Specialists Speaking- Randy Norton
Randy Norton
ARIZONA
As the 2026 cotton season winds down and much of the crop comes out of the field, now is a good time to evaluate the season and identify opportunities to improve production efficiency next year. Growers have several management tools within their control, including variety selection, fertility and irrigation management, plant growth regulator (PGR) applications, defoliation, and harvest timing. Research-based recommendations for many of these practices are available through the University of Arizona Cooperative Extension’s cotton resources website (extension.arizona.edu/topics/cotton).
Of course, not every factor affecting cotton production is within our control. Heat stress is a prime example. While we cannot control temperatures, understanding how heat stress develops and when it occurs can help us better manage its effects. The past three seasons provide an interesting comparison of how both the amount and timing of heat stress can influence cotton production.
At Maricopa, Arizona, the number of Level 2 (L2) heat-stress days recorded in 2024, 2025, and 2026 was 42, 23, and 43, respectively. The 2025 season produced some of the best yields observed in many years, and the relatively low number of L2 heat-stress days was likely an important contributing factor.
Although the total number of L2 days in 2024 and 2026 was similar, the timing of those days differed considerably. In 2024, L2 heat stress began in mid-June and persisted through much of the season, continuing into late August with few breaks. In 2026, L2 days began even earlier, in early June, but were followed by several weeks of less-intense conditions before heat stress increased again in late July.
That break in heat stress may have made an important difference. Much of the crop’s fruit set occurred during the earlier period before L2 conditions returned. Later-planted cotton, however, experienced greater heat stress during peak fruit set, potentially putting those fields at a disadvantage for yield.
Early indications suggest that 2026 yields will be above average, although they may not reach the levels observed in 2025. The season reinforces an important point: the timing of heat stress can be just as important as the total number of heat-stress days. Two seasons with similar heat-stress totals can produce different outcomes depending on when those conditions occur relative to crop development.
Our work continues to focus on identifying cotton varieties with greater resilience to heat stress and evaluating models that could help predict heat-stress patterns. Improved forecasting may eventually give growers additional opportunities to adjust management practices including irrigation scheduling, fertility management, and PGR applications to help mitigate heat stress and protect yield potential.
Randy Norton
ARIZONA
