Water-saving And Yield-increasing Effects Of Biochar On Maize Under Regulated Deficit Irrigation In Black Soil Region

Heilongjiang province is an important commodity grain base in China, is one of the largest maize producing areas as well. Sustained and stable maize yield in this area plays an irreplaceable role in ensuring national food security. However, Heilongjiang Provinc e water resources shortage, low agricultural water utilization and "spring drought" in Heilongjiang Province have seriously affected agricultural production and development in Heilongjiang Province. A pot experiment on maize was carried out in Hong Xing Farm in Bei An city in 2014. Different levels of water deficit treatments were proceeded at the initial growth stage of maize with less precipitation. And biochar was applied into soil to study their effects on maize biological index,WUE and coupling effect of water and biochar, providing a scientific method and technical support for straw resources recycling and water-saving agriculture sustainable development in Heilongjiang province. The results are summarized as follows:(1) A moderate amount of biochar can improve the plant height, stem diameter and leaf area under RDI at seedling stage,while high amount of biochar have little effect on them; The plant height and leaf area increase with the increasing amount of biochar under RDI at jointing stage,while biochar has little effect on maize stem diameter. Re-water after RDI at seedling stage shows obvious compensation and promotion effect on plant height, stem diameter and leaf area, compared with suitable irrigation treatments, and higher amount of biochar treatments have more obvious; Re-water after RDI at jointing stage shows obvious compensation and promotion effect on stem diameter, this re-water effect on plant height and leaf area is obvious under higher amount of biochar, while it isn’t under low amount.(2) Biochar can improve maize root dry weight, root dry weight, aboveground part dry weight and root shoot ratio of maize in different degrees under RDI at seedling stage and jointing stage. Compared with suitable irrigation treatments, heavily RDI inhibits the growth of maize root and aboveground part at seedling stage and jointing stage, root shoot ratio increases under higher amount of biochar while it decreases under lower amount of biochar when heavily RDI is carried out at seedling stage, root shoot ratio increases under heavily RDI at jointing stage; Heavily RDI improves root dry weight and root shoot ratio,while it has little effect on dry weight of aboveground part.(3) Biochar can improve water consumption, yield per plant and WUE under RDI at seedling stage and jointing stage. Compared with suitable irrigation treatments, water-saving effect of heavily RDI is significant at seedling stage, yield per plant decreases under lower amount of biochar, while less effect on it higher amount of biochar, WUE increases especially under higher amount of biochar; water-saving effect of lighter RDI is not significant, yield and WUE increase somehow. water-saving effect of RDI is significant at jointing stage, The yield reduced more under under lower amount of biochar, it has little effect on yield under higher amount, WUE decreases under lower amount of biochar, while it increases under higher amount of biochar.(4) Effects of water, biochar and their interaction on both yield and WUE reach e xtremely significant or significant level at seedling stage and jointing stage under RDI by variance analysis and regression analysis; Water and biochar have significant positive effects on yield and WUE of maize, biochar is more effective than RDI; Coupling effect of water and biochar has a significant negative interaction on yield and WUE; when irrigation upper limit reaches 66% and 57%,amount of biochar reaches 33g/kg and 36g/kg, yield and WUE reaches the maximum, 167.58g/pot and 4.38g/kg, respectively, at seedling stage; when irrigation upper limit reaches 80% and 0%,amount of biochar reaches 33g/kg and 51g/kg, yield and WUE reaches the maximum, 154.39g/pot and 4.29g/kg, respectively, at jointing stage.(5) The optimized water and biochar amount is obtained by considerin g both yield and WUE: upper limit of water amount: 63%, amount of biochar: 34.2g/kg at seedling stage; upper limit of water amount: 66%, amount of biochar: 38.4g/kg at jointing stage. Optimized water and biochar input at seedling stage under RDI is the best water and biochar coupling mode in this experiment by comparative analysis, yield and WUE are 167.34g/pot and 4.36g/kg, respectively, under this condition.