What it does

When seeds are poorly distributed, either crop stand of plants becomes too dense or have spaces in between when plants are too few. Weeds also grow and compete with the crop for nutrients.

Why and where it occurs

Crop density is a problem of direct seeded fields, especially when broadcast seeded. Crops can be surface broadcast (wet or dry), drill seeded (using machines) or broadcast and incorporated when sown on dry fields. Pre-germinated seed is typically used when wet direct seeding. Direct seeded fields tend to have greater problems of lodging, especially when the seed is surface sown. When broadcast, fields can have patches of either too many or too few plants depending on the skills of the broadcaster and the soil conditions where the seed lands. Farmers often use high seed rates due to poor seed quality, to compensate for losses to rats, birds and snails and to increase crop competition with weeds.

How to identify

Check the field for the following:

• Plant count too high (e.g., > 250 plants per m2) or too low (e.g., < 75) in direct seeded fields
• When too close, plants can have thin stems and possibly lodge
• When too few plants, there are spaces in the crop, weeds can grow and yield potential can be lost

Pattern of damage is usually uneven across the field.

Various problems causing problems of crop establishment (e.g., cloddy soil, seed too deep, soil too soft at seeding, poor emergence in low spots in fields, heavy rainfall at seeding, soil crusting, poor seed quality, low seed rate, water stress, muddy water at seeding, clogged seeder and/or pests such as ants, birds and rats that remove seed at planting. To confirm cause of problem, check or ask a farmer about seed rate and how the crop was planted.

Click on images to enlarge

Plant count is either too high or too low; weeds can grow where there are spaces between plants

How to manage

• For good establishment, manage water properly and ensure well leveled water, allowing water to settle
• Ensure an appropriate seed rate with even distribution of seed
• Crop stand should be of the order of 100 to 200 plants per m2, use seed rates between 40 to 100 kg per ha

Learn more

View full fact sheet:
Poor seed distribution on IRRI Rice Knowledge Bank