Note that before plowing the land, collect crop residues, especially weeds and flowers, and destroy them.

- Make the soil carefully, the field surface is even, well drained and fertilize according to the process, especially phosphate fertilizer in order to create conditions for the rice plants to have enough nutrients for the rice plants to absorb and grow after taking root. quickly overwhelm weed in order to create conditions for rice plants, after taking root back to green, to have enough nutrients for rice plants to absorb and grow quickly to overwhelm weeds , and at the same time enhance the resistance of rice when facing unfavorable external conditions.

- Use standard varieties for sowing, in order to limit the possibility of mixing weed seeds from the seed source. Before soaking, it is necessary to sift to remove unfilled seeds, loose seeds and weed seeds.

- After sowing, depending on the weather conditions and the growth stage of the rice, it is necessary to regulate the water level in the field appropriately to limit weed growth and when the weather is favorable (appropriate temperature). herbicides can be used to treat and based on the time and type of weeds in the field to choose suitable herbicides

2. Chemical measures

- There are many herbicides on the market. Each product has different herbicide active ingredients, Depending on the time and condition of the weeds in the field to choose the right product to use. Prioritize choosing products with high weed control efficiency and low toxicity to humans and the environment.

- Pre-emergence herbicides group: Used before weeds are seen in the field to prevent them from appearing

- Post-emergence herbicide group: Used when the weed has appeared in the field, the weed has 1-2 leaves.

- To help control weeds in rice fields during the cultivation period, we would like to introduce 2 rice herbicide products of Saigon Plant Protection Joint Stock Company:

+ Bebu herbicide 30 WP:

Bebu 30 WP is an early pre-emergence and post-emergence herbicide, containing 2 active ingredients of Butachlor 28.5% + Bensulfuron Methyl 1.5% (safener of Fenclorim 10%) effective against all three groups of grass weeds, sedge weeds and broadleaved weeds such as: Leptochloa chinensis , Echinochloa sp ,Digitaria ciliaris , Cyperus difformis ,Fimbristylis miliacea ,Monochoria vaginalis ,Marsilea quadrifolia , Rotala indica….safe for rice plant

The product has a selective, contact and internal absorption effect, penetrates into the plant through leaves, roots and shoots, so it has a very effective herbicide effect at the stage of ungrown weeds, newly-sprouted weed seeds and weeds grown but still young (1 - 2 leaves)

Spray when sowing 1-3 days, dosage 60g / 20-liter-watertank, spray 02 tanks for 1,000 m2

- Pataxim herbicide 55 EC:

+ Pataxim 55EC is a post-emergence herbicide, containing 2 active ingredients of Butachlor 275g/l and Propanil 275g/l. The combination of these 2 active ingredients has the effect of enhancing the effectiveness of all 3 groups of weeds and prolonging the use time

+ Spray when sowing from 4 to 12 days, corresponding from the time the weed grows to the weed with 3 leaves

+ The amount of product used is from 2 - 2.5 liters/ha, mix 80 - 120 ml of product/ 20 liters of water, spray the field surface from 2 - 2.5 bottles for 1 field of 1,000m2. Spray early, use low dose, spray late, use high dose according to the instructions on the product label.

- Note when spraying herbicides:

When spraying the field, it is necessary to drain the water, but keep it moist. After spraying 1-3 days, water should be applied to the field, adjusting the field water level in accordance with the growth stage of the rice plant.

Do not spray herbicides when it is about to rain, strong winds or when the outdoor temperature drops below 18⁰ C