玉米秸秆全量深翻还田对高产田土壤结构的影响

Effects of deep tillage and straw return on soil structure of high-yield spring maize field

为达到玉米生产耕层最适深度(22 cm)和耕层最适土壤容重(1.1~1.3 g×cm^(-3)),解决内蒙古平原灌区耕层浅、犁底层坚硬且厚的农田土壤结构问题,分别选用连续1、2、3、4年秸秆深翻还田定位试验地,秋收后玉米秸秆全量粉碎深翻还田,秸秆年均还田量为20 034.97 kg×hm-2,形成秸秆深翻还田1~4年的4个试验处理(SF1-SF4),以不深翻秸秆还田的处理为对照(CK),研究土壤容重、土壤坚实度、土壤团聚体及其稳定性、土壤肥力及p H随不同年限秸秆深翻还田的变化规律。结果表明:1)SF1-SF4处理0~40 cm土层,土壤容重和土壤坚实度比CK显著减小。2)0~20 cm土层,SF4处理>0.25 mm团聚体比例(R0.25)、几何平均直径(GWD)和平均重量直径(MWD)均比CK显著减小;SF1处理土壤团聚体破坏率(PAD)比CK显著降低9.56%,不稳定指数(SWA)随深翻年限增加而显著降低;团聚体分形维数SF4比CK显著增大7.30%。3)20~40 cm土层,SF1和SF2处理R0.25比CK分别显著增加13.69%和17.83%;SF2处理的MWD和GWD分别比CK显著增加23.92%和53.38%;SF1-SF4处理的PAD比CK显著降低,且SF2显著高于SF1和SF3;而SF1-SF4的SWA比CK显著增加,且随秸秆深翻年限的增加呈逐渐升高趋势;团聚体分形维数SF2比CK显著降低7.39%。4)土壤有机质含量SF1-SF4比CK显著增加,且SF2-SF4处理显著大于SF1;速效氮、速效磷和速效钾SF1-SF4比CK显著增加,土壤p H SF3、SF4比CK显著降低。总之,深翻秸秆还田1~4年对0~40 cm土层土壤影响显著;深翻秸秆还田2年适合土壤犁底层结构的改良,深翻秸秆还田3年和4年适合土壤耕层结构的改良。玉米秸秆全量深翻还田既能达到耕作土壤的目的,同时也增加了土壤有机质,降低土壤团聚体破坏率和土壤水稳性团聚体的不稳定系数,利于培肥耕层土壤。

There are some structural issues of farmland soils in the irrigated Inner Mongolia Plain,such as hard(bulk density of 1.55-1.62 g?cm-3),shallow plough layer(0–16 cm)and thick plow pan(45 cm).To solve these problems and achieve optimum tillage depth of 22 cm and soil bulk density of 1.1-1.3 g?cm-3 of the topsoil layer,a test with 1,2,3 and 4 years of continuous straw return plus deep tillage was conducted in a high-yield spring maize field in the Science-Technology Demonstration Garden of Inner Mongolia Agricultural University.The full maize straw(20 034.97 kg?hm-2)was crushed after autumn harvest and returned to soil combined with 40 cm deep tillage.Four treatments for 1-4 years of straw return plus deep tillage(SF1-SF4)were set and no deep tillage with maize straw return was the control(CK).The soil bulk density,hardness,aggregates and their stability,fertility and pH value were studied.The results showed that:1)in 0-40 cm layer,soil bulk density and hardness significantly decreased under SF1-SF4 treatments compared with CK.2)In 0-20 cm soil layer,the proportion of aggregates>0.25 mm(R0.25),mean weight diameter and geometric mean diameter of SF4 significantly dropped compared with CK.The percentage of aggregate disruption under SF1 significantly decreased by 9.56%compared with CK,the sabotage water-stable aggregates decreased significantly with years of the experiment.The fractal dimension of aggregates of SF4 significantly increased by 7.30%compared to CK.3)In 20-40 cm layer soil,the R0.25 of SF1 and SF2 were significantly increased by 13.69%and 17.83%,respectively,compared with CK;the mean weight diameter and geometric mean diameter of aggregates of SF2 were significantly increased by 23.92%and 53.38%.Then percentage of aggregate disruption of soil aggregates significantly decreased by 9.20%(SF1),3.02%(SF2),8.38%(SF3)and 3.16%(SF4)compared with CK.Sabotage water-stable aggregates significantly increased by 13.58%(SF1),16.49%(SF2),22.67%(SF3)and 25.42%(SF4)compared with CK.Fractal dimension of aggregates of SF2 significantly decreased by 7.39%compared with CK.4)Soil organic matter content significantly increased by 16.32%(SF1),24.78%(SF2),25.07%(SF3)and 25.56%(SF4)compared with CK.Also,available nitrogen,phosphorus and potassium significantly increased compared with CK.Soil pH of SF3 and SF4 significantly decreased respectively by 1.95%and 1.73%compared with CK.In conclusion,the 2-year deep tillage with maize straw return was most suitable for improving the structure of soil plow pan.The 3-year and 4-year deep tillage with maize straw return were suitable for improving the structure of topsoil layer.The application of deep tillage with maize straw return not only improved soil structure of plough layer,but also increased soil organic matter,decreased the percentage of aggregate disruption of soil aggregates and the sabotage water-stable aggregates,and enhanced tillage layer fertility.