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.

The social component of the environment associated mostly with human activities has significantly imposed a threat to the only life-support systems of the earth. Uganda made adjustments in its planning process to prioritize environment conservation. However, in the recent past years, mostly between 2013 and 2017, the country stretched its resources to increase agricultural production, both livestock and crops. The objective of this study was to establish and document the development and the environment conservation strategies at global and regional levels with an overview on the development planning process in agricultural sector, in Uganda. The results showed that the sustainable development plans with participatory approach at international, regional, national and local or community levels are the best methods to cope with and reduce the negative impacts of man&rsquo;s activities on the environment. The understanding of the complexes of the environment is very important to ensure the relationship between the social, economic and environmental protection for a sustainable development. The results also indicated that in Uganda, the agriculture industry made consistent efforts to increase agricultural production by 431,161 hectares and livestock heads by 7,878,000 (cattle, sheep, goats, pigs, and poultry) between 2013 and 2017. This increased agricultural greenhouse gas emission due to the use of synthetic fertilizers, burning of the cleared grasses, and use of manures applied to boost soil fertility and the reduction in the trees that sequester CO2. This study recommended that the agricultural sector should opt for sustainable agriculture by adopting practices like use of multipurpose crops that can offer environmental services like binding soil particles together to control erosion as well as yielding more food products. Dual-purpose livestock breeds should be adopted to avoid immense numbers that serve different purposes that will probably lead to increased GHG emissions.

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.

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 .

Water and nitrogen (N) are key interacting factors that control plant growth. The objective of the study was to determine the effect of N rates and drip irrigation regimes on water use efficiency (WUE) and N use efficiency (NUE) of apical rooted cuttings of potato (Solanum tuberosum L.) grown in a mollic Andosol. The treatments comprised four drip irrigation regimes of 50%, 75%, 85% and 100% of the crop evapotranspiration (ETC), where ETC100% was irrigated according to the soil water depletion 2 d after full irrigation and four N rates: 0 (N0), 60 (N1), 90 (N2) and 130 kg N ha −1 (N3). The results showed that potato tuber yield, WUE, and NUE were significantly (P < .001) affected by irrigation regimes, N rates, and the interaction of both factors. The highest potato tuber yield, 58.29 Mg ha −1 , was obtained under ETC100% with N3, whereas the highest WUE, 17.5 kg m −3 , was found under ETC50% with N3. The apical rooted cuttings of potato grown under ETC100% with N2 produced the maximum NUE, 208.30 kg kg −1 . The correlation coefficient (r = 0.31; P < .01) obtained between WUE and NUE was weak. It was also observed that an increase in irrigation amount decreased WUE and increased NUE, whereas a high N dosage increased WUE and decreased NUE of potato grown in a mollic Andosol. This study suggests that if the farmers aim to maximize NUE of apical rooted cuttings in a mollic Andosol, then they will do so at the expense of potato WUE, and yield will be looked at as a secondary factor. INTRODUCTIONPotato (Solanum tuberosum L.) is one of the major root and tuber food crops for many people around the world (FAO-STAT, 2017). Globally, 368 Tg of potato were produced in 2018 on an estimated area of 17.58 million ha (FAOSTAT, 2020). In Kenya, it is the second staple food and cash crop