Primary symptoms
Even when plant density appears appropriate spatial arrangement (or plant distribution) may be a problem. With more than two plants per hill, yield is reduced.
Confirm the problem by checking the tables below.
Summary
| Causes of high number of plants/hill | Additional evidence required |
|---|---|
| The farmer overplants to protect against possible losses from pests or disease. | Ask the farmer how many seeds are sown per hill and why. |
| Several seeds are sown per hill to reduce planting costs. | Ask the farmer how many seeds are sown per hill and why. |
Since hand planted maize is often arranged in hills (individual planting stations) with more than one plant per hill, spatial arrangement can sometimes be a problem, even where density is appropriate. Studies indicate that when more than two plants grow in the same hill, grain yield is affected by competition for water, nutrients, and light. If four or more plants grow in the same hill, one-to-three of them usually do not produce an ear.
Why do farmers often plant many seeds in one hill? When the farmer plants by hand, making more seed holes takes longer. If you recommend that the farmer make more holes per hectare, you need to be certain that the yield advantage will be profitable. In addition, farmers sometimes overplant and then remove plants during the season as forage for animals.
Is plant distribution a problem?
Evidence: observations.
- Are there more than two plants per hill?
- Is plant population above the optimum?
Possible solutions
- Thin overplanted hills to 2-3 plants/hill when plants are at the V3-V4 stage while maintaining adequate overall population density.
- Chemically protect seed with fungicide or pesticide to reduce need for overplanting.
- Demonstrate a yield advantage to planting more hills/ha that compensates for increased labor costs and produces higher profits.