Solomon W. Mwendia

Assessment of Napier grass accessions in lowland and highland tropical environments in east Africa: productivity and forage quality

Ten accessions of Napier grass (Pennisetum purpureum Schumach.) were evaluated for their dry matter (DM) yield and forage quality in a semi-arid lowland (Katumani) and a relatively wet highland (Muguga) over seven growth cycles from 2011 to 2013 in tropical Kenya. Three biomass yield clusters were identified from the 10 accessions as high-yielding (HYC), medium-yielding (MYC) and low-yielding (LYC) clusters for both sites. Total biomass (shoot and root) yields (t ha⁻¹) over the seven growth cycles were 25.3 for HYC, 22.2 for MYC and 19.6 for LYC at Katumani and 40.0, 41.4 and 29.1 at Muguga. Total biomass yield averaged over the study period was DM 22.4 t ha⁻¹ at Katumani and 36.8 at Muguga. Rainfall productivity was higher at Katumani (28.8 kg ha⁻¹ mm⁻¹) than 20.8 kg ha⁻¹ mm⁻¹ at Muguga. Neutral detergent fibre (NDF) was lower in LYC, which was more leafy than the other clusters and there was little difference in NDF between the two sites.

Evaluating oat cultivars for dairy forage production in the central Kenyan highlands

With the projected increase in future demand for animal products, efforts to raise animal productivity are necessary to match the rise. Already, the estimated per-capita milk consumption in Kenya has increased to 150 L from 100 L estimated in 1998 while the population is growing at 2.65% annually. Improving milk production is largely constrained by inadequate feeding, particularly from basal roughages. To contribute towards addressing this concern, five oat cultivars (Conway, Glamis, Balado, Mascani and Rhapsody) new to eastern Africa were evaluated versus a ‘Local’ check. Agronomic attributes, forage quality and farmers’ preferences were assessed in the 2015/16 growing season. Dry matter (DM) yields ranged from 5 to 22 t DM ha−1 with Conway accumulating most DM, whereas the relative feed value was in the order Balado > Mascani > Rhapsody > Conway > Glamis > Local. However, crude protein (CP) yield (kg CP ha−1) was highest in Conway and lowest in Mascani. The two most preferred cultivars by the farmers were Conway and Glamis. Based on DM and CP production, and farmers’ choice, we conclude that Conway and Glamis stand a high chance of improving forage production in the area and other similar systems.

Assessment of Napier grass accessions in lowland and highland tropical environments of east Africa: water stress indices, water‐use and water‐use efficiency

BACKGROUND Low rainfall is a major limitation to expanding the dairy industry in semi-arid environments in East Africa. In such dry areas, plants need to keep their tissues hydrated and stomata open for carbon exchange and to grow. On this basis, we assessed the productivity of 10 lines of Napier grass (Pennisetum purpureum Schum.), which formed three yield clusters: low yielding (LYC), moderate yielding (MYC), and high yielding (HYC), in a wet highland (Muguga) and semi-arid lowland (Katumani) of Kenya. Stomatal conductance (gs ), leaf water potential (LWP) and relative water content (RWC) were monitored, and water use simulated, over four growth cycles in 2012. These were used with measurements of leaf area index (LAI) and plant dry weight to explore the possible use of these physiological parameters for assessing productivity potential of Napier grass accessions. RESULTS The plants were less stressed at Muguga, where gs was 700-1000 mmol m-2 s-1 , LWP -0.4 to -0.9 MPa and RWC was 82-95%; these values at Katumani were 450-750 mmol m-2 s-1 , -0.7 to -1.4 MPa and 74-93%, respectively. Total water use at Katumani was of the order HYC ≈ MYC (390 mm) > LYC (370 mm), and water use efficiency (WUE, kg ha-1 mm-1 ) followed the same order HYC (34.3) > MYC (32.6) > LYC (24.9); whereas at Muguga water use averaged 710 mm for HYC and MYC, greater than 676 mm for LYC, and WUE (kg ha-1 mm-1 ) averaged 29.2 for HYC and MYC, and 19.4 for LYC. CONCLUSIONS The three water stress indices were poor, whereas vigorous early canopy development (determined as LAI) was a more reliable predictor of productivity potential of Napier grasses. In these dry environments, therefore, early rapid canopy development can be an effective indicator of yield potential and a credible selection criterion.