Evaluation of 1997 Late-Season Crop Conditions

Abstract

In the latter part of the 1997 season (August) many fields across Arizona, from Marana to the Mohave Valley, were experiencing premature senescence. In an effort to evaluate the conditions leading to the symptoms and to possibly determine the causes, an extensive series of field examinations were conducted in a number of representative fields in central Arizona. Soil samples were taken from selected fields that ranged in expression of the symptoms from very light to severe. Complete analyses of the soil samples were conducted. Plant tissue samples were also collected and analyzed for plant nutrient levels. No absolute causal agent was identified. However, a factor believed to be of significance was that of low soil K levels, where many of the fields expressing the most severe symptoms also had low soil K levels. It is also important to consider the fact that plants exhibiting K deficiency are very similar in appearance to plants affected by Verticillium wilt, which also appeared to be a primary or contributing factor in many cases.