Soil & Water
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Item Influence of Soil Types on Citrus Nematode Species Diversity and Abundance Under Varied Ecological Conditions in Kenya(Pakistan Journal of Nematology, 2022-05-21) Kiptoo, J.; Mutisya, D.; Ndegwa, P.; Amata, R.; Irungu, L.; Godfrey, R.; University of Nairobi ; Kenya Agricultural and Livestock Research Organization ; Machakos University ; Masinde Muliro University of Science and TechnologyPlant-parasitic nematodes (PPNs) cause major crop losses by damaging plant roots and causing reduced absorption of soil nutrient elements. A two-year survey in 2018 and 2019 was conducted in most citrus growing regions in Kenya to assess the abundance, distribution and diversity of plant parasitic nematodes from different soil rhizosphere. Nematode population in 200cc of soil and 5g of roots were collected for PPNs extraction by using modified Baermann’s technique and identification by morphological features. The findings indicated that four major genera were abundant in different citrus growing ecological zones in Kenya. The identified species were Meloidogyne incognita, Tylenchulus semipenetrans, Helicotylenchus dihystera and, Pratylenchus brachyurus. The most abundant species in all the surveyed localities was T. semipenetrans. Factor regression analysis results showed that modest rainfall amounts favoured high density populations of PPNs on citrus roots where soil types of Rackers in Baringo and Luvisols, Ferralsols and Cambisols in Machakos County were dominant. Tylenchulus, Meloidogyne and Helicotylenchus species were most abundant in Kitale, Taita-Taveta, Kilifi and Kwale. The results presented here show how possible population density of PPNs in varied soil class types, rainfall amounts and prevailing temperature would be influenced by abiotic factors therein.Item Fluoride Toxicity in Cropping Systems: Mitigation, Adaptation Strategies, and Related Mechanisms. A Review(Elsevier B.V., 2022-04-09) Makete, N.; Rizzu, M.; Seddaiu, G.; Gohole, L.; Otinga, A.; Kenya Agricultural & Livestock Research Organization ; University of Sassari ; University of EldoretEnvironmental fluoride (F−) contamination, mainly due to natural geogenic processes, and in spot cases also of anthropogenic origin, is a widespread global issue, which has been recognized to affect all living organisms. From the contaminated soil and water, F− is absorbed by plants which can manifest symptoms of abiotic stress including oxidative stress and interference with essential physiological and biochemical processes involved in seed germination and plant growth and development. Depending on the diet of the population living in the high F-polluted areas, F-contaminated crops can be key contributors to excessive F− intake along food chains which can lead to human and animal health issues. Various strategies are being explored with the objective of reducing both F− bioaccumulation and its damage on plants (e.g. by means of immobilization or phytoextraction processes) or aimed at limiting the F− anthropogenic input in the soil (e.g. through the use of alternative phosphate fertilizers) but the literature is still fragmented. After a brief overview on the effects of F− on the production and safety of food crops, its sources, mobility and bioavailability in agricultural soils, this paper reviews the available F− mitigation and adaptation options and the involved mechanisms with the aim of providing stakeholders with knowledge to make informed decisions when selecting methods for coping with F− impacts in agricultural systems. Research gaps and possible areas for future studies have also been suggested.Item Productivity and Nutritive Value of Urochloa Grass Cultivars in Semi-Arid Tropical Kenya(UKnowledge, 2021-10-17) Njarui, D.M.G.; Gatheru, M.; Kenya Agricultural & Livestock Research Organization (KALRO)There is increasing demand for high yielding and nutritious forages to meet the growing dairy farming in semi-arid Kenya. The productivity and nutritive value of seven Urochloa grass cultivars (Urochloa decumbens cv. Basilisk, U. brizantha cvs. Marandu, MG4, Piatá and Xaraes, U. humidicola cv. Llanero and U. hybrid cv. Mulato II) were evaluated in two diverse semi-arid environments, Katumani and Ithookwe in Kenya. At Katumani, the dry matter (DM) yield (5000-7500 kg/ha) was highest during the first harvest during the long rains (LR) 2014 season. Dry matter yield declined progressively with season and in the third season (LR 2015) only Xaraes achieved over 2000 kg/ha. All Urochloa cultivars died and no yield was recorded after the third harvesting season (LR 2015) due to prolonged dry season. At Ithookwe, all plants survived during the period of evaluation. Generally the DM yield was highest (4200–9200 kg/ha) in the second harvesting season during short rains (SR) 2014 with Llanero having the highest yield and Mulato II the lowest. Significant differences (P< 0.05) in forage quality was recorded in calcium, phosphorus, ash, neutral detergent fibres (NDF) and lignin content. However, none of the cultivars consistently contained more than the other cultivars in all the forage quality parameters analysed. The cv. Xaraes had the highest calcium content and Marandu had the lowest while MG-4 contained the highest phosphorus and Basilisk the lowest. Mulato II contained the highest crude protein and lowest NDF. The study revealed that Urochloa could increase forage resources in the semi-arid regions of Kenya where annual rainfall exceed 700 mm without prolonged dry season.Item Importance of Bio Fertilizers as Alternative Soil Fertility Amendments(SciCell publishing company, 2022) Mutebi, C.M.; Moranga, V.; Kenya Agricultural and Livestock Research OrganizationThere is a current interest in agrarian sustainability with soil microorganisms instead of agro-chemicals. Key constraints in the use of bio fertilizers are; inadequate awareness about bio inoculants and lack of promotion network and publicity among the end users. This review discusses current technical information a way of creating awareness in order to promote the use of bio fertilizers. Publon, Google Scholar, Science Direct and Microsoft Academic data bases were used for the review 2021. Research and review articles published from 2019 onwards were considered as current information for the review. The findings of the review are that; both primary and secondary macronutrients can be provided by bio fertilizers. Potential microbes are; free-living nitrogen fixing bacteria and cyanobacteria, symbiotic nitrogen-fixing bacteria and fungi such as mycorrhiza. Other important functions of bacteria are; conferring to plants the ability for salt tolerance, lignin degradation and remediation of heavy metals from the soil. Bio Compost, vermicompost and termite soil with their rich microorganism content can be used as bio fertilizers for soil nutrient increase. In order to reap maximum benefit from bio fertilizers there is need to formulate them in appropriate materials. Apart from addition of nutrients to the soil, bio fertilizers play an important role in plant health, conclusion. This paper has brought to the fore the need to improve rhizosphere management in a sustainable way particularly at this point in time when there are strong indications that it has deteriorated in the face of continued use of chemical fertilizers.Item Assessment of Soil Moisture and Nutrients on Terrace Slope of Hard-Setting Soils in Semi-Arid Eastern Kenya(Tropical and Subtropical Agroecosystems, 2022) Njiru, E.; Baaru, M.; Gachene, C.; University of Nairobi ; Kenyatta UniversityBackground. Terraces are structures consisting of ditches and embankments used to control erosion and increase land productivity. There is, however, little emphasis on the effects of the ditch dimensions on soil moisture and nutrient dynamics. Objective. To determine the effect of varying ditch depths on soil moisture and nutrient quantities and their variability within the terrace slope on hard-setting soils. Methodology. Soil samples were collected seasonally in 2014 and 2015 from terraces with different ditch depths (60, 30, and 0 [control] cm) for the determination of soil moisture content (SMC). The samples were collected from the upper, middle and lower slope positions of each terrace. Soil from the three slope positions of each terrace was also sampled at the end of the study and analyzed for total nitrogen (% TN), available phosphorous (Av. P), exchangeable potassium (K+) and% organic carbon (OC) contents. Data were subjected to a two-way analysis of variance and differences in means determined at a 95% level of confidence. Results. Significant interactions (P< 0.001) in SMC were observed between seasons, ditch depths and slope positions. Higher SMC was found in treatments with 30 and 60 cm ditch depths in all the slope positions and seasons compared to the control. Soil moisture contents in the lower and upper slope positions were significantly different between the terraces with 30 and 60 cm ditch depths when rainfall was high and evenly distributed, but non-significant in poorly distributed rainfall seasons. Significant differences (P≤ 0.05) in contents of total nitrogen and available phosphorous were found between the upper and lower slope positions of the terraces with ditches. Implications. The effect of ditch depths on moisture, total nitrogen and available phosphorous contents and their variability within the slope depended on the amount and distribution of rainfall. Conclusion. Construction of terraces with shallow ditch depths (of 30 cm) is recommended to conserve soil moisture and nutrients nitrogen and phosphorous on hard-setting soils in the marginal areas of semi-arid Eastern Kenya.Item Fanya Juu Terraces Improve Maize (Zea Mays L.) and Bean (Phaseolus Vulgaris L.) Grain Yields on Hardsetting Soils of Semi-Arid Eastern Kenya(International Journal of Plant & Soil Science, 2022-08-16) Njiru, E.N.; Gachene, C.K.; Baaru, M.W.; University of Nairobi ; Kenyatta UniversityAims. Fanya juu terraces are constructed by digging a ditch and throwing the soil up-slope with the sole purpose of maintaining an embankment to slow down runoff flow. The effect of the terraces on crop yields along the slope varies with the soil type. The aim of this study was to determine the effect of Fanya juu terraces on maize (Zea mays L.) and bean (Phaseolus vulgaris L.) yields and how these yields differ with slope positions and depth of the ditches. Study Design. Split-split plot design with four replications. Place and Duration of Study. The trial was established on Luvisols in Mua location, Machakos County in Eastern Kenya at 37o15’E 1o29’S and 37o15’E 1o29’S during both long rain (LR) and short rain (SR) seasons of 2014 and 2015 (February 2014 to March 2015). Methodology. Treatments consisted of three ditch depths (60 cm, 30 cm and 0 cm (control)) in the main plots and three cropping systems (maize/bean intercrop, sole maize and sole bean) in the sub plots. Grain yields were compared across the seasons at the upper, middle and lower slope positions of the terraces using analysis of variance and means separated using least significant difference at P≤0.05. Results. There were significant differences in maize grain yields in the interactions of ditch depth and slope position (P=0.004) and ditch depth and season (P<0.001). Higher maize yields were realized when ditches were constructed than in the control. Yields increased from the lower to the upper slope position of the terraces with 30 cm ditch by 49.8% and in the 60 cm by 41.6%. Average yields from treatments with 30 cm ditch were significantly higher than from the control but non-significant from those in the 60 cm ditch. Significant differences (P=0.037) in bean grain yields were observed in interactions of ditch depth and slope position. Higher yields were obtained from the lower position of the 30 cm ditch than the middle and upper positions. Significant differences (P=0.033) were also found in interactions of ditch depths, cropping systems and seasons. Conclusion. The results indicate that Fanya juu terraces had a significant effect on crop yields on hardsetting soils. The study recommends construction of Fanya juu terraces with a ditch depth of 30 cm and intensive management of the lower slope position for improved maize and bean production on hardsetting soils in marginal areas.Item Effect of Nitrogen Fertilizer on Nitrogen Use Efficiency and Yield of Selected Sorghum Genotypes in Semi-Arid Regions of Kenya(East African Journal of Science, Technology and Innovation, 2023-09-29) Kathuli, P.; Kinama, J.M.; Kitonyo, O.M.; Nguluu, S.N.; Muui, C.W.; Muasya, R.M.; Kenya Agricultural and Livestock Research Organization ; University of Nairobi ; South Eastern Kenya University ; Kenyatta UniversitySorghum production in semi-arid lands is constrained by inadequate soil moisture and low nitrogen. Research was carried out in semi-arid Machakos between 2018-2020 to determine the effect of nitrogen fertilizer on nitrogen use efficiency, yield on selected sorghum genotypes and genotypes suitable for low soil fertility in semi-arid lands. The experiment was a randomized complete block design (RCBD) in a split plot arrangement with 11 sorghum genotypes in the main plot and nitrogen (0, 6.5 and 32.5 kgha-1) as the sub-plots in three replicates. Nitrogen use efficiency (NUE) and its indices agronomic efficiency (AE), nitrogen internal utilization (IE), physiological efficiency (PE), nitrogen recovery efficiency, nitrogen harvest index (NHI) and partial factor productivity (PFP) were obtained from sorghum yield data and nitrogen uptake. The results showed that nitrogen application at 6.5 kgha-1 and 32.5 kgha-1 significantly increased grain yield, stover weight and total dry matter (TDM) by 43% and 116%, 39% and 85% and 42% and 57% respectively. Sorghum genotypes TTKKIAMA6, KTIRASTAMMA4, SNYAKTOSA5, and MKNKKIRWMA2 had significantly higher grain yield and low N uptake implying they are N-efficient genotypes. NUE of sorghum decreased with increasing N application. Nitrogen internal utilization efficiency (IE) was significantly higher at zero N application rate implying better N assimilation by sorghum genotypes at low N. AE, PE, RE and PFP were all significantly higher at 6.5 kg N ha-1. All tested genotypes had significantly high NUE (90 to 1148 kgkg-1, RE (27 to 94 kgkg-1), AE (41 to 139 kgkg-1), PE (27 to 84 kgkg-1) and IE (41 to 139 kgkg-1) than the check (Gadam). It was concluded that sorghum genotypes yield parameters were increased by nitrogen application, NUE was highest at low N levels and its indices were significantly higher at 6.5 kg Nha-1. Four genotypes were found to be highly N- efficient and are recommended for sorghum improvement.Item Soil Greenhouse Gas Emissions from Different Land Utilization Types in Western Kenya(Frontiers, 2022-11-30) Kibet, E.; Musafiri, C.M.; Kiboi, M.; Macharia, J.; Ng’etich, O.K.; Kosgei, D.K.; Mulianga, B.; Okoti, M.; Zeila, A.; Ngetich, F.K.; University of Embu ; Cortile Scientific Limited ; Kenyatta University ; Moi University ; Kenya Agricultural and Livestock Research Organization ; The World Bank ; Jaramogi Oginga Odinga University of Science and TechnologyIntroduction. There is a vast data gap for the national and regional greenhouse gas (GHG) budget from different smallholder land utilization types in Kenya and sub-Saharan Africa (SSA) at large. Quantifying soil GHG, i.e., methane (CH4), carbon dioxide (CO2), and nitrous oxide (N2O) emissions from smallholder land utilization types, is essential in filling the data gap. Methods. We quantified soil GHG emissions from different land utilization types in Western Kenya. We conducted a 26-soil GHG sampling campaign from the different land utilization types. The five land utilization types include 1) agroforestry M (agroforestry Markhamia lutea and sorghum), 2) sole sorghum (sorghum monocrop), 3) agroforestry L (Sorghum and Leucaena leucocephala), 4) sole maize (maize monocrop), and 5) grazing land. Results and discussion. The soil GHG fluxes varied across the land utilization types for all three GHGs (p ≤ 0.0001). We observed the lowest CH4 uptake under grazing land (−0.35 kg CH4–C ha−1) and the highest under sole maize (−1.05 kg CH4–C ha−1). We recorded the lowest soil CO2 emissions under sole maize at 6,509.86 kg CO2–Cha−1 and the highest under grazing land at 14,400.75 kg CO2–Cha−1. The results showed the lowest soil N2O fluxes under grazing land at 0.69 kg N2O–N ha−1 and the highest under agroforestry L at 2.48 kg N2O–N ha−1. The main drivers of soil GHG fluxes were soil bulk density, soil organic carbon, soil moisture, clay content, and root production. The yield-scale N2O fluxes ranged from 0.35 g N2O–N kg−1 under sole maize to 4.90 g N2O–N kg−1 grain yields under agroforestry L. Nevertheless, our findings on the influence of land utilization types on soil GHG fluxes and yield-scaled N2O emissions are within previous studies in SSA, including Kenya, thus fundamental in filling the national and regional data of emissions budget. The findings are pivotal to policymakers in developing low-carbon development across land utilization types for smallholders farming systems.Item Soil Organic Carbon Stocks under Different Land Utilization Types in Western Kenya(MDPI, 2022-07-06) Kibet, E.; Musafiri, C.M.; Kiboi, M.N.; Macharia, J.; Ng’etich, O.K.; Kosgei, D.K.; Mulianga, B.; Okoti, M.; Zeila, A.; Ngetich, F.K.; University of Embu ; Cortile Scientific ; KCA University ; Kenyatta University ; Moi University ; Kenya Agricultural and Livestock Research Organization (KALRO) ; The World Bank ; Jaramogi Oginga Odinga University of Science and Technology (JOOUST)The up-surging population in sub-Saharan Africa (SSA) has led to the conversion of more land for agricultural purposes. Resilient land utilization types that input carbon to the soil are key in enhancing climate change mitigation. However, there are limited data on different land utilization types’ contribution to climate mitigation through carbon input to soils. The study aims to quantify carbon stock across different land utilization types (LUT) practiced in Western Kenya. The following land utilization types were studied: agroforestry M (agroforestry with Markhamia lutea), sole sorghum, agroforestry L (agroforestry with Leucaena leucocephalaI), sole maize, and grazing land replicated thrice. To determine soil bulk density, SOC concentration, and soil carbon stock, soil samples were collected at depths of 0–5, 5–10, 10–20, and 20–30 cm from different LUTs. A PROC ANOVA was used to determine the difference in soil bulk density, SOC, and SOC stock between different LUTs and depths. The four variables differed across the LUTs and depths. A high soil bulk density was observed at 0–5 cm under grazing land (1.6 g cm−3) and the lowest under agroforestry M (1.30 g cm−3). Conversely, the soil bulk density was low at 20–30 cm under grazing land. The 0–5 cm depth accounted for a high share of SOC and SOC stock under Agroforestry M, while the 10–20 and 20–30 cm depth accounted for the high share of SOC stock under agroforestry L. The study showed differences in SOC across the different depths and LUTs. The findings highlight that agroforestry L and agroforestry M are promising interventions toward climate mitigation through carbon induction to soils.Item Development of Soil and Water Management Technologies to Increase Productivity of Salt-Affected Soils.(KARI, 1999-11-15) Mugwanja, P.N.; Radiro, M.P.O.Expansion of irrigated agriculture in Kenya would contribute significantly towards increasing food self-sufficiency and poverty alleviation. However, due to waste mismanagement and other natural factors irrigation schemes have been abandoned as a result of salt problems which arises after several years of operation. Examples of irrigated areas which have been abandoned due to salinity include Kimorigo, Kir Kamileza irrigation schemes in Taveta sub-district, Coast Province. The objective of this study were to carry out trials on leaching and crop managemt procedures for increased productivity of saline soils. The initial leaching and provision of drainage systems in the experimental fields proved very effective in removal of most of the salts which had led to the abandonment of the farms. At least three leachings salts in the soil were essential before seeds could germinate. The experiments were carried out in farmers field.Item Tillage System and Integrated Soil Fertility Inputs Improve Smallholder Farmers’ Soil Fertility and Maize Productivity in the Central Highlands of Kenya(Journal of Agriculture and Rural Development in the Tropics and Subtropics, 2021-09-20) Otieno, E.O.; Ngetich, F.K.; Kiboi, M.N.; Muriuki, A.; Adamtey, N.N.; University of Embu ; Kenyatta University ; Jaramogi Oginga Odinga University of Science and Technology (JOOUST) ; Kenya Agricultural and Livestock Research Organization (KALRO-NARL) ; Research Institute of Organic Agriculture (FiBL)We designed and implemented an on-farm trial in Meru South and Gatanga sub-counties to understand the effects of integrated soil fertility management (ISFM) technologies on soil nitrogen (N), phosphorus (P), potassium (K), and maize productivity. The technologies included combinations of mineral fertiliser and maize stover (CrMf); crop residue, Tithonia diversifolia and rock phosphate (CrTiP); crop residue, Tithonia diversifolia and goat manure (CrTiMan); crop residue, inorganic fertiliser and goat manure (CrMfMan); crop residue, goat manure and Dolichos lablab (CrManLeg), and sole inorganic fertiliser (Mf) executed under conventional (ConC) and minimum (MinTill) tillage methods. We interviewed the farmers who participated in implementing the trials at the end of the study to understand the likelihood to uptake the technologies. We observed that the technologies increased soil N, P, K, and maize productivity compared to ConC (the control). There was a high likelihood of uptake of high-performing ISFM technologies. We recommend CrTiP for the two sub-counties for the short-term. However, a long-term experiment is needed to evaluate performances of CrTiMan, CrTiP, CrMfMan, and CrManLeg under the two tillage methods for site-specific recommendations taking into consideration rainfall variations.Item Macro and Micro-Nutrient Status of Selected Kenya Soils(East African Agricultural and Forestry Journal, 2023-01-11) Omwakwe, J.A.; Chemining’wab, G.N.; Esilaba, A.O.; Thuraniraa, E.G.; Kenya Agricultural and Livestock Research Organization (KALRO) ; University of NairobiOver the years there has been a decline in soil fertility in Kenya, which is responsible for low crop yields. Macro and micronutrients should be added to the soil as they ensure healthy produce by supplying the right balance of nutrients to the soil. Most farmers rely on nutrient recycling in their farms which is not sustainable as it leaves the soils depleted of nutrients. A study was therefore conducted to assess the limiting nutrients of soils in Coastal, Eastern, Rift Valley and Western parts of Kenya. Twenty-three soil samples (0 to 30 cm) from 13 counties were collected and evaluated for total nitrogen, total organic carbon, phosphorus, potassium, calcium, magnesium, manganese, copper, iron, zinc, sodium, electrical conductivity, cation exchange capacity (CEC), base saturation and soil pH. The mean values were 0.12%, 1.12, 19.09, 220.43, 1397.39, 163.98, 120, 52, 3.95, 52.78, 1.86, 92.80 mg/kg, 0.11mS/c, 11.98 Cmol (+)/kg, 83.13% and, 5.96, respectively. The soil analysis results indicated that nitrogen, phosphorous and zinc were deficient in most soils in Kenya. Nitrogen and carbon were positively correlated with each other (P≤ 0.01). Phosphorous on the other hand was negatively correlated with carbon and nitrogen. Zinc was negatively correlated with soil pH. The exchangeable bases showed significant correlation with each other. It was evident that the inadequate nutrients need to be considered and supplied for restoration of soil fertility and productivity.Item The Effect of Integrated Soil Fertility Management Practices on Bell Pepper Under Controlled Environmental Conditions(East African Agricultural and Forestry Journal, 2023) Morit, C.H.; Mkandawire, F.L.; Moracha, O.H.; Kimani, S.K.; Njeru, P.N.M.; Sijali, I.; Gacheru, J.; University of Eastern Africa Baraton ; Food Crops Research Centre (FCRC) - KALROContinuous soil cultivation in tropical countries has resulted in depletion of nutrients that are essential for plant growth and development. Beside, adverse use of inorganic fertilizers has had implicating effects on availability of organic carbon, nutrients imbalance and deficiency, this over time has reduced production in horticultural crops. A study was conducted on bell pepper in a greenhouse to determine its response to different soil fertility management practices recorded by changes in plant height, number of fruits and weight, and crop yield. The experiment was set up at Nandi County. The treatments were laid out in randomized complete block design with four treatments; farmer Practice (25 t/ha organic manure), organic manure (50 t/ha), combined inorganic fertilizer (125 kg/ha 23:23:0 planting and 62.5 kg/ha 17:17:17 topdress) and organic manure (25 t/ha), and inorganic fertilizer (23:23:0) 250 kg/ha planting and 125 kg/ha 17:17:17 topdress. The results indicate that the treatments under organic manure recorded higher growth seen in the number of mean branches for organic manure -11.83, combined inorganic fertilizer -10.50, Farmer Practice -8.67, inorganic fertilizer -6.83 and plant height means for farmer Practice -53.8cm, organic manure -66.2cm, combined inorganic fertilizer -58.0cm, and inorganic fertilizer -44.2 cm. Yield was highest for the combined interaction of inorganic fertilizer and organic manure as seen on average number of fruits per plant for farmer Practice -24 fruits, organic manure -26 fruits, combined inorganic fertilizer -29 fruits and inorganic fertilizer -17 fruits and weight of fruits for farmer Practice -8.261, organic manure -9.083, combined inorganic fertilizer -9.611, inorganic fertilizer -6.539 kg). The results indicate that there is need to combine inorganic fertilizer and well decomposed organic manure for maximum yield of bell pepper. This should be done under greenhouse and other technologies where climatic conditions are controlled.Item Potassium Nutrient Status and Management in Kenyan Soils for Increased Productivity(East African Agricultural and Forestry Journal, 2022) Kathuku-Gitonga, A.N.; Esilaba, A.O.; Mangale, N.; Wasilwa, L.; Okoti, M.; Nyongesa, D.; Kamoni, P.T.; Waruru, B.K.; Muya, E.M.; Thuranira, E.; Mutisya, D.; African Plant Nutrition Institute (APNI) ; Kenya Agricultural and Livestock Research Organization (KALRO), Kabete & KatumaniNitrogen, phosphorus and potassium are regarded as the main basic nutrients necessary for plant growth and production and their functions are interrelated. Potassium is necessary for regulation of plant cells, for the production of proteins and enzymes. It improves crop's disease and pests' resistance, and it increases crop yield and plays a significant role in enhancing crop quality. Potassium deficiency inhibits protein production even when nitrogen is abundant. The objective of the study was to determine status of potassium in selected Kenyan soils and responses to applied potassium fertilizers. Studies were carried out in Kenya through laboratory soil analysis, meta-data analysis and fertilizer response studies. Soils were collected in the trial sites and analyzed using wet chemistry method. For meta-analysis, published materials were collected, collated, digitized and harmonized. Benefit cost ratios were calculated for each technology to ascertain its profitability. The soil analysis results showed that potassium, nitrogen, organic carbon and zinc were deficient. The meta-analysis results showed that, limited research studies had been conducted on potassium in Eastern, Coast and Rift Valley regions of Kenya. The most economical potassium responses were recorded under application of 60 kg K/ha, although the yields were not profitable. However, the fertilizer response studies showed increased crop yields on addition of potassium fertilizer up to 40 kg K/ha. Hence lower rates of potassium (less than or equal to 40 kg K/ha) are recommended to offset and maintain adequate potassium levels in the soil for optimal crop production and income. Nevertheless, soil analysis is key before any fertilizers are added to soils.Item Integrated Soil Fertility Management Prospects for Soil Productivity and Food Security in Machakos County(East African Agricultural and Forestry Journal, 2023) Wamalwa, S.W.; Danga, B.; Kwena, K.; Kenyatta University ; Kenya Agricultural and Livestock Research Organization (Machakos)Integrated soil fertility management is the most costeffective and time-efficient method of restoring soil fertility and increasing per capita yields on Sub-Saharan African smallholder farms. However, low acceptance has resulted from a lack of knowledge about the prospects of these strategies prior to promoting them. In 2016, the Mwania watershed in Machakos, eastern Kenya, was surveyed to fill this void. About 174 household heads were chosen using the “farmer-led adoption approach and a pretested structured questionnaire to obtain primary data on their household gender, education level, food security, cultivated land size, soil fertility practices, and constraints to determine the potential use of integrated soil fertility management practises at the watershed level. Data were analysed using the Statistical Package for Social Sciences Version 22 computer program for descriptive attributes. Relationships between dependent and independent variables were determined using the tobit regression model. According to the findings, 85% of households are headed by men, with over 82% being postprimary graduates, who are the main decision makers. The majority (83%) cultivate 2 ha and 57% acknowledged food insecurity, with 89.1%, 73.1%, and 45.1% blaming it on climate variability, limited soil moisture, and a lack of input access, respectively. Low fertility scored 40% at medium level with labour at 40% in low cluster constraints, could be because of high unemployment rates. Animal manure and chemical fertiliser use were reported at 95.5% and 76.6%, respectively, although they were using them separately, probably due to high cost, increased labour requirements, and accessibility problems resulting in continuous low yields. Therefore, huge prospects of integrated soil fertility management practices’ use exist in the Kenyan semi-arid, especially when promoted at community level.Item Overcoming Soil Acidity Constraints Through Liming and Other Soil Amendments in Kenya: A Review(East African Agricultural and Forestry Journal, 2022) Esilaba, A.O.; Mangale, N.; Kathuku-Gitonga, A.N.; Kamau, D.M.; Muriuki, A.W.; Mbakaya, D.; Zingore, S.Food production in Kenya is constrained by low and declining soil health resulting from low soil fertility and increasing widespread soil acidity, coupled with emerging climate change effects leading to recurrent food and nutrition insecurity. The major food production areas with high crop yield potential in the country are greatly affected by soil acidity due to continuous cropping, loss of organic carbon, nutrient leaching and inappropriate use of fertilizers. While use of organic and inorganic fertilizers, improved seed varieties and crop protection have received much research attention, liming as one way of improving soil health and crop production has not received similar attention. Consequently, potential yield of hybrid crops remains constrained. Soil acidity is mainly ameliorated by applying lime or other acid‐neutralizing materials, which neutralize the acidity, raises soil pH, increases the availability of plants’ nutrients and adds calcium and magnesium to the soil. It also improves the environment for beneficial soil microorganisms thus enhancing rapid breakdown of organic materials in the soil and releasing nutrients for growing plants. Soil buffer capacity determines the amount of lime per unit of soil volume needed to alter soil pH. Soils with low Cation Exchange Capacity (CEC) respond rapidly to liming than soils with high CEC. But the low-CEC soils have a high capacity for rapid leaching of the added bases, thus a quicker return to original acidity unless additional liming is done. Over-liming is recommended for soils which have low CEC, such as sand which is deficient in buffering agents such as organic matter and clay. There is therefore need for appropriate attention to to ameliorate soil acidity in order to maintain good soil health for food and nutrition security. A meta-analysis of a desk study supported by field experiment was carried out in areas viewed as most affected by soil acidity. The aim of the study was to evaluate amendments that can be used for alleviating soil acidity in acidic soils. The results showed that extensive work has been done in Western and Rift valley regions of Kenya targeting soil acidity alleviation and few studies in the coastal and eastern regions due to perception that these areas do not have acidic soils. Among the soil acidity amendments, use of lime and organic sources showed positive crop response and increased yields when applied in acidic soils.Item Evaluation of the Rhizosphere Soil pH and Electrical Conductivity of Bixa Treated with Different Fertilizer Amendments(African Journal of Horticultural Science, 2021-03) Pole, F.N.; Gweyi-Onyango, P. J.; Ambuko, J.; Wasilwa, L. A.Bixa orellana L. is a shrub that is commercially known as ‘annato’. The main product that is obtained from Bixa orellana is an organic dye which is present in the seed coat, commercially called ‘annatto’. It is widely used in the cosmetic and the food industry for giving red to orange-yellow colours. Bixa farming in Kenya has declined since the 1970’s due to the use of cheap synthetic materials. However, the limited use of synthetic food colours has triggered a high demand for natural bixa. A study was undertaken in Kwale County with the objective of evaluating the Rhizosphere soil pH and Electrical Conductivity (EC) of bixa plants treated with different fertilizer amendments. This was done in Shimoni at the Kenya bixa nucleus farm where bixa plants of the same age were subjected to treatments of different levels of organic (poultry manure at 5 tons/ha and 10 tons/ha respectively) and inorganic fertilizers (NPK 17: 17: 17 at 100 kg/ha and 150 kg/ha) as well as a combination of the two (manure 2.5 tons plus NPK 50 kg/ha and manure 5 tons plus NPK 75 kg/ha respectively) with a control, in a randomized complete block design with 3 replications. Bixa roots from each treatment were dug out and analysed for the rhizosphere soil pH and electrical conductivity respectively. The results revealed that the rhizosphere soil pH improved with the application of both organic and inorganic fertilizer soil amendments from 5.78 to 6.5. The treatment in which manure was applied at the rate of 10 tons/ha produced significantly higher levels of rhizosphere pH than the rest. On the soil rhizosphere EC, the study revealed that the EC significantly reduced with increased use of organic fertilizer amendments to as low as 0.2 (mS*/cm). The application rate of manure at 10 tons/ha recorded the lowest EC levels.Item Yield Response of Finger Millet (Eleusine Coracana L.) to Poultry Manure Application in Western Kenya(East African Agricultural and Forestry Journal, 2023) Makete, N.N.; Oduori, C.A.; Opole, R.A.; Mulindo, C.J.; Nungo, R.A.; Kenya Agricultural and Livestock Research OrganizationDeclining soil fertility is affecting finger millet production in western Kenya and inorganic fertilizer use is expensive for most small holder farmers. With over 90% of farmers keeping poultry, its manure appears to be a potential alternative source of fertilizer for finger millet production. An experiment was conducted at KALRO - Kakamega to evaluate the yield response of finger millet (Eleusine coracana L.) to different rates of poultry manure (0, 5, 10, 15, 20, 25 and 30 t/ ha). This was carried out during the long rains season (March - August) and short rains season (September - December) of 2016. Experimental layout was a Randomized Complete Block Design with three replications. Results indicated significant yield increase from 1,148 kg/ ha (control 0 t/ ha rate) to 1,925.9 kg/ ha (5 t/ ha rate), which was significantly different from the 10 t/ ha rate (2,463 kg/ha) during the long rains season. No significant yield increase was observed beyond 10 t/ha. Similarly, no significant yield difference was recorded with increasing rates of poultry manure during the short rains season. This clearly indicated that, during the short rains season, finger millet yield may have been affected by other factors besides poultry manure rates. Significantly higher mean yields were recorded during the long rains (2,431.7 k ha) when compared to the short rains season (936.5 kg/ ha). The positive yield response of finger millet to increased rates of poultry manure application during the long rains season indicates that smallholder farmers can consider using poultry manure (5-10 t/ha) as an alternative fertilizer for finger millet production.Item Water Use Efficiency of Taro (Colocasia esculenta) under Varying Watering Regimes and Planting Densities in Embu, Kenya(Tropical and Subtropical Agroecosystems, 2023) Njuguna, J. W.; Karuma, A. N.; Gicheru, P.; University of Nairobi ; Kenya Agricultural and Livestock Research OrganizationBackground. Taro (Colocasia esculenta) can be grown in a variety of environmental and edaphic conditions, but it is most typically grown in wetlands. The optimal conditions for its growth are two water regimes ie, waterlogged or flooded conditions to dryland or unflooded conditions. An important criterion in crop yield is water use efficiency (WUE), and it has been suggested that crop production per unit of water used can be increased. Objectives. To determine the WUE of taro in Kenya’s sub-humid environment under different watering regimes and planting densities. Methodology. A study was conducted at the Kenya Agricultural and Livestock Research Organization (KALRO)–Embu Research Centre, during the long rains (LR) 2021, short rains (SR) 2021/2022, and long rains (LR) 2022. A factorial experiment with a split-plot layout arranged in a completely randomized block design was used. The main factor was the irrigation levels while the sub-factor was the planting density, with three replications. The three irrigation levels were at 100%, 60%, and 30% based on the field capacity (FC). The planting densities used were 0.5 m× 0.5 m (40,000 plants ha-1), 1m× 0.5 m (20,000 plants ha-1), and 1m× 1m (10,000 plants ha-1), representative of high, medium, and low planting densities respectively. Results. The WUE was influenced by season and watering regime (P< 0.05). The 30% FC had the highest WUE with the 100% FC having the lowest. The high WUE under 30% FC (19.40 kg ha-1mm-1) was associated with the high biomass (1.97 kg) and low water use (2269.41 mm) recorded under limited water conditions. The medium (1m× 0.5 m) planting density attained the highest WUE (12.16 kg ha-1mm-1) with the high planting density (0.5 m× 0.5 m) having the lowest (10.65 kg ha-1mm-1), though no significant differences were recorded. Implications. The varying watering regimes and planting densities in this study have different capacities to utilize the supplied water. The total taro biomass increased with decrease in water supplied and in turn maximized the water use efficiency. Conclusion. To achieve the highest yield per unit of water consumed, a watering regime of 30% FC and a planting density of 1 m× 0.5 m (20,000 plants ha-1) is recommended.Item Salt Tolerance of Two Potato Cultivars(African Journal of Education, Science and Technology, 2023-03) Rutto, A.; Thagana, W.; Nyongesa, M.; Kenyatta University ; Kenya Agricultural and Livestock Research OrganizationPotato (Solanum tuberosum L.) is one of the leading crop plants used for food production globally. The varieties that are presently grown are greatly hampered productively by increased salinity. The repercussion of salinity stress on productivity of potato plant was assessed using Shangi and Unica varieties sourced from KALRO Tigoni. Potato tubers were grown in 4L polybags packed with coco peat media and kept under greenhouse conditions. A two-factorial experiment in CRD was used with factors being cultivar and treatments of salt concentrations. Twenty-one days after emergence, plants were subjected twice in seven days to six different treatments of salinity levels (0, 6, 8, 10, 12, 14dS/m) of NaCl in solution form prepared. Measurements of height 30 days after start of salt application, tuber weight and number at harvest were recorded. At 0dS/m, the two varieties performed optimally. Salt concentration significantly affected cultivars performance in height, weight of tubers and number of tubers. Both shangi and Unica demonstrated better performance at between 6-8 dS/m with less yield decrease than the other salt concentration. At 10dS/m, Unica’s performance was better as opposed to Shangi that was adversely affected by the salts though Shangi’s performance decreased at a higher rate with increase in salt.(Table 3). The tubers had the highest weight at 6 dS/m concentration while Unica species produced tubers with the highest weight.(16g). Unica therefore performed better than Shangi indicating that it’s more tolerant to salinity than Unica. This research was meant to identify a salt tolerant potato cultivar between Shangi and Unica which can be used for breeding for salt tolerant varieties. It was thus found that Unica is salt tolerant as had been found in other previous studies. Unica therefore is recommended for planting by farmers who cultivate in fields affected by high salinity incidences. In addition, Unica genes are recommended to breeders who can use them for breeding purposes to breed for salt tolerant cultivars.
