Diversification of potato farming systems through legume intercropping for improved resource use efficiency

A thesis submitted in fulfilment of the requirements for the degree of Doctor of Philosophy in Soil Science.Expanding production of potato to the midlands and lowlands of Kenya will only be possible if the effect of water deficit, high temperatures and nutrient limitation on potato growth is well understood. Potato (Solanum tuberosum L.) was grown singly and intercropped with lima bean (Phaseolus lunatus L.) or dolichos (Lablab purpureus L.), and the respective single crop of the legumes in three agro-ecological zones (AEZs) of Kenya; upper midland (1552 meters above sea level (masl)), lower highland (1894 masl) and upper highland (2552 masl). The objectives were as follows: i) determine the interelationships between soil water balance, soil temperatures and crop nutrient (NPK) uptake under potato-legume intercropping ii) assess the short-term effect of potato legume intercropping on dynamics of microbial activity and SOM fractions, iii) evaluate the effect of potato-legume intercropping on soil nitrogen balance and iv) quantify the radiation and crop water productivity of potato-legume intercropping system. The study was laid out in a randomized complete block design with four replications. All the potato treatments received basal fertilization at a rate of 50 kg N ha-1 , 90 kg P ha-1 and 100 kg K ha-1 and topdress of 40 kg N ha-1 . Soil temperatures and soil water contents (SWC) were quantified at different stages of potato growth. Residues from each cropping system were quantified at the end of each season and incorporated back into the soil at start of the subsequent season. Soil samples (0–120 cm depths) were taken at the interrows of each plot prior to planting, at vegetative growth, and at the end of each season. Physical and density fractionation procedure was used to separate the soil in macro-aggregates (>250 μm), micro-aggregates (250–50 μm) and silt plus clay fractions (<50 μm), while SOM was partitioned into labile (density of 1.65 to 1.85 g cm−3) and stable (2.60 g cm−3) fractions. Microbial biomass carbon was determined by chloroform fumigation while enzymatic activities were assessed by hydrolyses of fluorescein diacetate and dehydrogenase. Nitrogen gains from mineralization, fertilization, and outputs from biomass accumulation, leaching, and soil erosion were quantified throughout the potato growth cycle. N losses through volatilization were quantified using ventilation chambers while the amount of N leached was extracted using solusamplers located at vertical depths of 0–1.5 m and the leachetes analyzed for nitrate contents. Leaf area index (LAI) and light interception were quantified at different stages of potato growth and related with the radiation use efficiency (RUE) and crop water productivity (CWP). The data was subjected to mixed model analyses of variance using R software with Tukeys mean separation test set at 95% propability level. Intercropping increased LAI by 26–57% relative to sole potato and significantly (p < 0.05) lowered soil temperatures in the 0–30 cm depth by up to 7°C. This increased SWC by up to 38%, thus increasing RUE by 56–78%, CWP by 45–67% and nutrient use efficiency by 40–67%. Compared with the sole potato, intercropping increased the contents of labile fraction organic matter by 12–28%, dissolved organic matter by 7–21% and microbial biomass by 15–38%, thus stimulating enzyme activities. Trends in soil microbial respiration followed those of enzyme activity and were 20–34% higher in intercropping than in sole potato. Soil N balance was significantly influenced by legume intercropping (p<0.05) and ranged between -10.7 to -18.1 kg N ha-1 for sole potato, 4.1 to 6.6 kg N ha-1 for intercropping and 2.9 to 22.3 kg N ha-1 for sole legumes. The residue mixture of potato and legume intercrops enhanced N mineralization with peak N release of 5 to 9 kg N ha-1 occurring within 8 to 10 weeks of residue decomposition. This period coincided with the peak N uptake by potato (19.9 to 31.2 kg N ha-1 ) thus showing a close synchrony of N supply and potato N demand. These results provide a possible entry point to restoring the impoverished soil productivity in the smallholder potato farming systems and offer the possibility of potato expansion to midland agro-food systems

Effect of potato (Solanum tuberosum L.) cropping systems on soil and nutrient losses through runoff in a humic nitisol

Thesis submitted in partial fulfillment for the requirements of the degree of Master of Science in Land and Water Management, Department of Land Resource Management and Agricultural Technology, University of Nairobi.A field study was carried out using runoff plots during the short and long rainy seasons of 2014 and 2015 respectively at the Field Station of Upper Kabete Campus, University of Nairobi. The objectives of the study were to assess the effect of soil surface roughness and potato cropping systems on soil loss and runoff, to determine the effect of erosion on nutrient enrichment ratio and to evaluate the SOM fraction most susceptible to soil erosion. The treatments comprised of Bare Soil (T1); Potato + Garden Pea (Pisum sativa) (T2); Potato + Climbing Bean (Phaseolus vulgaris) (T3); Potato + Dolichos (Lablab purpureus) (T4) and Sole Potato (Solanum tuberosum L.) (T5). Soil loss and runoff recorded in each event differed significantly between treatments (p<0.05) and were consistently highest in T1 and lowest in T4. Mean cumulative soil loss from T5, T2, T3 and T4 was 39.2, 31.8, 23.5 and 11.0% respectively compared to bare plots, suggesting that T4 plots provided the most effective cover in reducing soil loss. Intercropping potatoes with cover crops reduced runoff by 22-72% when compared with the sole potato, and by 55 to 84% when compared with the bare plots. Regression analyses revealed that both runoff and soil loss related significantly with surface roughness and percent cover (R2 =0.83 and 0.73 respectively, p<0.05). Statistically significant linear dependence of runoff and soil loss on surface roughness and crop cover was found in T4 (p<0.05) indicating that this system was highly effective in minimizing soil loss and runoff. Enrichment ratio was on average greater than unity for all soil elements analyzed indicating that the erosion process was selective. The correlation coefficients between enrichment ratio of clay and soil nutrients showed strong associations, the highest being with P (r=0.88) and the lowest with K (r=0.75), suggesting that clay particles better account for nutrient losses. Concentrations of SOM in the eroded sediment were higher in the stable fraction, MOC (18.43-19.30 g kg-1 ), MN (1.67-1.93 g kg-1 ) than in the labile fraction, POC (7.72-9.39 g kg-1 ), PN (0.62-0.84 g kg-1 ) indicating that much of the eroded SOM was in stable form. The highest decline in SOM contents occurred in stable fractions in which MOC reduced by 6.2 to 22% while MN reduced by 6.1 to 21%

Rickets in Rural Kenyan Preschool Children: Case Report

Clinical rickets has not been reported previously in Embu district, Kenya. Baseline clinical assessments performed for a nutrition intervention study in preschool children (n=324) identified 28 cases of rickets (8.6% of study sample). Clinical characteristics included: delays of sitting, walking, and teething; bone and chest deformities; widened wrists and ankles; and bowed lower extremities. Risk factors identified were short duration of breastfeeding with feeding of cereal-based supplements with little or no milk, low calcium intake, limited sunlight exposure. Vitamin D and calcium deficiencies likely contributed to these cases. Treatment with Vitamin D3 and milk resulted inclinical improvement

Synthesis, characterization and antibacterial activity studies of new 2‑pyrral‑L‑amino acid Schif base palladium (II) complexes.

Three new 2-pyrral amino acid Schif base palladium (II) complexes were synthesized, characterized and their activity against six bacterial species was investigated. The ligands: Potassium 2-pyrrolidine-L-methioninate (L1), Potassium 2-pyrrolidine-L-histidinate (L2) and Potassium 2-pyrrolidine-L-tryptophanate (L3) were synthesized and reacted with dichloro(1,5- cyclooctadiene)palladium(II) to form new palladium (II) complexes C1, C2 and C3, respectively. 1 NMR, FTIR, UV–Vis,elemental analysis and conductivity measurements were used to characterize the products. The antibacterial activities of the compounds were evaluated against Gram-positive Staphylococcus aureus (S. aureus, ATCC 25923), methicillin-resistant Staphylococcus aureus (MRSA, ATCC 33591), Staphylococcus epidermidis (S. epidermidis, ATCC 12228) and Streptococcus pyogenes (S. pyogenes, ATCC 19615) and, gram-negative Pseudomonas aeruginosa (P. aeruginosa, ATCC 27853) and Klebsiella pneumoniae (K. pneumoniae, ATCC 13883) using the agar well difusion assay and microtitre plate serial dilution method. The palladium complexes were active against the selected bacteria with the imidazole ring containing complex C2 and indole heterocyclic ring containing complex C3 showing the highest activity