Soil moisture conservation practices (SMCPs) have been adopted in Uganda to adapt to the effects of climate variability. However, limited information exists on how conservation measures influence the physico-chemical properties of soil and coffee leaf nutrient concentrations. Thus, we determined the effects of selected SMCPs on the soil physio-chemical properties and leaf nutrient concentrations in Robusta coffee in a randomized incomplete block design, replicated three times, in Kituza, Uganda. Soil samples were collected from 0 to 20 cm and 20 to 40 cm depths, and analyzed in the laboratory following standard procedures for selected physio-chemical properties. Coffee leaf samples were picked from each treatment (open sun coffee (COSS), coffee cover crop, Desmodium intortum (CCS), coffee mulch, Miscanthidium violoceum (CMS), and coffee A. coriaria (ACS)). Bulk density was significantly (p < 0.001) the highest under ACS (1.61 gcm⁻³) and lowest under CCS (1.29 gcm⁻³), and it significantly (p < 0.001) increased with depth. The soil organic matter was higher than the optimum range of 1–3% at the 0–20 cm depth across different SMCPs, but within the optimum range at the 20–40 cm depth. Leaf nitrogen was significantly the highest under ACS (3.19%) and lowest under COSS (2.30%). Overall, the findings suggest that SMCPs improve the soil physio-chemical attributes and leaf nutrients for sustainable coffee productivity. However, ACS improved the leaf plant nutrition better compared to other SMCPs.

Coffea canephora has high but inadequately exploited genetic diversity. This diversity, if well exploited, can sustain coffee productivity amidst climate change effects. Drought and heat stress are major global threats to coffee productivity, quality, and tradable volumes. It is not well understood if there is a selectable variation for drought stress tolerance in Robusta coffee half-sibs as a result of watering deficit pre-exposure at the germination stage. Half-sib seeds from selected commercial clones (KR5, KR6, KR7) and a pipeline clone X1 were primed with deficit watering at two growth stages followed by recovery and later evaluated for tolerance to watering deficit stress in three different temperature environments by estimation of plant growth and wilt parameters. Overall, the KR7 family performed the best in terms of the number of individuals excelling for tolerance to deficit watering. In order of decreasing tolerance, the 10 most promising individuals for drought and heat tolerance were identified as: 14.KR7.2, 25.X1.1, 35.KR5.5, 36.KR5.6, 41.KR7.5, 46.KR6.4, 47.KR6.5, 291.X1.3, 318.X1.3, and 15.KR7.3. This is the first prospect into the potential of C. canephora half-sibs’ diversity as an unbound source of genetic variation for abiotic stress tolerance breeding.

In Uganda, most farmers grow their Robusta coffee, Coffea canephora in association with a diversity of shade tree species. Shade tree species diversity and density influence abiotic variables particularly, temperature and relative humidity. In turn, these may negatively or positively influence the population dynamics and damage caused by pest and diseases. Understanding these relationships is therefore vital for informing selection of shade tree species for ecological management of pests and diseases. We thus conducted a study in Kaweri Coffee Plantation Limited located in central Uganda to determine the effect of shade tree species diversity on the incidence and damage caused by pests and diseases on Robusta coffee. One plot measuring 100 x 100 m was demarcated in each of the four sections of the plantation: Kitagweta, Kyamutuma, Luwunga and Nonve. All the shade trees/shrubs and saplings (≤3 m) in the plot were counted and identified to species level. Additionally, incidence and damage of pests and diseases were assessed on 20 Robusta coffee trees selected along two diagonals in the plots. We recorded a total of 299 trees comprising of 22 species, with Solanum giganteum being the most abundant shrub (19.8 shrubs/ha) whereas, the most abundant shade tree species were Albizia chinensis (9.3 trees/ha) and Markhamia lutea (6.0 tree/ha). Eight (8) insect pests and two (2) diseases were recorded on Robusta coffee. These included, Xylosandrus compactus, Leucoptera coffeella, Leucoplema dohertyi, Epicampoptera andersoni, Prophantis smaragdina, Planococcus spp., Hypothenemus hampei, leaf eating beetles, Hemilleia vastatrix and Cercospora coffeicola. Our results further showed contrasting effects of shade tree species diversity on the incidence and damage of pests and diseases of Robusta coffee. Damage caused by X. compactus and E. andersoni as well as the incidence of H. vastatrix and C. coffeicola decreased significantly (p≤0.05) with increasing shade tree species diversity. Contrary, damage caused by all the other insect pests increased with increasing shade tree species diversity but, only significant (p≤0.05) in case of P. smaragdina, and Planococcus spp. There is therefore a need to thoroughly understand these dynamics if agroforestry systems are to be utilized as a strategy for ecological management of pests and diseases of Robusta coffee. Keywords:Agroforestry-systems, Cercospora-coffeicola, Coffea-canephora, ecological-management, Epicampoptera-andersoni, Hemilleia-vastatrix, pest-and-disease-dynamics, Xylosandrus-compactus DOI: 10.7176/JBAH/14-1-03 Publication date: January 31^st 2024

In response to the outbreak of Coffee Wilt Disease (CWD) which wiped out almost 50% of Robusta coffee in Uganda, the National Coffee Research Institute (NaCORI) released 10 varieties (KR1-10) which are resistant to the disease. These varieties are being multiplied by stem cuttings for commercialization, although some of them present challenges in rooting. Research shows that rooting ability of stem cuttings is a function of the variety, their morphological status and rooting hormone used, among other factors. We therefore conducted an on-station study to determine the effect of morphological age of the stem cuttings and Indole-3-Butyric Acid (IBA) rooting hormone concentration on the rooting ability of varieties, KR1, KR3 and KR4. A factorial experiment with three stem segments with differing morphological age (softwood, semi-hardwood and hardwood) and five IBA concentrations (0, 1, 2, 4, 7 and 10g/l) was set up for each variety in a completely randomized design and replicated five times. Results showed that the number of roots produced by stem cuttings varied significantly (p?0.05) across varieties and IBA concentration level but not the morphological age of the cuttings. The highest number of roots was recorded on variety KR4, (35.3), 2 g/l of IBA (31.5) and softwood cuttings (29.1). Furthermore, the number of roots produced by stem cuttings varied significantly (P<0.00001) across combinations of factors. The highest number of roots was recorded on softwood treated with 10 g/l of IBA rooting hormone for KR1, hardwood cuttings treated with 2 g/l of IBA for KR3 and softwood cuttings treated with 2 g/l of IBA for KR4. Our findings provide a guide on variety-specific approaches for enhancing rooting ability of stem cuttings of these CWD-r Robusta coffee varieties. We therefore recommend that similar studies be conducted on variety, KR8 which also has been recently reported for challenges of rooting of its stem cuttings.