Based annual classification of precipitation fallow period in dryland the Loess Plateau of China

In order to clarify the relationship between wheat yield and precipitation in dryland region, the annual classification method of precipitation in fallow period was summarized in this paper by analyzing precipitation, precipitation distribution and its relationship with yield in Wenxi Experimental Base of Shanxi Province and major meteorological stations on the Loess Plateau from 1983 to 2020.The results showed that the average precipitation during fallow period was 296mm (coefficient of variation CV = 10%), accounting for 58% (coefficient of variation CV = 6%) of annual precipitation in the upland region of the Loess Plateau. With the increase of precipitation in fallow period, the wheat yield in dryland increased logarithmically (Y = 2526.5 lnX-10148, R2 = 0.42, P   Pm + 0.33δ; Pm-0.33 δ ≤ Pi ≤ Pm + 0.33δ; Dry years: Pi < Pm-0.33 δ, Pi was annual precipitation (mm); Pm is perennial average annual precipitation (mm); δ is mean variance of annual precipitation (mm). The proportion of perennial and humid fallow precipitation was lower than the multi-year average were defined as abnormal years, and the years in which the proportion of arid fallow precipitation was higher than the multi-year average were defined as abnormal years.