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Background Low soil fertility and reduced seasonal rainfall contribute to low potato (Solanum tuberosum L.) yield in Kenya. Nitrogen (N) deficiency is the major problem facing by the smallholder farmers of Kenya due to lack of fallow. Hence an introduction of supplemental irrigation with an adequate application of this nutrient could increase potato yield. The objective of this study was to determine the effects of supplemental irrigation and N-fertilisation on potato tuber yield, water use efficiency (WUE) and nitrogen use efficiency (NUE). The experiment was conducted in Nakuru County, Kenya for two seasons. The experimental soils are classified as mollic Andosols. The treatments comprised two irrigation treatments of full supplemental irrigation (FI) and rainfed production (RF) and four N levels of four N levels of 0 (N0), 60 (N1), 90 (N2) and 130 kg N/ha (N3). Results The results showed that total tuber yield, marketable tuber yield and NUE were significantly (P < 0.001) affected by irrigation × N-fertilisation while WUE was only affected (P < 0.001) by N-fertilisation. The highest total tuber yield, 58.28 tonnes/hectare (t/ha), was recorded under FI combined with N3. Treatment FI significantly increased marketable tuber yield by approximately 125.58% in all N treatments compared to RF. The highest NUE of potato (236.44 kg/kg of N) was obtained under FI combined with N3 but not significantly different from the NUE of potato obtained under FI with N2. N-fertilisation N3 produced the highest WUE of 14.24 kg/m3. Significant correlation was obtained between tuber yield and number of tubers/plant (r = 0.75, P < 0.001), NUE (r = 0.95, P < 0.001) and WUE (r = 0.72, P < 0.001). Conclusion High potato yield and marketable tuber yield can be achieved in mollic Andosols when water deficits of the growing season are eliminated with supplemental irrigation and an application of 130 kg N/ha.

This study evaluated the possibility of the use of GreenSeeker sensor and CM-100 chlorophyll content meter for in-season N and yield prediction in order to promote timely split N application in potato production in Kenya. Four N-fertilization rates; N0 (0), N1 (60), N2 (90) and N3 (130 kg N/ha) were led out in a Randomized Complete Block Design (RCBD) in a Greenhouse for two seasons. The results showed that % N leaf content was significantly affected by N rates. The % N leaf content and potato leaf chlorophyll content decreased as the season continued whereas the Normalized Difference Vegetation Index (NDVI) increased as the season continued. CM-100 values were significantly correlated with % N leaf content at vegetative (r=0.86***) and tuber initiation (r=0.74***) growth stages of the crop whereas the NDVI values were only significantly correlated with % N leaf at tuber initiation (r=0.82***). A significant relationship was found between CM-100 values taken at different potato stages (end of vegetative, tuber initiation, bulking and maturation stages) and tuber yield (r=0.90***, 0.82***, 0.47* and 0.41*). The NDVI values at end of vegetative growth, tuber initiation and maturation of potato were also significantly correlated with tuber yield (r=0.81***, 0.43* and 0.54*), except at bulking stage (r=0.33). For efficient in-season N management and yield prediction, CM-100 and GreenSeeker are recommended at an early stage of the crop. Further research in the different potato growing areas in Kenya to establish the different thresholds at different potato growth stages is recommended.

Solid waste management is challenging and incineration technique is more preferred to other methods in reduction of mass and volume, removal of odour and energy recovery in both industrial and residential environments. The challenges facing residents at Njokerio, Ng’ondu and Green Valley estates in Njoro, Kenya included poorly designed open-wastes collection systems, exceeding incinerator loading rates and inappropriate operating temperatures. It also include inadequate design specifications, poorly mixed solid wastes with high moisture contents resulting to high emissions of noxious heavy dense smoke. The aim of this study was to evaluate factors influencing flue gas emissions and performance of small-scale incinerators. Data collected were statistically analysed to determine trends, means, F-values and Least Significant Different (LSD) at . Wastes incineration at varying moisture contents (MC) from 15 to 75% produced mean emission values for carbon monoxide (CO), carbon dioxide (CO2), and hydrocarbon (HC) ranging between 5 and 11 ppm, 5 and 14%, and from 508 to 1168 ppm, respectively. Varying the incinerator loading rates from 15 to 75 kg/h yielded means CO ranging between 5 and 12 ppm, CO2 from 5 to 14%, and HC between 252 and 1096 ppm. Waste incineration at varying operating temperature levels from 180 to 900°C contributed to mean emissions for CO, CO2 and HC ranging from 14 to 5 ppm, 15 to 6% and 1253 to 316 ppm, respectively. The Egerton University dispensary incinerator had the best incineration performance compared to the rest. High moisture contents, overloaded incinerators and low operating temperature levels contributed to high emission levels of flue gases leading to dark and dense smoke which resulted into incomplete wastes combustion indicating poor incineration performance. Wastes incineration at low loading rates, low moisture contents and high operating temperatures produced white and fine bottom ash, low levels of carbon, implying complete wastes combustion.

Potato productivity (Solanum tuberosum L) is generally influenced by several factors, including water and nitrogen (N), and potato requirement for these factors varies depending on the soil type and potato variety. This research aimed to determine the performance of apical rooted cuttings of potato grown in Mollic Andosols under different nitrogen fertilization and irrigation regimes. The treatments comprised 4 irrigation regimes of 100%, 85%, 75% and 50% of the crop evapotranspiration (ETC), where ETC100% was irrigated based on water depletion in the root zone two days after full irrigation, and 4 nitrogen rates of 0 (N0), 60 (N1), 90 (N2) and 130 kg.ha À1 (N3) applied in splits at 10 (40%), 30 (40%) and 50 (20%) days after planting. The results revealed that the water demand for apical rooted cuttings of potato (ETa) was on average 201.4, 302.1, 342.4 and 402.8 mm under ETC50%, ETC75%, ETC85% and ETC100%, respectively. It was observed that plant height and number of branches significantly (P < 0.001) varied under different N rates with the highest plant height (92.67 cm) and number of branches per potato plant (17) achieved when applying N3. Potato grown under full irrigation (ETC100%) with N3 produced the highest total potato tuber yield (58.28 t.ha À1 ) and marketable tuber yield (54.21 t.ha À1 ). The number of tubers per plant statistically reduced as the N deficit increased, with the maximum tuber number, 23, achieved under N3. It was observed that a significant Pearson correlation (r ¼ 0.7***) existed between tuber number and total tuber yield. The maximum harvest index (HI), 57.12 %, was obtained under ETC50% with N3, while the highest tuber dry matter, 30 %, was observed under N3. To achieve a high tuber yield from apical rooted cuttings of potato in Mollic Andosols, this study recommends an irrigation regime of ETC100% and a nitrogen rate of 130 kg.ha À1 .