Are all three components of conservation agriculture necessary for soil conservation in the Sudan Savanna?

ABSTRACT

Conservation agriculture (CA) as recommended by the Food and Agriculture Organization of the United Nations consists of three components: minimum soil disturbance, soil cover, and crop rotation/association. CA was expected to become an effective countermeasure against water erosion in the Sudan Savanna, but it has not been adopted by local smallholder farmers. As markets for grain legumes (including cowpea) have not been developed in the Sudan Savanna, crop rotation/association should be considered impractical for these farmers. Therefore, we examined whether legume intercropping as a crop rotation/association component is necessary for preventing soil erosion in the Sudan Savanna. Three-year field experiments were conducted in runoff plots at Institute of Environment and Agricultural Research Saria station. The four treatments were conventional practice (full tillage, no sorghum residue mulching, and no intercropping), two-component CA (minimum tillage (MT) and sorghum residue mulching without intercropping), and three-component CA with velvet bean (VB) or pigeon pea (PP) intercropping. It was revealed that: (1) MT and sorghum residue mulching (without intercropping) effectively reduced the annual soil loss by 54% mainly due to the improvement of soil permeability by the boring of termites and wolf spiders found under the sorghum stover mulch; (2) intercropping in combination with MT and crop residue mulching had no effect on soil erosion control mainly because: (a) PP did not survive the long dry season; (b) VB did not serve effectively as a cover crop since soil loss was concentrated at the beginning of the rainy season when VB was still too small; (c) unexpectedly, in combination with MT and crop residue mulching, intercropping with VB did not increase mulch biomass, especially sorghum biomass which prompts the boring of termites and wolf spiders. These results demonstrate that the third component of CA, namely legume intercropping, is not always necessary; rather, the two remaining components – minimum soil disturbance and soil cover – are sufficient for soil conservation in the Sudan Savanna. This finding lightens the burden of adopting CA and thus facilitates its future promotion to the smallholder farmers in the Sudan Savanna.     

环境教育视角下的南粤古驿道保护和活化策略研究

南粤古驿道历史悠久,其丰富的自然资源和人文资源创造了得天独厚的环境教育条件。以西京古道为例,通过现场勘查和文献阅读,以历史文化、生态环境、科学研究和环境道德教育资源4个角度阐述古驿道承载的环境教育优势,并提出以挖掘古道历史、引入生态旅游、完善基础设施为途径,实现古驿道环境教育和以环境教育为导向的古驿道保护与活化,以期为南粤古驿道的保护和发展提供新的路径和思考方向。     

中国南方农业生态系统可持续发展面临的问题及对策

南方农业生态系统在我国整个农业生态系统中占有重要地位和作用,具有结构的复杂性、功能的多样性、生产的高效性、价值的珍贵性和开发利用潜力的巨大性等特征。当前,南方农业生态系统存在着耕地撂荒、地力下降、土壤污染、灾害频繁、效益低下和后劲不足等方面的问题,严重制约着生态系统的可持续发展。为实现南方农业生态系统的可持续发展,应采取以下对策和措施:(1)实行集约用地;(2)开展环境整治;(3)推行轮作休耕;(4)实施用养结合;(5)优化系统结构;(6)深化农村改革。     

华南四省区木薯施用氮磷钾肥效果分析

为解析华南四省区木薯施用氮磷钾肥效果,指导木薯合理施肥,总结分析2005—2015年华南四省区44组木薯肥料试验数据,计算推荐施肥条件下,氮(N)、磷(P_2O_5)、钾(K_2O)肥的增产量、增产率、肥料产量贡献率、偏生产力。得出木薯施用氮肥的增产量、增产率、产量贡献率、偏生产力均值分别为8.5t/hm~2、39.4%、24.4%、203.5kg/kg,97.7%的试验有增产效果;磷肥的对应指标均值分别为5.5t/hm~2、20.8%、13.6%、639.2kg/kg,93.2%的试验有增产效果;钾肥的对应指标均值分别为5.5t/hm~2、21.9%、16.8%、209.1kg/kg,95.5%的试验有增产效果;氮、磷、钾肥的增产效果YIE表现为YIENYIEKYIEP,偏生产力PFP为PFPPPFPKPFPN。在现有推荐施肥技术水平下,氮、磷、钾肥的平均推荐配比为W(N)∶W(P_2O)_5∶W(K_2O)=2.9∶1∶3,最高推荐施用量分别为257.4、90.0、271.4kg/hm~2。针对现存问题,提出各地区需遵循"大配方,小调整"的施肥原则,并构建木薯推荐施肥网络体系,以促进木薯高产高效施肥。     

Response of Ugandan common bean varieties to Pseudocercospora griseola and Angular leaf spot disease development in varietal mixtures

Angular leaf spot (ALS) is one of the most economically important bean diseases in Africa. One promising control option for the disease is the use of mixtures of resistant and susceptible varieties. This research evaluated (1) the reaction of farmer preferred bean varieties to ALS in the screenhouse and on-station and (2) the effect of different spatial arrangements of resistant and susceptible bean varieties on ALS disease development. For the latter, five mixture combinations and two controls were laid out in a Randomized Complete Block Design having three replicates. Analysis of variance and least significant differences (LSDs) were used to compare disease levels in both studies above. Varietal screening showed significant differences in varietal reaction to ALS. Screenhouse disease scores ranged between 0 and 5, compared to 0.7–3.9 in the field. For the varietal mixture trial, the lowest disease levels and the highest mixture efficiencies were observed for the combination of equal proportions of the susceptible and resistant varieties randomly mixed (even mixture) prior to planting. We conclude that even mixtures reduce the amount of ALS disease that develops in the season.     

Examining Human Perception of Elephants and Large Trees for Insights Into Conservation of an African Savanna Ecosystem

African elephants (Loxodonta africana) and large trees have ecological and human value, but elephant impact on large trees may influence conservation strategies. We used a self-administered questionnaire to examine perceptions of elephants, large trees, and elephant management endeavors among tourists and residents in the Associated Private Nature Reserves, South Africa to inform management approaches. The questionnaire included photographs of different elephant types and of vegetation with varying degrees of elephant-impact. Respondents reported high attractiveness rankings for all elephant types, but they scored non-impacted trees higher than photos of trees with visible elephant impact. Results also revealed a significant positive correlation between elephant types known to cause high tree impact and attractiveness of non-impacted trees. Residents favored more intrusive elephant management methods, with environmental manipulation representing the most supported and balanced option for both interest groups. Respondents advocated management that focuses on ecosystem functioning more so than elephant population control.     

南海海洋生态安全及渔业可持续发展研究

随着环南海地区的经济发展及我国向南海进军步伐的不断加快,不合理的人类涉海活动,导致一系列难以逆转的海洋生态安全问题随之而来,制约着南海渔业的健康发展。依据相关文献资料,在已有研究成果的基础上,阐述海洋生态安全的概念,探讨南海海洋生态安全与渔业可持续发展的关系,分析南海海洋生态安全问题的深层原因,提出提升公民的海洋生态安全意识及治理能力、健全海洋生态安全管理制度、完善海洋生态安全法律体系和建立海洋生态安全多元化投融资体系等保护南海海洋生态安全的对策,以实现南海渔业可持续发展。     

南海区驯养条石鲷亲鱼的初次性成熟和产卵

2008年4月初在广东省饶平县对2006年5月人工孵化和培育的2龄条石鲷（ Oplegnathus fasciatus）成熟亲鱼进行激素诱导,研究和观察条石鲷亲鱼初次性成熟的繁殖生物学。结果显示,在南海区全人工养殖的条石鲷亲鱼初次性成熟年龄为2龄,成熟亲鱼的最小型为全长245 mm、体质量610 g,最大个体为全长300 mm、体质量1450 g;产卵季节为4月10日~7月15日,产卵盛期为4月中旬至6月下旬;为升温产卵型鱼类,产卵温度为20.0~28.8℃,适宜的产卵温度为20.7~27.6℃;雌、雄亲鱼发育同步,个体大小和成熟年龄差别不大;雌鱼属于一年一次分批产卵类型,产卵期超过3个月;24尾初次性成熟雌性亲鱼的总产卵量为3180.0×104粒,日最高产卵量为341.5×104粒;其产卵量和受精卵质量与水温的变化关系密切,受精卵的浮卵率随温度的变化而变化,在水温相对衡定时,浮卵率相对稳定并维持在80%~95%的较高水平;受精卵平均卵径为（0.860±0.023）mm,油球径为（0.191±0.009）mm。     

南德温杂交肉牛生长分化因子10基因多态性与体尺性状的关联分析

以98头南德温杂交肉牛血样为材料,随机抽样构建混合DNA池,利用高分辨率熔解曲线分析技术和直接测序法检测生长分化因子10(growth differentiation factor 10,GDF10)基因的序列变异,研究分析GDF10基因的多态性.采用SHEsis和PHASE软件对GDF10基因多态位点进行配对连锁不平衡和单倍型分析,采用SPSS 17.0进行基因多态位点和单倍型组合与体尺性状关联性分析.结果显示,南德温杂交肉牛GDF10基因检测到3个多态位点1113(G/A)、9569(G/A)和9628(G/A);关联分析表明,南德温杂交肉牛GDF10基因不同突变位点的基因型与体斜长、体高、胸围和管围差异显著(P<0.05);单倍型分析后在群体中发现8种单倍型组合,其中AAA、GGA与南德温杂交肉牛的体高、体斜长、胸围和管围显著相关(P<0.05).由此推断,南德温杂交肉牛GDF10基因3个多态位点和2个单倍型组合与体斜长、体高、胸围和管围显著相关,可以作为肉牛生产性状的候选分子标记,为肉牛遗传资源开发与利用提供科学依据.     

基于3S集成平台的南海渔业信息动态采集与实时自动分析系统研发

以全球定位系统(GPS)、地理信息系统(GIS)和遥感(RS)等3S技术集成平台,并结合船舶监控系统(VMS)、北斗卫星短报文信道、ARM高性能处理器、NR嵌入式操作系统等前沿技术,建立"南海渔业信息动态采集与实时自动分析系统"。该系统是一个分布式系统,包括船载捕捞信息实时采集装备、南海渔业数据集成中心、南海渔业捕捞地理信息系统及外海渔场预报系统等4个完全独立分布的子系统。本系统自主研发了具备北斗通信功能的船载捕捞实时采集装备,并创新性地利用北斗卫星短报文信道实现了海上渔船与地面数据中心的实时信息交互,此外利用VPN信道实现了数据中心与数据处理分析应用系统之间安全可靠的数据共享,从而最终建立了海上渔船与岸上数据分析系统之间的无缝连接虚拟网络。基于这一网络,海上渔船将渔业捕捞数据实时发送至南海渔业捕捞GIS系统,进行实时分析与显示海洋捕捞(分)渔区/渔船/鱼类产量的数据分析专题图;外海渔场预报系统依据多年的捕捞、渔业生物学及渔场环境数据收集与分析将南海外海鸢乌贼渔场信息发送给海上渔船,推进海上渔业捕捞的高效生产。