直播稻播前不同土壤火焰温度条件下杂草种子发芽率试验

Experiment on Weed Seed Germination Rate in Soil under Different Flame Temperature Conditions before Sowing of Direct-seeded Rice

杂草的有效控制是降低直播稻稳产风险的重要措施,播前土壤火焰处理是以非化学方法在进行播种前抑制杂草种子萌发的有效手段。为明确土壤火焰处理中温度场对杂草种子发芽率的影响规律,采用数值模拟方法对燃料分流部件中集管结构参数进行了研究,数值模拟和验证试验结果表明,当集管内径d为20 mm、气体输入流量为1.0~3.5 m^(3)/h时,最大流量偏差系数Δη在3.0%以内,支管间气体流量分配较均匀。基于数值模拟结果设计了火焰燃烧装置,研究6种输入流量(1.0~3.5 m^(3)/h)的液化石油气燃料对火焰高度和火焰温度分布的影响,以拖拉机行进速度、燃料输入流量和土壤深度作为试验因素,进行了全因素试验,采用稻田间常见的杂草种子研究温度场对杂草种子发芽率的影响规律。试验结果表明,在常温常压工作环境下,火焰高度和火焰温度最高值均随着燃料输入流量的增大而增大;当拖拉机行进速度为2.36 km/h,燃料输入流量为2.5、3.0、3.5 m^(3)/h时,土壤温度最高值可分别达到92.83、116.58、156.83℃;相比未经火焰处理的对照组,当土壤温度达到92.83℃时,在α=0.05的显著性水平下,千金子、异型莎草种子发芽率显著降低,但马唐、鳢肠种子发芽率受影响不显著,当土壤温度达到116.58℃和156.83℃时,4种杂草种子发芽率均显著降低;当土壤温度达到156.83℃时,马唐、鳢肠、千金子和异型莎草4种杂草种子发芽率分别降低94.82%、87.81%、86.54%和84.05%。田间试验结果表明,土壤火焰处理对稗草、马唐、鳢肠和异型莎草有显著的抑制萌发作用,其相对除草率Y≥80.00%。

Effective weed control is an important measure to reduce the risk of stable yields in direct seeded rice,and pre-sowing soil flame treatment is an effective means of suppressing weed seed germination prior to sowing by non-chemical methods.In order to clarify the law of the influence of the temperature field on the germination rate of weed seeds in soil flame treatment,the structural parameters of the header pipe in the fuel diversion component were investigated by using numerical simulation.The results of the numerical simulation and validation test showed that when the inner diameter of the header pipe d was 20 mm and the gas input flow rates were 1.0~3.5 m^(3)/h,the maximum flow deviation ratesΔηwere within 3.0%,more uniform gas flow distribution between outlet branches.Based on the numerical simulation results,a flame combustion device was designed to study the effects of six types of LPG fuels with input flow rates(1.0~3.5 m^(3)/h)on the flame height and the flame temperature distribution,and a full-factorial test was carried out by using the tractor traveling speed,fuel input flowrate,and soil depth as test factors,and the effect of temperature field on the germination pattern of weedseeds was studied using common weed seeds among rice fields. The test results showed that the flameheight and the maximum value of flame temperature were both increased with the increase of fuel inputflow rates under normal temperature and pressure operating environment;when the tractor traveled at aspeed of 2. 36 km /h and the fuel input flow rates were 2. 5 m^(3) /h,3. 0 m^(3) /h and 3. 5 m^(3) /h,the soiltemperature could reach 92. 83℃,116. 58℃ and 156. 83℃,respectively;compared with the un-flamedtreatment control group,when the soil temperature reached 92. 83℃,the germination rate of seeds ofLeptochloa chinensis ( L. ) Nees and Cyperus difformis were significantly reduced at the significance levelof α = 0. 05,but the germination rate of seeds of Digitaria sanguinalis and Eclipta prostrata were notsignificantly affected,and the germination rate of seeds of the four weeds were significantly reduced whenthe soil temperature reached 116. 58℃ and 156. 83℃ . When the soil temperature reached 156. 83℃,the germination of seeds of four weed species Digitaria sanguinalis,Eclipta prostrata,Leptochloa chinensis( L. ) Nees and Cyperus difformis were decreased by 94. 82% ,87. 81% ,86. 54% and 84. 05% ,respectively. The results of the field test showed that the soil flame treatments had significant germinationinhibiting effects on Echinochloa crusgalli, Digitaria sanguinalis, Eclipta prostrata, and Cyperusdifformis,and their relative weed control rates Y was greater than or equal to 80. 00% .