Impact of water and temperature on spring maize emergence speed and emergence rate

Maize emergence speed and the emergence rate relate to soil moisture and air temperature,and they largely determine the corn growth and yield.In order to obtain the relationships between seedling emergence speed,seedling rate of spring maize(Zea mays) and soil moisture and air temperature respectively,the experiments of water stress and by-stage sowing for spring maize were conducted at an agro-meteorological experiment station in the central part of Northeastern China.In an artificial rain-proof cover,4 water treatments(not drought,light drought,drought and severity drought) and 3 sowing treatments(early,middle and late) were set to create soil moisture variation and air temperature difference during the period from sowing to germination.And soil moisture,water amount for irrigation,rainfall,air temperature,the seedling stage and emergence rate were observed.The results showed that the relationships between soil moisture and emergence rate,period of emergence both were significantly quadratic function during the periods of sowing and emerging.Below field capacity,the greater soil moisture was,the faster the corn came out and the higher the emergence rate was.Soil drought delayed the period of emergence and decreased emergence rate.Low temperature slowed down the emergence,but had little effect on emergence rate.The equation of relationship between days from sowing to emerging(D),soil moisture(S) at a depth of 0 to 20 cm and average air temperature(T) was D=63.450—1.194S-1.442T.The equation of relationship between emergence rate(P),S and T was P=5.107 S +1.857 T-56.5.Combinational influence indexes of average soil moisture,effective soil water(H) and air temperature on maize emergence speed were that corn emerged quickly when 25%S21%,70 mmH45 mm and T18 ℃;it would emerge normally when 21%S18%,45 mmH 35 mm and 18 ℃T16.5 ℃;and it would emerge slowly when 18%S16%,35 mmH 25 mm and 16.5 ℃T15.5 ℃;and the emergence was postponed remarkably when S16%,H25 mm and T15.5 ℃.Germination rate depended mainly on soil moisture in this study.The highest germination rate(more than 95%) occurred when S85% and H50mm;the higher one(about 90%) when relative humidity was about 80% and 50 mmH40 mm;and the lower one when relative humidity was less than 70% and 50 mmH40 mm;and the one was less than 65% when relative humidity was less than 60% and H30 mm,and the serious drought happened.