Browsing by Author "Ngetich, F.K."
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Item Adapting African Agriculture to Climate Change(Springer, 2015) Kisaka, Oscar M.; Mucheru-Muna, M.; Ngetich, F.K.; Mugwe, Jayne; Mugendi, Daniel N.; Mairura, F.Drier parts of Embu County, Eastern Kenya, endure persistent crop failure and declining agricultural productivity which have been attributed, in part, to prolonged dry-spells and erratic rainfall. Nonetheless, understanding spatialtemporal variability of rainfall especially at seasonal level, is an imperative facet to rain-fed agricultural productivity and natural resource management (NRM). This study evaluated the extent of seasonal rainfall variability and the drought characteristics as the first step of combating declining agricultural productivity in the region. Cumulative Departure Index (CDI), Rainfall Anomaly Index (RAI) and Coefficients-of-Variance (CV) and probabilistic statistics were utilized in the analyses of rainfall variability. Analyses showed 90 % chance of below croppingthreshold rainfall (500 mm) exceeding 213.5 mm (Machanga) and 258.1 mm (Embu) during SRs for one year return-period. Rainfall variability was found to be high in seasonal amounts (CV = 0.56 and 0.38) and in number of rainy-days (CV = 0.88 and 0.27) at Machang’a and Embu, respectively. Monthly rainfall variability was found to be equally high even during April (peak) and November (CV = 0.42 and 0.48 and 0.76 and 0.43) with high probabilities (0.40 and 0.67) of droughts exceeding 15 days in Embu and Machang’a, respectively. Dry-spell probabilities within growing months were high (81 %) and (60 %) in Machang’a and Embu respectively. To optimize yield in the area, use of soil-water conservation and supplementary irrigation, crop selection and timely accurate rainfall forecasting should be prioritizedItem Applicability of conservation agriculture for climate change adaptation in Rwanda’s situation(Academic Journals, 2015-09) Kabirigi, M.; Musana, B.; Ngetich, F.K.; Mugwe, Jayne; Mukuralinda, A.; Nabahungu, N. L.Improving food security and environmental conservation should be the main targets of innovative farming systems. Conservation agriculture (CA), based on minimum tillage, crop residue retention and crop rotations has been proposed against poor agricultural productivity and soil degradation. This paper discusses the applicability and potential benefits of CA in Rwanda under the unfolding climate change scenario. The potential and benefits from CA may vary with rainfall regime. In high rainfall areas (For example North and West of Rwanda), the soils are susceptible to soil erosion and face fertility decline while in low rainfall areas (For example East of Rwanda) crops fail due to sub-optimal water use efficiency. Furthermore, low organic carbon content lower fertilisers response and government targets of increasing production through Crop Intensification Program, is limited. It has been shown that CA can: Reduce soil loss from 35.5 to 14.5 t/ha/year, have 50-70% greater infiltration and increase 42% of organic carbon. Long term analysis using Agricultural Production System Simulator showed that CA can increase yield from 3.6 to 4.4t/ha in areas having >770 mm. Based on the evidence from regional research, CA has a good potential for climate change adaptation in both high and low rainfall areas of Rwanda. However, decreased yield observed in high rainfall areas, increased labour requirements when herbicides are not used and lack of mulch due to priority given to feeding of livestock constrained CA adoption. We conclude that there is a need for critical assessment under which ecological and socio economic conditions CA is suited for smallholder farming in Rwanda.Item Effects of selected soil and water conservation techniques on runoff, sediment yield and maize productivity under sub-humid and semi-arid conditions in Kenya(Elsevier, 2014-05) Ngetich, F.K.; Diels, J.; Shisanya, C.A.; Mugwe, Jayne; Mucheru-muna, M.; Mugendi, Daniel N.tillage practices on runoff amounts, sediment yield and maize yields under semi-arid and sub-humid environments. Field trials were set in Kigogo primary school in Meru South Sub-County, Tharaka Nithi County, representing the sub-humid conditions, and Machang'a secondary in Mbeere South Sub-County, Embu County (semi-arid) in the central highlands of Kenya. The experiment layout was a randomized complete block design and the treatments were implemented in runoff plots. Tied ridging (TR) was the most efficient technique in reducing runoff and sediment yield and at the same time boosting crop yields in the semi-arid region. It significantly (p b 0.05) reduced sediment yields by 94% compared to the conventional tillage (CT) during the study period. The effects were particularly strong in periods of belowaverage rainfall (dry seasons). During the drier season of short rains 2010 (SR10), grain yield under TR was 7 times higher compared to CT (p b 0.01). In the sub-humid region, minimum tillage (MT) generated high runoff but relatively low sediment yield compared to CT. During periods of enough rainfall (over 450mmper season) in the drier site, intercropping suppressed maize yields significantly (p b 0.01) by 42% compared to conventional tillage in the drier site. The results on the magnitude of runoff and sediment under the different soil and farm management practices are crucial in selection and promotion of valid farm management practices and tillage alternatives that not only abate soil erosion but also boost agricultural productivity in both sub-humid and semi-arid agro-ecological zones.Item Effects of selected soil and water conservation technologies onnutrient losses and maize yields in the central highlands of Kenya(Elsevier, 2014-02) Okeyo, A.I.; Mucheru-Muna, M.; Mugwe, Jayne; Ngetich, F.K.; Mugendi, Daniel N.; Diels, J.; Shisanyaaa, C.A.tMitigating nutrient loss is a prerequisite of sustainable agriculture in the tropics. We evaluated threesoil and water conservation technologies (mulching, minimum tillage and tied ridging) for two croppingseasons (long rains 2011, short rains 2011) at two sites in the central highlands of Kenya. The objectiveswere: to determine effects of the technologies on runoff, sediment yield and nutrient loads in sediment,and to assess influence of the technologies on maize yields. Experimental design was a randomizedcomplete block with 3 treatments replicated thrice. At the beginning of experiment, soil was sampledat 0–15 cm depth and analyzed for pH, N, P, K, C, Ca and Mg. Mulch was applied at a rate of 5 t ha−1.Runoff was sampled, sediments extracted by drying in oven at 105◦C, and analyzed for NPK and C loads.Data were subjected to analysis of variance using SAS 9.1.3 and means separated using Fishers’ LSD at5% level of significance. Results showed reduced nutrient losses with the technologies. In Meru South,sediment yield was reduced by 41 and 7% during long rains 2011 (p = 0.03), and by 71 and 68% duringshort rains 2011 (p = 0.01) under mulching and minimum tillage, respectively. Runoff and maize yieldswere positively influenced by mulching. In Mbeere South, sediment yield was lower under soil and waterconservation technologies. Runoff was reduced by 52 and 49% during long rains 2011 and by 51 and30% during short rains 2011 under tied ridging and mulching respectively, compared with control. Totalcrop failure occurred during long rains 2011 due to erratic rains. During short rains 2011 tied ridging andmulching increased maize yield by 94 and 75%, respectively, compared with control. This study highlightsthe importance of analyzing soil and water conservation technologies within rain-fed farming systemsperspective in response to declining food production and supports a focus on tied ridging and mulchingItem Household's socio-economic factors influencing the level of adaptation to climate variability in the dry zones of Eastern Kenya(Elsevier, 2015-11) Mugendi, Daniel N.; Mugi-Ngenga, E.W.; Mucheru-Muna, M.W.; Mugwe, Jayne; Ngetich, F.K.; Mairura, F.S.Climate variability has a negative impact on crop productivity and has had an effect on many small-holder farmers in the arid and semi-arid lands (ASALs). Small-holder farmers in Eastern Kenya are faced with the constraint associated with climate variability and have consequently made effort at local level to utilize adaptation techniques in their quest to adapt to climate variability. However, documentation of the factors that influence the level of adaptation to climate variability in the study area is quite limited. Hence, this study aimed at assessing how the household's socio-economic factors influence the level of adaptation to climate variability. The study sites were Tharaka and Kitui-Central sub-Counties in Tharaka-Nithi and Kitui Counties of Eastern Kenya respectively. The data collected included the household demographic and socio-economic characteristics and farmers' adaptation techniques to cope with climate variability. Triangulation approach research design was used to simultaneously collect both quantitative and qualitative data. Primary data was gathered through a household survey. Both random and purposive sampling strategies were employed. Data analysis was done using descriptive and inferential statistics. Multinomial and Binary logistic regression models were used to predict the influence of socioeconomic characteristics on the level of adaptation to climate variability. This was done using variables derived through a data reduction process that employed Principal Component Analysis (PCA). The study considered five strategies as measures of the level of adaptation to climate variability; crop adjustment; crop management; soil fertility management; water harvesting and crop types; boreholes and crop variety. Several factors were found significant in predicting the level of adaptation to climate variability as being either low or medium relative to high. These were average size of land under maize; farming experience; household size; household members involved in farming; education level; age; main occupation and gender of the household head. Household socio economic factors found significant in explaining the level of adaptation should be considered in any efforts that aim to promote adaptation to climate variability in the agricultural sector amongst smallholder farmers.Item Length of growing season, rainfall temporal distribution, onset and cessation dates in the Kenyan highlands(Elsevier, 2013-12) Ngetich, F.K.; Mugendi, Daniel N.; Mucheru-Muna, M.; Mugwe, Jayne; Shisanya, C.A.; Diels, J.Dependence on uncertain rainfall and exposure to unmitigated climate risk are major obstacles in efforts to sustainably intensify agricultural production and enhance rural livelihoods. There is generally enough seasonal total rainfall; the challenge is its poor distribution over time and across the season. The amount of water available to plants strongly depends on the rainy season’s onset, length, temporal distribution and cessation and can indirectly indicate the climatic suitability of the crop and its chances of success or failure in a season. Thus, the objective was to determine rainfall pattern; temporal distribution, onset, cessation and length of growing seasons in the tropical sub-humid and a semi-arid regions with contrasting rainfall patterns and agricultural potential in central highlands of Kenya. The study was carried out in Maara and Meru South Sub-Counties in Tharaka Nithi County and Mbeere North and South Sub-Counties in Embu County of the central highlands of Kenya (CHK). Central highlands of Kenya cover both areas with high potential for crop production and low potential, attributed to rainfall differences. Meteorological data were sourced from Kenya Metrological Department (KMD) headquarters and research stations within the study areas. Length of growing season, onset and cessation dates for both Long (LR) and short (SR) rains seasons were determined based on historical rainfall data using RAIN software and derived using various spatial analysis tools in ArcGIS software and presented spatially. Generally there was high frequency of dry spells of at least 5 days length in all the sites with Kiamaogo site having the highest (84 occurrences during LR season) and Kiambere having the least (44 occurrences during LR season) in 10 years. The occurrence of dry spells longer than 15 days in a season was more rampant in the lower altitude parts (semi-arid regions) of the study area as reflected by the Kiambere, Kiritiri, Machang’a and Kamburu sites in both seasons. For the higher altitude regions, average LR onset, representative of the normal/conventional growing period, ranged from 22nd to 26th March to end of April in the region. For the lower altitude region, it ranged from 16th to 30th March. For SR, onset was generally earlier in the high altitude areas with Kiamaogo having the earliest on 13th October. In the low altitude region, onset was comparatively late compared to the higher potential region, but unlike the LR season, spatial and temporal variation was narrower. The high frequency of dry spells more than 15 days long, coupled with the generally low total amount of rainfall receive per season makes agriculture a risk venture. Homogeneity test revealed that the generated onset and cessation dates for the two rain seasons were homogeneous over the 10 years for each of the seven stations. This indicates that, there has been no shift in onset and cessation within the period under consideration. Dynamic derivation of the spatial onset and cessation data at a local scale can be useful in monitoring shifts in onset dates and hence advice small scale farmers and other stakeholders in agriculture sector accordingly in the quest for enhanced agricultural productivity.Item Long-term effects of tillage, sub-soiling, and profile strata on properties of a Vitric Andosol in the Kenyan highlands(2008) Ngetich, F.K.; Wandahwa, P.; Wakindiki, I.Tillage alters the structure and composition of soil aggregates affecting infiltration rate (IR) and hydraulic conductivity (K). This study investigated the long-term effects of conventional, minimum, and no-tillage with or without subsoiling on aggregate stability, soil organic carbon (SOC), bulk density, IR, and K of a stratified Vitric Andosol in Kenyan highlands. The experiment was laid out in a spilt-split plot design with three replicates. Stepwise profiles were dug in order to expose the soil layers at 0 to 30, 30 to 60, and 60 to 90 cm depths. Soil bulk density was 6% lower in the minimum tilled and 12% lower in the conventionally tilled plots that were subsoiled compared to treatments with no subsoiling and tillage. Subsoiled treatments also increased sequestration of SOC by 20% in the 30 to 60 cm layer. Conventional tillage, however, decreased aggregate stability by 32% compared to no-tillage treatments. Subsoiling in combination with minimum tillage decreased IR by 25% but increased IR about three-fold in conventionally tilled plots. Hydraulic conductivity in the 60 to 90 cm layer was lowest, which constrained water movement in this stratified soil.Item Long-term effects of tillage, sub-soiling, and profile strata on properties of a Vitric Andosol in the Kenyan highlands(2008-09) Ngetich, F.K.; Wandahwa, Philip; Wakindiki, Isaiah I.C.Tillage alters the structure and composition of soil aggregates affecting infiltration rate (IR) and hydraulic conductivity (K). This study investigated the long-term effects of conventional, minimum, and no-tillage with or without subsoiling on aggregate stability, soil organic carbon (SOC), bulk density, IR, and K of a stratified Vitric Andosol in Kenyan highlands. The experiment was laid out in a spilt-split plot design with three replicates. Stepwise profiles were dug in order to expose the soil layers at 0 to 30, 30 to 60, and 60 to 90 cm depths. Soil bulk density was 6% lower in the minimum tilled and 12% lower in the conventionally tilled plots that were subsoiled compared to treatments with no subsoiling and tillage. Subsoiled treatments also increased sequestration of SOC by 20% in the 30 to 60 cm layer. Conventional tillage, however, decreased aggregate stability by 32% compared to no-tillage treatments. Subsoiling in combination with minimum tillage decreased IR by 25% but increased IR about three-fold in conventionally tilled plots. Hydraulic conductivity in the 60 to 90 cm layer was lowest, which constrained water movement in this stratified soil.Item Microbial biomass and acid phosphomonoesterase activity in soils of the Central Highlands of Kenya(Elsevier, 2018-12) Kiboi, Milka N.; Ngetich, F.K.; Mugendi, Daniel N.; Muriuki, A.; Adamtey, N.; Fliessbach, A.Soil biological properties are the most sensitive soil quality indicators that respond quickly to short-term soil fertility management changes. We studied the combined effects of tillage and soil external inputs on total soil organic carbon and nitrogen, microbial biomass carbon (MBC) and nitrogen (MBN) and acidphosphomonoesterase activity (ACP). This was done in Meru South and Kandara sub-counties in Kenya for three consecutive cropping seasons. Tillage was the main factor [minimum (D0) and conventional (D15)], and soil external inputs were the sub-factors: sole mineral fertiliser (F), crop residues + mineral fertiliser (RF), crop residues + animal manure + legume intercrop Dolichos lablab L. (RML), crop residues + mineral fertiliser + animal manure (RFM), crop residues + Tithonia diversifolia + animal manure (RTiM), crop residues + Tithonia diversifolia + rockphosphate (RTiP) and an unfertilized treatment (Control). During the study period, we experienced frequent dry spells and meteorological droughts in the two sites. We found no significant effects of the tillage systems and mineral fertilisers applied alone or combined with crop residues on the biological properties. All additional organic inputs to the soils enhanced the biological soil properties. On average, MBC in the treatments with organic inputs only was enhanced by 51% in Meru South and 19% in Kandara. MBC-to-TOC ratio was significantly different (p = .0003) under soil external inputs in Meru South. On average, MBN in the treatments with organic inputs was enhanced by 66% in Meru South and 25% in Kandara. Compared with the control, ACP was higher under RML, RTiP and RTiM by 26%, 20% and 17%, respectively in Meru South. In Kandara, ACP was higher under RTiM and RTiP by 25% and 23%, respectively, compared with the control. The increase in microbial biomass indicates that application of organic inputs contributed to soil organic C, thereby stimulating the microbial growth and enzyme activity. Thus, use of organic inputs or in combination with mineral fertilisers are feasible alternatives for sustaining soil organic carbon through increased microbial biomass leading to soil organic matter build-up, which is a vital element of soil quality and fertilityItem Potential of deterministic and geostatistical rainfall interpolation under high rainfall variability and dry spells: case of Kenya’s Central Highlands(Springer Vienna, 2015-03) Kisaka, Oscar M.; Mucheru-Muna, Monicah; Ngetich, F.K.; Mugwe, JayneDrier parts of Kenya’s Central Highlands endure persistent crop failure and declining agricultural productivity. These have, in part, attributed to high temperatures, prolonged dry spells and erratic rainfall. Understanding spatial-temporal variability of climatic indices such as rainfall at seasonal level is critical for optimal rain-fed agricultural productivity and natural resource management in the study area. However, the predominant setbacks in analysing hydro-meteorological events are occasioned by either lack, inadequate, or inconsistent meteorological data. Like in most other places, the sole sources of climatic data in the study region are scarce and only limited to single stations, yet with persistent missing/unrecorded data making their utilization a challenge. This study examined seasonal anomalies and variability in rainfall, drought occurrence and the efficacy of interpolation techniques in the drier regions of eastern Kenyan. Rainfall data from five stations (Machang’a, Kiritiri, Kiambere and Kindaruma and Embu) were sourced from both the Kenya Meteorology Department and on-site primary recording. Owing to some experimental work ongoing, automated recording for primary dailies in Machang’a have been ongoing since the year 2000 to date; thus, Machang’a was treated as reference (for period of record) station for selection of other stations in the region. The other stations had data sets of over 15 years with missing data of less than 10 % as required by the world meteorological organization whose quality check is subject to the Centre for Climate Systems Modeling (C2SM) through MeteoSwiss and EMPA bodies. The dailies were also subjected to homogeneity testing to evaluate whether they came from the same population. Rainfall anomaly index, coefficients of variance and probability were utilized in the analyses of rainfall variability. Spline, kriging and inverse distance weighting interpolation techniques were assessed using daily rainfall data and digital elevation model in ArcGIS environment. Validation of the selected interpolation methods were based on goodness of fit between gauged (observed) and generated rainfall derived from residual errors statistics, coefficient of determination (R 2), mean absolute errors (MAE) and root mean square error (RMSE) statistics. Analyses showed 90 % chance of below cropping-threshold rainfall (500 mm) exceeding 258.1 mm during short rains in Embu for 1 year return period. Rainfall variability was found to be high in seasonal amounts (e.g. coefficient of variation (CV) = 0.56, 0.47, 0.59) and in number of rainy days (e.g. CV = 0.88, 0.53) in Machang’a and Kiritiri, respectively. Monthly rainfall variability was found to be equally high during April and November (e.g. CV = 0.48, 0.49 and 0.76) with high probabilities (0.67) of droughts exceeding 15 days in Machang’a. Dry spell probabilities within growing months were high, e.g. 81 and 60 % in Machang’a and Embu, respectively. Kriging interpolation method emerged as the most appropriate geostatistical interpolation technique suitable for spatial rainfall maps generation for the study region. Theoretical and Applied Climatology Theoretical and Applied Climatology Look InsideItem Potential of deterministic and geostatistical rainfall interpolation under high rainfall variability and dry spells: case of Kenya’s Central Highlands(Springer, 2015-03) Kisaka, Oscar M.; Mucheru-Muna, M.; Ngetich, F.K.; Mugwe, Jayne; Mugendi, Daniel N.; Mairura, F.; Shisanya, C.A.; Makokha, G. L.Drier parts of Kenya’s Central Highlands endure persistent crop failure and declining agricultural productivity. These have, in part, attributed to high temperatures, prolonged dry spells and erratic rainfall. Understanding spatial-temporal variability of climatic indices such as rainfall at seasonal level is critical for optimal rain-fed agricultural productivity and natural resource management in the study area. However, the predominant setbacks in analysing hydro-meteorological events are occasioned by either lack, inadequate, or inconsistent meteorological data. Like in most other places, the sole sources of climatic data in the study region are scarce and only limited to single stations, yet with persistent missing/unrecorded data making their utilization a challenge. This study examined seasonal anomalies and variability in rainfall, drought occurrence and the efficacy of interpolation techniques in the drier regions of eastern Kenyan. Rainfall data from five stations (Machang’a, Kiritiri, Kiambere and Kindaruma and Embu) were sourced from both the Kenya Meteorology Department and on-site primary recording. Owing to some experimental work ongoing, automated recording for primary dailies in Machang’a have been ongoing since the year 2000 to date; thus, Machang’a was treated as reference (for period of record) station for selection of other stations in the region. The other stations had data sets of over 15 years with missing data of less than 10 % as required by the world meteorological organization whose quality check is subject to the Centre for Climate Systems Modeling (C2SM) through MeteoSwiss and EMPA bodies. The dailies were also subjected to homogeneity testing to evaluate whether they came from the same population. Rainfall anomaly index, coefficients of variance and probability were utilized in the analyses of rainfall variability. Spline, kriging and inverse distance weighting interpolation techniques were assessed using daily rainfall data and digital elevation model in ArcGIS environment. Validation of the selected interpolation methods were based on goodness of fit between gauged (observed) and generated rainfall derived from residual errors statistics, coefficient of determination (R 2), mean absolute errors (MAE) and root mean square error (RMSE) statistics. Analyses showed 90 % chance of below cropping-threshold rainfall (500 mm) exceeding 258.1 mm during short rains in Embu for 1 year return period. Rainfall variability was found to be high in seasonal amounts (e.g. coefficient of variation (CV) = 0.56, 0.47, 0.59) and in number of rainy days (e.g. CV = 0.88, 0.53) in Machang’a and Kiritiri, respectively. Monthly rainfall variability was found to be equally high during April and November (e.g. CV = 0.48, 0.49 and 0.76) with high probabilities (0.67) of droughts exceeding 15 days in Machang’a. Dry spell probabilities within growing months were high, e.g. 81 and 60 % in Machang’a and Embu, respectively. Kriging interpolation method emerged as the most appropriate geostatistical interpolation technique suitable for spatial rainfall maps generation for the study region.Item The Potential of Organic and Inorganic Nutrient Sources in Sub-Saharan African Crop Farming Systems(2012-02) Ngetich, F.K.; Shisanya, C.A.; Mugwe, Jayne; Mucheru-Muna, Monicah; Mugendi, Daniel N.he Potential of Organic and Inorganic Nutrient Sources in Sub-Saharan African Crop Farming SystemItem The Potential of Organic and Inorganic Nutrient Sources in Sub-Saharan African Crop Farming Systems(2012-02) Ngetich, F.K.; Shisanya, C.A.; Mugwe, Jayne; Mucheru-Muna, M.; Mugendi, Daniel N.Item Rainfall Variability, Drought Characterization, and Efficacy of Rainfall Data Reconstruction: Case of Eastern Kenya(Hindawi Publishing Corporation, 2015) Kisaka, Oscar M.; Mucheru-Muna, M.; Ngetich, F.K.; Mugwe, Jayne; Mugendi, Daniel N.; Mairura, F.This study examined the extent of seasonal rainfall variability, drought occurrence, and the efficacy of interpolation techniques in eastern Kenya. Analyses of rainfall variability utilized rainfall anomaly index, coefficients of variance, and probability analyses. Spline, Kriging, and inverse distance weighting interpolation techniques were assessed using daily rainfall data and digital elevation model using ArcGIS. Validation of these interpolationmethods was evaluated by comparing the modelled/generated rainfall values and the observed daily rainfall data using root mean square errors and mean absolute errors statistics. Results showed 90% chance of below cropping threshold rainfall (500 mm) exceeding 258.1mmduring short rains in Embu for one year return period. Rainfall variability was found to be high in seasonal amounts (CV = 0.56, 0.47, and 0.59) and in number of rainy days (CV = 0.88, 0.49, and 0.53) inMachang’a, Kiritiri, and Kindaruma, respectively.Monthly rainfall variability was found to be equally high during April and November (CV = 0.48, 0.49, and 0.76) with high probabilities (0.67) of droughts exceeding 15 days in Machang’a and Kindaruma. Dry-spell probabilities within growing months were high, (91%, 93%, 81%, and 60%) in Kiambere, Kindaruma, Machang’a, and Embu, respectively. Kriging interpolation method emerged as the most appropriate geostatistical interpolation technique suitable for spatial rainfall maps generation for the study region.Item Rainfall Variability, Drought Characterization, and Efficacy of Rainfall Data Reconstruction: Case of Eastern Kenya(Hindawi Publishing Corporation, 2014-08) Kisaka, Oscar M.; Mucheru-Muna, Monicah; Ngetich, F.K.; Mugwe, Jayne; Mugendi, Daniel N.; Mairura, F.This study examined the extent of seasonal rainfall variability, drought occurrence, and the efficacy of interpolation techniques in eastern Kenya. Analyses of rainfall variability utilized rainfall anomaly index, coefficients of variance, and probability analyses. Spline, Kriging, and inverse distance weighting interpolation techniques were assessed using daily rainfall data and digital elevation model using ArcGIS. Validation of these interpolation methods was evaluated by comparing the modelled/generated rainfall values and the observed daily rainfall data using root mean square errors and mean absolute errors statistics. Results showed 90% chance of below cropping threshold rainfall (500 mm) exceeding 258.1 mm during short rains in Embu for one year return period. Rainfall variability was found to be high in seasonal amounts (CV = 0.56, 0.47, and 0.59) and in number of rainy days (CV = 0.88, 0.49, and 0.53) in Machang’a, Kiritiri, and Kindaruma, respectively. Monthly rainfall variability was found to be equally high during April and November (CV = 0.48, 0.49, and 0.76) with high probabilities (0.67) of droughts exceeding 15 days in Machang’a and Kindaruma. Dry-spell probabilities within growing months were high, (91%, 93%, 81%, and 60%) in Kiambere, Kindaruma, Machang’a, and Embu, respectively. Kriging interpolation method emerged as the most appropriate geostatistical interpolation technique suitable for spatial rainfall maps generation for the study region.Item Soil fertility inputs and tillage influence on maize crop performance and soil water content in the Central Highlands of Kenya(Elsevier, 2019-05) Kiboi, Milka N.; Ngetich, F.K.; Fliessbach, A.; Muriuki, A.; Mugendi, Daniel N.Rigorous land ploughing and cropping fertiliser treatment and mineral fertiliser combined with animal manure treatment) consistently enhanced maize crop growth and development as observed through enhanced chlorophyll content, plant height and yields. Application of soil fertility inputs significantly improved grain and stover yields except in the crop residue combined with animal manure and legume intercrop treatment (perhaps due to nutrients’ competition since Lablab has an intensive rooting system). Sole organic inputs enhanced soil moisture content in both sites. Emerging from the study, however, is the lack of advantage of minimum tillage over the conventional tillage, within the period under consideration. Thus, this study highlights the possibility of improving soil water holding capacity through application of organic inputs such as crop residues, Tithonia diversifolia and manure, either singly or in combination. It further underpins the uniqueness of an integrated approach to soil fertility and low soil moisture content in the tropical sub-humid regions experiencing erratic rainfallivity in the Central Highlands of Kenya due to low and declining soil fertility, inappropriate tillage methods, soil water scarcity and prolonged dry-spells. In this study, we assessed the effects of two tillage systems and soil fertility inputs on maize crop performance and soil water content. The research was carried out in Chuka and Kandara sites in the Central Highlands of Kenya for four seasons; long rains 2016, short rains 2016, long rains 2017 and short rains 2017. The experimental design was a split plot with tillage method (minimum and conventional) as the main treatments and soil fertility inputs as the sub-treatments: Sole mineral fertiliser, mineral fertiliser combined with crop residue, mineral fertiliser combined with animal manure, Tithonia diversifolia combined with phosphate rock (Minjingu), animal manure intercropped with Dolichos Lablab L. and a Control (conventional tillage with no inputs). Except for the control, and sole mineral fertiliser, crop residue was applied as mulch in all treatments. Based on the results, the treatments with mineral fertiliser (sole mineral fertiliser combined with mineral fertiliser treatment and mineral fertiliser combined with animal manure treatment) consistently enhanced maize crop growth and development as observed through enhanced chlorophyll content, plant height and yields. Application of soil fertility inputs significantly improved grain and stover yields except in the crop residue combined with animal manure and legume intercrop treatment (perhaps due to nutrients’ competition since Lablab has an intensive rooting system). Sole organic inputs enhanced soil moisture content in both sites. Emerging from the study, however, is the lack of advantage of minimum tillage over the conventional tillage, within the period under consideration. Thus, this study highlights the possibility of improving soil water holding capacity through application of organic inputs such as crop residues, Tithonia diversifolia and manure, either singly or in combination. It further underpins the uniqueness of an integrated approach to soil fertility and low soil moisture content in the tropical sub-humid regions experiencing erratic rainfall.Item Staff Profile - Dr. Ngetich, Kipchirchir Felix(UoEm., 2015-07) Ngetich, F.K.Soil and Water Resources Management, Soils, Crop Modeling, Biofertilizers, Land Use Change, Land Use Planning, Rural Livelihoods, Remote Sensing Applications, Sustainable Agriculture, Remote Sensing and GIS, Geostatistics, Rainfall AnalysisItem Tied-ridging and soil inputs enhance small-scale maize productivity and profitability under erratic rainfall conditions in central Kenya(UoEM, 2023) M., Ndung’u; Mugwe, J.N.; Mucheru-Muna, M.W; Ngetich, F.K.; Mairura, F.S.; Mugendi, D.NDeficits in soil moisture and low soil fertility are the major constraints to smallholder farming systems in the SSA (sub-Saharan Africa) region. This study evaluated the effects of tied ridging and selected soil fertility inputs on; soil water content at different depths, maize yields, and economic returns. The treatments were: Tithonia diversifolia + inorganic fertilizer, manure + inorganic fertilizer, inorganic fertilizer, and control with or without tied ridging as the soil water conservation factor. Data were subjected to analysis of variance, and the means were separated using LSD at p ≤ 0.05. Treatments with Tithonia diversifolia or manure combined with inorganic fertilizer with or without tied ridging consistently affected soil water content positively. The effect of tied ridging on soil water content was greater during the short rain season compared to the long rains. In addition, there was evidence that tied ridging and organic soil inputs resulted in greater soil moisture conservation during the critical silking and tasselling maize phenological stages during the short rain season. Treatments had significant effects on grain and stover yields during the long rain 2016 season (p < 0.0001 and p = 0.0477, respectively) and the short rain 2016 season (p < 0.0001 and p = 0.0035, respectively). The highest (4.87 Mg ha− 1 ) maize grain yield was recorded in Tithonia diversifolia plus inorganic fertilizer under tied ridging in the long rain 2016 season, while manure + inorganic fertilizer without tied ridging gave the highest yields (1.27 Mg ha− 1 ) in the short rain 2016 season. The highest net benefits of US$ 1229.90 ha− 1 and US$ 171.57 ha− 1 were recorded under Tithonia diversifolia plus inorganic fertilizer with tied ridging during the long and short rain seasons, respectively. Overall, the best-performing treatments in yields and profitability were those that combined organic and inorganic fertilizers, regardless of the presence or absence of tied ridging. Climate-smart agricultural strategies combining tied ridges and organic inputs should be an integral component of farmer management if losses related to soil fertility and water stress are to be minimized under erratic rainfall regimes in the semiarid farming systems of the SSA region.Item Using Apsim-Model as A Decision-Support-Tool for Long-Term Integrated-Nitrogen-Management and Maize productivity under Semi-Arid Conditions in Kenya(Cambridge University Press, 2015-04) Kisaka, Oscar M.; Mucheru-Muna, M.; Ngetich, F.K.; Mugwe, Jayne; Mugendi, Daniel N.; Mairura, F.; Muriuki, J.There is continued decline in per capita agricultural productivity in the drier parts of Kenya’s central highlands. The declines have been linked to low and declining soil fertility, soil water, high atmospheric heat, prolonged dry-spells and erratic rainfall. Integrated soil fertility management (ISFM) technologies have been developed and tested in the region. Despite their significant impacts, high variability in local soils and climate contributes to large variations and inconsistency in research results among replications. Experimentation is expensive and limited to a few years, sites and scenarios. Crop-growth simulation models suitably complement experimental research, to support decision making regarding soil fertility and water management. This study evaluated the performance of the Agricultural Production Systems Simulator (APSIM) model. APSIM was parameterized and calibrated based on a rain-fed randomized complete block trial (2009–2012) at a research station in Machang’a, Embu County. The study further reported on long-term effects of integrated Nitrogen (N) management from organic residues (goat manure, Lantana camara, Tithonia diversifolia and Mucuna pruriens) and their combination with mineral fertilizers in maize production. The model adequately reproduced the observed trends of maize leaf area index (LAI) and yield response to the testNamendments. Long-termsimulations showed that application of 0, 20 and 40 Kg Nha−1 had low inter-seasonal variations (CV = 18–33%) in yields. High yield variability (CV > 56%) was observed in the application of 60 and 80 Kg N ha−1. Application of 40 Kg N ha−1 by combining mineral fertilizer and manure showed 80% chance of harvesting more than 2.5 Mg ha−1 of maize grain yield. Maize stover mulching at 5 and 6 Mg ha−1 with the same N application increased long-term guaranteed grain harvests to 3.5 Mg ha−1. This is when complemented with 90 Kg P ha−1. This integrated N and soil water management is thus recommended. For subsistence farming, low-cost recommendations are geared towards some ‘guaranteed’ yield stability each cropping season. This recommendation underpins low-cost technologies that reduce production risks among small-holder farmers who faced with intermittent financial problems, to improve food security. However, there is need to evaluate and verify that there is a positive balance of primary nutrients such as N, P and K in such a fertility and water management option. Its effects on C:N levels ought to be evaluated as well.