Dynamics of residue decomposition and N2 fixation of grain legumes upon sugarcane residue retention as an alternative to burning

Burning of sugarcane residues contributes to air pollution and sugarcane producers have been forced to abandon it. The change from burning to residue retention is likely to alter the cycling of nutrients. Additionally, there is often a time gap of 6–8 months between two different sugarcane cycles during which legumes could be planted. Thus, the objective of this study was to assess the effects of burning, mulching or incorporation of sugarcane residues on residue decomposition and N mineralization (sugarcane residue management period) and subsequently upon ploughing (legume period) on N dynamics, N₂ fixation, development and nutrient yields of groundnut and soybean grown between two sugarcane cycles on a sandy soil in Northeast Thailand.

Soil microbial biomass N increased when sugarcane residues were incorporated instead of burned or surface applied at 14 days after initiation of cane residue management. Thereafter, high net N mineralization was accompanied by a reduction in microbial biomass N, indicating that mineralized N was derived from microbial N turnover. However, upon ploughing after 96 days the different previous sugarcane residue management strategies had no significant (P > 0.05) effect on net mineral N and microbial biomass N during the subsequent legume period. Although, ¹⁵N enrichment in control reference plants and plant N uptake indicated significant N immobilization effects persisting into the legume crop phase, the proportion of N derived from N₂ fixation (%Ndfa) or amount of N₂ fixed were not significantly different between sugarcane residue management treatments. Soybean fixed more N₂ (78%Ndfa, 234 kg N fixed ha⁻¹) than groundnut (67%Ndfa, 170 kg N fixed ha⁻¹) due to its larger N demand and a poorer utilization of soil N (64 kg N ha⁻¹ vs. 85 kg N ha⁻¹). Groundnut led to a positive soil N balance while that of soybean was negative due to its high nitrogen harvest index. Legume residues returned 61 and 146 kg N ha⁻¹ to the soil for soybean and groundnut, respectively, compared to only 34–39 kg N ha⁻¹ by fallow weeds. Sugarcane residue retention improved soil organic carbon and N content. The results suggested that although a change from burning to sugarcane residues retention led to alterations in N cycling and improved soil organic matter it did not significantly affect N₂ fixation due to the uniforming action of ploughing and the extended time gap between sugarcane residue incorporation and legume planting.     

长期地膜覆盖及不同施肥处理对棕壤中全硫和有效硫的影响

对长期连续覆膜(1987年～2005年)及不同施肥处理的棕壤中土壤全硫及有效硫进行动态变化研究。结果表明:表层土壤全硫及有效硫含量差异显著,土壤全硫含量的垂直分布随土层加深而逐渐降低。四种施肥处理对全硫和有效硫含量有一定影响,全硫含量高低顺序为M2N2>M2>N2>CK;有效硫的顺序为N2>M2N2>M2>CK。裸地土壤全硫和有效硫含量随时间变化总体呈下降趋势,而覆膜土壤总体上升。     

地膜覆盖对土壤微生物群落结构的影响

采用磷脂脂肪酸(PLFA)法测定了沈阳农业大学棕壤长期定位试验站地膜覆盖条件下土壤微生物磷脂脂肪酸图谱及群落结构。结果表明:在玉米苗期,长期施氮肥处理土壤覆膜后大部分脂肪酸含量都有所提高;施有机肥处理的土壤覆膜后脂肪酸的含量有降低的趋势;有机无机肥配合施用处理的土壤覆膜会增加真菌的含量,但却降低了其他脂肪酸的含量;在不施肥处理的土壤中,覆膜会使一些支链脂肪酸的含量降低。抽雄期,施有机肥的土壤覆膜后除单饱和脂肪酸含量有所下降外,其他脂肪酸都会提高;不施肥土壤覆膜处理双不饱和支链脂肪酸及放线菌标志性脂肪酸10Me18:0的含量会有所提高。成熟期,施氮肥的土壤覆膜处理大部分脂肪酸的含量降低;有机肥处理土壤中各种脂肪酸如:15∶0,a17∶0,i17∶0,i19∶0,18∶0,10Me18∶0含量覆膜高于裸地;有机无机配施处理土壤中17∶0,br17∶0,18∶0,18∶2w6,10Me18∶0含量覆膜处理高于裸地;对照土壤中i15∶0,16∶0,17∶0,a17∶0,18∶0,18∶2w6,19∶0含量覆膜高于裸地。另外,从脂肪酸的变化看出,覆膜处理土壤微生物群落整体结构发生了改变,没有表现出明显的种群优势。但是,尽管土壤的施肥处理不同,覆膜处理土壤微生物群落结构有一致化发展的趋势。     

基于传统和高通量测序技术研究地膜对辣椒土壤特性及细菌多样性的影响

以不同种类地膜覆盖条件下辣椒菜园土壤为研究对象,运用传统和高通量测序技术,研究南方地区不同种类地膜覆盖对辣椒菜园土壤理化、生物学性状和细菌多样性的影响。结果表明：南方地区蔬菜生产中利用不同种类地膜,尤其以聚乙烯为原料的白色透明地膜、黑色地膜和银色地膜不仅有助于提高辣椒耕作层土壤温度与含水量,而且对减缓土壤pH的下降具有显著效果。此外,在细菌门分类水平上,不同种类地膜覆盖条件下土壤细菌的优势菌群表现为变形菌门（Proteobacteria）、拟杆菌门（Bacteroidetes）、酸杆菌门（Acidobacteria）和芽单胞菌门（Gemmatimonadetes）细菌,其中以变形菌门（Proteobacteria）细菌的丰度最高;属分类水平上,不可培养细菌属、黄杆菌属（Flavobacterium）、溶杆菌属（Lysobacter）、芽孢杆菌属（Bacillus）、H16（Ralstonia eutropha）和鞘氨醇单胞菌属（Sphingomonas）细菌是南方地区不同种类地膜覆盖土壤中的优势菌属。此外,地膜覆盖不仅降低了土壤中对环境条件要求苛刻的不可培养细菌的丰度,而且有助于溶杆菌属和芽孢杆菌属等部分具有促生功能细菌的积聚。上述结果表明：南方地区蔬菜生产中利用地膜并没有导致菜园土壤质量劣化,而且有助于提高土壤肥力和保持土壤健康。     

Influence of mulching and tree shelters on 4-year survival and growth of zeen oak (Quercus canariensis) seedlings

We assessed the effect of mulching and tree shelters on the establishment and early growth of zeen oak(Quercus canariensis Willd.) during the first 4 years after planting in Northwestern Tunisia. Five mulch types(Italian Stone Pine(Pinus pinea L.), Lentisk(Pistacia lentiscus L.),and a combination of Italian Stone Pine and Lentisk(organic mulches), gravel(inorganic mulch) and control), and three tree shelter types(non-vented and vented tree shelters, and control) were tested. An increase in the number of internodes occurred under the gravel mulch, while a reduction in survival was found for the lentisk mulch. Tree shelters had no effect on survival, but increased mean height growth and reduced mean diameter growth during the 4 years(excepting a non-significant effect for vented tree shelter at year four). Comparison of the annual shoots and growth units(GU) between sheltered and unsheltered plants according to year of formation revealed two growth phases. In first phase, shoots were totally or partially inside the shelters; mean length of annual shoots and GU were greater for sheltered plants. The second phase was characterized by shoots emerging from shelters; mean length of annual shoots and GU were similar for all plants, with or without tree shelters. Results suggest that the use of tree shelters, particularly vented shelters, could contribute to the improvement of the artificial regeneration of zeen oak.The use of mulching alone or in combination with tree shelters did not improve zeen oak performance in the field.     

旱塬地膜冬小麦增产机理研究初报

对不同年型地膜冬小麦增产内在机制的研究表明,旱地冬小麦全生育期覆膜穴播具有：（１）明显的抗旱、保水及增效果,将旱年及旱年最大增产率分别达１５７．６５％和６２．８５％,ＷＵＥ提高４７．５％－１３７．８％和３６．２％－６０．４％;（２）植株个体、１群体发育良好,蒸腾速率增大,光合速率显著提高,合成源扩大;（３）有利于提高地温,全生育期０－５ｃｍ土层≥０℃地温较露地（２０５６．１℃）提高１０．４％,１ｍ     

Establishment of Hybrid Arctic Bramble under Field Conditions

The effect of different factors on plant diameter and yield in hybrid arctic bramble (Rubus arcticus nothosubsp. stellarcticus) was examined in two field experiments with a factorial design. The studied factors included planting time (August, September, May or June), plant type (bare-rooted or potted plants) and ground cover (no ground cover or mulching with a dark plastic film). Development of bare-rooted and potted plants did not differ when transplanted in the autumn and in May. Potted plants developed better than bare-rooted plants when transplanted in June. In one year, plants transplanted in May developed best, while in another, plants transplanted in the autumn developed best. Mulching with a dark plastic film improved plant development. The rate of vegetative development during the first growth season was reflected in the yields in both the first and the second harvest year; the greater the plant diameter after the first growth season, the higher the yield.     

山区旱地间套种春玉米的覆盖效果研究

3年定位试验结果表明,栏肥、秸秆、地膜和杂草覆盖对山区旱地间套种春玉米具有显著的增产增效作用,增产幅度18.1%～36.4%,其中以秸秆覆盖最为明显,且以前作秸秆全部覆盖最好.栏肥、秸秆和杂草覆盖保水效果好,具增降温的双重功效,并能明显提高土壤肥力,而地膜覆盖保水抗旱效果差,又耗地力,不利于山区旱地的可持续生产。     

皖南山区冷浸田水稻垄作覆膜栽培技术研究

[目的]探讨皖南山区冷浸田水稻高产栽培技术。[方法]采用田间试验的方法,研究了垄作和覆膜栽培对水稻生长的影响。[结果]垄作和覆膜栽培能够提高冷浸田土壤温度,促进水稻早期的生长发育,提高叶面积指数和干物质积累量,水稻增产129.8～652.5kg/hm2,增产率达2.25%～11.32%。[结论]垄作和覆膜栽培两者结合的增产效果优于单一垄作处理,其中以窄垄+覆膜栽培增产效果最为显著。     

液体地膜对棉花生长发育的影响

研究了液体地膜对棉花生长发育的影响。结果表明：液体地膜能加快棉花前期生长速度、适度抑制后期旺长、调控和优化棉花株型，使棉花早发、早熟。