Integrated Crop Management News

Water is extremely important for crop production. When water becomes limiting to the plant it is important to understand how plants use water. We often hear the term evapotranspiration (ET) in relation to plant water demand. ET is a combination of soil water evaporation (E) and water used by the plant during transpiration (T). Soil evaporation is the major loss of water surface and typically is higher after rain and under high temperature conditions.

The 2017 growing season for much of Iowa so far has been characterized by low rainfall and high temperatures. This has generated concerns about water stress and yield reductions. In particular, 2017 maximum temperatures are 2-6 percent above average and precipitation 4-75 percent below average (equivalent to 0.3 to 5 inches deficit) from June 1 to July 15 (Figure 1). Radiation is 5-15 percent above average across Iowa. Minimum temperatures and growing degree days (GDD) are below average in northern parts of Iowa and above average in the central and southern parts of Iowa.

Bacterial leaf streak was confirmed for the first time in Iowa and other states in 2016. There is not a lot known about the disease but researchers at Colorado State University, Iowa State University, Kansas State University and University of Nebraska are collaborating to understand the disease and its impact on corn with partial funding through the Farm Bill.

Corn roots grow rapidly starting at the 4th-leaf stage and continue throughout vegetative development. This typically occurs from June to early July. Several factors affect root growth, but temperature and soil moisture are the most relevant factors in the absence of soil constraints. Well-developed, deep root systems are essential to support water and nutrient uptake and thus high yield potential. Hot and dry weather results in a depletion of moisture in the top 6-inch soil layer.