| Water is a key factor impacting crop growth and yield in agroecosystem. Black soil region in Northeast China located in semi-arid and semi-humid climate zone is one of important agricultural production areas, with limitation factor associated with water in agricultural production. Black soil zone in Northeast China is belonging to rain-fed agriculture, and most of water storied in soil profile comes from precipitation, which resulted in effect on water migration and store in soil profile. The precipitation distribution is uneven in a year and year to year, which resulted in the reduction of crop yield. Therefore, the increase in water use efficiency is an urgent scientific by suitable irrigation schedule in study site. Soil water dynamics impacted soybean growth and yield in this irrigation experiment. So Based on long-term field experiment in National Field Research Station of Agro-ecosystem in Hailun in this research, soil water dynamics in farmland un irrigation schedule was considerate, and soybean yield and water use efficiency were discussed, the objections of this study is to propose the suitable irrigation level and to enhance soybean water use efficiency. The main conclusions were drawn as follows:Four irrigation levels were test in this study including natural rainfall (R), over water treatment (I1), suitable water treatment (I2), drought water treatment (I3). The great variation of soil water contents between different treatments was in0-70cm soil depth, water could infiltrate into110cm soil depth when amount of water entered into soil. The variation of soil water content between different treatments was decreased with the soil depth increasing, and the smallest variation was observed below110cm soil depth, indicating that0-110soil layer has strong soil water capacity. Acute change layer and active change layer were not found in all tested treatments in2011and2012. In20110-150cm soil layer was relative stable layer for I1treatment;0-10cm and10-150cm soil layers were sub-active layer and relative stable layer for12treatment, respectively;0-20cm and20-150cm soil layers were sub-active layer and relative stable layer for13treatment, respectively;0-10cm and10-150cm soil layers were sub-active layer and relative stable layer for R treatment, respectively. There were deeper sub-active layers for I1and12in2012. Soil water storage in0-150cm soil depth was different for four treatments after starting irrigation with the largest difference range in R treatment. The similar trend of soil water storage in0-150cm soil depth was observed in I1,I2and I3, indicating that the time and amount of water entry decided soil water dynamics.Different irrigation level impacted soybean yield and water use efficiency. The largest biomass was observed in I1treatment in soybean flower and pod stages in both2011and2012, and significant difference was recorded compared with R,12,13treatments. Soybean height was in a decreasing order of I1> I2> R> I3.I2treatment obtained the largest soybean yield in2011and2012. Soybean yield in12treatment was increased13.78%、12.47%and34.14%in2011and19.24%、14.35%and30.8%in2012compared with R, I1and13, respectively. Water use efficiency was in a decreasing order of I3> I2> R> I1. Sufficient water supply could enhance soybean growth,11treatment obtained largest biomass and plant height. But only suitable water supply (12) could obtain largest yield.The construction of soybean yield included number of nodes per plant, number of pods per plant, number of grains per plant, number of flat pods per plant and100-grain weight. The number of nodes per plant and number of pods per plant of I1treatment were significantly higher than R,12and13.13and R treatments obtained relative higher flat pod ratio because of the occurrence of water deficit, with1.89and1.09flat pods plant, respectively.12treatment obtained the largest100-grain weight due to the suitable irrigation schedule; however,13treatment was in the least100-grain weight because of serious water deficit.Therefore, irrigation levels have affected soil water dynamics, soybean yield, water use efficiency and the construction of yield. Suitable irrigation level (12) could improve soil water conditions, enhance soybean growth, finally increase soybean yield and water use efficiency. |
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