Protein content of wheat grain: Protein content of wheat grain is affected by soil moisture and the amount of available nitrogen (among other things). Figure 1.45 shows27 the percent of protein content of wheat grain versus pounds of nitrogen per acre applied in three separate situations. In each case soil moisture refers to moisture at the soil depth of 2 inches to 12 inches.
• Situation 1: Irrigation was used when soil moisture dropped to 49%.
• Situation 2: Irrigation was used when soil moisture dropped to 34%.
• Situation 3: Irrigation was used when soil moisture dropped to 1%.
a. If irrigation begins when soil moisture reaches 49%, what application of nitrogen will result in the lowest percentage of protein in wheat grain?
b. If irrigation begins when soil moisture reaches 34%, what application of nitrogen will result in the same protein content of wheat grain as beginning irrigation when soil moisture reaches 1%?
c. If you irrigate when soil moisture reaches 34%, how much nitrogen should you apply to achieve a 13% protein content in wheat grain?
d. Does Figure 1.45 indicate that, for nitrogen levels at 45 pounds per acre or higher, increased protein content in wheat grain is associated with higher or lower soil moisture?