University studies in commercial fields tried to determine the relationship between high nighttime temperatures and the subsequent abortion of cotton fruiting structures.
The correlation between heat stress events and aborted cotton bolls is being studied in a region of California that can produce epic Upland yields amid some of the hottest temperatures in the U.S. Cotton Belt.
Studies in 2023 and 2024 by Michael Rethwisch, crop production and entomology adviser with the University of California Cooperative Extension in Blythe, are trying to help farmers mitigate crop losses linked to summertime heat.
Last year some of those farmers saw two- to four-bale losses from early-season heat stress. This in a region that can see some plots yield as much as seven bales to the acre.
The most critical part of heat stress is not the daytime temperatures that can exceed 120 degrees in the region, but the nighttime temperatures that fail to drop below 90 degrees, Rethwisch said.
University studies in commercial fields tried to determine the relationship between high nighttime temperatures and the subsequent abortion of cotton fruiting structures, Rethwisch told San Joaquin Valley cotton growers. Moreover, Rethwisch says that there is an apparent gap between heat stress events and when the plants abort bolls, which can happen at various stages of boll maturity, from pinhead square to bolls larger than 20mm in diameter.
While farmers from Bakersfield to Los Banos tend not to experience the same nighttime temperatures that their Palo Verde Valley counterparts experience each summer, the kinds of high-stress events that can lead to aborted cotton bolls and other production problems do exist.
Water stress in the Palo Verde Valley tends not to be an issue as fields are furrow irrigated from the Colorado River and farmers still have adequate access to surface irrigation supplies. According to Rethwisch, the losses likely happen when nighttime temperatures remain above 80 degrees, a common occurrence in the low desert of California.
Normal plant respiration from daytime photosynthesis tends to cool the cotton fields by as much as 10-15 degrees from what the California Irrigation Management Information System (CIMIS) stations in the area are reporting, he added. That photosynthesis stops at night, and so too does the plant’s ability to recover.
Rethwisch is testing about eight different products created to mitigate these losses. Some are showing promise as research applications boosted lint production by 6-10% on average with some products. Additional testing is still needed to determine the best application rates of these products and fine tune efficacy and economics, he said.
Source: https://www.farmprogress.com/