Research On Rice Growth And The Characteristics Of Soil Nutrient By Underground Pipe Drainage

Affected by global climate change,the frequency and intensity of extreme precipitation are increasing,which has seriously affected the harvest of rice and the sowing of wheat.In the rice cultivation areas in the middle and lower reaches of the Yangtze River,due to poor drainage of the paddy fields,there is water accumulation in the paddy fields,especially in large-scale farms,causing the machines to be unable to work in the fields,resulting in practical problems such as difficult rice harvesting and difficult wheat sowing,and even"snow covered rice" And "January wheat",it seriously affect food safety production.In order to cope with the impact of extreme precipitation and weather on rice and wheat production caused by global changes,and to quickly discharge excess water in rice fields while increasing the water retention capacity of rice fields,underground pipe drainage has been widely promoted and applied.In order to study the effects of underground pipe drainage on soil nutrient migration and rice growth,this experiment conducted a comparison test between underground pipe drainage and traditional open ditch drainage in two large-scale farmland at Donglin Farm in Taicang,Suzhou City,Jiangsu Province from 2018 to 2019.Taking Nanjing 46 as the tested variety,the rice samples were collected at different locations from the ditch(seedling ditch spacing)and the pipe(seedling pipe spacing)in the underground pipe drainage field blocks and the sampling of the traditional open ditch drainage field blocks was used as a control to analyze the difference of the growth indicators and yield of aboveground part of rice,at the same time,the differences in the nitrogen,phosphorus and potassium contents of plant organs and the soil nutrients were analyzed at the tillering stage,long earing stage and fruiting stage and the yield composition.This study provides a theoretical basis for improving the water and fertilizer management that is matched with the concealed drainage,coordinating soil nutrients and rice physiology and yield,and improving the absorption and utilization of nitrogen,phosphorus,and potassium by rice.The main research results are as follows:1.Underground pipe drainage has different effects on rice population quality at tillering stage and heading stage.Under the higher leakage at the tillering stage,it is not conducive to the growth of rice plants at the tillering stage.As a result,the closer to the dark tube and the farther away from the ditch at the tillering stage,the population quality of rice plants tends to decrease,and both are smaller than the control field.During field drying,quickly reduce moisture in underground pipe drainage fields effectively inhibited the flourishing growth of rice.From heading stage to maturity stage,the accumulation of dry matter in concealed drainage fields increases rapidly,the matter weight of the underground pipe drainage field compared to the control field is significantly reduced.2.The effect of the underground pipe drainage on rice nutrient absorption is mainly manifested in the tillering stage and heading stage.Seedling pipe spacing has a more significant effect on the absorption of nitrogen,phosphorus,and potassium at each growth stage of rice.Among them,the impact on the absorption of phosphorus is the largest,potassium is the second,and nitrogen is the least,up to 30%,5%and 2%respectively.The nitrogen content of rice plant stems and sheaths,leaves and panicles directly above the underground pipe drainage was significantly less than that of the plants deviating from the concealed pipe treatment,and even less than that of the control group,the average dry matter weight of underground pipe drainage field decreased by 20%.The peak period of nitrogen uptake of rice plants from the booting stage to the heading stage,so seedling pipe spacing has a very significant impact on the nitrogen content of rice plants at this time.Under the conditions of the same seedling ditch spacing,the nitrogen,phosphorus and potassium content of rice showed a trend of first increasing and then decreasing with the increase of seedling pipe spacing.The nitrogen,phosphorus and potassium content of plant organs at the tillering stage,heading stage and seed setting stage The content reached the maximum under the treatment of 15 m seedling ditch spacing&2.5 m seedling pipe spacing3.In this experiment,underground pipe drainage mainly affects rice yield by affecting the number of grains per panicle,seed setting rate and thousand-grain weight.With the increase of the seedling ditch spacing,the rice seed setting rate and 1000-grain weight showed a downward trend;with the increase of the seedling pipe spacing,the grain number per ear,the seed setting rate and the 1000-grain weight all showed a trend of first increasing and then decreasing,among them,the difference in the number of grains per ear is the largest.The yield reached the maximum value of 9.97 t·hm-2 under the treatment of 15 m seedling ditch spacing&2.5 m seedling pipe spacing,which was 15.22%higher than that of the control group.The number of ears at 15 m seedling ditch spacing&0 m seedling pipe spacing was less than that of the control group by 7.19%.The seed setting rate and 1000-grain weight were higher than those of the control group,while the yield was lower than that of the control group by 2.44%.The results showed that the grain number per spike and 1000 grain weight were increased in the field with underground pipe laying,while the grain number per spike and seed setting rate were the main reasons for the decrease of yield.4.The underground pipe drainage has different effects on the physical and chemical properties of the soil at different growth stages of rice,but the 0-60cm soil nutrient of the concealed drainage field has a higher correlation with the growth vigor index and yield of rice.in the jointing and booting stage when the water demand of rice is large,underground pipe drainage field has a significant effect of water leakage and drainage,the soil moisture of 0-20cm and 0-60cm soil layers was significantly higher than that of the control field,and the distance between the seedling ditch spacing and the seedling pipe spacing had an extremely significant impact on the soil moisture content,however,the leaching loss of surface soil nitrate nitrogen and ammonium nitrogen is relatively large,which is lower than the control group by more than 40%.In the heading stage,the paddy field is at the stage of laying the field,and the concealed pipe drainage field has a significant function of reducing waterlogging,the soil moisture content is lower than that of the control field,the accumulation of soil nutrients is generally higher than that of the control field,the field nutrient content is higher in the soil at 2.5 m seedling pipe spacing due to the leakage of the underground pipe drainage,with the increase of the seedling ditch spacing,the soil nutrient generally decreases.During the grain-setting period,the underground pipe drainage field can maintain a low field humidity,which is convenient for mechanized operation.5.This experiment found that the nutrients leached from the topsoil of the subsurface drainage field will be more leached into the deep soil with the field leakage,increasing the deep soil nutrients,which has a certain effect on the absorption of nitrogen,phosphorus and potassium by rice plants in local areas of the field,and can increase the rice yield.However,free concealed pipe drainage will cause the loss of water-soluble nitrogen,phosphorus and potassium directly above the concealed pipe,which is not conducive to the growth of rice roots and the absorption of nutrients in the early stage,resulting in a decline in yield.Proper drainage intensity of the concealed pipe in the paddy field is conducive to the early root growth of rice,but the artificially changing the way of field leakage has an important impact on the characteristics of solute migration,which may cause the loss of soil nutrients in the cultivated layer,which is not conducive to plant growth.Therefore,the drainage system should be based on the nutrient absorption characteristics of rice to support the appropriate control drainage measures,block the concealed drainage outlet at the stage of establishing a water layer in the rice field at the tillering stage,and maintain an appropriate water level difference between the field and the ditches to control field leakage and avoid nutrient loss.In addition,fertilizer management should focus on increasing the application of nitrogen and phosphate fertilizers in the area directly above the concealed tube during the tillering stage to prevent the reduction in production caused by insufficient nutrients.