Study On Compensated Growth And Water Use Efficiency Under Regulated Deficit Irrigation For Rice In Black Soil

The black soil region of Heilongjiang Province is an important japonica rice production base in China.The content of soil organic matter in this region is relatively high er,which provides good conditions for rice production.However,the lack and uneven distribution of water resources restrict the sustainable production of rice in the black soil region of Northeast China.Therefore,it is of great significance to study the water-saving and yield increasing mechanism of rice in black soil area for promoting the rational use of water resources,ensuring rice yield and improving water use efficiency.The pot experiment was carried out in Qing’an national irrigation experimental station of Heilongjiang Province from May to September in 2019.Light(-10 k Pa),medium(-25 k Pa)and heavy(-40 k Pa)water deficit treatments were set at tillering stage,jointing stage,heading stage and milk maturity stage respectively.Meanwhile,shallow water irrigation was used as control.The effects of different degree of water deficit on rice growth,physiology,yield and water use efficiency in black soil region were studied.The TOPSIS method was used to evaluate the effects,and the optimal water management model at different growth stages was proposed.The main results of this experiment are as follows:The effects of water deficit at different growth stages on the growth characteristics of rice were showed that the tiller numbers of each water deficit treatment at tillering stage were increased rapidly at first,then decreased slowly and finally tended to be stable during the whole growth period,and decreased with the aggravation of water deficit,among which light and medium water deficit treatments at tillering stage could effectively reduce ineffective tillers.In the whole growth period,the processing plant height was the“S”type curve of monotone increasing,LAI,leaf and sheath dry matter weight showed an inverted V-shaped change,stem and spike dry matter weight increase gradually.Except that light and medium water deficit had no influence on plant height,LAI and dry matter weight of aboveground organs in the milk maturity stage,the other growth stages of water deficit on plant height,LAI and dry matter weight of aboveground organs had different effects,bu t the treatments of light water deficit and medium water deficit at tillering stage all produced definite compensatory growth after rewatering.Root-shoot ratio of all treatments decreased gradually with the development of growth stage,except for light and medium water deficit at milk maturity stage,the root-shoot ratio of the other water deficit treatments increased significantly,and the increase increased with the aggravation of water deficit degree,but the treatment of light water deficit and medium water deficit at heading stage showed a certain compensatory growth after rewatering.The effects of water deficit at different growth stages on the physiological characteristics of rice were showed that P_n,T_r,g _S and C_i were showed an inverted V-shaped trend,and reached the peak value at heading stage,P_n,T_r and g _S were decreased with the increase of water deficit degree at regulating deficit stage,while C_i increased with the increase of water deficit degree.After rewatering,P_n and g _S were significantly compensated by light water deficit treatments at different growth stage,medium water deficit treatments at tillering stage and milk maturity stage,T_r could be compensated by light and medium water deficit treatments at tillering stage and light water deficit treatments at jointing stage.Except for the tillering stage,light water deficit treatments at different growth stage and medium water deficit treatment at milk maturity stage had a certain compensation effects on C_i.The SPAD of all treatments increased first and then decreased with the development of growth period,and reached the peak value of water deficit treatment at tillering stage and jointing stage were 51d after transplanting,while the peak value of other treatments were 61d after transplanting.The SPAD of water deficit treatments at tillering stage increased with the increase of water deficit degree,while the SPAD of other treatments decreased with the increase of water deficit degree.With the except of milk maturity stage,the light water deficit at each growth stage recovered to normal level after rewatering,indicated a certain compensation effect.The effect of water deficit at different growth stages on water saving and increase yield of rice were showed that all water deficit treatments could effectively reduce water consumption,water consumption intensity and water consumption model coefficient in the deficit stages,and the difference with CK is reduced after rewatering.There were no significant change of leaf water use efficiency under water deficit treatment at tillering stage,while water deficit treatments at the other growth periods increased with the aggravation of water deficit degree.However,due to rebound of the transpiration rate after rewatering,the leaf water use efficiency decreased with the increase of deficit degree.The effective panicle numbers,grain numbers per panicle and seed setting rate of rice were significantly affected by water deficit treatments at tillering stage,heading stage and milking stage,respectively.However,light water deficit at tillering stage could significantly increase spike grain numbers and 1000-grain weight,and the yield,water use efficiency,stem and sheath material output rate and conversion rate were significantly higher than those of other treatments.The entropy weight method and TOPSIS model were combined to compreh ensively evaluate rice growth indexes,physiological indexes and water-saving and yield increasing effect.The results showed that light water deficit at tillering stage was the best regulated deficit irrigation scheme,followed by light and medium water deficit at milk maturity stage.Through the analysis of test results and comprehensive evaluation of TOPSIS model,it is concluded that light water deficit at tillering stage could not only improve rice yield,but also effectively reduce water consumption and improve water use efficiency.The research results c ould provide theoretical basis and reference for water saving and yield increase of rice in black soil area.