The efficient use of resources for crop production is challenging. Water is in many cases the first limiting factor, particularly in semiarid regions, followed by nutrients. When water is limiting, it is extremely difficult to determine the most suitable crop and the best combination of row spacing, plant population, length of maturity, and date of seeding to make the most efficient use of the limited water. While the most important goal is perhaps to deplete as much of the plant-available water as possible from the soil profile before the end of the growing season, depleting it too early will result in a lot of biomass production early in the season and a critical shortage of water during the reproductive stage late in the season. A shortage of water late in the season generally results in low harvest index (HI) values for crops like maize (Zea mays), sorghum (Sorghum bicolor), wheat (Triticum aestivium), and cotton (Gossypium hirsutum). The HI is the weight of the harvested product as a percentage of the total aboveground biomass.