关键词: 旱地小麦, 翻耕时间, 降水量及其分布, 产量, 水分利用率

Abstract:

【Objective】 Aiming to solve the problems of low precipitation and uneven distribution of precipitation during the growth period, significant inter-annual variability, large proportion of precipitation during fallow period, and low water use efficiency (WUE) of precipitation, the objective of this study is to investigate the impact of deep ploughing time during fallow period in different precipitation years on soil water storage and wheat yield, and to provide a theoretical basis for revealing the yield depending precipitation years in southern Shanxi.【Method】 The field experiment was laid out following a randomized complete block design from 2010 to 2021, with three deep ploughing times set on August 10th (P₁), August 20th (P₂), and August 30th (P₃) to investigate the effects of ploughing time, precipitation, and its distribution on wheat yield, soil water storage characteristics during fallow periods, water consumption during growth periods, and their correlations.【Result】 (1) The precipitation year type exhibited a strong correlation with the average yield of dryland wheat, which ranged from 2 400.0-6 298.0 kg·hm^-2, with the coefficient 29.8%. The average yields for wet years (2012, 2014 and 2015), normal years (2011 and 2013), and dry years (2010, 2016, 2019, 2020 and 2021) were 5 524.6, 3 048.2, and 4 088.7 kg·hm^-2, respectively. The impact of precipitation year type on yield followed a descending order: annual precipitation, precipitation in the fallow period, and precipitation in the growth period. Both precipitation in the fallow period and the growth period primarily affected yield through their effect on spike number and kernels per spike. Additionally, an increase in both annual precipitation and March to April’s precipitation led to a significant increase in yield. The effect of deep ploughing time on wheat yield in dryland was closely related to the precipitation distribution in fallow period, which showed that P₁ yield was higher with more precipitation in July-August, and P₂ or P₃ yield was higher with more precipitation in September. (2) Precipitation, its distribution, and ploughing time had an impact on soil storage and consumption characteristics before sowing and after harvest. Precipitation during the fallow period mainly affected the soil water storage capacity in the lower layer (100-200 cm) before sowing and after harvest. The water storage capacity of the upper layer (0-100 cm) and the lower layer was similar or slightly low before sowing under the water-rich type in the fallow period. The water storage capacity of the lower layer was 6.17% and 24.66% lower than that of the upper soil under normal water and low water in the fallow period, respectively. More precipitation in July led to greater water storage in the lower soil, while more precipitation in August and September resulted in greater water storage in the upper soil. During growth periods, precipitation primarily impacted water storage capacity of the upper soil at harvest time, especially precipitation occurring in May. The average soil water storage capacity in the upper layer was the highest in P₂ before sowing and at harvest time, and the water storage capacity of subsoil and the average water storage capacity of 0-200 cm soil was the highest in P₂ or P₃ at harvest time. (3) The effects of ploughing time and precipitation on water consumption and WUE were relatively small. The water consumption of dryland wheat during the growing period was affected by the annual precipitation, especially the precipitation in March.【Conclusion】 Precipitation and its distribution during the fallow period affect the soil water storage capacity of 0-200 cm before sowing of dryland wheat, and affect the yield of dryland wheat through spike number, kernels per spike together with the precipitation in March and April. There is a significant positive correlation between WUE and yield. In dryland wheat fields in south Shanxi Province, when there is more precipitation in July-August, deep ploughing is done on August 10th, and when there is less precipitation, deep ploughing is properly delayed from 10 to 20 d, which can effectively maintain soil water content during fallow period and achieve high yield.

Key words: dryland wheat, ploughing time, precipitation and its distribution, yield, water use efficiency (WUE)