College of Agriculture

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The College of Agriculture is committed to advancing agricultural education, research, and community service. It serves as a center for knowledge creation and dissemination in crop science, animal production, natural resource management, and sustainable agriculture.

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    AGRO-MORPHOLOGICAL VARIABILITY, GENOTYPE BY ENVIRONMENT INTERACTION, NUTRIENT AND LAND-USE EFFICIENCY, AND NUTRITIONAL PROFILE OF OAT (Avena sativa L.) GENOTYPES IN ETHIOPIA
    (Hawassa University College of Agriculture, 2024) GEZAHAGN KEBEDE BUNARE
    Agro-morphological variability, genotype by environment interaction, nutrient and land-use efficiency, and nutritional profile of oat (Avena sativa L.) genotypes in Ethiopia Oat (Avena sativa L.) is one of the useful annual cereal crops grown at higher altitudes in the tropics and temperate regions. It is a dual-purpose crop cultivated for fodder and grain production in the central highlands of Ethiopia. This crop is mainly cultivated for fodder production and the grain is also used for human food and animal feed in Ethiopia. Oat generally produces high amounts of fodder which has better nutritional quality and it can be used as a green feed and the excess production can be conserved as hay and silage to utilize during the feed scarcity period. Despite its significance, oat production, and productivity are highly influenced by genetics, environments, agronomic management, and their interactions. Therefore, developing high-yielding oat varieties with stable performance under diverse environmental conditions and improving the productivity of oat through various agronomic management are the major research areas for oat improvement in Ethiopia. However, studies on agromorphological based genetic diversity and yield stability of oat genotypes under diverse environmental conditions and the optimum nutrient requirements of oat for higher yield and nutritional quality under sole and mixed cultures with vetch have not been well studied and properly documented in the country. Thus, the overall aim of this study was to enhance the productivity of oat genotypes through proper exploitation of genetic variability and agronomic management under different environments and management conditions. The first experiment was conducted using 120 oat genotypes using a randomized complete block design with three replications at Holetta and Ada-Berga research stations in the 2020/2021 cropping season. The objectives of this study were to estimate the extent of agro-morphological based genetic variability, heritability, and genetic advance in oat genotypes, to investigate the phenotypic and genotypic relationships between the studied quantitative traits, to determine the direct and indirect effects of measured quantitative traits on fodder and grain yields, and to evaluate the genetic variations using cluster, genetic divergence, and principal component analyses for oat yield improvement. The results revealed that moderately high to very high heritability (62.9– 86.4%) coupled with high to moderate genetic advance as percent of mean (16.0–26.1%) were recorded for forage dry matter yield (FDMY), number of leaves at forage harvest (NLFH), stem dry matter yield (SDMY), forage yield production rate (FYPR), grain yield (GY), panicle length at grain harvest (PLGH), number of spikes per panicle (NSPP), and harvest index (HI). This result demonstrated that the selection of oat genotypes based on these traits could be effective for yield improvement. The genotypic and phenotypic correlation and path coefficient analyses indicated that the FYPR had a significant positive association and high direct effect on FDMY and also the biological yield production rate (BYPR) and HI had a significant positive association and high direct effect on GY. This indicated that selection based on FYPR and BYPR/HI would simultaneously improve the FDMY and GY in oat genotypes, respectively. The multivariate analysis revealed that the studied genotypes grouped into four clusters with the intra and inter-cluster genetic distances ranging from 2.3 to 4.3 and 11.7 to 63.2, respectively. The principal component analysis showed that traits such as FYPR, BYPR, PLGH, FDMY, and xxxi number of spikelets per panicle (NSLPP) contributed more for the first component whereas HI, GY, NLFH, and plant height at grain harvest (PHGH) had a high contribution for the second component. The presence of genotype by environment interaction (GEI) complicates the selection of genotypes with high yielding coupled with stable performance across environments. Twenty-four oat genotypes were selected and sown during the 2020/2021 cropping season at Holetta (E1), Ada-Berga (E2), Ginchi (E3), Jeldu (E4), D/Zeit (E5), Kulumsa (E6), Bekoji (E7), Kuyu (E8), and D/Markos (E9) agricultural research stations using a randomized complete block design with three replications. Thus, the second experiment aimed to assess the magnitude of GEI and to evaluate the fodder and grain yield stability performance of oat genotypes using univariate and multivariate statistical models. The additive main effects and multiplicative interaction (AMMI) analysis of variance for fodder yield showed that the total variation was highly contributed by the environment (E) main effect followed by GEI and genotype(G). Moreover, the GGE biplot analysis for fodder yield showed that G6 was the ideal genotype while G2, G3, G10, and G23 were desirable genotypes. Among environments, E7 was an ideal environment whereas E1 and E8 were favorable environments. The results of univariate stability analysis indicated that selection of oat genotypes using genotypic superiority index (Pi), yield stability index (YSI), coefficient of determination (R2 ), and coefficient of variation (CVi) stability parameters would be effective for fodder yield improvement. Similarly, the AMMI analysis of variance for grain yield showed that the E main effect was the highest contributor to the total variation followed by G and GEI. Based on the GGE biplot analysis for grain yield, G19 was an ideal genotype while G8, G11, G12, G14, G17, and G22 were desirable genotypes. Moreover, the ideal environment was E2 whereas E1, E4, and E5 were favorable environments. The univariate stability analysis for grain yield indicated that high grain yield-producing oat genotypes had stable performance using the stability parameters of Pi , the Perkins and Jinks adjusted linear regression coefficient (Bi), and YSI. The yield and nutritional quality of oat can be improved through the application of optimum fertilizer at the right time. Oat can be cultivated using the blanket recommended fertilizer rate in Ethiopia. Thus, the optimum fertilizer rate for fodder and grain production of oat has not been well studied and documented in the country. Therefore, this study aimed to assess the effect of fertilizer rates on agro-morphological traits, nutrient uptake and use efficiency, nutritive value, and economic feasibility of oat varieties at Holetta. The study was carried out during the 2020/2021 and 2021/2022 cropping seasons using a factorial arrangement of eight levels of the blanket recommended fertilizer (0, 25, 50, 75, 100, 125, 150, and 175%) and three oat varieties (CI-8251, SRCPX80Ab2291, and Sorataf) in a randomized complete block design with three replications. The results showed that variety, fertilizer, and year had significant effects on FDMY. The FDMY of oat varieties increased with increasing fertilizer rates and the highest (15.9 t/ha) yield was obtained from the application of 175% (71.8 kg N + 35 kg P/ha) fertilizer. Among oat varieties, the highest FDMY was obtained from CI-8251 (forage type oat) followed by SRCPX80Ab2291 (dual type oat) and Sorataf (grain type). The number of tillers per plant (NTPP), yields of morphological fractions (leaf, stem, and grain), FYPR, nutrient concentration, and uptake had significant positive associations with fertilizer levels and FDMY. However, all the nutrient use efficiencies except agro-physiological efficiency (APE) had inverse associations with fertilizer levels and FDMY. Similar to FDMY, the GY of oat varied significantly for variety, fertilizer, and year effects. Application of 150% (61.5 kg N + 30 kg P/ha) fertilizer rate produced the highest GY (6.5 t/ha) and grain nutrient uptakeGNU (141.7 kg/ha) while the lowest GY and GNU were recorded from oat sown without fertilizer application. Sorataf (grain type) variety gave the highest GY, GNU, partial factor xxxii productivity (PFP), and agronomic efficiency (AE) compared to forage and dual-type oat varieties. Oat varieties sown with 25% (10.3 kg N + 5 kg P/ha) fertilizer rate produced the highest PFP (346.6 kg/ha) and AE (164.8 kg/ha) while PFP and AE decreased with increasing fertilizer rates. The nutrient concentration and uptake had positive associations with fertilizer level and GY while nutrient harvest index (NHI) and nutrient use efficiency had inverse associations with fertilizer level and GY. The nutritional quality analysis indicated that digestible yield (DY) and total digestible nutrient yield (TDNY) varied significantly with variety, fertilizer, and year effects. Among oat varieties, CI-8251 gave the highest TDNY while SRCPX80Ab2291 gave the highest DY but the Sorataf variety gave the lowest TDNY and DY. Most of the measured nutritional quality parameters varied for the interaction effect of variety by fertilizer by year effect. Sorataf variety sown with 175% fertilizer rate in 2020 gave the highest crude protein-CP (113.9 g/kg DM), crude protein yield-CPY (1.66 t/ha), and digestible crude protein-DCP (68.2 g/kg DM). Application of fertilizer and FDMY had significant positive associations with CP, CPY, DY, DCP, and TDNY. The combined partial budget analysis for the three oat varieties showed that application of 125% (51.3 kg N + 25 kg P/ha ) fertilizer rate produced higher net benefit (83,440 ETB) and marginal rate of return (12,635.6%) from fodder production. On the other hand, the application of 150% fertilizer rate produced the highest net benefit from grain production. Oat can be also cultivated with vetch (annul forage legume) to improve the quantity and quality of feed in the central highlands of Ethiopia. The oat/vetch mixtures are sown with the same blanket recommended fertilizer rate that is used for the production of sole oat in the country. This indicated that the application of fertilizer on oat/vetch mixtures does not depend on the nutrient requirements of oat and vetch for better growth and development under a mixed cropping system. Accordingly, the optimum fertilizer rate for the oat/vetch mixed cropping system has not been well studied and documented in the country. Therefore, this study aimed to investigate the effect of fertilizer rates on agro-morphological traits, nutrient uptake and use efficiency, competitive ability, and economic feasibility of oat under oat/vetch mixed cropping and nutritive value of mixtures at Holetta Agricultural Research Center during the 2020/2021 and 2021/2022 cropping seasons. In this study, the oat/vetch mixture was sown with eight fertilizer rates (0, 25, 50, 75, 100, 125, 150, and 175%) and also sole oat and sole vetch were sown with their recommended fertilizer rate (100%) using a randomized complete block design with three replications. The results showed that fertilizer and year had significant effects on all measured agro-morphological traits, nutrient concentration, and nutrient uptake and use efficiency of oat. Accordingly, all the measured agro-morphological traits increased with increasing fertilizer rates, and the highest values were recorded in the second year. Application of 150% fertilizer rate increased the FDMY of oat/vetch mixtures by 107.4% compared to oat/vetch mixtures sown without fertilizer application. However, the highest nutrient use efficiency was recorded with the application of fertilizer at the rate of 25% while the nutrient use efficiency was the lowest with the highest fertilizer (175%) application rate. The FDMY of oat under oat/vetch mixtures was associated significantly and positively with all measured agro-morphological traits, nutrient concentration, and uptake while it had significant inverse associations with nutrient use efficiencies. The highest net benefit and marginal rate of return were recorded from the application of 150% fertilizer rate. The productivity of oat under oat/vetch mixed cropping was also assessed using different indices. The results showed that over-yielding oat (OYO), land equivalent coefficient (LEC), area-time equivalent ratio (ATER), and land equivalent ratio (LER) were higher in the first year while oat equivalent yield (OEY) and system productivity index (SPI) were higher in the second year. All xxxiii the aforementioned biological efficiency indices increased with increasing fertilizer rates and the highest values were recorded from the application of 150% fertilizer rate. Similarly, all the measured competitive indices such as crowding coefficient of oat (KO), actual yield loss of oat (AYLO), intercropping advantages of oat (IAO), and the competitive ratio of oat (CRO) were higher in the first year. All the values of competitive indices except aggressivity of oat (AO) increased with increasing fertilizer rates and the highest values were recorded from the application of 150% fertilizer. The economic efficiency indices of oat/vetch mixtures showed that the higher values of monetary advantages index (MAI), relative value total (RVT), replacement value of intercropping (RVI), and relative net return index (RNRI) were recorded in the first year. All the values of economic efficiency indices increased with increasing fertilizer rates and the highest values were recorded from 150% fertilizer rate. The nutritive values of oat/vetch mixtures also varied with fertilizer application and year of production. All the measured nutritive values except fiber contents (NDF-neutral detergent fiber, ADF-acid detergent fiber, ADL-acid detergent lignin, HC-hemicellulose, and C-cellulose) were higher in the second year. Application of fertilizer at the rate of 150% gave the highest ash, CPY, digestible dry matter (DDM), dry matter intake (DMI), in-vitro dry matter digestibility (IVDMD), DY, total digestible nutrients (TDN), TDNY, relative feed value (RFV), and relative feed quality (RFQ). On the other hand, oat/vetch mixtures sown without fertilizer gave the highest fiber contents. The person correlation analysis indicated that fertilizer application had significant inverse associations with fiber contents while it had significant positive associations with the remaining measured nutritional quality parameters. In conclusion, oat genotypes such as CI-715, CI-1463, SRCPX80Ab2806, A-505, CI-1480, S-122, Bona-bas, and CI-1674 were selected for fodder yield and grain yield improvement. Based on the AMMI, GGE, and univariate stability parameters, G6 (CI-1512), G9 (CI-1629), G10 (C-12), and G23 (CI-8235) were selected for fodder yield improvement while G8 (SRCPX80Ab2267), G17 (SRCPX80Ab2310), and G22 (SRCPX80Ab2691) were selected for grain yield improvement of oat. Application of 125% (51.3 kg N + 25 kg P/ha) fertilizer rate for fodder production and 150% (61.5 kg N + 30 kg P/ha) fertilizer rate for grain production could increase the respective yield and farm profitability in the study area. Similarly, application of 150% fertilizer rate would increase the fodder yield, competitive ability, and economic profitability of oat under oat/vetch mixtures and nutritive value of mixtures. However, the selected genotypes and fertilizer rates should be verified under diverse environments of oat-growing areas in Ethiopia.