By Dior Pote, Seed Co Limited
Head of Agronomy & Extension Services – Zimbabwe
For Zimbabwe’s winter wheat farmers, the countdown to the 2026 harvest has entered its most critical phase. As the calendar turns to September, crops across the Highveld and Middleveld are moving from Week 14 to Week 19 after planting. This is what we call the grain fill to maturity window. According to agricultural experts, this “final lap” is where 30 to 50 percent of potential yield is either secured or lost.
In my recent farm visits I came across something interesting from some of our renowned commercial farmers from Mashonaland Central, Mashonaland West and Midlands. “August is the month that decides profit,” said one commercial farmer. “Water stress for just one week during grain fill results in small, light grains. Disease burns leaves, cutting off photosynthesis. Mistakes now are direct yield loss.”
How to protect your crop and maximize returns.
Weeks 14-15: Grain Fill Start
During this critical phase, one has to keep the Moisture Coming. With the grain now filling, the plant’s demand for water is at its peak. Farmers are advised to maintain soil moisture with 30 to 40mm of irrigation per week. The last irrigation should be scheduled around Week 18, when roughly 50 percent of the crop has turned yellow. Irrigation requirements for winter wheat in Zimbabwe typically range between 450 and 600mm per hectare over the season. On lighter sandy soils, irrigate more frequently (7-9 day cycles), while heavier clays can support a 10-14 day schedule with larger amounts.
During this stage of growth there is serious need to watch crop’s health. This scientifically regarded as the disease watch. August dew creates ideal conditions for Stripe Rust, Leaf Rust, and Septoria. Agronomists urge farmers to scout fields regularly. If leaf infection exceeds 10 percent, apply an approved fungicide immediately. It is not only disease. This is also a favourable stage which allows pests to thrive. Pests, which include aphids, start to make headways. A proactive farmer has to check the heads. If aphid counts exceed 20 per head, spraying is necessary to prevent sap-sucking damage and virus transmission.
Weeks 16-17: Grain Fill Peak
During this week there is need to stop nitrogen, and start watching for Lodging. As grain filling reaches its peak, farmers must cease all nitrogen application. “Applying nitrogen at this late stage delays maturity and increases the risk of lodging,” warned experts. Lodging, where the crop is flattened by wind or rain, can lead to harvest losses and increased disease risk. During this stage, weed control is no longer a priority, and herbicide applications should be avoided.
Bird control
Quelea birds pose a significant threat during the late grain-fill period. Effective bird-scaring using bells, whistles, or reflective discs is essential. For larger operations, consider approved bird repellents applied at the soft dough stage.
Weeks 18-19: Maturation and Harvest Prep – Ready the Combines
Harvest readiness is the final, critical step. The golden rule: harvest at 12 to 13 percent grain moisture. Harvesting too wet leads to storage losses, while waiting too long causes shattering losses as heads break and grain falls to the ground. Farmers should use Grain Moisture Meters to accurately assess moisture levels, especially if rains threaten.
In recent years, early rains have caused quality degradation for late harvesters. Prepare combine harvesters, tarpaulins, and GMB-approved bags. Deliver wheat to the Grain Marketing Board within one month to benefit from prompt payment schemes. Farmers are also encouraged to use the Zimbabwe Mercantile Exchange platform for price discovery and marketing.