This study was carried out in Kilombero District, Tanzania with the objective of characterizing the soils in terms of their morphology, genesis, physico-chemical properties and classification. Three pedons KISA-P1, MKU-P1 and MBA-P1 were identified within the Kilombero Valley, dug, described and sampled. Disturbed and undisturbed soil samples were taken from designated pedogenic horizons for physical and chemical analysis in the laboratory. Using both field and laboratory data soils were classified using both USDA Soil Taxonomy and World Reference Base for Soil Resources schemes of classification. Results show that the three pedons were developed under Isohyperthemic temperature and Aquic moisture regimes. All pedons were deep (100 - 120 cm). Whereas Pedons KISA-P1 and MBA-P1 had sandy clay loam topsoils overlying sandy clay subsoils, Pedon MKU-P1 had clayey texture throughout its profile depth. All pedons had low chromas of ≤ 3 and redoximorphic features in form of abundant mottles particularly in the subsoils. Topsoils of Pedons KISA-P1 and MBA-P1 had dominantly friable to very friable moist consistence while those of Pedon MKU-P1 had very firm moist consistence. Subsoil moist consistence varied from firm to extremely firm (Pedons KISA-P1 and MKU-P1) and from friable to very firm (Pedon MBA-P1). Structures were dominantly weak to moderate subangular blocky in all studied soils but some horizons were structureless single grained and massive. Soil reaction ranged from extremely acid (topsoil of MBA-P1) to mildly alkaline (subsoil of MKU-P1) with pH values of 4.44 and 6.73 respectively. Topsoil organic carbon and total nitrogen contents in the studied pedons were low (0.66 to 1.4%) and very low to low (0.08 to 0.19%) respectively. CEC_soil values were rated as low to medium ranging from 8.4 to 23.8 cmol (+)/kg respectively in Pedon KISA-P1 and Pedon MKU-P1. Percent BS values varied between and within studied pedons and ranged from low < 50% to high > 50%. Studied soils manifested nutrient imbalances in respect of basic cations. On the overall, fertility of the studied soils was rated as low to medium. According to USDA Keys to Soil Taxonomy, Pedons KISA-P1 and MKU-P1 classified as Inceptisols, equivalent to Cambisols in WRB for Soil Resources whereas Pedon MBA-P1 classified as Entisols equivalent to Fluvisols. All three sites were recommended for paddy production.

Soils formed from volcanic materials have high potential for agricultural production and support high human population densities. This study was carried out on soils developed from volcanic parent materials of Northern Province of Rwanda aiming largely on pedological characterization but to a certain extent on assessment of potentials of soils for production of major crops in the area. Three representative pedons namely Kinigi Pedon 1 (KNG-P1), Kinigi Pedon 2 (KNG-P2) and Gahunga Pedon 1 (GHNG-P1) were identified and described. Sixteen soil samples were collected from different pedogenic horizons and analyzed in the laboratory for physico-chemical properties. Pedons were classified using USDA Soil Taxonomy and FAO-WRB for Soil Resources. Potentials and limitations of the soils were also identified. Results show that soils were shallow to very deep and well drained. Topsoils were very dark coloured with colour values of ≤ 2 in all pedons. Texture was generally loamy with bulk densities of < 0.47 g/cm3 in Pedons KNG-P1 and KNG-P2 while they ranged from 0.94 to 1.34 g/cm³ in Pedon GHNG-P1. Topsoils were medium acid (KNG-P1, KNG-P2) and mildly alkaline (GHNG-P1), with high to very high OC ranging from 3.97 to 13.03%. CEC_soil was high (> 32 cmol (+)/kg) in Pedons KNG-P1 and KNG-P2. Base saturation was low (< 30%) in Pedons KNG-P1 and KNG-P2 while it was high (> 50%) in Pedon GHNG-P1. pH_NaF was > 9.5 in Pedons KNG-P1 and KNG-P2 reflecting exchange complex dominated by amorphous materials and/or humus complexes. Phosphorus retention capacity ranged from 6.25% to 99.58% and only Pedons KNG-P1 and KNG-P2 met the “andic properties” requirement of PRC ≥ 85%. Melanic index values indicated that these two pedons were characterized more by fulvic than humic acids. Nutrient imbalance with reference to basic cations was common in all studied soils, implying suboptimal nutrient uptake and toxicity. Fe₂O₃, SiO2 and Al2O3 were the dominant oxides in the studied soils. Degree of weathering of studied soils was low as indicated by their weathering indices. Using field and laboratory data, Pedons KNG-P1 and KNG-P2 classified as Andisols/Andosols and GHNG-P1 as Mollisols/Phaeozems. Land units represented by Pedons KNG-P1 and KNG-P2 were rated as marginally suitable while land unit represented by Pedon GHNG-P1 was rated as moderately suitable for the major crops of the area. Application of P fertilizers coupled with efficient placement was recommended to enhance P, and soil conservation should be underscored in study area.

Plant roots may have a strong erosion-reducing effect. However, little is known about root characteristics of tropical plants used for erosion control. A study was thus conducted in the Western Usambara Mountains, Tanzania to investigate rooting characteristics of Guatemala grass (Tripsacum andersonii), Napier grass (Pennisetum purpureum) and Tithonia shrub (Tithonia diversifolia), also referred to as wild sunflower, and to evaluate their potential for erosion control. For each plant species, mean root diameter (D), root density (RD), root length density (RLD) and root area ratio (RAR) were assessed for six plants in each species and relative soil detachment rate (RSD) predicted. Mean RD values in the 0 - 0.4 m soil depth for Majulai village and Migambo village respectively were 50.9 and 58.6 kg/m³ for Guatemala grass, 30.4 and 31.3 kg/m³ for Napier grass and 22.1 and 23.0 kg/m³ for Tithonia shrub. RLD values were 35.9 and 45.0 km/m³ for Guatemala grass, 31.3 and 150.0 km/m³ for Napier grass and 10.5 and 6.4 km/m³ for Tithonia shrub. Predicted RSD values were 4.43*10^-12 and 1.20*10^-14 for Guatemala grass, 6.10*10^-5 and 2.74*10^-4 for Napier grass and 4.43*10^-3 and 2.24*10^-4 for Tithonia shrub in the 0 - 0.4 m soil depth. The results indicate that Guatemala grass has a higher potential to reduce soil erosion rates by concentrated flow as compared to Napier grass or Tithonia shrub in the 0 - 0.4 m soil depth. These findings have implications on the selection and use of appropriate plants for soil erosion control.

Drought is a major crop production constraint worldwide. Some legume crops are known for their ability to resist water deficit stress. This study evaluated the responses of bambara groundnut (Vigna subterranea (L.) Verdc) and groundnut (Arachis hypogaea (L.) to soil water deficit stress. The experiment was set as a split-plot randomized complete block design. Three bambara groundnut landraces: viz DodR, NALBAM 4 and S19-3, and one groundnut variety, MNANJE, were assigned to subplots with three water regimes assigned to main plots (regime one: irrigated throughout the growing period, regime two: water deficit stress was imposed at the start of flowering to the end of first flush flowering, regime three: water was withheld during the pod development). Water deficit stress increased proline content by 123% in stressed plots. The highest (174%) and lowest (89%) proline increases were evident in the genotypes MNANJE and NALBAM 4, respectively. Water deficit decreased stomatal conductance, transpiration rate and photosynthetic rate, with MNANJE and S19-3 showing the smallest percentage decrease in most of the traits. This suggests that the two genotypes are drought resistant. The variations observed among landraces could be exploited to breed resilient varieties for cultivation in drought-prone areas, ultimately improving food security.

Irish potato (Solanum tuberosum) is a critical crop for food security and economic growth in Tsangano and Angónia districts, central Mozambique. Challenges like inconsistent yields and variable quality are often linked to suboptimal soil conditions, and limit production. This study aimed to classify and evaluate the suitability of soils for potato cultivation, filling gaps in detailed soil assessments for sustainable agriculture. Using combined pedological approach and laboratory soil analysis, four pedons TSA-P01 and TSA-P02 in Tsangano, and ANGO-P01 and ANGO-P02 in Angónia were analyzed for bulk density, texture, pH, organic carbon, and nutrient content. The pedons were very deep (> 150 cm) and had textures ranging from sandy clay loam to sandy loam. TSA-P02 had the lowest bulk density (0.78 Mg m-3) and the highest available water capacity (182.0 mm m-1). Soil pH ranged from 5.6 to 7.9, indicating neutral to slightly acidic conditions. Nutrient analysis revealed low total nitrogen (0.12 - 0.22%), varying soil organic carbon (0.16 - 2.73%), and cation exchange capacity (10.1 - 11.33 cmol(+) kg-1). Pedons TSA-P01, ANGO-P1, and ANGO-P02 were characterized by eluviation and illuviation as dominant pedogenic processes while in pedon TSA-P02 shrinking and swelling were the pedo-genic processes. Weathering indices identified ANGO-P01 as the most highly weathered, while TSA-P02 was the least weathered and had better fertility indicators. According to USDA Taxonomy, the soils were classified as Ultisols, Vertisols, and Alfisols, corresponding to Acrisols, Alisols, Vertisols, and Luvisols in the WRB for Soil Resources. All studied soils were marginally suitable for potato production (S3f) due to dominant fertility constraints but with varying minor limitations in climate, topography, and soil physical properties. The findings hence recommended targeted soil fertility management to enhance productivity and sustainability in potato cultivation.