超声波辅助提取杠柳脂溶性成分工艺优化

为了优化超声波辅助提取杠柳脂溶性成分的工艺,该文在单因素试验基础上,选取超声波功率、提取时间、液料比为主要影响因素,分析了3个主要影响因素对杠柳脂溶性成分提取结果的影响,应用响应面分析法优化了超声波辅助提取杠柳脂溶性成分的工艺方法,并使用GC-MS联用仪检测了杠柳脂溶性提取物的主要成分。结果表明:超声波辅助提取杠柳营养体脂溶性成分的最佳工艺为:在室温(20℃)及超声波频率20kHz条件下,提取试剂为石油醚,超声波辅助提取时间为70min,超声波功率为730W,料液比为1∶10g/mL。该工艺条件下,杠柳脂溶性成分的实际提取得率可达到6.14%。     

Nitrogen-Fixing Trees in Small-Scale Agriculture of Mountainous Southeast Guatemala

Abstract

Intensive, subsistence agriculture on hillsides of southeast Guatemala has caused extensive soil degradation. This retrospective study evaluated the success of an agroforestry treatment in improving the sustainability of mountainous agricultural systems in terms of soil nutrient status and erosion control. Three years after maize (Zea mays) and pasture fields were alley-cropped with N-fixing Gliricidia sepium trees, soil nutrient levels were examined and compared to nonalley-cropped controls. Agroforestry treatment showed significantly higher soil organic matter (SOM) over paired plots with no alley-cropping (mean 4.3% vs. 3.2% C, p < 0.05). Mean total N was also higher, with 0.12% in the nonagro-forestry control plots compared to 0.16% underthe agroforestry treatment (p <0.05). Some improvement in soil water-holding capacity(WHC) was also observed in the agroforestry systems. Differences in soil levels of available P, ranging from 8.0 to 64.4 μg/g, were not significant and correlated more with site than with agroforestry treatment versus control. Specific soil and site properties such as texture and slope as well as land use and ground cover management largely influenced improvements in soil nutrient status under the agroforestry treatment at each site. Despite increases in soil nutrients, maize plant productivity showed no response to the agroforestry treatment in terms of leaf chlorophyll index or maize plant height. Three years after the initiation of agroforestry, soil erosion rates showed no difference from paired controls; rates were correlated with ground cover and soil characteristics such as texture and surface rockiness rather than with agroforestry treatment. While soil nutrient status had not reached levels optimum for maize growth after three years, the positive trajectory of change in soil nutrients suggests the potential for using agroforestry systems in mountainous regions of Guatemala to increase the sustainability of agricultural production.     

Liming and Fertilizer Potentials of Some Underutilized Plant Materials in Southwestern Nigeria

Soil acidification and phosphorus deficiency are a major constraint to crop production in tropical soils.Use of conventional liming materials is associated with some limitations viz:inability to solely improve nitrogen and available phosphorus in soils,loss of soil organic carbon and soil aggregate stability.Liming and fertilizer potentials of leaves from three plant materials(Tithonia diversifolia(TL),Imperata cylindrica(SG)and Gliricidia sepium(GL))widely growing in Ogbomoso,southwest Nigeria,were tested under incubation condition.Each of the plant material was applied at the rate of 10 t·hm~(-2) with and without 50%concentration of NPK 15:15:15-urea mix in 500 g acidic soil.Sole lime applied at 1 t·hm~(-2),sole NPK 15:15:15 applied at 60 kg·hm~(-2) mixed with urea at 60 kg N·hm~(-2) and an unamended soil were compared in completely randomized design in three replicates.The treated soils were incubated for 12 weeks.Thereafter,maize seeds were raised in each pot for a period of 3 weeks.Data collected were subjected to analysis of variance.Regression analysis was used to predict contributions of increased soil p H in plant material treated soils to exchangeable Al,H,dry root weight of maize and available phosphorus.Results indicated that sole plant materials were the order SGTLGL significantly(p0.05)reduced exchangeable acidity compared to unamended and sole NPK.Sole NPK had the highest exchangeable acidity(4.7 cmol·kg~(-1))compared to unamended soil(3.3 cmol·kg~(-1))and sole lime(2.7 cmol·kg~(-1)).Application of sole Tithonia diversifolia increased available phosphorus by 214%and 97%compared to unamended and sole NPK treated soils respectively.Sole plant materials increased maize root weight by 33%compared to sole NPK.Increasing soil p H at harvesting in plant material treated soils significantly reduced exchangeable H and A_1.Soil p H was responsible for up to 33%and 53%reductions in exchangeable Al and H,respectively.This culminated into up to 22%increases in dry root weight of maize seedling.Present results showed ability of the plant materials tested to ameliorate soil acidity and improved soil available phosphorus.The plant materials should be explored for using as green manure and composting feedstock.It will go a long way to reduce high dosage use of conventional liming and fertilizer materials on acidic nutrient degraded soils.