Dynamics of productive moisture reserves in grain sorghum crops depending on sowing time

Under the conditions of the increasing climate aridity, the urgent issue of Donbass rain fed steppe farming is further expanding of the sowing of drought-resistant, heat-resistant and high-yielding crop - grain sorghum. To optimize the parameters of sowing time of the crop, the goal was to study the dynamics of productive moisture reserves in the soil when growing a mid-early hybrid Sprint W in the most contrasting years on moisture (2011, 2012, 2016 and 2017) in the conditions of the experimental field with ordinary chernozem of the state educational institution of the Lugansk People's Republic "Lugansk State Agrarian University". On average for 2008-2017 at sowing and in the stage of sprouting sorghum crop was provided with productive moisture in the meter layer of soil (on average 141 mm), and from the moment of heading the crop has already lacked it (74.8 mm). Moisture reserves vary greatly from year to year both in initial stage of growth (V = 19.1-20.9-21.5%), during panicle heading (V = 43.8%) and during ripening period (V = 47.1%). The average direct correlation of productive moisture with grain productivity of sorghum was noted during the period of grain ripening - milky ripeness (r = 0.61 ± 0.28) and strong - in the stage of full ripeness (r = 0.79 ± 0.21). The greatest reserves of productive moisture in the main stage of sorghum growth were observed in the first sowing period (April 25). However, during the first sowing period by the stage of heading their average reserve was insufficient: 79.5 mm - in the meter and 12,8 mm - in the arable (0-20 cm) soil layers. The strongest reliable correlation of productive moisture with sorghum yield was obtained during the last fifth sowing period (June 5) - at sowing (0.94±0.25), at heading (0.96±0.19), at grain ripening (0.91±0.29) and full ripeness (0.91±0.29). At earlier sowing time, a strong (0.90±0.31 to 0.99±0.11) correlations were observed only at grain ripening and full ripeness.