Effects Of Irrigation Methods On Growth,Yield And Quality Of Directly-sown Rice In Cold Region

Directly-sown rice is a streamlined cultivation mode with the advantages of labor saving and water saving.The experiment was conducted at the Northeast Agricultural University farm,Acheng in 2018.With Longqingdao 21 and Suijing18 as experimental materials,In order to explore the effects of different irrigation methods on growth characteristics,dry matter accumulation and transportation,yield and its components and quality of directly-sown rice in cold regions,we designed four irrigation methods,flooding irrigation(T1),mild dry and wet alternate irrigation(T2),severe dry and wet alternate irrigation(T3)and drought management(T4).Meanwhile,the optimal irrigation method was further defined to provide theoretical basis and yield increase and quality of directly-sown rice in cold regions.The main results of this study are as follows:(1)Under different irrigation methods,plant height,maximum tiller number,final tiller number and leaf area index of directly-sown rice in cold region were affected to varying degrees.Compared with T1 treatment,plant height,maximum tillering number,final tillering number and leaf area index of T2,T3 and T4 treatment all decreased in varying degrees,but the decrease was not significant in T2 treatment,which inhibited ineffective tillering,increased earing rate,increased leaf area efficiency and reduced leaf area attenuation rate.The final plant height,tiller number,leaf area index at heading and maturity of Suijing 18 were higher than Longqingdao 21.(2)Different irrigation methods have significant effects on dry matter accumulation in the above-ground and under-ground parts of directly-sown rice in cold regions.Compared with the T1 treatment,the above-ground dry matter accumulation,output and output rate of the T2 treatment did not reach a significant level(P>0.05),but the T3 and T4 treatments decreased significantly.the conversion of the stem and sheath material of T2 treatment was significantly increased compared to the T1 treatment,but the T3 and T4 treatments were significantly reduced.Under the T2 treatment condition,the directly-sown rice can accumulate more dry matter and distribute it,which is the optimal irrigation mode.(3)Different irrigation methods have a significant effect on the photosynthetic potential,net assimilation rate and population growth rate of direct seeding rice in cold region.The photosynthetic potential,population growth rate and net assimilation rate of the two rice varieties were T1>T2>T3>T4,and there was no significant difference between T1 and T2 treatment(except for the difference of population growth rate between heading and maturity of Longqingdao 21),but the net assimilation rate of T3 and T4 treatment decreased significantly(except tillering-jointing stage of the two rice varieties).(4)Different irrigation methods have significant effects on grain-leaf ratio of direct seeding rice in cold regions.The change trend of grain-leaf ratio of the two rice varieties was generally the same.There was no significant difference between T1 and T2 treatments,which were significantly higher than those of T3 and T4 treatments.(5)Different irrigation methods have a significant effect on the yield of direct seeding rice in cold regions.Both rice yields decreased with the decrease of soil water potential.Compared with T1 treatment,the effective panicle number,grain number per panicle and 1000-grain weight of Longqing rice 21 under T2 treatment were not significantly different from those under T1 treatment,but the seed setting rate was significantly reduced,which led to a decline in yield,and the yield and its components of T3 and T4 treatment were significantly reduced.Compared with T1 treatment,there was no significant difference in yield and yield components of Suijing 18 under T2 treatment,but T3 and T4 treatment decreased significantly.The harvest index of Longqing rice 21 was T1>T2>T3>T4,and Suijing 18 was T2>T1>T3>T4.For Suijing 18,T2 treatment has great potential for water saving and yield increase,which is the best irrigation method.(6)The effects of different irrigation methods on the water use efficiency of directly-sown rice in cold regions reached significant differences.The water use efficiency of Longqing rice 21 was T4>T3>T2>T1,and Suijing 18 was T3>T4>T2>T1.According to the analysis of economic benefit and yield,the irrigation water saving of Suijing 18 was 32%,and the yield decreased slightly.So Suijing 18 is the most suitable direct seeding rice variety,and T2 treatment is the best irrigation method.(7)Different irrigation methods have significant effects on rice quality of direct seeding rice in cold regions.Compared with T1 treatment,T2 treatment can significantly improve the polished rice rate and the whole milled rice rate of the two rice varieties.There is no significant difference in the brown rice rate,and the whiteness and chalkiness rate are reduced,but the T3 and T4 treatment results are opposite.All four treatments had no significant effect on the ratio of length to width.The taste value of the two rice varieties decreased with the decrease of soil water potential,while the and amylose content increased.The protein content of Longqingdao 21 rice was T3>T4>T2>T1,and that of Suijing 18 was T4>T3>T2>T1.