Antimalarial potential and phytochemical composition of fractions of Lippia kituiensis Vatke (Verbenaceae) growing in Northern Tanzania

This research article published by Journal of Medicinal Plants Research, 2020Despite past decades of steady advances in the fight against Malaria, statistics show that the disease is still a threat to human health. Previous successes in the development of antimalarial drugs from medicinal plants have fuelled research in this area. However, antimalarial studies on fractionated extracts from such plants have progressed slowly. This study reports the antimalarial potential of fractions from Lippia kituiensis Vatke, for the first time. Column chromatography was used during fractionation. Antiplasmodial assay against chloroquine-sensitive (D6) and resistant (W2) plasmodium strains were done using hypoxanthine incorporation assay. MTT assay was used to assess the cytotoxicity of fractions against the Vero cell line. Fractions obtained exhibited varied inhibitory concentrations (IC50); with the most efficacious being, Lk-5 (19.45 ± 6.20 μg/ml), Lk-3 (30.43 ± 0.68 μg/ml), Lk-4 (30.82 ± 18.01 μg/ml), and Lk-6 (36.53 ± 14.42 μg/ml) against D6. Generally, lower activity against W2 was obtained with the most active being LK-4 (24.18±2.50 μg/ml), and Lk-5 (24.42±5.95 μg/ml), while chloroquine (positive control) exerted IC50 of 77.86±4.09 ng/ml (W2) and 15.71±6.49 ng/ml (D6). LK-4 was the most cytotoxic showing cytotoxic concentration (CC50), 46.26 μg/ml. When tested in mice, fractions suppressed Plasmodium berghei significantly compared to the negative control with Lk-3 being most efficacious (80.01±1). Due to substantive efficacy, GC-MS done on Lk-3 revealed 8 compounds where three have previously been ascribed to antimalarial activity and other pharmacological effects. This study adds to present knowledge of antimalarial efficacy of L. kituiensis and provides the basis for further work to be done on the isolation of compounds from its extracts

Impact of Nitrogen Fertilizer Applications on Surface Water Nitrate Levels within a Kenyan Tea Plantation

Tea production in the Kenyan Rift Valley uses high rates of nitrogenous fertilizer. Nitrates can be discharged to water bodies through leaching and surface run-off. Nitrate levels above 10 mg/L NO3-–N cause methemoglobinemia which is fatal. A study to monitor changes in surface water nitrate levels was carried out in ten rivers within a Kenyan tea plantation for three years. Water samples were obtained before and after fertilizer application in 2004, 2005, and 2006. Nitrate-nitrogen (NO3-–N) was determined colorimetrically by the cadmium reduction method using HACH-DR 2400 dataloging spectrophotometer. For the three years, the highest nitrate-nitrogen levels were in river Temochewa in 2005 during the first fertilizer applications (4.9 mg/L to 8.2 mg/L). There was no established trend between surface water nitrate levels and the time of fertilizer applications; however, fertilizer application contributed to an increase in nitrate levels. The initial nitrate-nitrogen levels in most of the rivers were high, indicating that contamination could have been upstream; hence, further research is required to establish this. Nitrogen-nitrogen levels in the three years were below the maximum contaminant level of 10 mg/L NO3-–N; however, the rivers should be monitored frequently

Influence of soybean residue management on nitrate nitrogen accumulation and subsequent sorghum yield in Kanhaplic Haplustults of Western Kenya

Journal of Agriculture and Ecology Research International, 2017; 13 (3): 1-12Crop residues are overlooked when making fertilizer recommendations, yet have potential to contribute to soil nitrogen in addition to mineral fertilizer use. A study was carried out in western Kenya to establish the contribution of soybean residues under varied management options and nitrogen fertilizer rates on nitrogen supply to subsequent sorghum crop. Six soybean residue management options were evaluated; sole sorghum, sorghum + soybean left to maturity, sorghum + soybean mulched, sorghum + soybean incorporated, sorghum + soybean exsitu and sorghum + soybean exsitu and plot tilled. Three levels of nitrogen (0 kg N ha -1 , 40 kg N ha -1 , and 80 kg N ha -1 ) as urea were applied as top-dress and treatments arranged in randomized complete block design. -1 Soybean left to maturity at 40 kg N ha indicated significant (P < 0.001) increase (56%) in soil NO 3 -N. Removal of soybean residues resulted in significantly (P < 0.001) lower soil NO 3 -N increase while control treatment and sole sorghum indicated the lowest soil NO 3 -N accumulation irrespective of nitrogen fertilizer rates. Soybean left to maturity indicated significant (P < 0.001) increase (43%) -1 in leaf NO 3 -N accumulation at 40 kg N ha while treatments with soybean residues mulched showed 39% increase and those with residues incorporated, 25% increase. Soybean residues ex- situ and ex-situ and till indicated a decrease (-6% and -7%) in leaf NO 3 -N accumulation, respectively. Sole sorghum had a uniform NO 3 -N increase of 4% irrespective of nitrogen fertilizer rates. It was observed that insitu soybean residues and nitrogen fertilizer application had no significant (P < 0.05) influence on sorghum yield. In conclusion, soil and leaf NO 3 -N accumulation by soybean residues in addition to nitrogen fertilizer does not translate to optimum nor potential research sorghum yields. There is need to research on sulphur and nitrogen to establish their interactive effects on sorghum yields

Effects of nitrogen fertilizer rates and soybean residue management on nitrate nitrogen in sorghum-soybean intercropping system

This article is available at www.sciencedomain.orgAn experiment was carried out in Busia County, Kenya at Emalomba (N 00°25′28.8″ E 034°15′ 51.9″), Nambale District to assess the effects of nitrogen fertilizer rates and legume management options on nitrate nitrogen (NO3-N) under intercropping system. Six soybean residue management options were considered: Sole sorghum, sorghum + soybean left to maturity, sorghum + soybean mulched, sorghum + soybean incorporated, sorghum + soybean exsitu and sorghum + soybean exsitu and plot tilled. Three levels of nitrogen (0kg N ha-1, 40kg N ha-1, and 80kg N ha-1 as urea were applied as top-dress and treatments arranged in randomized complete block design. Soil NO3-N was significantly high (P<0.0010) in topsoil with a notable leaching to subsoil due to precipitation. Control treatments had low soil NO3-N in comparison to other treatments implying that, use of inorganic fertilizers to supplement soil N is important. Fertilizer application at 40kg N ha- 1 with respect to on-farm soybean residue management was in relation to NO3-N supply was in the order: sorghum + soybean left to maturity > sorghum + soybean mulched = sorghum + soybean incorporated. Experimental plots with legume residues removed had significantly (P<0.001) low NO3-N. High leaf NO3-N observed points to transfer of N to sorghum by nitrogen fixation signifying importance of intercropping. There was no significant difference between nitrogen fertilizers applied at 40kg N ha-1 and 80kg N ha-1 irrespective of field managed legume residues. Sorghum intercropped with soybean left to maturity with nitrogen fertilizer applied at 40 kg N ha-1 reflected high (P< 0.001) soil NO3-N in comparison to the other management options. It is therefore recommended as a possible optimum rate and legume residue management option to improve soil NO3-N among small scale households with stretched socio-economic ability in Busia County

Pedological characterization of some typical soils of Busia county, Western Kenya: soil morphology, physico-chemical properties, classification and fertility trends

Standard soil survey was carried out in Western Kenya to establish representative research sites on the basis of landforms and other physiographic attributes. Soil profiles were characterized at Emalomba (Nambale District) designated (EMA-P1) and at Bukhalalire (Butula District) named BUMA-P1. Both pedons formed from in-situ weathering of granitic rocks under ustic moisture and iso-hyperthermic temperature regimes. Fourteen soil samples from genetic horizons were analyzed for physico-chemical properties. Both pedons had dark brown sandy clay and sandy clay loam topsoils overlying dominantly clayey subsoils. Both pedons indicate clay eluviation-illuviation as a dominant pedogenic process with strong acidic soil conditions and available phosphorus of < 7 mg/kg soil. Organic carbon (OC) is high in EMA-P1 and medium to very low in BUMA-P1 while total nitrogen is medium and low to very low. EMA-P1 and BUMA-P1 have C/N ratios of 8.6 - 9.6 and 12.9 - 24.8 respectively. Both pedons have low to very low exchangeable bases with cation exchange capacity (CEC) < 16 cmol(+)/kg soil. CEC clay values in both pedons are < 24 cmol(+)/kg with BUMA-P1 having < 10 cmol(+)/kg. Both soils are highly weathered with BUMA-P1 depicting more advanced stage of weathering. In the USDA Soil Taxonomy, EMA-P1 was classified as Kanhaplic Haplustults and BUMA-P1 as Typic Kandiustults, both corresponding to Haplic Cutanic Acrisols in WRB. As regards soil fertility trends, OC showed positive correlation with calcium and magnesium indicating organic matter as the main source of plant nutrients. The two pedons differed noticeably in terms of physico-chemical characteristics emphasizing the need to characterize soils before fertilizer recommendations are made. Organic fertilizers are recommended to increase organic matter content and intercropping of cereals with nitrogen fixing legumes to enhance nitrogen in the soils. Use of non-acidifying inorganic fertilizers and lime as soil amendments should also be considered to correct acidity

Effects of Nitrogen Fertilizer Rates and Soybean Residue Management on Nitrate Nitrogen in Sorghum-Soybean Intercropping System

An experiment was carried out in Busia County, Kenya at Emalomba (N 00°25′28.8″ E 034°15′ 51.9″), Nambale District to assess the effects of nitrogen fertilizer rates and legume management options on nitrate nitrogen (NO3-N) under intercropping system. Six soybean residue management options were considered: Sole sorghum, sorghum + soybean left to maturity, sorghum + soybean mulched, sorghum + soybean incorporated, sorghum + soybean exsitu and sorghum + soybean exsitu and plot tilled. Three levels of nitrogen (0kg N ha-1, 40kg N ha-1, and 80kg N ha-1 as urea were applied as top-dress and treatments arranged in randomized complete block design. Soil NO3-N was significantly high (P&lt;0.0010) in topsoil with a notable leaching to subsoil due to precipitation. Control treatments had low soil NO3-N in comparison to other treatments implying that, use of inorganic fertilizers to supplement soil N is important. Fertilizer application at 40kg N ha-1 with respect to on-farm soybean residue management was in relation to NO3-N supply was in the order: sorghum + soybean left to maturity &gt; sorghum + soybean mulched = sorghum + soybean incorporated. Experimental plots with legume residues removed had significantly (P&lt;0.001) low NO3-N. High leaf NO3-N observed points to transfer of N to sorghum by nitrogen fixation signifying importance of intercropping. There was no significant difference between nitrogen fertilizers applied at 40kg N ha-1 and 80kg N ha-1 irrespective of field managed legume residues. Sorghum intercropped with soybean left to maturity with nitrogen fertilizer applied at 40 kg N ha-1 reflected high (P&lt; 0.001) soil NO3-N in comparison to the other management options. It is therefore recommended as a possible optimum rate and legume residue management option to improve soil NO3-N among small scale households with stretched socio-economic ability in Busia County

Pedological characterization of some typical soils of Busia county, Western Kenya: soil morphology, physico-chemical properties, classification and fertility trends

Standard soil survey was carried out in Western Kenya to establish representative research sites on the basis of landforms and other physiographic attributes. Soil profiles were characterized at Emalomba (Nambale District) designated (EMA-P1) and at Bukhalalire (Butula District) named BUMA-P1. Both pedons formed from in-situ weathering of granitic rocks under ustic moisture and iso-hyperthermic temperature regimes. Fourteen soil samples from genetic horizons were analyzed for physico-chemical properties. Both pedons had dark brown sandy clay and sandy clay loam topsoils overlying dominantly clayey subsoils. Both pedons indicate clay eluviation-illuviation as a dominant pedogenic process with strong acidic soil conditions and available phosphorus of < 7 mg/kg soil. Organic carbon (OC) is high in EMA-P1 and medium to very low in BUMA-P1 while total nitrogen is medium and low to very low. EMA-P1 and BUMA-P1 have C/N ratios of 8.6 - 9.6 and 12.9 - 24.8 respectively. Both pedons have low to very low exchangeable bases with cation exchange capacity (CEC) < 16 cmol(+)/kg soil. CEC clay values in both pedons are < 24 cmol(+)/kg with BUMA-P1 having < 10 cmol(+)/kg. Both soils are highly weathered with BUMA-P1 depicting more advanced stage of weathering. In the USDA Soil Taxonomy, EMA-P1 was classified as Kanhaplic Haplustults and BUMA-P1 as Typic Kandiustults, both corresponding to Haplic Cutanic Acrisols in WRB. As regards soil fertility trends, OC showed positive correlation with calcium and magnesium indicating organic matter as the main source of plant nutrients. The two pedons differed noticeably in terms of physico-chemical characteristics emphasizing the need to characterize soils before fertilizer recommendations are made. Organic fertilizers are recommended to increase organic matter content and intercropping of cereals with nitrogen fixing legumes to enhance nitrogen in the soils. Use of non-acidifying inorganic fertilizers and lime as soil amendments should also be considered to correct acidity

Effects of nitrogen fertilizer rates and soybean residue management on nitrate nitrogen in sorghum-soybean inter-cropping system

An experiment was carried out in Busia County, Kenya at Emalomba (N 00°25′28.8′′ E 034°15′ 51.9′′), Nambale District to assess the effects of nitrogen fertilizer rates and legume management options on nitrate nitrogen (NO 3 -N) under intercropping system. Six soybean residue management options were considered: Sole sorghum, sorghum + soybean left to maturity, sorghum + soybean mulched, sorghum + soybean incorporated, sorghum + soybean exsitu and sorghum + soybean exsitu and plot tilled. Three levels of nitrogen (0kg N ha -1 , 40kg N ha -1 , and 80kg N ha -1 as urea were applied as top-dress and treatments arranged in randomized complete block design. Soil NO 3 -N was significantly high (P<0.0010) in topsoil with a notable leaching to subsoil due to precipitation. Control treatments had low soil NO 3 -N in comparison to other treatments implying - that, use of inorganic fertilizers to supplement soil N is important. Fertilizer application at 40kg N ha1 with respect to on-farm soybean residue management was in relation to NO 3 -N supply was in the order: sorghum + soybean left to maturity > sorghum + soybean mulched = sorghum + soybean incorporated. Experimental plots with legume residues removed had significantly (P<0.001) low NO 3 -N. High leaf NO 3 -N observed points to transfer of N to sorghum by nitrogen fixation signifying importance of intercropping. There was no significant difference between nitrogen fertilizers applied -1 -1 at 40kg N ha and 80kg N ha irrespective of field managed legume residues. Sorghum -1 intercropped with soybean left to maturity with nitrogen fertilizer applied at 40 kg N ha reflected high (P< 0.001) soil NO 3 -N in comparison to the other management options. It is therefore recommended as a possible optimum rate and legume residue management option to improve soil NO 3 -N among small scale households with stretched socio-economic ability in Busia County

Socioeconomic factors and soil fertility management practices affecting sorghum production in Western Kenya: a case study of Busia county

Sorghum (Sorghum bicolor L. Moench), though ranked as the third most important staple food crop in Kenya, farmers still experience periodic crop failure and this is a threat to food and income security. This paper attempts to find the underlying factors responsible for low production and establish farmers’ perceptions on soil fertility management. A cross-sectional study was carried out in Busia County, to relate socioeconomic factors and soil fertility management aspects affecting sorghum yields. Structured interviews and observations were used for data collection, considering the variables: demographic factors, income, farmers’ perception on soil fertility replenishing options, access to agricultural advisory services and yields of sorghum. Results indicate that women are predominant (57.3%) sorghum producing farmers in the County. Literacy level reveals majority of the farmers (49.3%) have primary education as optimum suggesting sorghum production to be through hands-on experience. Individual land ownership was the norm with most farms being 1.5 to 2.0 hectares. Income among respondents is below USD 1.25 per day. Sorghum is ranked very important (56.7%) and is a resource against food shortage. Many farmers (41.3.0%) use traditional seed from previous harvests with 24.0% purchasing seed from agro-dealers or being provided by non-Governmental organizations/projects. Intercropping is associated with food security, improved yields and land inadequacy and not to soil fertility restoration. Inadequate knowledge on the role of legumes and crop residue recycling in soil fertility improvement exists and 38.7% of farmers have access to agricultural information. Gender, social norms, literacy, fertilizer use, accessibility to advisory services and farmers’ perception on soil fertility management options are concluded to impact on sorghum production in Busia County. The existing database on the alternative researched options to restore soil fertility and increase crop yields could be channeled through demonstration plots to farmers in a participatory manner in order to facilitate adoption

Phosphorus Sorption and Lime Requirements of Maize Growing Acid Soils of Kenya

In Kenya, maize (Zea mays L.) is mainly grown on acid soils in high rainfall areas. These soils are known for low available phosphorus (P), partly due to its sorption by aluminium (Al) and iron oxides. The study determined soil P sorption, lime requirements and the effects of lime on soil pH, Al levels and available P on the main maize growing acids soils in the highlands east and west of Rift Valley (RV), Kenya. Burnt lime containing 21% calcium oxide was used. The soils were strongly to extremely acid (pH 4.85-4.07), had high exchangeable Al3+ (> 2 cmol Al kg-1) and Al saturation (> 20% Al), which most maize germplasm grown in Kenya are sensitive to. The base cations, cation exchange capacity and available P (< 10 mg P kg-1 bicarbonate extractable P) were low, except at one site in the highlands east of RV indicative with history of high fertilizer applications. Highlands east of RV soils had higher P sorption (343-402 mg P kg-1) than the west (107-258 mg P kg-1), probably because of their high Al3+ ionsand also the energies of bonding between the soil colloids and phosphate ions. Highlands east of RV also had higher lime requirements (11.4-21.9 tons lime ha-1) than the west (5.3-9.8 tons lime ha-1). Due to differences in soil acidity, Al levels and P sorption capacities within and between highlands east and west of RV, blanket P fertilizer and lime recommendations may not serve all soils equally well