I suspect this is low on the list of possible stressors for Indiana most years (because of our typically high humidity levels), but may play a role in some fields once in a while. Severe drought stress coupled with excessive heat and low humidity can desiccate emerged silks to the point that they become non-receptive to pollen grain germination. The simultaneous effects of severe drought stress on silk emergence can easily amplify the consequences of severe silk clipping. Persistent severe silk clipping by insects such as the corn rootworm beetle or Japanese beetle throughout the active pollen shed period can also limit the success of pollination. Without a pollen source, ovule fertilization cannot occur. Severe drought stress, aggravated by excessive heat, can delay silk emergence to the extent that pollen shed is complete or nearly complete by the time the silks finally emerge from the husk. Pollination problems may be due to several stress factors, sometimes working together to influence kernel set. In other words, all you see is cob tissue. Ineffective pollination is characterized by an absence of noticeable kernel development. Poor kernel set may be caused by ineffective pollination (the transfer of pollen from the tassel to the silks) and/or the subsequent failure of the pollen's male gametes to fertilize the female gametes of the ovules on the cob. For example, the loss of only 1 kernel per row for a hybrid with 16-row ears and a stand count of 30,000 ears per acre would equal a potential yield loss of approximately 5 to 6 bushels per acre (1 x 16 x 30 divided by 85 ). of Illinois many years ago ( Nafziger, 2017 Nielsen, 2018b). The potential loss in grain yield caused by lower kernel numbers per ear can be estimated using the formula of the so-called Yield Component Method first described by the Univ. Determining the exact cause of the problem is sometimes difficult. Problems with kernel set stem from ineffective pollination, ineffective fertilization of the ovaries, kernel abortion, or all three. Good or poor kernel set is determined from pollination through the early stages of kernel development typically 2 to 3 weeks after pollination is complete. Poor kernel set, meaning an unacceptably low kernel number per ear, is not surprising in fields that are obviously severely stressed by drought, but can also occur in fields that otherwise appear to be in good shape. Growers' interest in this topic obviously lies with the fact that the number of kernels per ear is a rather important component of total grain yield per acre for corn. The post-pollination scuttlebutt overheard in coffee shops throughout Indiana during late summer often revolves around the potential for severe stress that might reduce kernel set or kernel size in neighborhood cornfields.
0 kommentar(er)
