Effect of the application of the leaf mulch of Gliricidia sepium on early development,leaf nutrient contents and tuber yields of water yam (Dioscorea alata)

This paper describes the effects of the leaf mulch of Gliricidia sepium on the development and yield of Water Yam, Dioscorea alata. Using leaf mulch, the time taken for the yam setts to sprout can be shortened by approximately 20 percent.Organic mulches contain considerable quantities of plant nutrients. Increasing amounts of mulch improved the leaf nutrient contents of the yam crop and resulted in significantly higher tuber yields. Over a tuber yield range up to c. 15 tons ha^–1 each additional ton DM Gliricidia sepium mulch applied resulted in a yield increment of about 2 ton yam tubers. A nutrient supply — nutrient extraction balance is discussed, comparing mulch applied and yam tubers harvested.Mulching as agricultural technique is a useful and affordable tool in adapting low external input cropping systems to local economic and environmental conditions.     

The performance of selected leaf mulches in temperature reduction and moisture conservation in the upper soil stratum

This paper reports on the effect of the leaf mulches of Leucaena leucocephala, Gliricidia sepium and Flemingia macrophylla on moisture content and temperature in the first 5 cm of the soil. The mulches were applied at a standard quantity of 5,000 kg ha^–1 DM.In order to characterise a mulch material two parameters are distinguished; the initial impact (I _i ) and the effective lifetime (T _e ) of a mulch material. I is expressed in terms of percentage surplus moisture or degrees Celsius average temperature reduction. T quantifies the duration of the effect. Of the three mulch materials that of Flemingia macrophylla performs best in terms of moisture retention and lowering soil temperatures as well as in terms of longevity of the effect. Leucaena leucocephala mulch shows the smallest impact, over the shortest period.     

Improving rumen fermentation and milk production with legume-tree fodder in the tropics

Feeding leguminous fodder that is high in protein can improve rumen fermentation parameters leading to increased digestibility and intake of low quality fibrous feeds, and hence improved animal production. The effect on dry matter (DM) degradation and rumen fermentation parameters of feeding urea or tree legume foliage (Erythrina poeppigiana or Gliricidia sepium), as protein supplements to a basal diet of Hyparrhenia rufa hay, rice bran and molasses, was studied with rumen fistulated steers (Zebu × Creole crossbreeds). In a second experiment, Jersey × Creole crossbreeds were used to determine the effect of the above three treatments on milk production. Both experiments were conducted at CATIE's experimental farm, Turrialba, Costa Rica (9°58 N; 83°31 W; 639 m above sea level; mean annual precipitation of 2600 mm; mean daily temperature 22 °C). The disappearance of hay DM in the rumen increased with time to 144 hours and potential degradation of hay DM was significantly higher (P < 0.05) for the legume diets compared to urea but there were no differences between legume species. Legume based rations resulted in total volatile fatty acid concentrations of rumen licor that were 15 to 24% higher than for urea based rations (P < 0.05). The concentration of rumen NH₃-N was highest two hours after feeding and tended to decrease in time. The urea ration resulted in significantly higher NH₃-N than the legume rations, reaching 45 mg/100 mL two hours after feeding. Milk yields did not differ (P > 0.05) when cows received either E. poeppigiana or G. sepium foliages as protein supplements (7.3 and 7.4 kg milk/cow/day, respectively) but they were superior (P < 0.05) to urea supplementation (6.7 kg milk/cow/day).     

Soil water regime under rotational fallow and alternating hedgerows on an Ultisol in southern Cameroon

Soil moisture depletion during dry seasons by planted hedgerows to lower levels than under natural fallow, would reduce drainage and nutrient losses in the following rainy season when food crops are grown. The volumetric water content of the 0–150 cm soil profile was measured under planted hedgerows (alternating Leucaena leucocephala and Gliricidia sepium) and natural fallow, both either annually cropped to sole maize or in a two-year crop/two-year fallow rotation, in the humid forest zone (annual rainfall 1700 mm) of southern Cameroon during the 1995–1996 and 1996–1997 dry seasons. Hedgerows were cut to 0.05 m height, largely eliminating trees’ water consumption during cropping phases. Differences in total soil water content at 0–150 cm depth, between systems, occurred only in the early phases of the 1996–1997 dry season. In both dry seasons, differences between systems in water content were found in some soil layers, all within 0–60 cm depth, yet, without consistent advantage of any system in exploiting the topsoil water resources. Soil water content was lower under L. leucocephala than G. sepium at 20–40 cm depth only. Below 60 cm depth, no differences in water regimes between systems were found. Under southern Cameroonian conditions it is unlikely that any of the systems has an advantage in accessing or recovering water and thus, if available, nutrients from the sub-soil. None of the systems examined was capable of delaying drainage and thus it appears unlikely that downward displacement of nutrients is delayed after the start of the rains.     

The performance of the leaf mulches ofLeucaena leucocephala,Flemingia macrophylla andGliricidia sepium in weed control

The performance of the leaf mulches ofLeucaena leucocephala, Gliricidia sepium andFlemingia macrophylla in weed control has been tested in two trials. The length of the period during which a mulch layer yields significantly less weedbiomass compared to the control plots is called the effective life-span of the mulch.Of the three mulch materials only that ofF. macrophylla shows promise in retarding weed development.In the second trialF. macrophylla leaf mulch was applied at rates of 3, 6 and 9 tons dry matter per ha. The effective lifespan of a mulch layer of 3 tons is between 12 and 13 weeks. The treatments 6 and 9 tons have effective life-spans of over 14 weeks.For moderate quantities (up to 5 tons of dry leaf mulch per ha) the effective life-span is estimated at about a 100 days.The value of mulching in weed control is limited to the control of weed species that multiply by seed. Regrowth originating from roots or stumps from former vegetation is unlikely to be checked by a mulch layer.The subject of this paper is part of a broader study, presently conducted in Southern Ivory Coast, on the production, agronomical value and use in alley-cropping systems of the species mentioned in the title of the paper. A final report is scheduled for publication in 1988.     

杠柳天然橡胶合成相关R2R3−MYB基因克隆及表达分析

首次克隆了杠柳中调控天然橡胶生物合成途径的R2R3−MYB基因,为杠柳天然橡胶生物合成调控机制的研究提供候选基因。利用生物信息学的方法,对杠柳的基因组数据进行分析,发现122条R2R3−MYB基因。通过构建系统进化树、氨基酸多序列比对、保守结构域和三级结构分析,确定杠柳中可能参与调控天然橡胶合成的R2R3−MYB基因,并进行基因在杠柳中的组织特异性表达分析。结果表明：PsMYB79、PsMYB102、PsMYB159和PsMYB178与巴西橡胶树 HbMYB在同一分支上,均具有典型的R2R3−MYB结构域及SHAQKYF保守基序,而且氨基酸之间序列相似性分别为72.5%、64.5%、61.6% 和57.8%。RT− PCR分析结果表明,4个基因在乳胶形成的部位中均表达,其中PsMYB79和PsMYB178在根中表达最强,PsMYB102在幼叶中表达强烈, PsMYB159在根、茎、幼叶和老叶中普遍表达。因此推测杠柳R2R3−MYB转录因子家族中PsMYB79、PsMYB102、PsMYB159和PsMYB178基因可能参与调节植物不同组织器官中天然橡胶生物合成过程。     

杠柳的不同溶剂提取分离物对小菜蛾幼虫的拒食和毒杀作用

以生物活性跟踪法测定了杠柳Periploca sepium Bunge 的不同溶剂提取液及其不同馏份对小菜蛾幼虫的拒食和毒杀活性。结果表明,杠柳根皮的乙醇提取液和氯仿提取液对小菜蛾具有较强的拒食和毒杀活性,该生物活性高于石油醚提取液。乙醇提取物水溶后分别用苯、正丁醇溶剂萃取。生物测定结果显示,苯萃取物对小菜蛾的活性最高,表明其活性成分主要分布在苯萃取物中。苯萃取物通过硅胶柱层析分离,淋洗液为石油醚、石油醚/乙酸乙酯不同比例混合液、乙酸乙酯、乙酸乙酯/甲醇不同比例混合液和甲醇,根据颜色和极性,将收集到的淋洗液分成8个馏份,其中5、6、7号3个馏份对小菜蛾幼虫具有强烈的拒食和毒杀作用,其200倍液对小菜蛾幼虫的拒食率分别为99.8%、99.1%和98.6%,校正死亡率分别为92.1%、91.5%和100%。     

杠柳根皮化学成分及杀虫活性的初步研究

采用试管预试和圆形滤纸层析预试法,对杠柳根皮的化学成分进行了初步研究.结果表明,杠柳根皮中含有氨基酸、糖及其苷类、有机酸、皂苷、生物碱、酚类、强心苷类、内酯、香豆素及其苷类、甾醇、三萜类、挥发油、油脂等多种化学成分,其中生物碱类为首次检测到.同时对杠柳根皮的甲醇粗提物,经石油醚、乙酸乙酯、正丁醇及水等不同极性溶剂进行萃取浓缩,选用麦二叉蚜、粘虫为测试对象,对其萃取物进行杀虫活性初步测定,结果表明杠柳根皮的正丁醇提取物对麦二叉蚜有较强的触杀活性,对粘虫有一定胃毒活性.     

Selective control of weeds in an arable crop by mulches from some multipurpose trees in Southwestern Nigeria

The use of agroforestry systems in which pruning from trees is used to mulch the companion crops is an important area of research in the tropics. However, previous studies mostly evaluated the contribution of mulch to soil improvement and rarely examined the effect of mulch on weeds. Field experiments were conducted during the 1995 and 1996 growing seasons to investigate the effects of mulch from three woody fallow species on weed composition, biomass and maize grain yield. Treatments consisted of mulch from Leucaena leucocephala, Gliricidia sepium, and Senna siamea applied at rates of five and three tons dry matter ha^–1 at planting and three weeks after planting (WAP), respectively, an unmulched treatment that received 90 kg N ha^–1 of inorganic fertiliser, and an unmulched control plot that received no fertiliser. In both years and sampling dates, plots mulched with G. sepium and S. siamea had significantly lower weed density and biomass than the control plot in each of the sampling times and year of study. There was no significant difference in either weed density or biomass between the plot mulched with L. leucocephala and the unmulched plots. Mulches from G. sepium and S. siamea reduced weed density and weed biomass, while L. leucocephala was less effective in reducing weed biomass and weed density. Weed reduction by the mulches was in the order G. sepium S. siamea > L. leucocephala. Sedges were the dominant species in all the treatments except in G. sepium plots, where Talinum triangulare and other broadleaved species were dominant.This revised version was published online in November 2005 with corrections to the Cover Date.