Impact of fertilization and high grain production on groundwater exploitation in Shijiazhuang Plain

Shijiazhuang Plain is one of the main grain production areas in Hebei Province, cultivating mainly winter wheat and summer maize. Increased grain production in the plain is closely related with groundwater exploitation. This is because there is almost no surface runoff in the plain and winter wheat and summer maize cannot do well without irrigation. Generally, production increases with increasing groundwater exploitation. However, the rate of increase in grain production is bigger than that of groundwater recent years due to fertilization. Hence groundwater consumption intensity for wheat and maize yield is dropping. It is therefore critical to study the impact of fertilizer use on groundwater consumption in the agricultural sector. This paper analyzed the variations in groundwater exploitation for wheat and maize production. It also analyzed the effect of increased grain production on groundwater exploitation. Furthermore, the paper discussed the relationship between fertilizer use and per-unit wheat and maize yield. The results showed that increasing fertilizer use had led to decreasing groundwater exploitation for wheat and maize yield. While groundwater use was 1.86 m³·kg^-1 in the 1970s, it dropped to 0.72 m³·kg^-1 at the start of the 21^st century. According to 0.17 t·hm^-2 fertilizer use in the 1970s without considering yield-increasing effect of fertilization, groundwater exploitation sharp increased to get the total production levels of today. For example, groundwater exploitation respectively increased by 10.35×10⁸ m³, 18.88×10⁸ m³ and 20.12×10⁸ m³ in the 1980s, 1990s and 2000—2005. From the relationship between fertilizer use and per-unit wheat and maize yield, fertilizer use reached 0.76 t·hm^-2 to have the max per-unit wheat and maize yield. In the early 21^st century, however, fertilizer use per-unit area was 0.72 t·hm^-2, which was close to the 0.76 t·hm^-2 dose for max yield. Hence with increasing fertilizer use, there was little potential to increase production and decrease groundwater use.