Identifying key meteorological factors to yield variation of potato and the optimal planting date in the agro-pastoral ecotone in North China

Precipitation is the key yield-determining factor for rainfed agricultural production such as the agro-pastoral ecotone in North China with high variation in precipitation. However, the yield-precipitation relationship depends on the distribution and amount of precipitation over the crop growth period. Understanding crop yield responses to precipitation can help develop appropriate measures to ensure stable crop production in the agro-pastoral ecotone. In this study, an experiment was conducted consisting of five planting dates each year across four years and three planting dates in one year, to investigate the potato yield response to precipitation at a representative site (Wuchuan) in the ecotone. The optimal planting date, with the highest potato yield, varied substantially in different years during the experimental period. It was found that potato yield had the highest correlation with the ratio of precipitation to potential evapotranspiration during the tuberization stage (PT/ETpT) (R2 = 0.51, P < 0.01), followed by the effective precipitation during the post-tuber bulking period (EPpoTB) (R2 = 0.43, P < 0.01) and during the entire growth period (EPgp) (R2 = 0.28, P < 0.05). The potato yield was positively related to total solar radiation during the growth period (Sgp) (R2 = 0.37, P < 0.01), especially during the pre-tuber bulking period (SprTB) (R2 = 0.44, P<0.01), while growth-period maximum temperature (Tmaxgp) had a negative effect on potato yield (R2 = 0.27, P < 0.05). The multiple linear regression equation of potato yield and meteorological factors during the potato growth period showed that the variation in PT/ETpT, EPpoTB and SprTB could explain 71% of the variation in potato yield. The optimal planting dates, based on the 80 t h percentile of the highest yield related to PT/ETpT, EPpoTB and SprTB within the potential planting window from 1961 to 2010, were found to be May 27-June 12 for a wet year, May 3-May 26 for a normal year, and April 4-May 2 for a dry year, if sufficient soil moisture could ensure emergence of potato.