Answer:
There are several factors that have contributed to the decrease in grain production in the US since 1990. One factor is the decrease in the amount of water used for irrigation. As water resources have become more scarce in some areas, farmers have had to reduce the amount of water they use for irrigation, which can lead to lower crop yields.
Other factors that have contributed to the decrease in grain production in the US include:
1.Changes in land use: As land is developed for other purposes, such as housing or industry, the amount of land available for farming can decrease, leading to lower crop yields.
2.Changes in crop prices: If the price of a particular grain falls, farmers may be less likely to plant that crop, leading to lower production.
3.Drought and other weather-related events: Drought, extreme heat, and other weather events can affect crop yields and lead to lower production.
4.Competition from other countries: As other countries increase their grain production, they can become more competitive in the global market, which can lead to lower demand for US grains.
5.Changes in farm policies: Changes in government policies, such as farm subsidies, can affect the profitability of farming and influence the amount of grain produced.