两种耕作方式下施肥对水稻产量及稻田氮、磷质量分数的影响

采用常规施肥、减20%施肥和不施肥3种施肥水平,研究两种耕作方式(半旱式、平作)对水稻产量、品质、稻田土壤和水体中氮、磷质量分数的影响.结果表明:①半旱式耕作方式在3种施肥水平下水稻产量均比平作同等施肥水平高,半旱式耕作有利于水稻增产.②半旱式常规减20%施肥水平下,土壤中氮、磷质量分数明显升高,水体中氮、磷呈现降低的趋势,有效地降低了氮、磷流失的风险;半旱式耕作对减少氮、磷流失的效果较平作方式好.     

下垫面变化对喀斯特坡地地下产流产沙的影响

通过人工模拟降雨试验,探索表土剥离对喀斯特坡耕地侵蚀产沙的影响。采用钢槽装填土石模拟喀斯特坡地的二元结构,通过正交试验分析了下垫面类型(坡耕地、裸坡地)、雨强(0.5,0.8,1.3mm/min)和地下孔(裂)隙度(1%,2%,3%,4%,5%)对坡地地下产流、产沙的影响。结果表明:表土剥离导致下垫面土壤物理性质改变,是影响坡地产流、产沙特征变化的主要因素。降雨强度主要影响坡地地下产流量和产沙量,地下孔(裂)隙度主要影响径流和泥沙在地表和地下的分配比例。表土剥离后表层土壤的容重和土壤颗粒分形维数呈显著性增大,导致土壤透水性、孔隙大小等发生改变。相比之下,在0.5mm/min雨强下,裸坡地的地下产流量、产流系数、产沙比重均大于坡耕地,雨强增大至0.8,1.3mm/min后,则是坡耕地大于裸坡地。同时,随着降雨强度的增大,坡耕地产流量和产沙量随雨强的变化顺序为0.5mm/min雨强0.8mm/min雨强1.3mm/min雨强。而裸坡地的产流量大小随雨强的变化顺序为0.8mm/min雨强1.3mm/min雨强0.5 mm/min雨强,产沙量大小随雨强的变化顺序为0.5 mm/min雨强0.8mm/min雨强1.3mm/min雨强。增大地下孔裂隙度能显著(p0.05)的增大两种坡地的地下产流、产沙的贡献量。地下孔裂隙度为1%~3%条件下,2种坡地地下侵蚀产沙比重存在极显著差异(p0.01),随着地下孔(裂)隙度增大至4%和5%,两者间的差异缩小。虽然裸坡地的地下侵蚀产沙量小于坡耕地的,但是其地下产沙比重更大。在喀斯特地区进行开发建设时,应注重地下漏失的防治工作。研究成果能够为喀斯特坡地土壤侵蚀研究和水土流失防治提供重要参考。     

油茶间作不同绿肥的土壤分形及养分损耗特征

为探讨油茶林间作不同绿肥对耕作层土壤颗粒分形特征及养分退化产生的影响,在野外调查与室内分析的基础上,分析了间作不同绿肥下油茶林的土壤颗粒分形维数及其与土壤粒径分布、养分含量的关系。结果表明：（1）该区域土壤粒径分布主要以粘粒（＜0.002 mm）和粉粒（0.002～0.05 mm）为主,土壤分形维数为2.681~2.882,顺序为：CK＜黑麦草＜鼠茅草。（2）研究区土壤体积分形维数与粘粒（<0.002 mm）体积百分含量呈极显著正相关关系（P＜0.01）,与粉粒（0.002～0.05 mm）体积百分含量呈显著正相关（P＜0.05）,与砂砾（0.05～2.00 mm）体积百分含量呈显著负相关关系（P＜0.05）;分形维数与土壤含水量呈显著正相关（P＜0.05）,而与有机质、全氮、水解性氮、全磷、有效磷、全钾、速效钾及土壤容重的相关性未达到显著水平（P＞0.05）。（3）3月至8月,两种绿肥间作均显著提高了油茶林耕作层土壤的含水量,减少了养分的损耗,其中以鼠茅草改良效果最好。综上,土壤分形维数能够很好地表征土壤质地、粒径组成以及土壤养分状况,为油茶林地复合经营土壤质量评价提供一定的参考。     

烟草粉螟危害对储存烟叶经济损失的研究

研究了不同数量的烟草粉螟繁殖1代和2代（1a）幼虫危害所造成的烟叶重量和叶面积损失以及烟叶的被害率和各级烟叶的伤残率，核算了1-5对烟草粉螟繁殖2代危害所造成的经济损失。结果表明，1，2，3对烟草粉螟繁殖1代幼虫取食的烟叶重量分别为0.53，1.07，2.93g；损失的烟叶面积分别为37.32,75.59,206.34cm^2.1,2,3,4,5对烟草粉螟繁殖2代幼虫取食的烟叶重量分别为1.37，3.57,6.30,13.42,24.20g；损失的烟叶面积分别为88.39,230.32,406.45,865.81,1561.29cm^2；幼虫取食造成的直接经济损失分别为0.010,0.026,0.047,0.100,0.180元；因伤残降级降价造成的经济损失分别为0.316,1.051,1.932,2.896,4.392元；1a中共损失金额分别为0.326,1.077,1.978,2.996,4.572元。并将试成虫对数与繁殖2代幼虫取食烟叶重量、损失烟叶面积及经济损失进行理论曲线拟合，经F检验，方程代表性均好。     

海藻酸增效尿素对夏玉米氮素吸收利用及氮肥损失的影响

针对玉米氮肥施用量大、利用率低、环境负荷日益严重的现状,本研究以活性海藻酸为增效剂,对普通尿素进行改性增效,开展海藻酸增效尿素对夏玉米产量形成、氮素吸收利用及损失的调控作用研究,为实现氮肥减量、提高氮肥利用率、降低环境负荷提供理论依据。本试验以夏玉米为供试作物,采用 ¹⁵N同位素示踪技术与田间试验结合的方法,以不施尿素为对照,共设置7个处理：CK（不施尿素）、U（普通尿素）、AU1（0.5%海藻酸增效尿素）、AU2（2.5%海藻酸增效尿素）、AU3（5.0%海藻酸增效尿素）、U-N（普通尿素减量 20%）、AU2-N（2.5%海藻酸增效尿素减量 20%）。采用一次性施肥方式,并在施肥后测定氨挥发和氧化亚氮排放量。结果表明：海藻酸增效尿素在1 038 cm^-1左右出现糖类C—OH伸缩振动,且在3 426~3 325 cm^-1范围和1 584 cm^-1的NH₂、1 450 cm^-1和1 143 cm^-1处的C—N振动峰强度增大;常量处理中,施用海藻酸增效尿素使玉米平均增产5.04%,氮素积累量平均增加13.55 kg·hm^-2,氮肥利用率平均提高4.63个百分点;减量处理中,U-N处理没有显著减产,AU2-N处理玉米产量较AU2处理增产 2.30%,氮肥利用率提高 7.16 个百分点;与 U 处理相比,AU1、AU2 处理 0~60 cm 土壤中氮素残留量分别增加了 2.94、8.21 kg·hm^-2;海藻酸增效尿素可减少氧化亚氮排放和淋洗等其他途径氮损失,与普通尿素处理相比,常量海藻酸增效尿素处理氮肥损失率平均降低6.16个百分点,与U-N处理相比,AU2-N处理氮肥损失率降低9.95个百分点。在本试验条件下,综合考虑玉米产量、氮素吸收利用、残留及损失,2.5%海藻酸增效尿素减量施用20%可以取得较好效果。     

不同厚度降解地膜对坡耕地溶解态氮磷流失的影响

[目的]为探究降解地膜覆盖对径流及溶解态氮磷流失的影响。[方法]利用野外原位径流小区,以覆膜垄作花生种植为研究对象,设置0.003 mm厚聚乙烯普通地膜覆盖处理(PF)和厚度为0.006 mm(BF1),0.008 mm(BF2),0.010 mm(BF3),0.012 mm(BF4)的降解地膜覆盖处理及未覆膜处理(CK),测定不同处理在自然降雨条件下的径流量及径流中铵态氮(NH₄⁺—N)、硝态氮(NO₃^-—N)、速效磷(PO₄^3-—P)浓度,分析不同厚度降解地膜覆盖条件下径流及养分流失特征。[结果](1)降解地膜降解所需时间随地膜厚度的增加而增加。(2)各处理的累积径流量由小到大为BF14⁺-N和NO_3<...     

施苯菌灵抑制丛枝菌根真菌对污染土壤-玉米系统镉迁移的影响

【目的】为探讨土壤丛枝菌根真菌(Arbuscular mycorrhizal fungi,AMF)对污染土壤-作物系统Cd迁移行为的影响。【方法】采用云南兰坪铅锌矿周边重金属污染的土壤,开展室内试验,施杀真菌剂 (苯菌灵) 特异性抑制土壤土著AMF,研究抑制AMF对玉米生长、Cd含量与累积量、土壤Cd淋溶流失的影响。【结果】结果表明:(1)施苯菌灵显著抑制土壤AMF生长,导致AMF侵染率、孢子数、土壤球囊霉素相关蛋白(Glomalin related soil protein,GRSP)含量显著降低;并显著影响玉米生长与矿质营养,导致玉米地上部生物量、叶绿素与磷含量增加,而地上部氮钾含量降低。(2)施苯菌灵促进Cd向玉米根部和地上部迁移,主要富集在玉米地上部,导致玉米地上部的Cd含量和累积量显著增加。(3)施苯菌灵导致10 cm和20 cm壤中流的Cd浓度显著增加。此外,土壤GRSP含量与玉米地上部Cd累积量和壤中流的Cd流失浓度均呈极显著负相关。【结论】研究结果表明,土壤土著AMF有助于抑制土壤Cd向植株地上部迁移,减少壤中流Cd的流失浓度,降低污染土壤-作物系统Cd的环境迁移。     

气压式玉米精量播种机均匀低损配气机构设计与试验

针对气压式玉米精量播种机配气系统存在各行气流分配不均、气压损失及气流速度损耗较大的问题,基于加压导管定常不可压缩湍流模型损失理论,探明了气流损失及分配不均的原因。采用等效仿真简化模型,通过 CFD （computational fluid dynamic,CFD）仿真4种不同气路结构中气压损失及气流速度损耗,分析得出最佳气流分配方式;通过正交试验,得出分配器最优结构形式;确定了配气机构连接段最优母线形状为内凹-外凸组合型曲线,连接段长度以及组合曲线内凹外凸水平长度比是2个影响配气机构性能的关键参数,连接段长度值越大,节锥角越小,且组合曲线内凹外凸水平长度比在3附近时气压损失及速度损耗最小。与常用配气机构进行对比试验,试验结果表明,常用配气机构的气压损失在30%以上,而该低损配气机构能够将气压损失减小到10%以内,气流速度损耗不显著,各行压力一致性变异系数在4%以内。     

Invasion and management of a woody plant, Lantana camara L., alters vegetation diversity within wet sclerophyll forest in southeastern Australia

Plant invasions of natural communities are commonly associated with reduced species diversity and altered ecosystem structure and function. This study investigated the effects of invasion and management of the woody shrub Lantana camara (lantana) in wet sclerophyll forest on the south-east coast of Australia. The effects of L. camara invasion and management on resident vegetation diversity and recruitment were determined as well as if invader management initiated community recovery. Vascular plant species richness, abundance and composition were surveyed and compared across L. camara invaded, non-invaded and managed sites following L. camara removal during a previous control event by land managers. Native tree juvenile and adult densities were compared between sites to investigate the potential effects of L. camara on species recruitment. Invasion of L. camara led to a reduction in species richness and compositions that diverged from non-invaded vegetation. Species richness was lower for fern, herb, tree and vine species, highlighting the pervasive threat of L. camara. For many common tree species, juvenile densities were lower within invaded sites than non-invaded sites, yet adult densities were similar across all invasion categories. This indicates that reduced species diversity is driven in part by recruitment limitation mechanisms, which may include allelopathy and resource competition, rather than displacement of adult vegetation. Management of L. camara initiated community recovery by increasing species richness, abundance and recruitment. While community composition following L. camara management diverged from non-invaded vegetation, vigorous tree and shrub recruitment signals that long-term community reinstatement will occur. However, secondary weed invasion occurred following L. camara control. Follow-up weed control may be necessary to prevent secondary plant invasion following invader management and facilitate long-term community recovery.     

Effects of insect predation on hypocotyl survival and germination success of maturequercus variabilis acorns

The rates of hypocotyl and radicle survival and of germination success were investigated in mature acorns ofQuercus variabilis Blume in relation to endosperm loss due to seed insects. The acorns were damaged by curculio weevils (Coleoptera: Curculionidae) and moths, including tortricid moths (Lepidoptera: Tortricidae); the former were more abundant than the latter. Acorns damaged by curculio weevils showed a significantly lower germination rate when there was a large endosperm loss than the rate for sound acorns. The survival rate of the hypocotyl and radicle also decreased as endosperm loss increased. These results suggest that acorn germination is directly inhibited by damage to the hypocotyl and radicle, which depends on the amount of endosperm eaten by the weevils. However, the germination rate of acorns with hypocotyl and radicle was consistently high, irrespective of the degree of endosperm loss, which suggests that weevil-damaged acorns probably germinate, provided the hypocotyl and radicle survive until the cessation of damage. Research Fellow of the Japan Society for the Promotion of Science. This study was supported in part by Grants-in-Aid for Scientific Research from the Japan Ministry of Education, Science and Culture (No. 09001647, No. 10660144, and No. 11460068) and the Nippon Life Insurance Foundation.