Adaptability To Soil Drought And High-yielding And Water-saving Irrigation Technology In Maize

Water shortage and drought are the worldwide serious problems.Maize is the largest grain crop in China with its largest planting area,and water shortage and drought seriously impact on maize production.Therefore,it would have great scientific significance and practical significance in increases in grain yield and water use efficiency and the development of water-saving agriculture by clarifying the adaptability of maize to soil drought and establishing high-yielding and water-saving irrigation technology.In this study,the local high-yielding maize varieties were used,and three experiments,response of abscisic acid(ABA)to drought,the performance of grain yield and physiology under moderate soil drought,and the effect of alternate partial root-zone irrigation on yield,were conducted.The adaptability to soil drought and the effect of water-saving irrigation on grain yield were studied through investigating endogenous hormone levels,dry mater production and assimilate remobilization,grain filling and grain yield of maize.The main results are as follows:1.When soil water potential was ranged from-15 to-75 kPa,ABA content in maize roots was increased with the decrease of soil water potential.The transpiration rate of leaves was decreased linearly with the increase of ABA content.But the leaf photosynthetic rate was not significantly decreased with the increase of ABA content if the ABA content was lower than 19 nmol g-1 DW.The relationship of leaf water use efficiency(photosynthetic rate/transpiration rate)with the root ABA content showed a downward parabola curve.When the ABA content in roots was approximately 19 nmol g-1 DW,the leaf water use efficiency reached the maximum.The grain yield was increased first and then decreased with the increase in root ABA content,and the peak appeared when the ABA content was about 12 nmol g-1 DW.2.Compared with the well-watered control(WW,soil water potential kept at-2015 kPa),the moderate soil drought treatment(MD,soil water potential kept at-40±5 kPa)during the whole growth period could enhance superoxide dismutase(SOD)activity,decrease malondialdehyde(MDA)content,increase the leaf photosynthetic rate and contents of zeatin +zeatin riboside(Z+ZR),indole-3-acetic acid(IAA)and ABA in maize leaves,promote the remobilization of non-structural carbohydrates(NSC)from the stem and sheath to grain,and increase grain filling rate and grain weight of inferior kernels.Compared with WW,the MD increased grain yield by 2.1-4.5%,reduced irrigation water by 30.6-31.4%,and increased irrigation water use efficiency(grain yield/amount of irrigation water)by 48-52%.3.Compared with the conventional irrigation,alternate partial root-zone irrigation by controlling the low limits of soil water potential in each growth period(shortly called alternate partial root-zone irrigation)reduced irrigation water by 39.9-43.2%,increased grain yield by 6.9-11.1%and water use efficiency[grain yield/(irrigation+ rainfall)]by 27.3-37.9%.In the drying period of alternate partial root-zone irrigation,the transpiration rate was decreased significantly,but leaf photosynthetic rate was not markedly affected.While during the re-watering period,the Z+ZR content and photosynthetic rate of leaves and sucrose synthase(SuSase)activity in kernels were substantially increased.The alternate partial root-zone irrigation reduced the leaf angle of canopy,enhanced sucrose phosphate synthase(SPS)activity in the stem and sheath,promoted the remobilization of NSC from the stem to grain after silking,and increased harvest index.4.The alternate partial root-zone irrigation technology of maize was demonstrated in the production.Compared with the local conventional irrigation technology,the alternate partial root-zone irrigation technology increased grain yield by 7,1-9.5%,decreased irrigation water by 33.3-37.7%,and increased water use efficiency[grain yield/(irrigation+ rainfall)]by 21.6-26.1%.