School of Agriculture and Biotechnology
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Item Do Mixed-Species Legume Fallows Provide Long-Term Maize Yield Benefit Compared with Monoculture Legume Fallows?(Wiley, 2009-11-01) Ndufa, James K.; Gathumbi, Stanley M.; Kamiri, Hellen W.; Giller, Ken E.; Cadisch, GeorgThe deliberate planting of fast-growing N2–fixing legume monoculture species in rotation with cereal crops can be an important source of N for soil fertility replenishment. We hypothesized that mixed-species fallows have a higher potential of giving long-term residual benefits in terms of biomass, nutrients, and quality of residuals leading to long-term nutrient supply to postfallow maize (Zea mays L.) crops. To test these hypotheses, two experiments were established in farmers' fields on very fine Kandiudalfic Eutrudox soils with monoculture and mixed-species fallows. Treatments included: sesbania [Sesbania sesban (L.) Merr.], crotalaria (Crotalaria grahamiana Wight and Arn.), pigeonpea [Cajanus cajan (L.) Millsp.], siratro [Macroptilium atropurpureum (DC.) Urb.], and calliandra (Calliandra calothyrsus Meissn.) as monoculture-species fallow and mixture fallows of sesbania + crotalaria, sesbania + pigeonpea, sesbania + siratro, or sesbania + calliandra compared with continuous maize cropping with or without N fertilizer, and natural weed fallow. Total aboveground biomass ranged from 4.1 to 20.5 Mg ha−1 for monoculture and 7.8 to 23.3 Mg ha−1 for mixed-species fallows. Recyclable fallow biomass N ranged from 70 to 313 kg ha−1 and there was a positive interaction in some mixtures leading to increased N accumulation. Postfallow maize yields for fallows over five cropping seasons were 161–272% or 61–103% higher when compared with continuous maize without or with N fertilizer, respectively. Long-term postfallow effects on maize yield were linearly related to the amount of recycled fallow N yield. Thus, choice of fallow species to mix should be primarily driven by a better risk management strategy and an increased basket of multiple products and services.Item Effects of Blended Fertilizers on Leaf Nutrients Content of Mature Clonal Tea in Kenya. Journal of Experimental Research. Volume 6 (2).(Enugu State University of Science & Technology, 2018-06) itienei, Kibet S; Kamiri, Hellen W.; Kamau, David M.; Nyabundi, Wilson K.; Morogo, MaureenFertilizer studies in Kenya tea industry have focused predominantly on compound NPK. These fertilizers cannot be easily manipulated for specific soils and tea clones. In this respect, Athi River Mining limited has produced Mavuno blended NPK fertilizers with calcium (Ca) and magnesium (Mg). However, their application rates that would result in optimal nutrients uptake are lacking. This is the knowledge gap that this study sought to address. Therefore, the fertilizer blends were assessed for their effects on nutrients uptake at different rate in two sites. The sites were selected purposefully, one in the eastern and the other in the western tea growing areas. Randomized complete block design (RCBD) were used to select 36 trial plots in the two areas which were treated with three fertilizer types where one type was control, and four fertilizer application rates with one rate being a control. The trial was replicated three times Leaf samples were collected and analyzed for nutrients content. The data were then subjected to the analysis of variance (ANOVA) using Mstat C computer software package. Two leaves and a bud had higher nitrogen content (Timbilil 4.84%; Kagochi 4.53%) compared to deficient levels in mature leaf (Timbilil 2.26%; Kagochi 2.95%). This study has shown that supplementing the soil applied NPK fertilizers with calcium, magnesium and micronutrients resulted in better nutrients uptake.Item Effects of blended fertilizers on soil chemical properties of mature tea fields in Kenya(2018-06) Sitienei, Kibet; Kamiri, Hellen W.; Nduru, Gilbert M.; Kamau, David M.Kenya’s tea industry depends predominantly on imported NPK fertilizers to replenish nutrients removed through plucking. In this respect, two blended fertilizers containing NPKS 25:5:5:4+9Ca+2.6Mg and NPKS 23:5:5:4+10Ca+3Mg with trace elements have been produced in the country. However, contribution of the blended fertilizers to optimal tea yields had not been determined. The study aimed to evaluate the optimal levels of the two blended fertilizers on tea grown in the highlands of Kenya. The blended fertilizers were evaluated in two sites, i.e. Timbilil estate in Kericho and Kagochi farm in Nyeri. The trial was laid out in a randomized complete block design with two blended fertilizers and the standard NPK 26:5:5 as a control. The treatments were applied at four fertilizer rates (0-control, 75, 150 and 225 kg N ha-1 yr-1), with three replications. The results showed that application of 225 kg N ha-1 yr-1 blended fertilizer NPKS 25:5:5:4+9Ca+2.6Mg in Timbilil produced mean yield of 2,995 kg Mt ha-1 compared with 3,099 kg Mt ha-1 from the standard NPK. In Kagochi, the highest yield was 1,975 kg Mt ha-1 obtained from the application of the same blended fertilizer NPKS 25:5:5:4+9Ca+2.6Mg at 75 kg N ha-1 yr-1. The highest yields in both sites were obtained during a warm-dry season except in 2015–2016. This study concluded that based on the annual and seasonal yields, the two blended fertilizers and the standard type had the same effectiveness, irrespective of clones and sites. However, the fertilizer rates affected the tea yield.Item Nutrient Budget and Economic Assessment of Blended Fertilizer Use in Kenya Tea Industry(Hidawi, 2018-11-18) Sitienei, Kibet; Kamiri, Hellen W.; Nduru, Gilbert M.; Kamau, David M.Kenya’s tea industry depends predominantly on imported compound NPK fertilizers to replenish nutrients removed through plucking. These fertilizers cannot be easily manipulated for specific soils and tea clones. They also frequently become hazardous within tea-growing environments. In this respect, two fertilizer blends containing NPKS 25 : 5 : 5 : 4 + 9Ca + 2.62Mg and NPKS 23 : 5 : 5 : 4 + 10Ca + 3Mg with trace elements have been produced commercially in the country. However, the extent to which the blended fertilizers may contribute to optimal economic gains without degrading the environment has not been determined. This was the knowledge gap that this study seeks to address. The goal of this study was to evaluate the economic efficacy of fertilizer blends with the aim of identifying optimal levels of application which would maximize tea productivity with minimal negative impacts on the environment. The study hypothesized that blended fertilizers maximize productivity of tea clones with minimal environmental damage. The fertilizer blends were evaluated in two study sites, i.e., Timbilil Estate in Kericho and Kagochi farm in Nyeri. The sites were selected purposefully, one in the eastern and the other in the western tea-growing areas. The trial was laid out in randomized complete block design with two fertilizer blends and the standard NPK 26 : 5 : 5 as control. The treatments were applied at four fertilizer rates (0 (control), 75, 150, and 225 kg·N·ha−1·yr−1), replicated thrice. Leaf samples were collected and analyzed for nutrient uptake as well as associated yields and economic trends. The economic optimum nitrogen rate (EONR) was achieved at 75 kg·N·ha−1·yr−1 at Kagochi with all fertilizers, while at Timbilil, EONR was variable, between 75 and 225 kg·N·ha−1·yr−1 with fertilizer types. This study has shown that, based on the economic point of view, Blend “A” was the most efficient and consistent fertilizer in production and economic returns across the two sites.Item Climate Variability and Adaptation Among Small Holder Banana Farmers in Mountain Regions of Kenya(Geography, Environment, Sustainability,, 2021-04-01) Karienye, David K.; Nduru, Gilbert M.; Kamiri, Hellen W.Banana production is the mainstay industry for majority of small holder farmers living in the mountain regions of Kenya. These regions are affected by climate-related impacts at all levels of the value chain. This paper therefore discusses climate trends, related impacts, and adaptations in banana value chain in Mt. Kenya region for the period between 1980 and 2017. The study locations were purposively selected from Mt. Kenya region to include both Imenti South and Mukurweini sub-counties. A sample of 381 respondents was selected using simple random sampling. Triangulation research design was used to guide the study by integrating both qualitative and quantitative methods in data collection and analysis. Historical document analysis was used to examine climatic data (temperature and rainfall) from the Kenya Meteorological Department, Nairobi. Results showed that rainfall and temperature have changed during the study period. Temperature trends in Mukurweini showed R2 = 0.3314 while in Imenti South R2=0.3441 with an overall annual increase in temperature in Mukurweini by 0.02°C while in Imenti South we registered an increase by 0.016°C for the study period. Mukurweini sub-county rainfall trend line had R2=-0.1064 while Imenti South sub-county had R2=-0.1014. Adverse effects of climate variability on banana value chain included low yields in both Mukurweini (79.2%) and Imenti South (60.2%) sub-counties. Farmers in the study area preferred irrigation (57.2%) followed by crop diversification (13.9%) as adaptive strategies to climate variability.