稻茬高度影响轮作紫云英生长及还田效应

大田试验条件下,研究了水稻机械收割不同留茬高度(15cm 、30cm 、40cm,分别标注低茬、中茬、高茬)对轮作紫云英生长、养分积累以及翻压还田后土壤养分、化学性状和微生物量等的影响。结果表明：稻茬高度显著影响轮作紫云英生长、养分积累以及翻压还田效果。紫云英单位面积株数随留茬高度的降低而显著减少；除单株分枝数外,植株株高、茎粗、单株鲜、干重均表现为高茬处理＞中茬处理＞低茬处理,高、低茬处理间差异显著或极显著。产草量受稻茬高度影响明显,单位面积鲜、干草产量均随稻茬高度的降低而显著减少,高茬处理的紫云英鲜、干草产量均最高,分别达到19.22t.hm_^-2和3.27 t.hm_^-2,较低茬处理每公顷增加15.21 t和2.53 t。不同稻茬高度处理的紫云英植株碳及氮、磷、钾含量无显著差异,植株养分积累量则随稻茬高度增加而显著增加,各养分积累量变化趋势一致；不同处理紫云英翻压还田后土壤pH值变化差异不显著,但均较试验前略有上升；土壤电导率则表现为高茬处理大于中、低茬处理,处理间差异极显著; 翻压后土壤养分变化差异较大,各养分含量均表现为随水稻留茬高度降低而减少的趋势,高留茬处理土壤的有机质、全氮、碱解氮、有效磷、速效钾含量分别较低留茬处理增加41.51%、27.35%、34.96%、68.78%、82.12%。不同处理紫云英翻压还田后,土壤可培养微生物数量存在差异。三大类微生物细菌、真菌、放线菌的数量均以高茬处理最高,除放线菌外,差异均达显著水平,其中,对细菌数量的影响最为明显,高茬处理极显著大于中、低茬处理,中、低茬处理间差异显著。综上,水稻留高茬(茬高40cm)轮作紫云英可获得较高的生物量和养分积累,翻压还田后土壤培肥效果显著优于中、低茬(茬高≦30cm)收割的处理。

Rice Stubble Height Affects Growth and Returning Effect of Chinese Milk Vetch (Astragalussinicus L.) Rotated with Rice

A field experiment was conducted to study the effects of different stubble heights (15cm, 30cm and 40cm, marked with low stubble, middle stubble and high stubble respectively) on the growth, nutrient accumulation of Chinese milk vetch and soil nutrients, chemical properties and microbial biomass after returning Chinese milk vetch to the field. The results showed that rice stubble height significantly affected the growth, nutrient accumulation and the returning of Chinese milk vetch. The number of Chinese milk vetch plants per unit area decreased significantly with the decrease of stubble height. the plant height, stem diameter, fresh and dry weight per plant were show as follows high stubble treatment > middle stubble treatment > low stubble treatment, except the number of branches per plant, and the difference between high stubble treatment and low stubble treatment was significant or extremely significant. Grass yield was significantly affected by the height of rice stubble, and the fresh and hay yields per unit area decreased significantly with the decrease of rice stubble height. The fresh and hay yields of Chinese milk vetch with high stubble treatment were the highest, reaching 19.22t.hm_^-2and 3.27t.hm_^-2, and increased by 15.21 t and 2.53 t per hectare compared with lower stubble treatment. There is no significant difference in carbon, nitrogen, phosphorus and potassium contents of Chinese milk vetch plants treated with different rice stubble heights, but the plant nutrient accumulation increased significantly with the increasing of rice stubble height, and the change trend of each nutrient accumulation is consistent. There is no significant difference in soil pH value after returning milk vetch to field under different treatments, but it is slightly higher than before the test. Soil conductivity is higher in high stubble treatment than in middle and low stubble treatment, and the difference between treatments is very significant. There are great differences in soil nutrients after returning, and showed decreasing trend with the decrease of rice stubble height. The contents of organic matter, total nitrogen, alkali-hydrolyzable nitrogen, available phosphorus and available potassium in high stubble treatment increased by 41.51%, 27.35%, 34.96%, 68.78% and 82.12% respectively compared with those in low stubble treatment. There are differences in culturable microbe population after returning to the field with different treatments. The number of bacteria, fungi and actinomycetes in three kinds of microorganisms is the highest in high stubble treatment, and the differences are significant except