Effects Of Water-nitrogen Management And Straw Returning On The Growth Of Rice And Physical And Chemical Properties Of Paddy Soil In Ditch Under No-tillage

Rice planting in ditches under no-tillage are widely extended in Sichuan province. Studying the effect of irrigation methods, fertilizer management and straw returning on the yield of rice and physical and chemical properties of soil could provide a basic for efficient water and fertilizer use in rice production. In this study, Hybrid Rice F you 498 served as a test material. Two experiment were conducted under low carbon rice farming-no-tillage ditch mode, as below:?1? Effects of different water and nitrogen management on rice growth and paddy soil of hybrid rice under no-tillage ditch mode?2014?. A two-factor split-plot design field experiment was conducted. The main plot was two irrigation modes:flooding irrigation ?Wi? and Alternating wet-dry irrigation ?W2?, the subplot was three N application ratios in total amount of 150 kg/hm² rate. The ratios of basal:tillering:panicle were 6:2:2?N₁?> 4:2:4?N₂? and 2:2:6?N₃?, no N application ?No? was set as control. ?2? Effects of different straw returning and nitrogen application on rice growth and paddy soil of hybrid rice under no-tillage ditch mode?2015?. Optimized mode of Water and nitrogen management under the basis of experiment in 2014, the main plot design with three different straw returning types:whole wheat straw returning to the surface ?Si?, straw returning to the ditch ?S₂?, no wheat straw returning ?So?. Nitrogen application level as sub-plots combined with three different level:0?No?,120kg/hm²?Ni2o?, 150kg/hm²?N₁50?,180kg/hm²?N₁8o?. Effects of different water and nitrogen management, different straw-returning types and nitrogen application level on Photosynthetic characteristics, grain quality, nitrogen use efficiency, Physical and chemical Properties of hybrid rice and straw composting under no-tillage ditch mode were investigated systematically. The main research results are as follows:?1? Effects of Different Water and Nitrogen Management on Rice Growth and Paddy soil of Hybrid Rice under No-tillage Ditch Mode?2014?.The different irrigation methods and nitrogen management affected the biomass, nitrogen accumulation, transport and grain yield at main growth stages significantly. Alternating wet-dry irrigation benefited the formation of expanded "Library" by the "source", which in turn ensured adequate spikes and high biomass accumulation. Flooding irrigation resulted in more ineffective tillers and poor population quality, thus adversely affects biomass accumulation, N uptake and yield formation. Postponing nitrogen fertilization provided a more balanced N supply in the whole growing period, which can promote the total absorption of nitrogen and accumulation of nitrogen. The highest apparent N use efficiency rate was 69% in N₂ treatment, in which the partial actor productivity of applied nitrogen, the N agronomic efficiency, the N apparent use efficiency and the yield were 4.50%?36.85%,8.09%?28.54% and 7.47%?15.76% higher than those of N₁?6:2:2? and N₃?2:2:6?. Rational management of water and nitrogen increased the amount of nitrogen accumulated at each growth stage significantly. Compared to flooding irrigation, alternating wet -dry irrigation can reduce soil bulk density, improve soil total nitrogen and organic matter content in different topsoil. In the rice growing period, due to the paddy field stayed in flooding state of long-term, the effects of many obstacles factors resulted low organic matter and total nitrogen content, such as low temperature of water and soil, the lower the effectiveness of nutrients, soil acidification and so on. With the increasing of the proportion in postponing N application, bulk density decreased at the first and then increased; soil total nitrogen and organic matter of 0-10cm increased first and decreased, N₂ was the highest; soil nitrogen content and organic matter content of 10-20cm were inconsistent, total nitrogen content of N₃ was the highest at maturity, while the majority of organic matter in N₂ treatment showed a higher. Alternating wet-dry irrigation ?W2? in combination with Nitrogen Application ratio of 4:2:4 ?N₂? was the optimal water and nitrogen mode under no-tillage ditch mode. The water and nitrogen management had significant coupling effect in promoting the formation of large nutrient source and effective transfer to the "reservoir" after full heading stage, which was favor of buildup high yield and N use efficiency; What's more, improving per panicle and seed setting rate can reach a significant yield. And it was more beneficial to improve soil structure and soil environment, to increase soil fertility, to conducive to crop growth than the other treatments.?2? Effects of Different straw-returning types and Nitrogen application level on Rice Growth and Paddy soil of Hybrid Rice under No-tillage Ditch Mode?2015?.Based on the optimal mode of Water and Nitrogen management, straw-returning types and Nitrogen application level was investigated.In terms of straw decomposition:Straw returning to the ditch kept the straw been in a state of water, lead to the straw decomposition efficiency be less than S₁. The decomposition and nitrogen release of wheat straw both shows:in the former stage The decomposition and N-release very fast, but along with the rice growth, the speed were slow down. Straw decomposition amount increase gradually with the growing period. With the increase of nitrogen amount, straw decomposition amount was first increased and then decreased. Nitrogen release of wheat straw increase gradually with the growing period yet. In the jointing stage, the nitrogen release rate could reach about 50%. Straw decomposition rate and the nitrogen release rate of S₁ is higher than S₂ Significantly.In terms of Physical and Chemical Properties of soil, wheat straw returning can decrease bulk density, increasing soil total nitrogen and organic matter of 0?20cm. Whole wheat straw returning to the surface was better than wheat straw returning to the ditch in improving soil fertility, more than no wheat straw returning. Along with the increase tend of Nitrogen application level, soil total nitrogen and organic matter of 0?10cm increase first and decrease then in the condition of straw returning, N₁50 is the highest.In the terms of growth of Hybrid Rice, straw returning can increase spike rate, straw returning to the surface can increase the amount of biomass accumulation, contribution rate of export and transfer rate from stem and sheath; Straw returning along with N can reduce the descent rate of net photosynthetic rate after full heading Significantly especially S₁N₁50, it can keep a high level of SPAD, can ensure sustainable and efficient photosynthetic capacity of flag leaves in late stage. Straw returning along with N can coordinate the relationship between the "library" and the "source",and then it is beneficial to improve the amount of biomass accumulation after full heading. Straw returning add up to the root length, root diameter, root volume and root surface area of individual plant. Increasing nitrogen application rate can Increase the root surface area and root diameter, N₁50 is the highest.In the terms of Nitrogen transport and absorption:Straw returning was beneficial to accumulate nitrogen of steam, leaves and spike in growing period. Straw returning increase N transportation and N increment in panicle. The N agronomic efficiency and theN apparent use efficiency in the proportion of Si were increased by 5.52%?25.58%? 17.02%?40.95%, compared to those of S0 and S₂. Increasing nitrogen fertilizer can improve the N agronomic efficiency and the N apparent use efficiency, but the higher the amount of nitrogen, N harvest index and N use efficiency for grain production decreased in different degrees.In the terms of Yield and its components:Straw returning was beneficial to increase 1000-grain weight, Straw returning to surface was beneficial to increase effective panicles and then increase yield, the yield of S₁ were increased by 2.71%?10.69% than others.Straw returning to the surface, the optimal nitrogen application rate of 150kg/hm² and Alternating wet-dry irrigation is the optimal model under no-tillage ditch mode. It can make full use of the effects of straw to field on the paddy soil, rice roots and the upper part, and play the advantages of interaction with the appropriate amount of nitrogen fertilizer. Promote the growth of rice roots, the amount of biomass accumulation and transportation, improving N increment in panicle, The N agronomic efficiency and the N apparent use efficiency, and late the nutrient release of straw to prevent plants from premature aging, promote the yield formation.